This is a solution for today’s questions

29 martie 2009
In this Parenting Class finding help for…
Education in how and why young children think, feel and act
Having appropriate developmental expectations for behavior
Avoiding power struggles with sleeping, eating, potty training and tantrums
Making your child’s training more important than what other parents think
Distinguishing between misbehavior and developmental issues
Teaching non-punitive discipline instead of punishment
How to set limits kindly and firmly
Feeling guilty about day care
How do you know when to discipline your toddler
Have an effective long term parenting strategy

of course we have interesting equipment to measure every step.


Supporting Information for the catterpilar article

28 martie 2009
Bookmark: pone.0002276.s001

Movie S1.

A
parasitized caterpillar, bent over the parasitoid pupae that have
egressed from it, defends itself and the parasitoid pupae against a
predator with violent head-swings, resulting in the predator being
knocked off the twig.

(2.59 MB WMV)

Bookmark: pone.0002276.s002

Movie S2.

A non-parasitized caterpillar hardly responds to a predator

(1.43 MB WMV)

Acknowledgments Top

Dr. Jos Cola Zanuncio generously supplied S. cincticeps
for laboratory experiments. Special thanks to Seu Geraldo and Prof.
Gilberto de Freitas for allowing us on their guava plantations, to
Prof. Ayres Menezes Jr (University of Londrina, Brazil) for
identification of the parasitoids and to Prof. Lino Neto (Federal
University of Viosa) for discussions and assistance. Comments by Dr.
Rob Knell, Dr. Nigel Raine, and an anonymous reviewer resulted in
substantial improvements of the manuscript. We thank Paulien de Bruijn,
Martijn Egas, Tom Groot, Tessa van der Hammen, Jeroen Hoffer, Roos van
Maanen, Andr de Roos, Nicola Tin, Yasuyuki Choh, Sam Elliot and
Michiel van Wijk for suggestions and discussions.

Author Contributions

Conceived
and designed the experiments: AP MS AJ AG EL. Performed the
experiments: AJ AG Ed EC FC JO. Analyzed the data: AJ AG. Wrote the
paper: MS AJ AG.

References Top

  1. Bookmark: pone.0002276-Thomas1Thomas F, Adamo S, Moore J (2005) Parasitic manipulation: where are we and where should we go? Behavioural Processes 68: 185199. Find this article online
  2. Bookmark: pone.0002276-Cezilly1Cezilly F, Thomas F (2005) Host manipulation by parasites. Behavioural Processes 68: 185295. Find this article online
  3. Bookmark: pone.0002276-Hohorst1Hohorst W, Graefe G (1961) Ameisen – obligatorische Zwischenwirte des Lanzettegels (Dicrocoelium dendriticum). Naturwissenschaften 48: 229230. Find this article online
  4. Bookmark: pone.0002276-Poulin1Poulin R
    (1995) Adaptive changes in the behaviour of parasitized animals: A
    critical review. International Journal for Parasitology 25: 13711383. Find this article online
  5. Bookmark: pone.0002276-Moore1Moore J (2002) Parasites and the behaviour of animals. Oxford Series in Ecology and Evolution. Oxford, UK: Oxford University Press.
  6. Bookmark: pone.0002276-Thomas2Thomas F, Schmidt-Rhaesa A, Martin G, Manu C, Durand P, et al. (2002) Do hairworms (Nematomorpha) manipulate the water seeking behaviour of their terrestrial hosts? Journal of Evolutionary Biology 15: 356361. Find this article online
  7. Bookmark: pone.0002276-Eberhard1Eberhard WG (2000) Spider manipulation by a wasp larva. Nature 406: 255256. Find this article online
  8. Bookmark: pone.0002276-Ponton1Ponton F, Lebarbenchon C, Lefvre T, Biron DG, Duneau D, et al. (2006) Parasite survives predation on its host. Nature 440: 756. Find this article online
  9. Bookmark: pone.0002276-Vyas1Vyas A, Kim S-K, Giacomini N, Boothroyd JC, Saposky RM (2007) Behavioral changes induced by Toxoplasma
    infection of rodents are highly specific to aversion of cat odors.
    Proceedings of the National Academy of Sciences 104: 64426447. Find this article online
  10. Bookmark: pone.0002276-Adamo1Adamo SA
    (2002) Modulating the modulators: Parasites, neuromodulators and host
    behavioral change. Brain Behavior and Evolution 60: 370377. Find this article online
  11. Bookmark: pone.0002276-Roy1Roy HE, Steinkraus DC, Eilenberg J, Hajek AE, Pell JK
    (2006) Bizarre interactions and endgames: Entomopathogenic fungi and
    their arthropod hosts. Annual Review of Entomology 51: 331357. Find this article online
  12. Bookmark: pone.0002276-Elliott1Elliott SL, Blanford S, Thomas MB
    (2002) Host-pathogen interactions in a varying environment:
    temperature, behavioural fever and fitness. Proceedings of the Royal
    Society of London Series B-Biological Sciences 269: 15991607. Find this article online
  13. Bookmark: pone.0002276-Mller1Mller CB, Schmid-Hempel P (1993) Exploitation of cold temperature as defense against parasitoids in bumblebees. Nature 363: 6567. Find this article online
  14. Bookmark: pone.0002276-Thomas3Thomas F, Poulin R
    (1998) Manipulation of a mollusc by a trophically transmitted parasite:
    convergent evolution or phylogenetic inheritance? Parasitology 116:
    431436. Find this article online
  15. Bookmark: pone.0002276-Dawkins1Dawkins RA (1982) The extended phenotype. Oxford, UK: Freeman.
  16. Bookmark: pone.0002276-Czilly1Czilly F, Perrot-Minnot MJ
    (2005) Studying adaptive changes in the behaviour of infected hosts: a
    long and winding road. Behavioural Processes 68: 223228. Find this article online
  17. Bookmark: pone.0002276-Baudoin1Baudoin M (1975) Host castration as a parasitic strategy. Evolution 29: 335352. Find this article online
  18. Bookmark: pone.0002276-Mller2Mller CB (1994) Parasitoid induced digging behaviour in bumblebee workers. Animal Behaviour 48: 961966. Find this article online
  19. Bookmark: pone.0002276-Godfray1Godfray HCJ
    (1994) Parasitoids: Behavioral and evolutionary ecology. In: Krebs JR,
    Clutton-Brock T, editors. Monographs in behavior and ecology.
    Princeton, NJ, USA: Princeton University Press.
  20. Bookmark: pone.0002276-Brodeur1Brodeur J, Vet LEM (1994) Usurpation of host behavior by a parasitic wasp. Animal Behaviour 48: 187192. Find this article online
  21. Bookmark: pone.0002276-Brodeur2Brodeur J, McNeil JN
    (1989) Seasonal microhabitat selection by an endoparasitoid through
    adaptive modification of host behaviour. Science 244: 226228. Find this article online
  22. Bookmark: pone.0002276-Adamo2Adamo SA, Linn CE, Beckage NE (1997) Correlation between changes in host behaviour and octopamine levels in the tobacco hornworm Manduca sexta parasitized by the gregarious braconid parasitoid wasp Cotesia congregata. Journal of Experimental Biology 200: 117127. Find this article online
  23. Bookmark: pone.0002276-Carney1Carney WP (1969) Behavioral and morphological changes in carpenter ants harboring Dicrocoeliid metacercariae. American Midland Naturalist 82: 605611. Find this article online
  24. Bookmark: pone.0002276-Mouritsen1Mouritsen KN, Poulin R
    (2003) Parasite-induced trophic facilitation exploited by a non-host
    predator: a manipulator’s nightmare. International Journal for
    Parasitology 33: 10431050. Find this article online
  25. Bookmark: pone.0002276-Poulin2Poulin R, Thomas F (1999) Phenotypic variability induced by parasites: extent and evolutionary implications. Parasitology Today 15: 2832. Find this article online
  26. Bookmark: pone.0002276-Combes1Combes C (1991) Ethological aspects of parasite transmission. American Naturalist 138: 866880. Find this article online
  27. Bookmark: pone.0002276-Brodeur3Brodeur J, Boivin G (2004) Functional ecology of immature parasitoids. Annual Review of Entomology 49: 2749. Find this article online
  28. Bookmark: pone.0002276-Gelman1Gelman DB, Reed DA, Beckage NE (1998) Manipulation of fifth-instar host (Manduca sexta) ecdysteroid levels by the parasitoid wasp Cotesia congregata. Journal of Insect Physiology 44: 833843. Find this article online
  29. Bookmark: pone.0002276-Siegel1Siegel S, Castellan NJ (1988) Nonparametric statistics for the behavioral sciences. New York, USA: McGraw-Hill.
  30. Bookmark: pone.0002276-Crawley1Crawley MJ (2007) The R Book. Chichester, England: John Wiley & Sons Ltd.
  31. Bookmark: pone.0002276-Miles1Miles CI, Booker R (2000) Octopamine mimics the effects of parasitism on the foregut of the tobacco hornworm Manduca sexta. Journal of Experimental Biology 203: 16891700. Find this article online
  32. Bookmark: pone.0002276-Adamo3Adamo SA, Shoemaker KL (2000) Effects of parasitism on the octopamine content of the central nervous system of Manduca sexta: a possible mechanism underlying host behavioural change. Canadian Journal of Zoology 78: 15801587. Find this article online
  33. Bookmark: pone.0002276-Gelman2Gelman DB
    (1999) Parasitoid physiology and biochemistry effects on the host
    insect – Preface. Archives of Insect Biochemistry and Physiology 40: 1.
    Find this article online
  34. Bookmark: pone.0002276-Adamo4Adamo SA (2005) Parasitic suppression of feeding in the tobacco hornworm, Manduca sexta: Parallels with feeding depression after an immune challenge. Archives of Insect Biochemistry and Physiology 60: 185197. Find this article online
  35. Bookmark: pone.0002276-Gelman3Gelman DB, Kelly TJ, Reed DA, Beckage NE (1999) Synthesis/release of ecdysteroids by Cotesia congregata, a parasitoid wasp of the tobacco hornworm, Manduca sexta. Archives of Insect Biochemistry and Physiology 40: 1729. Find this article online
  36. Bookmark: pone.0002276-Beckage1Beckage NE, Riddiford LM (1978) Developmental interactions between the tobacco hornworm Manduca sexta and its Braconid parasite Apanteles congregatus. Entomologia Experimentalis et Applicata 23: 139151. Find this article online
  37. Bookmark: pone.0002276-Schneider1Schneider G, Hohorst W (1971) Wanderung der Matacercarien des Lanzett-Egels in Ameisen. Naturwissenschaften 58: 327328. Find this article online
  38. Bookmark: pone.0002276-Wickler1Wickler W (1976) Evolution-oriented ethology, kin selection, and altruistic parasites. Zeitschrift fr Tierpsychologie 42: 206214. Find this article online
  39. Bookmark: pone.0002276-Poulin3Poulin R, Fredensborg BL, Hansen E, Leung TLF (2005) The true cost of host manipulation by parasites. Behavioural Processes 68: 241244. Find this article online
 I believe you enjoyed the article.
article possible thanks to this team

part 04 – final discussion is soon to come up


Supporting Information for the catterpilar article

28 martie 2009

Movie S1.

A
parasitized caterpillar, bent over the parasitoid pupae that have
egressed from it, defends itself and the parasitoid pupae against a
predator with violent head-swings, resulting in the predator being
knocked off the twig.

(2.59 MB WMV)

Movie S2.

A non-parasitized caterpillar hardly responds to a predator

(1.43 MB WMV)

Acknowledgments Top

Dr. Jos Cola Zanuncio generously supplied S. cincticeps
for laboratory experiments. Special thanks to Seu Geraldo and Prof.
Gilberto de Freitas for allowing us on their guava plantations, to
Prof. Ayres Menezes Jr (University of Londrina, Brazil) for
identification of the parasitoids and to Prof. Lino Neto (Federal
University of Viosa) for discussions and assistance. Comments by Dr.
Rob Knell, Dr. Nigel Raine, and an anonymous reviewer resulted in
substantial improvements of the manuscript. We thank Paulien de Bruijn,
Martijn Egas, Tom Groot, Tessa van der Hammen, Jeroen Hoffer, Roos van
Maanen, Andr de Roos, Nicola Tin, Yasuyuki Choh, Sam Elliot and
Michiel van Wijk for suggestions and discussions.

Author Contributions

Conceived
and designed the experiments: AP MS AJ AG EL. Performed the
experiments: AJ AG Ed EC FC JO. Analyzed the data: AJ AG. Wrote the
paper: MS AJ AG.

References Top

  1. Thomas F, Adamo S, Moore J (2005) Parasitic manipulation: where are we and where should we go? Behavioural Processes 68: 185199. Find this article online
  2. Cezilly F, Thomas F (2005) Host manipulation by parasites. Behavioural Processes 68: 185295. Find this article online
  3. Hohorst W, Graefe G (1961) Ameisen – obligatorische Zwischenwirte des Lanzettegels (Dicrocoelium dendriticum). Naturwissenschaften 48: 229230. Find this article online
  4. Poulin R
    (1995) Adaptive changes in the behaviour of parasitized animals: A
    critical review. International Journal for Parasitology 25: 13711383. Find this article online
  5. Moore J (2002) Parasites and the behaviour of animals. Oxford Series in Ecology and Evolution. Oxford, UK: Oxford University Press.
  6. Thomas F, Schmidt-Rhaesa A, Martin G, Manu C, Durand P, et al. (2002) Do hairworms (Nematomorpha) manipulate the water seeking behaviour of their terrestrial hosts? Journal of Evolutionary Biology 15: 356361. Find this article online
  7. Eberhard WG (2000) Spider manipulation by a wasp larva. Nature 406: 255256. Find this article online
  8. Ponton F, Lebarbenchon C, Lefvre T, Biron DG, Duneau D, et al. (2006) Parasite survives predation on its host. Nature 440: 756. Find this article online
  9. Vyas A, Kim S-K, Giacomini N, Boothroyd JC, Saposky RM (2007) Behavioral changes induced by Toxoplasma
    infection of rodents are highly specific to aversion of cat odors.
    Proceedings of the National Academy of Sciences 104: 64426447. Find this article online
  10. Adamo SA
    (2002) Modulating the modulators: Parasites, neuromodulators and host
    behavioral change. Brain Behavior and Evolution 60: 370377. Find this article online
  11. Roy HE, Steinkraus DC, Eilenberg J, Hajek AE, Pell JK
    (2006) Bizarre interactions and endgames: Entomopathogenic fungi and
    their arthropod hosts. Annual Review of Entomology 51: 331357. Find this article online
  12. Elliott SL, Blanford S, Thomas MB
    (2002) Host-pathogen interactions in a varying environment:
    temperature, behavioural fever and fitness. Proceedings of the Royal
    Society of London Series B-Biological Sciences 269: 15991607. Find this article online
  13. Mller CB, Schmid-Hempel P (1993) Exploitation of cold temperature as defense against parasitoids in bumblebees. Nature 363: 6567. Find this article online
  14. Thomas F, Poulin R
    (1998) Manipulation of a mollusc by a trophically transmitted parasite:
    convergent evolution or phylogenetic inheritance? Parasitology 116:
    431436. Find this article online
  15. Dawkins RA (1982) The extended phenotype. Oxford, UK: Freeman.
  16. Czilly F, Perrot-Minnot MJ
    (2005) Studying adaptive changes in the behaviour of infected hosts: a
    long and winding road. Behavioural Processes 68: 223228. Find this article online
  17. Baudoin M (1975) Host castration as a parasitic strategy. Evolution 29: 335352. Find this article online
  18. Mller CB (1994) Parasitoid induced digging behaviour in bumblebee workers. Animal Behaviour 48: 961966. Find this article online
  19. Godfray HCJ
    (1994) Parasitoids: Behavioral and evolutionary ecology. In: Krebs JR,
    Clutton-Brock T, editors. Monographs in behavior and ecology.
    Princeton, NJ, USA: Princeton University Press.
  20. Brodeur J, Vet LEM (1994) Usurpation of host behavior by a parasitic wasp. Animal Behaviour 48: 187192. Find this article online
  21. Brodeur J, McNeil JN
    (1989) Seasonal microhabitat selection by an endoparasitoid through
    adaptive modification of host behaviour. Science 244: 226228. Find this article online
  22. Adamo SA, Linn CE, Beckage NE (1997) Correlation between changes in host behaviour and octopamine levels in the tobacco hornworm Manduca sexta parasitized by the gregarious braconid parasitoid wasp Cotesia congregata. Journal of Experimental Biology 200: 117127. Find this article online
  23. Carney WP (1969) Behavioral and morphological changes in carpenter ants harboring Dicrocoeliid metacercariae. American Midland Naturalist 82: 605611. Find this article online
  24. Mouritsen KN, Poulin R
    (2003) Parasite-induced trophic facilitation exploited by a non-host
    predator: a manipulator’s nightmare. International Journal for
    Parasitology 33: 10431050. Find this article online
  25. Poulin R, Thomas F (1999) Phenotypic variability induced by parasites: extent and evolutionary implications. Parasitology Today 15: 2832. Find this article online
  26. Combes C (1991) Ethological aspects of parasite transmission. American Naturalist 138: 866880. Find this article online
  27. Brodeur J, Boivin G (2004) Functional ecology of immature parasitoids. Annual Review of Entomology 49: 2749. Find this article online
  28. Gelman DB, Reed DA, Beckage NE (1998) Manipulation of fifth-instar host (Manduca sexta) ecdysteroid levels by the parasitoid wasp Cotesia congregata. Journal of Insect Physiology 44: 833843. Find this article online
  29. Siegel S, Castellan NJ (1988) Nonparametric statistics for the behavioral sciences. New York, USA: McGraw-Hill.
  30. Crawley MJ (2007) The R Book. Chichester, England: John Wiley & Sons Ltd.
  31. Miles CI, Booker R (2000) Octopamine mimics the effects of parasitism on the foregut of the tobacco hornworm Manduca sexta. Journal of Experimental Biology 203: 16891700. Find this article online
  32. Adamo SA, Shoemaker KL (2000) Effects of parasitism on the octopamine content of the central nervous system of Manduca sexta: a possible mechanism underlying host behavioural change. Canadian Journal of Zoology 78: 15801587. Find this article online
  33. Gelman DB
    (1999) Parasitoid physiology and biochemistry effects on the host
    insect – Preface. Archives of Insect Biochemistry and Physiology 40: 1.
    Find this article online
  34. Adamo SA (2005) Parasitic suppression of feeding in the tobacco hornworm, Manduca sexta: Parallels with feeding depression after an immune challenge. Archives of Insect Biochemistry and Physiology 60: 185197. Find this article online
  35. Gelman DB, Kelly TJ, Reed DA, Beckage NE (1999) Synthesis/release of ecdysteroids by Cotesia congregata, a parasitoid wasp of the tobacco hornworm, Manduca sexta. Archives of Insect Biochemistry and Physiology 40: 1729. Find this article online
  36. Beckage NE, Riddiford LM (1978) Developmental interactions between the tobacco hornworm Manduca sexta and its Braconid parasite Apanteles congregatus. Entomologia Experimentalis et Applicata 23: 139151. Find this article online
  37. Schneider G, Hohorst W (1971) Wanderung der Matacercarien des Lanzett-Egels in Ameisen. Naturwissenschaften 58: 327328. Find this article online
  38. Wickler W (1976) Evolution-oriented ethology, kin selection, and altruistic parasites. Zeitschrift fr Tierpsychologie 42: 206214. Find this article online
  39. Poulin R, Fredensborg BL, Hansen E, Leung TLF (2005) The true cost of host manipulation by parasites. Behavioural Processes 68: 241244. Find this article online
 I believe you enjoyed the article.
article possible thanks to this team

part 04 – final discussion is soon to come up


Final Discussion about infested caterpillar behaveiour – part 04

27 martie 2009

The behaviour of
parasitized hosts changed dramatically after the egression and pupation
of parasitoid larvae. Hosts stopped walking and feeding and remained
near parasitoid pupae. In addition, they performed 10 times more
head-swings than unparasitized hosts during encounters with predators.
As a result, predators were deterred in 58% of the encounters with
parasitized hosts, but gave up in only 15% of the encounters with
unparasitized hosts. It could be argued that this behavioural change
serves the parasitoids as well as the host, because both would suffer
less predation. However, the guarding caterpillar always died shortly
after the adult parasitoids emerged from their pupae. Thus increased
caterpillar survival during the period in which parasitoids pupate does
not result in increased host fitness. Hence, the hosts appear to behave
as a bodyguard of the parasitoid pupae.

The field experiment
further confirmed that parasitoid pupae indeed suffered less predation
in presence of their host. Host defence of parasitoid pupae was
ineffective against hyperparasitoids, but this did not appear to
represent an important parasitoid mortality factor. Possibly, these
specialized natural enemies have adapted to the defending host. We
conclude that the parasitoids, and not the hosts, benefited from the
behavioural changes of the host that appear to be induced by the
parasitoids.

It is unlikely that
parasitoids select hosts that showed atypical behaviour at the time of
parasitism as we used unparasitized and parasitized caterpillars
emerging from the same batches of eggs. The sudden cessation of
movement and feeding of parasitized caterpillars upon parasitoid
egression, the increased number of head-swings, and the total lack of
such behavioural changes in unparasitized caterpillars further confirms
this. Hence, the behavioural changes described here are consistent with
the hypothesis that they are induced by the parasites. This begs for an
explanation of how the parasitoid induces behaviour changes in its host
and which stage induces it. Given the long time (2 weeks) between
parasitism and the behavioural change, the adult parasitoid is not
likely to be the inducer. Furthermore, the changes in host locomotion
behaviour were not induced by stimuli from the parasitoid pupae,
because removal of the pupae from parasitized hosts or adding pupae to
unparasitized host did not alter or induce the behavioural changes.
Moreover, the mechanical damage caused by egressing parasitoid larvae
is probably not the cause of the behavioural change. In pilot
experiments, artificially damaging unparasitized hosts did not induce
modified behaviour (F. Colares pers. obs.).

Parasitoid larvae
are known to interfere with host endocrine functions, causing the host
to stop feeding before parasitoid larvae egress [10], [28], [31][35].
Levels of juvenile hormone, ecdysteroids and neurotransmitters (e.g.
octopamine) have been found to increase shortly before parasitoid
egression [33][35]. However, it is not clear whether parasitoid larvae produce these substances in sufficient quantity to change host behaviour [10], [34].
Moreover, the most important behavioural changes in the present study
occur only after the parasitoids have egressed. The egression usually
takes about 1 hour, and the caterpillars do not respond strongly to
disturbance during egression, but only 12 hours after the event. This
casts doubt on the role of the parasitoid larvae in the behavioural
changes. However, when we dissected caterpillars from which parasitoids
had egressed 34 days before, we found 12 active parasitoid larvae
that had remained behind in the host, as has been found in another
system [36].
We hypothesise that these parasitoid larvae are responsible for the
changes in host behaviour. A similar mechanism has been described for
the trematode D. dendriticum [37] and the liver fluke Brachylecithum mosquensis [23],
which both use ants as an intermediate host. One or two of the
parasites migrate to the ant’s brain, where they encyst and are
believed to affect the ant’s behaviour. These so-called brainworms are
not transmitted, and appear to be sacrificed to enable transmission of
their kin [38].
If the parasitoid larvae of the system described here also stay behind
to manipulate the host and do not pupate later, this would represent a
cost of host manipulation: some offspring are sacrificed for higher
survival of their kin [39]. This hypothesis needs further investigation.

There has been
considerable debate on behavioural changes of hosts being true
manipulations by the parasitoid or by-products of infection [2], [4].
Although we do not yet know the mechanisms that induce behavioural
changes in our system, it is clear that the modified behaviour is
beneficial to the parasitoid. Hence, even if behavioural changes were
initially by-products of infection, parasitoids would be strongly
selected to induce these by-products more effectively, and it would be
currently impossible to distinguish between coincidentally beneficial
by-products and parasitoid adaptation [1].

 

article possible thanks to this team

part 04 – final discussion is soon to come up


Defensive behaviour in the laboratory – part 03

25 martie 2009

In contrast,
all unparasitized caterpillars continued feeding and moving, any
difference in locomotion before and after the time at which egression
would have taken place (had they been parasitized) was not significant
(Wilcoxon Matched Pairs test: V = 44, P = 0.23). The difference in the
number of parasitized and unparasitized caterpillars moving after the
time of parasitoid egression was highly significant (Fisher’s exact
test: p<0.0001), as was the difference in distance travelled (Fig. 2, KW = 24.0, d.f. = 3, P<0.001).

There were no
significant differences in distance travelled comparing either
parasitized (Kruskal Wallis test: KW = 0, d.f. = 1,
Bonferroni-corrected P = 1) or unparasitized (KW = 0.011, d.f. = 1,
Bonferroni-corrected P = 0.92) caterpillars with and without pupae.
This indicates that the presence of parasitoid pupae does not induce a
change in host behaviour.

Defensive behaviour in the laboratory

When
detecting a predator that was introduced on the twig, 17 out of 19
parasitized caterpillars lashed out at the bug with repeated violent
head-swings (see Movie S1).
Only one of 20 unparasitized caterpillars showed this behaviour,
whereas the others hardly responded to the presence of the predator,
even when it was walking on the host (see Movie S2).
The difference in the number of parasitized and unparasitized
caterpillars that showed head-swings was highly significant (Fisher’s
exact test: P<0.0001). Prior to parasitoid egression, parasitized
caterpillars also do not respond to disturbance with head-swings (A.H.
Grosman and A. Janssen , pers. obs.). Parasitized caterpillars showed a
significantly higher number of head-swings towards the predator than
unparasitized caterpillars (Fig. 3A, GLM with quasi-Poisson errors, F1,37
= 57.6, P<0.001). In more than half of the encounters of a predator
with a parasitized caterpillar, the repeated head-swings caused the
predators either to give up and leave the twig or to be knocked off (Fig. 3B),
and the predators succeeded in contacting the pupae in only 35% of the
interactions. Predators were never knocked off by unparasitized
caterpillars, and gave up in only 15% of the cases (Fig. 3B, difference between parasitized and unparasitized caterpillars: Fisher’s exact test, P = 0.008).

 

 

Figure 3. Effect of parasitism on host-predator interactions in the laboratory.

A
predator was introduced on a twig, 24 cm away from a parasitized or
unparasitized caterpillar, without disturbing the caterpillar. A. Upon
being encountered by a predator, parasitized caterpillars (black bars:
mean+s.e.m.) swung their heads more frequently than unparasitized
(white bars: mean+s.e.m.) caterpillars (***: GLM with quasi-Poisson
errors, F1,37 = 57.6, P<0.001). B. The proportion of
predators that gave up or were knocked off the twig was higher for
parasitized compared with unparasitized hosts (**: Fisher’s Exact Test,
P = 0.008). Numbers of replicates are given in brackets.

doi:10.1371/journal.pone.0002276.g003

Effect of host on parasitoid pupa mortality in the field

In the field, parasitoid pupae were readily attacked by various ant species, predatory bugs such as Supputius spp.,
and four species of hyperparasitoid wasps. Significantly more pupae
were damaged or disappeared from batches of pupae that were exposed to
predators and parasitoids than from unexposed batches in sleeve cages
(average mortality per batch: unexposed = 4.2%1, exposed: 26.6%3.2,
GLM, F1,132 = 10.5, P<0.005). We scored predation in the
exposed batches as the proportion of pupae per batch that had
disappeared or was damaged.

Removal of the caterpillars resulted in a two-fold increase in mortality of batches of parasitoid pupae (Fig. 4A, GLM, F1,116 = 8.25, P<0.005). Contrary to what has been suggested [19], this was mainly due to differences in predation (Fig. 4A, F1,116
= 8.85, P<0.005) and not hyperparasitism, which accounted for only
3.1 (0.8) % mortality and did not differ between treatments (Fig. 4A. F1,116
= 0.09, P = 0.76). Caterpillars disappeared from 25% of the (exposed)
batches of parasitoid pupae in the field. This is likely to be due to
predation because parasitized caterpillars hardly move once parasitoid
larvae egress (Fig. 2),
and caterpillars inside sleeve cages did not disappear. The mortality
in batches of parasitoid pupae from which the caterpillars disappeared
was as high as that in batches from which caterpillars were
experimentally removed (Fig. 4, F1,66 = 0.27, P = 0.60), and much higher than in batches from which the caterpillar survived the period of field exposure (Fig. 4, F1,65
= 23.9, P<0.0001). We do not know whether death of these pupae
occurred before or after the disappearance of the caterpillar, or was
actually causally related to it. Possibly, some predators were
attracted by the caterpillar and subsequently also fed on the
parasitoid pupae. If this were the case, this suggests that there may
also be costs involved with the behavioural changes in the caterpillar:
behavioural changes might attract some predators against which the
caterpillar cannot defend the parasitoid pupae. Nevertheless, the
overall effect of caterpillar presence on survival of parasitoid pupae
was positive (Fig. 4A).
 
 

Figure 4. Effect of removing the guarding host on field mortality of parasitoid pupae.

Twigs
with known numbers of parasitoid pupae were attached to a leaf of a
guava tree (each batch to a different tree) mimicking the natural
situation. The guarding caterpillar was removed at random from 43% of
the batches of parasitoid pupae. A. Total mortality, expressed as mean
proportion of pupae per batch eaten by predators (white bars:
mean?s.e.m.) or hyperparasitized (black bars: mean+s.e.m.). The mean
proportion of pupae lost per batch (presumably eaten by predators) was
significantly lower in the presence of the host (+ host) than when the
caterpillar was absent (- host) (total: ***: GLM with quasi-binomial
errors, F1,116 = 8.25, P<0.005, predation: F1,116
= 8.85, P<0.005). Levels of hyperparasitism per batch were not
significantly different in the presence or absence of the host (F1,116
= 0.09, P = 0.76). B. Of the batches of pupae with host (+ host in A),
total mortality and predation with a live host was lower than when the
host was missing at the end of the period of field exposure (total: **:
F1,65 = 23.9, P<0.0001, predation: F1,65 = 32.7, P<0.0001), but hyperparasitism did not differ significantly between treatments (F1,65 = 2.78, P = 0.10). Numbers of replicates are given in brackets.

doi:10.1371/journal.pone.0002276.g004

 
article possible thanks to this team

part 04 – final discussion is soon to come up


Materials and Methods – part 02

24 martie 2009

Thyrinteina leucocerae and Glyptapanteles sp. were collected from guava (Psidium guajava) and Eucalyptus grandis
trees on the campus of the Federal University of Viosa, Minas Gerais,
Brazil (2045? S, 4251? W). The parasitoid species awaits further
taxonomic description, and voucher specimens are deposited with Prof.
A. Menezes Jr. at the University of Londrina, Brazil. Caterpillars were
reared either in groups on small eucalyptus or guava trees (3090 cm
high) in cages (7070 cm, 100 cm high) outside the laboratory, or
individually in plastic cups (500 ml) in the laboratory at ambient
temperature and light conditions. The cups contained small (510 cm)
twigs of eucalyptus or guava with some 17 leaves, and were closed with
a mesh. The twigs were inserted into moist vermiculite to maintain leaf
turgor. Fresh twigs were added twice per week. Moth pupae were
transferred to cages (as above) outside the laboratory, each containing
a small tree and filter paper moistened with a solution of honey in
water (10% v/v). Moths were allowed to emerge and adults mated and
oviposited inside the cages. Eggs were collected from the cages once a
week, and were left to emerge in cages containing small trees. The host
cultures were frequently supplemented with field-collected individuals.

Recently emerged
adult parasitoids, one female and 12 males, were incubated for 24
hours in a glass tube containing a piece of host plant leaf to allow
them to mate. They were subsequently placed in glass tubes (containing
agar and some honey, closed with foam rubber) and either kept in the
laboratory when caterpillars were available or stored in a climate box
(12C3, L12: D12 ) until there was a supply of caterpillars.
Subsequently, the adult parasitoids were incubated for 24 hours in a
plastic cup (500 ml) containing some leaves and up to 8 first-instar T. leucocerae
caterpillars of the same age. Parasitism is very rapid, occurring as a
female parasitoid apparently walks over a host caterpillar. Immediate
dissection of the caterpillar reveals up to 80 eggs inside (A. Janssen ,
pers. obs.). Parasitoid larvae egress from parasitized caterpillars
through exit holes they make in the host cuticle and pupate after 1116
days (A.H. Grosman, pers. obs). Parasitoid pupae were collected from
the cups and incubated in glass tubes in the laboratory until adult
emergence. As with the host, the parasitoid cultures were frequently
supplemented with field-collected individuals.

For all experiments,
we used caterpillars emerging from the same egg batches, which were
subdivided into groups: one group was exposed to parasitoids to obtain
parasitized caterpillars, whereas the other group was not exposed (i.e.
caterpillars remained unparasitized). Because each group had an equal
probability of containing hosts with aberrant behaviour, this minimized
the possibility that any behavioural changes observed were due to
parasitoids selecting hosts with atypical behaviour, rather than a
consequence of parasitism [4].

Effect of parasitism on host locomotion

First-instar hosts (parasitized and unparasitized) were placed individually on small E. grandis
trees (c. 50 cm high) in cages outside the laboratory. Caterpillars
were prevented from walking off the plant using a ring of insect glue
(Cola Entomolgica, Bio Controle, So Paulo, Brazil) applied to the
stem of the seedlings. Replicates in which the caterpillar disappeared
(<16%) were discarded. Upon egression, half of the twigs with
parasitoid pupae were cut off, while the caterpillar was left
undisturbed on the plant. The twigs with pupae were stapled to a leaf
close by an unparasitized caterpillar, resulting in four treatments:
parasitized and unparasitized caterpillars either with or without
parasitoid pupae close by. We marked the position of the caterpillars
by tying a thin thread on the plant just behind the abdominal prolegs,
taking care not to disturb the caterpillars. Each subsequent day, we
measured the distance moved by the caterpillar from the original thread
(by tying another thread just behind the abdominal prolegs).
Caterpillar locomotion was scored until either five days after
parasitoid egression or five days after the addition of parasitoid
pupae. Caterpillar size was measured in a similar way with another
piece of thread. Locomotion of unparasitized caterpillars without pupae
was scored until 5 days after the average caterpillar age at parasitoid
egression (23 days). Although no parasitoid larvae egressed from
unparasitized caterpillars, for brevity we refer to the movement of
parasitized and unparasitized host before and after egression in all
treatments. The distribution of movement data was non-normal due to
zero inflation, even after transformations; we therefore used the more
conservative non-parametric Kruskal-Wallis test [29] to compare locomotion among treatments before or after parasitoid egression. A Wilcoxon matched pairs test [29] was used to compare caterpillar locomotion before and after egression within treatments [29]
using R statistical software (R, version 2.3.1, 2006. R Development
Core Team 2006, R Foundation for Statistical Computing, Vienna,
Austria). Caterpillar body length was compared using a t-test.

Defensive behaviour in the laboratory

We used third-instar stinkbugs (Supputius cincticeps
(Stl), Heteroptera, Pentatomidae) to quantify the response of
parasitized and unparasitized hosts to predators. Predators of this
genus attack parasitoid pupae as well as T. leucocerae
caterpillars in the field (A.H. Grosman, pers. obs.). Predators were
obtained from a mass culture at the Federal University of Viosa fed
with Tenebrio molitor L. larvae and were individually incubated
for one day in Petri dishes (14 cm diameter) containing a source of
water (a moist piece of cotton wool) and some parasitoid pupae to
familiarize predators with pupae as food. Subsequently, they were
incubated for another day without parasitoid pupae to starve them, thus
increasing their tendency to search for prey.

Twigs with
unparasitized or parasitized caterpillars with their pupae were
inserted into a foam block, so that the twig was positioned vertically.
A starved predator was introduced gently at some 24 cm from the
caterpillar without disturbing the latter, and was allowed to search.
It was reintroduced if it left the twig before encountering the
caterpillar or pupae. Parasitized and unparasitized caterpillars were
tested in an alternate sequence, and each caterpillar and each predator
was tested once. Average observation time was 5.40.87 min
(means.e.m.) for parasitized caterpillars and 6.70.87 min for
unparasitized caterpillars. When the predator encountered the
caterpillar, we scored the number of head-swings the caterpillar
directed towards the predator, as well as the outcome of the
interaction (escape of the predator, predator knocked off by the
head-swings). The number of head-swings by parasitized and
unparasitized caterpillars were compared with a generalized linear
model with quasi-Poisson error distribution to correct for
overdispersion [30],
using R statistical software. The numbers of predators that gave up or
were chased away by the defending caterpillar were compared with a
Fisher’s exact test [29].

Effect of host on parasitoid pupa mortality in the field

Field
experiments were carried out from 1 July to 17 August 2005 in two guava
plantations on the campus of the Federal University of Viosa. The
vegetation covering the soil consisted mainly of grasses; the
plantations were surrounded by more diverse native vegetation. One of
the guava plantations was managed organically; the other plantation was
not managed.

We obtained
parasitized caterpillars as described above. All batches of parasitoid
pupae that emerged on the same day were placed in the same field within
one day of egression and pupation of the parasitoids. The guarding
caterpillar was removed from 43% of the batches. Each batch was
attached to a separate guava tree by stapling the twig (with or without
caterpillar, depending on the treatment) to a leaf, thus exposing it to
predators and parasitoids. The number of pupae in batches with and
without host did not differ significantly between treatments (with
host: 35.51.8, without host: 33.12.0, t-test, P = 0.37). A total of
118 batches of parasitoid pupae were exposed in the two guava
plantations.

To measure
mortality due to causes other than predation and hyperparasitism, we
covered branches, to which twigs with pupae and caterpillars were
attached, with a sleeve cage of fine mesh (below referred to as
unexposed batches). Insect glue applied to the base of each branch
prevented walking predators and parasitoids from accessing these
unexposed batches. Batches were recollected after three days (c. half
of the pupal period), pupae were counted, and the presence or absence
of the caterpillar recorded. Pupae were subsequently incubated for one
month (25C5, L12:D12) to allow emergence of parasitoids and
hyperparasitoids. The proportion of pupae per batch which were eaten by
predators or hyperparasitized was compared among treatments using GLM
with quasi-binomial error distributions to correct for overdispersion [30], using R statistical software.

Results

Effect of parasitism on host locomotion

Before
egression of the parasitoid larvae, parasitized and unparasitized
caterpillars did not differ in body length (parasitized: n = 17,
2.84014 cm (means.e.m.); unparasitized: n = 17, 3.000.08 cm, t-test:
t = 0.995, P = 0.33). All caterpillars moved, and although parasitized
caterpillars moved more than unparasitized caterpillars (7.30.50 and
5.60.45 cm/day respectively), there were no significant differences in
movement among treatments (Fig. 2, Kruskal Wallis test: KW = 7.12, d.f. = 3, P = 0.068).

Fifteen out
of 17 (88%) parasitized caterpillars stopped feeding and moving over
the plant within one day after the parasitoids had egressed (and
pupated), and all remained close to the parasitoid pupae, standing on
their two pairs of abdominal prolegs, often bent over the cluster of
pupae (Fig. 1).
The two parasitized caterpillars that moved following parasitoid
egression (one with pupae and one without pupae) covered a distance of
0.12 and 0.67 cm respectively. There was a highly significant
difference in distances travelled by caterpillars before and after
parasitoid egression (Wilcoxon Matched Pairs test: V = 153,
P<0.001). All parasitized caterpillars died soon after the adult
parasitoids emerged from the pupae, some 67 days after egression of
the larvae. This shows that the behavioural changes described here (and
below) do not benefit the parasitized host.
 
 
 

Figure 2. Effect of parasitism on host locomotion on the plant.

The
distance covered by parasitized and unparasitized caterpillars was
measured daily. Parasitoid pupae were either removed from parasitized
caterpillars (No pupae) or not (With pupae). Unparasitized caterpillars
were supplied with pupae (With pupae) or not (No pupae). Before
parasitoid egression (black bars: mean+s.e.m.), the difference in
displacement of parasitized and unparasitized caterpillars was not
significant (Kruskal-Wallis test, KW = 7.12, d.f. = 3, P = 0.068).
After egression (white bars: mean+s.e.m.), parasitized caterpillars
moved significantly less far than unparasitized caterpillars (KW =
24.0, d.f. = 3, P<0.001). The difference in displacement of
parasitized caterpillars before and after egression was significant
(**: Wilcoxon Matched Pairs test, P<0.01). Numbers of replicates are
given in brackets.

doi:10.1371/journal.pone.0002276.g002

 
10x to this great website

 part 03 soon to come up


Parasitoid turns host into bodyguard – part01

23 martie 2009

Parasitoid Increases Survival of Its Pupae by Inducing Hosts to Fight Predators

Amir H. Grosman1, Arne Janssen 1*, Elaine F. de Brito2, Eduardo G. Cordeiro2, Felipe Colares2, Juliana Oliveira Fonseca2, Eraldo R. Lima2, Angelo Pallini2, Maurice W. Sabelis1

Bookmark: aff11
Institute for Biodiversity and Ecosystem Dynamics, Section Population
Biology, University of Amsterdam, Amsterdam, The Netherlands, Bookmark: aff22 Department of Animal Biology, Section Agricultural Entomology, Federal University of Viosa, Minas Gerais, Brazil

Abstract

Many
true parasites and parasitoids modify the behaviour of their host, and
these changes are thought to be to the benefit of the parasites.
However, field tests of this hypothesis are scarce, and it is often
unclear whether the host or the parasite profits from the behavioural
changes, or even if parasitism is a cause or consequence of the
behaviour. We show that braconid parasitoids (Glyptapanteles sp.) induce their caterpillar host (Thyrinteina leucocerae)
to behave as a bodyguard of the parasitoid pupae. After parasitoid
larvae exit from the host to pupate, the host stops feeding, remains
close to the pupae, knocks off predators with violent head-swings, and
dies before reaching adulthood. Unparasitized caterpillars do not show
these behaviours. In the field, the presence of bodyguard hosts
resulted in a two-fold reduction in mortality of parasitoid pupae.
Hence, the behaviour appears to be parasitoid-induced and confers
benefits exclusively to the parasitoid.

Introduction

Diseases, parasites and parasitoids can induce spectacular changes in the behaviour of their host [1][11]. Some of these changes, such as behavioural fevering [12] and exposure to cold temperatures [13], are thought to benefit the host, but others have been suggested to result in increased transmission of parasites [1], [3], [4], [14][17] or increased survival of parasitoids [18][22]. One of the most famous examples is the parasitic trematode Dicrocoelium dendriticum,
which induces its intermediate host, ants, to move up onto blades of
grass during the night and early morning, and firmly attach themselves
to the substrate with their mandibles [3].
This is believed to enhance parasite transmission due to increased
ingestion of infected ants by grazing sheep, the final host [23].
In contrast, uninfected ants return to their nests during the night and
the cooler parts of the day. Other examples of such spectacular
behavioural changes include parasitoid larvae (Hymenoepimecis sp.) that induce their spider host (Plesiometa argyra) to construct a special cocoon web in which the larvae pupate [7], rodents infected by Toxoplasma that lose their innate aversion to odours of cats, the parasite’s final host [9],
and hairworms that induce their terrestrial arthropod hosts to commit
suicide by jumping into water, after which the hairworms desert the
host to spend their adult stage in their natural habitat [6], [8].

Although many of
these examples are consistent with host manipulation, concern has been
voiced over this interpretation of the existing evidence [1], [2], [4].
For example, supporting evidence for increased transmission of
parasites comes mainly from laboratory studies and consists of
correlations between behavioural changes and a higher risk of predation
of intermediate hosts by the final host [4], [5].
Obviously, fitness consequences for the host and parasite should be
evaluated under field conditions, where the host-parasite complex may
also suffer increased predation from organisms that are not hosts of
the parasite [1], [4], [14], [24].

The key problem with
field experiments is the difficulty in assessing whether a behavioural
change is adaptive for the parasite, adaptive for the host, or actually
represents a non-adaptive and/or accidental pathological side-effect
resulting from infection of the host [1], [4], [10], [18], [25]. Moreover, it is possible that parasites more readily infect or parasitize hosts that behave differently to conspecifics [4], [25]. In the latter case, the observed behaviour would not be a consequence, but rather a cause, of parasitism.

In contrast to the case of true parasites [1], [2], [4],
behavioural changes in parasitoid hosts are hypothesized to result in
increased parasitoid survival through decreased host predation [19][22], [26],
because parasitoids typically die with the host. Although such
behavioural manipulation of hosts by parasitoids has been reported
frequently [19][22], [27], [28], field evidence for the advantages of the behavioural change for parasitoids is even scarcer than for true parasites [10], [18], [21], and is also constrained by the possibility that parasitoids selected hosts with aberrant behaviour [4].

In this study we
present evidence for behavioural changes in a host that are beneficial
to its parasitoid under field conditions. We studied the consequences
of behavioural manipulation of the geometrid moth Thyrinteina leucocerae by its parasitoid wasp (Glyptapanteles
sp., Braconidae) on parasitoid survival in the field in Brazil. Adult
female parasitoids oviposit in first- and second-instar caterpillars of
the moth, which feed on foliage of various trees of the Myrtaceae
family, such as guava and eucalyptus. Parasitized caterpillars continue
developing and feeding until the 4th or 5th
instar, when up to c. 80 full-grown parasitoid larvae egress from the
host to pupate (A.H. Grosman and A. Janssen, pers. obs.). The larvae
spin cocoons on a twig or leaf close to the caterpillar and pupate (Fig. 1).
Subsequently, the host undergoes a series of behavioural changes,
including cessation of feeding and moving. The most profound change in
behaviour, however, is a strong increase of violent head-swings upon
disturbance, in an apparent attempt to hit the agent of disturbance
(A.H. Grosman and A. Janssen, pers. obs.). It has been suggested that
such head-swings could serve as a defence of the parasitoid pupae
against predation or hyperparasitism [20], [22],
but evidence is lacking. We therefore quantified the effects of these
behavioural changes on interactions with predators in the laboratory,
as well as on survival of the parasitoid pupae in the field.
 
 
 

Figure 1. A caterpillar of the geometrid moth Thyrinteina leucocerae with pupae of the Braconid parasitoid wasp Glyptapanteles sp.

Full-grown
larvae of the parasitoid egress from the caterpillar and spin cocoons
close by their host. The host remains alive, stops feeding and moving,
spins silk over the pupae, and responds to disturbance with violent
head-swings (supporting information). The caterpillar dies soon after
the adult parasitoids emerge from the pupae. Photograph by Prof. Jos
Lino-Neto.

doi:10.1371/journal.pone.0002276.g001

10x to this great website
part 02 soon to come up


Low Attention Span/High Curiosity Rate, Tiago Carneiro, 2000

20 martie 2009
this is a video from youtube. interesting to watch

 
  Thank you for watching, have a pleasent and intereting day.

The Brain in the Gut The Enteric Nervous System:

18 martie 2009
The gut has a mind of its own, the "enteric nervous system". Just like the larger brain in the head, researchers say, this system sends and receives impulses, records experiences and respond to emotions. Its nerve cells are bathed and influenced by the same neurotransmitters. The gut can upset the brain just as the brain can upset the gut.

The gut’s brain or the "enteric nervous system" is located in the sheaths of tissue lining the esophagus, stomach, small intestine and colon. Considered a single entity, it is a network of neurons, neurotransmitters and proteins that zap messages between neurons, support cells like those found in the brain proper and a complex circuitry that enables it to act independently, learn, remember and, as the saying goes, produce gut feelings.

The gut’s brain is reported to play a major role in human happiness and misery. Many gastrointestinal disorders like colitis and irritable bowel syndrome originate from problems within the gut’s brain. Also, it is now known that most ulcers are caused by a bacterium not by hidden anger at one’s mother.

Details of how the enteric nervous system mirrors the central nervous system have been emerging in recent years, according to Dr. Michael Gershon, professor of anatomy and cell biology at Columbia-Presbyterian Medical Center in New York. He is one of the founders of a new field of medicine called "neurogastroenterology."

The gut contains 100 million neurons – more than the spinal cord. Major neurotransmitters like serotonin, dopamine, glutamate, norephinephrine and nitric oxide are in the gut. Also two dozen small brain proteins, called neuropeptides are there along with the major cells of the immune system. Enkephalins (a member of the endorphins family) are also in the gut. The gut also is a rich source of benzodiazepines – the family of psychoactive chemicals that includes such ever popular drugs as valium and xanax.

In evolutionary terms, it makes sense that the body has two brains, said Dr. David Wingate, a professor of gastrointestinal science at the University of London and a consultant at Royal London Hospital. "The first nervous systems were in tubular animals that stuck to rocks and waited for food to pass by," according to Dr. Wingate. The limbic system is often referred to as the "reptile brain." "As life evolved, animals needed a more complex brain for finding food and sex and so developed a central nervous system. But the gut’s nervous system was too important to put inside the newborn head with long connections going down to the body," says Wingate. Offspring need to eat and digest food at birth. Therefore, nature seems to have preserved the enteric nervous system as an independent circuit inside higher animals. It is only loosely connected to the central nervous system and can mostly function alone, without instructions from topside.

This is indeed the picture seen by developmental biologists. A clump of tissue called the neural crest forms early in embryo genesis. One section turns into the central nervous system. Another piece migrates to become the enteric nervous system. According to Dr. Gershon, it is only later that the two systems are connected via a cable called the vagus nerve.

The brain sends signals to the gut by talking to a small number of "command neurons," which in turn send signals to gut interneurons that carry messages up and down the pike. Both command neurons and interneurons are spread throughout two layers of gut tissue called the "myenteric plexus and the submuscosal plexus." Command neurons control the pattern of activity in the gut. The vagus nerve only alters the volume by changing its rates of firing.

The plexuses also contain glial cells that nourish neurons, mast cells involved in immune responses, and a "blood brain barrier" that keeps harmful substances away from important neurons. They have sensors for sugar, protein, acidity and other chemical factors that might monitor the progress of digestions, determining how the gut mixes and propels its contents.

As light is shed on the circuitry between the two brains, researchers are beginning to understand why people act and feel the way they do. When the central brain encounters a frightening situation, it releases stress hormones that prepare the body to fight or flee. The stomach contains many sensory nerves that are stimulated by this chemical surge – hence the "butterflies." On the battlefield , the higher brain tells the gut brain to shut down. A frightened running animal does not stop to defecate, according to Dr. Gershon.

Fear also causes the vagus nerve to "turn up the volume" on serotonin circuits in the gut. Thus over stimulated, the gut goes into higher gear and diarrhea results. Similarly, people sometimes "choke" with emotion. When nerves in the esophagus are highly stimulated, people have trouble swallowing.

Even the so-called "Maalox moment" of advertising can be explained by the interaction of the two brains, according to Dr. Jackie D. Wood, chairman of the department of physiology at Ohio State University in Columbus, Ohio. Stress signals from the head’s brain can alter nerve function between the stomach and esophagus, resulting in heartburn .

In cases of extreme stress, Dr. Wood say that the higher brain seems to protect the gut by sending signals to immunological mast cells in the plexus. The mast cells secrete histamine, prostaglandin and other agents that help produce inflammation. This is protective. By inflaming the gut, the brain is priming the gut for surveillance. If the barrier breaks then the gut is ready to do repairs. Unfortunately, the chemicals that get released also cause diarrhea and cramping.

There also is an interaction between the gut brain and drugs. According to Dr. Gershon, "when you make a drug to have psychic effects on the brain, it’s very likely to have an effect on the gut that you didn’t think about." He also believes that some drugs developed for the brain could have uses in the gut. For example, the gut is loaded with the neurotransmitter serotonin. According to Gershon, when pressure receptors in the gut’s lining are stimulated, serotonin is released and starts the reflexive motion of peristalsis. A quarter of the people taking Prozac or similar antidepressants have gastrointestinal problems like nausea, diarrhea and constipation. These drugs act on serotonin, preventing its uptake by target cells so that it remains more abundant in the central nervous system.

Gershon also is conducting a study of the side effects of Prozac on the gut. Prozac in small doses can treat chronic constipation. Prozac in larger doses can cause constipation – where the colon actually freezes up. Moreover, because Prozac stimulates sensory nerves, it also can cause nausea.

Some antibiotics like erythromycin act on gut receptors to produce ascillations. People experience cramps and nausea. Drugs like morphine and heroin attach to the gut’s opiate receptors, producing constipation. Both brains can be addicted to opiates.

Victims of Alzheimer’s and Parkinson’s diseases suffer from constipation. The nerves in their gut are as sick as the nerve cells in their brains. Just as the central brain affects the gut, the gut’s brain can talk back to the head. Most of the gut sensations that enter conscious awareness are negative things like pain and bloatedness.

The question has been raised: Why does the human gut contain receptors for benzodiazepine , a drug that relieves anxiety? This suggests that the body produces its own internal source of the drug. According to Dr. Anthony Basile, a neurochemist in the Neuroscience Laboratory at the National Institutes of Health in Bethesda, MD, an Italian scientist made a startling discovery. Patients with liver failure fall into a deep coma. The coma can be reversed, in minutes, by giving the patient a drug that blocks benzodiazepine. When the liver fails, substances usually broken down by the liver get to the brain. Some are bad, like ammonia and mercaptan, which are "smelly compounds that skunks spray on you," says Dr. Basile. But a series of compounds are also identical to benzodiazepine. "We don’t know if they come from the gut itself, from bacteria in the gut or from food, but when the liver fails, the gut’s benzodiazepine goes straight to the brain, knocking the patient unconscious, says Dr. Basile.

The payoff for exploring gut and head brain interactions is enormous, according to Dr. Wood. Many people are allergic to certain foods like shellfish. This is because mast cells in the gut mysteriously become sensitized to antigens in the food. The next time the antigen shows up in the gut, the mast cells call up a program, releasing chemical modulators that try to eliminate the threat. The allergic person gets diarrhea and cramps.

Many autoimmune diseases like Krohn’s disease and ulcerative colitis may involve the gut’s brain, according to Dr. Wood. The consequences can be horrible, as in "Chagas disease," which is caused by a parasite found in South America. Those infected develop an autoimmune response to neurons in their gut. Their immune systems slowly destroy their own gut neurons. When enough neurons die, the intestines literally explode.

A big question remains. Can the gut’s brain learn? Does it "think" for itself? Dr. Gershon tells a story about an old Army sergeant, a male nurse in charge of a group of paraplegics. With their lower spinal cords destroyed, the patients would get impacted. "At 10am every morning, the patients got enemas. Then the sergeant was rotated off the ward. His replacement decided to give enemas only after compactions occurred. But at 10 the next morning everyone on the ward had a bowel movement at the same time, without enemas." Had the sergeant trained those colons?

The human gut has long been seen as a repository of good and bad feelings. Perhaps emotional states from the head’s brain are mirrored in the gut’s brain, where they are felt by those who pay attention to them.
 
Reference: Taken from "A contemporary view of selected subjects from the pages of The New York Times, January 23, 1996. Printed in Themes of the Times: General Psychology, Fall 1996. Distributed Exclusively by Prentice-Hall Publishing Company.
10x to KPN

Reductionism = static world = Let’s find out!

17 martie 2009
We live in the 21th Century. This is a fast moving, energy filled, quantic world. It is not anymore a mechanic, almost static one.
Relevance?
"Reductionism can either mean (a) an approach to understanding
the nature of complex things by reducing them to the interactions of
their parts, or to simpler or more fundamental things or (b) a
philosophical position that a complex system is nothing but the sum of
its parts, and that an account of it can be reduced to accounts of
individual constituents.[1] This can be said of objects, phenomena, explanations, theories, and meanings.

Reductionism is strongly related to a certain perspective on causality.
In a reductionist framework, phenomena that can be explained completely
in terms of other, more fundamental phenomena, are called epiphenomena. Often there is an implication that the epiphenomenon exerts no causal agency on the fundamental phenomena that explain it.

Reductionism does not preclude emergent phenomenon but it does imply the ability to understand the emergent in terms of the phenomena from and process(es) by which it emerges.
 
 
 
 

History

Reductionism dates back to ancient Greek philosophy in which some philosophers, notably Democritus, viewed the world as a mechanistic, material machine.[2] Democritus was famous for his theory of atomism.

It was introduced later by Descartes in Part V of his Discourses
(1637). Descartes argued the world was like a machine, its pieces like
clockwork mechanisms, and that the machine could be understood by
taking its pieces apart, studying them, and then putting them back
together to see the larger picture. Descartes was a full mechanist,
but only because he did not accept the conservation of direction of
motions of small things in a machine, including an organic machine.
Newton’s theory required such conservation for inorganic things at
least. When such conservation was accepted for organisms as well as
inorganic objects by the middle of the 20th century, no organic
mechanism could easily, if at all, be a Cartesian mechanism.
 

Types of reductionism

The distinction between the processes of theoretical and ontological
reduction is important. Theoretical reduction is the process by which
one theory is absorbed into another; for example, both Kepler’s laws of the motion of the planets and Galileos
theories of motion worked out for terrestrial objects are reducible to
Newtonian theories of mechanics, because all the explanatory power of
the former are contained within the latter. Furthermore, the reduction
is considered to be beneficial because Newtonian mechanics
is a more general theorythat is, it explains more events than
Galileo’s or Kepler’s. Theoretical reduction, therefore, is the
reduction of one explanation or theory to anotherthat is, it is the
absorption of one of our ideas about a particular thing into another
idea.

Methodological reductionism is the position that the best scientific
strategy is to attempt to reduce explanations to the smallest possible
entities. Methodological reductionism would thus hold that the atomic
explanation of a substances boiling point is preferable to the
chemical explanation, and that an explanation based on even smaller
particles (quarks, perhaps) would be even better.

Theoretical reductionism is the position that all scientific
theories either can or should be reduced to a single super-theory
through the process of theoretical reduction.

Finally, ontological reductionism is the belief that reality is
composed of a minimum number of kinds of entities or substances. This
claim is usually metaphysical, and is most commonly a form of monism, in effect claiming that all objects, properties and events are reducible to a single substance. (A dualist who is an ontological reductionist would presumably believe that everything is reducible to one of two substances.)
 

Reductionism and science

Reductionist thinking and methods are the basis for many of the well-developed areas of modern science, including much of physics, chemistry and cell biology. Classical mechanics in particular is seen as a reductionist framework, and statistical mechanics can be viewed as a reconciliation of macroscopic thermodynamic laws with the reductionist approach of explaining macroscopic properties in terms of microscopic components.

In science, reductionism can be understood to imply
that certain fields of study are based on areas that study smaller
spatial scales or organizational units. While it is commonly accepted
that most aspects of chemistry are based on physics, and similarly many aspects of microbiology are based on chemistry , such statements become controversial when one considers larger-scale fields. For example, claims that sociology is based on psychology, or that economics is based on sociology and psychology
would be met with reservations. These claims are difficult to
substantiate even though there are clear connections between these
fields (for instance, most would agree that psychology can impact and inform economics.) The limit of reductionism’s usefulness stems from emergent properties of complex systems which are more common at certain levels of organization. For example, certain aspects of evolutionary psychology and sociobiology are rejected by some who claim that complex systems are inherently irreducible and that a holistic approach is needed to understand them.

Daniel Dennett defends scientific reductionism, which he says is really little more than materialism, by making a distinction between this and what he calls "Greedy reductionism": the idea that every explanation in every field of science should be reduced all the way down to particle physics or string theory.
Greedy reductionism, he says, deserves some of the criticism that has
been heaped on reductionism in general because the lowest-level
explanation of a phenomenon, even if it exists, is not always the best
way to understand or explain it.

Some strong reductionists believe that the behavioral sciences
should become "genuine" scientific disciplines by being based on
genetic biology, and on the systematic study of culture (cf. Dawkins’s
concept of memes). In his book The Blind Watchmaker, Richard Dawkins introduced the term "hierarchical reductionism"[3]
to describe the view that complex systems can be described with a
hierarchy of organizations, each of which can only be described in
terms of objects one level down in the hierarchy. He provides the
example of a computer, which under hierarchical reductionism can be
explained well in terms of the operation of hard drives, processors,
and memory, but not on the level of AND or NOR gates, or on the even lower level of electrons in a semiconductor medium.

Both Dennett and Steven Pinker
argue that too many people who are opposed to science use the words
"reductionism" and "reductionist" less to make coherent claims about
science than to convey a general distaste for the endeavor, saying the
opponents often use the words in a rather slippery way, to refer to
whatever they dislike most about science. Dennett suggests that critics
of reductionism may be searching for a way of salvaging some sense of a
higher purpose to life, in the form of some kind of non-material /
supernatural intervention. Dennett terms such aspirations "skyhooks,"
in contrast to the "cranes" that reductionism uses to build its
understanding of the universe from solid ground.

Others argue that inappropriate use of reductionism limits our understanding of complex systems. In particular, ecologist Robert Ulanowicz
says that science must develop techniques to study ways in which larger
scales of organization influence smaller ones, and also ways in which
feedback loops create structure at a given level, independently of
details at a lower level of organization. He advocates (and uses) information theory as a framework to study propensities in natural systems.[4] Ulanowicz attributes these criticisms of reductionism to the philosopher Karl Popper and biologist Robert Rosen.[5]
 

Reductionism in mathematics

In mathematics,
reductionism can be interpreted as the philosophy that all mathematics
can (or ought to) be built off a common foundation, which is usually axiomatic set theory. Ernst Zermelo
was one of the major advocates of such a view, and he was also
responsible for the development of much of axiomatic set theory. It has
been argued that the generally accepted method of justifying
mathematical axioms by their usefulness in common practice can potentially undermine Zermelo’s reductionist program.[6]

As an alternative to set theory, others have argued for category theory as a foundation for certain aspects of mathematics.[citation needed]

 

 

Ontological reductionism

Ontological reductionism is the claim that everything that exists is
made from a small number of basic substances that behave in regular
ways (compare to monism). Ontological reductionism denies the idea of ontological emergence, and claims that emergence is an epistemological phenomenon that only exists through analysis or description of a system, and does not exist on a fundamental level.[7]

Ontological reductionism takes two different forms: Token ontological reductionism
is the idea that every item that exists is a sum item. For perceivable
items, it says that every perceivable item is a sum of items at a
smaller level of complexity. Type ontological reductionism is
the idea that every type of item is a sum (of typically less complex)
type(s) of item(s). For perceivable types of item, it says that every
perceivable type of item is a sum of types of items at a lower level of
complexity. Token ontological reduction of biological things to
chemical things is generally accepted. Type ontological reduction of
biological things to chemical things is often rejected.[citation needed]

Michael Ruse has criticized ontological reductionism as an improper argument against vitalism.[8]

Reductionism in linguistics

Linguistic reductionism is the idea that everything can be described
in a language with a limited number of core concepts, and combinations
of those concepts. The most known form of reductionist constructed
language would be Esperanto (Also See Basic English and the constructed language Toki Pona).[citation needed]

 

Limits of reductionism

A contrast to the reductionist approach is holism or emergentism.
Holism recognizes the idea that things can have properties as a whole
that are not explainable from the sum of their parts (emergent
properties). The principle of holism was concisely summarized by
Aristotle in the Metaphysics: "The whole is more than the sum of its
parts".

The term Greedy reductionism, coined by Daniel Dennett, is used to criticize inappropriate use of reductionism. Other authors use different language when describing the same thing.

 

In philosophy

The concept of downward causation poses an alternative to reductionism within philosophy. This view is developed and explored by Peter Bgh Andersen, Claus Emmeche, Niels Ole Finnemann, and Peder Voetmann Christiansen,
among others. These philosophers explore ways in which one can talk
about phenomena at a larger-scale level of organization exerting causal
influence on a smaller-scale level, and find that some, but not all
proposed types of downward causation are compatible with science. In
particular, they find that constraint is one way in which downward causation can operate.[9] The notion of causality as constraint has also been explored as a way to shed light on scientific concepts such as self-organization, natural selection, adaptation, and control.[10]
 

In science

Phenomena such as emergence and work within the field of complex systems theory pose limits to reductionism. Stuart Kauffman is one of the advocates of this viewpoint.[11] Emergence is strongly related to nonlinearity.[12] The limits of the application of reductionism become especially evident at levels of organization with higher amounts of complexity, including culture, neural networks, ecosystems, and other systems formed from assemblies of large numbers of interacting components. Symmetry breaking is an example of an emergent phenomenon. Nobel laureate P.W.Anderson used this idea in his famous paper in Science in 1972, ‘More is different’[13]
to expose some of the limitations of reductionism. The limitation of
reductionism was explained as follows. The sciences can be arranged
roughly linearly in a hierarchy as particle physics, many body physics, chemistry, molecular biology, cellular biology, …, physiology, psychology and social sciences.
The elementary entities of one science obeys the laws of the science
that precedes it in the above hierarchy. But, this does not imply that
one science is just an applied version of the science that precedes it.
Quoting from the article, "At each stage, entirely new laws,
concepts and generalizations are necessary, requiring inspiration and
creativity to just as great a degree as in the previous one. Psychology
is not applied biology nor is biology applied chemistry
."

Sven Erik Jorgensen, an ecologist, lays out both theoretical and practical arguments for a holistic approach in certain areas of science, especially ecology.
He argues that many systems are so complex that it will not ever be
possible to describe all their details. Drawing an analogy to the Heisenberg uncertainty principle
in physics, he argues that many interesting and relevant ecological
phenomena cannot be replicated in laboratory conditions, and thus
cannot be measured or observed without influencing and changing the
system in some way. He also points to the importance of
interconnectedness in biological systems. His viewpoint is that science
can only progress by outlining what questions are unanswerable and by
using models that do not attempt to explain everything in terms of
smaller hierarchical levels of organization, but instead model them on
the scale of the system itself, taking into account some (but not all)
factors from levels both higher and lower in the hierarchy.[14]

Disciplines such as cybernetics and systems theory
strongly embrace a non-reductionist view of science, sometimes going as
far as explaining phenomena at a given level of hierarchy in terms of
phenomena at a higher level, in a sense, the opposite of a reductionist
approach.[15].

 

In decision theory

In decision theory, a nonlinear utility function for a quantity such as money
can create a situation in which all relevant decisions to be made in a
given time period must to be considered simultaneously in order to
maximize utility, if all relevant decisions act on utility
only through this quantity. In such a situation, the optimal choice for
a given decision depends on the possible outcomes of all other
decisions, including those which may have no causal
relationship to the decision at hand. Breaking such a problem apart
into individual decisions and optimizing each smaller decision can lead
to drastically sub-optimal decisions. Such nonlinear utility functions
for money are used in economics
and are necessary in order to satisfy reasonable assumptions about
rational behavior. Such decision making situations are the norm, rather
than the exception, in many business settings.[16]

In religion

Certain religious beliefs
or doctrines assign supernatural original causes to phenomena. In this
context, even if a given system appears to operate by causes and
effects that can be explained within a strict reductionist framework,
belief or doctrine might hold that its true genesis and placement
within larger (and typically unknown) systems is bound up with an
intelligence or consciousness that is beyond normal or uninvited human
perception. Some such beliefs constitute a form of teleology, a perspective which is generally in conflict with reductionism.

Benefits of reduction

An ontological reduction reduces the number of ontological primitives that exist within our ontology.
Philosophers welcome this, because every ontological primitive demands
a special explanation for its existence. If we maintain that life is
not a physical property, for example, then we must give a separate
explanation of why some objects possess it and why others do not. This
is more often than not a daunting task, and such explanations often
have the flavor of ad hoc contrivances or deus ex machina.
Also, since every ontological primitive must be acknowledged as one of
the fundamental principles of the natural world, we must also account
for why this element in particular should be considered one of those
underlying principles. (To return to an earlier example, it would be
extremely difficult to explain why planets are so fundamental that
special laws of motion should apply to them.) This is often extremely
hard to do, especially in the face of our strong preference for simple
explanations. Pursuing ontological reduction thus serves to unify and
simplify our ontology, while guarding against needless multiplication of entities in the process.

At the same time, the requirements for satisfactorily showing that
one thing is reducible to another are extremely steep. First and
foremost, all features of the original property or object must be
accounted for. For example, lightning would not be reducible to the electrical activity of air molecules
if the reduction explained why lightning is deadly, but not why it
always seeks the highest point to strike. Our preference for simple and
unified explanations is a strong force for reductionism, but our demand
that all relevant phenomena be accounted for is at least as strong a
force against it.

Alternatives to reductionism

In recent years, the development of systems thinking has provided methods for tackling issues in a holistic rather than a reductionist way, and many scientists approach their work in a holistic paradigm. When the terms are used in a scientific context, holism and reductionism refer primarily to what sorts of models
or theories offer valid explanations of the natural world; the
scientific method of falsifying hypotheses, checking empirical data
against theory, is largely unchanged, but the approach guides which
theories are considered. The conflict between reductionism and holism
in science is not universal–it usually centers on whether or not a
holistic or reductionist approach is appropriate in the context of
studying a specific system or phenomenon.

In many cases (such as the kinetic theory
of gases), given a good understanding of the components of the system,
one can predict all the important properties of the system as a whole.
In other cases, trying to do this leads to a fallacy of composition. In those systems, emergent properties of the system are almost impossible to predict from knowledge of the parts of the system. Complexity theory studies such systems.
 

References

  1. ^ see eg Reductionism in the Interdisciplinary Encyclopedia of Religion and Science
  2. ^ Burns, Tony (2000), "Materialism in Ancient Greek Philosophy and in the Writings of the Young Marx", Historical Materialism 7: 3, doi:10.1163/156920600100414623 
  3. ^ "[]" Interview with Third Way magazine in which Richard Dawkins discusses reductionism and religion, February 28, 1995
  4. ^ R.E. Ulanowicz, Ecology: The Ascendant Perspective, Columbia University Press (1997) (ISBN 0231108281)
  5. ^ TITLE
  6. ^ [1] R. Gregory Taylor, "Zermelo, Reductionism, and the Philosophy of Mathematics". Notre Dame Journal of Formal Logic, Vol. 34, No. 4 (Fall 1993)
  7. ^ [2] Michael Silberstein, John McGeever, "The Search for Ontological Emergence", The Philosophical Quarterly, Vol. 49, No. 195 (April 1999), (ISSN: 0031-8094).
  8. ^ [3] Michael Ruse, "Do Organisms Exist?", Amer. Zool., 29:1061-1066 (1989)
  9. ^ P.B. Andersen, C. Emmeche, N.O. Finnemann, P.V. Christiansen, Downward Causation: Minds, Bodies and Matter, Aarhus University Press (ISBN 8772888148) (2001)
  10. ^ http://pespmc1.vub.ac.be/Einmag_Abstr/AJuarrero.html – A. Juarrero, Causality as Constraint
  11. ^ Beyond Reductionism: Reinventing the Sacred by Stuart Kauffman
  12. ^ http://personal.riverusers.com/~rover/RedRev.pdf A. Scott, Reductionism Revisited, Journal of Consciousness Studies, 11, No. 2, 2004 pp. 51-68
  13. ^ Anderson, P.W. (1972). "More is Different". Science 177 (4047): 393396. doi:10.1126/science.177.4047.393. PMID 17796623. http://www.cmp.caltech.edu/~motrunch/Teaching/Phy135b_Winter07/MoreIsDifferent.pdf. 
  14. ^ S. E. Jrgensen, Integration of Ecosystem Theories: A Pattern, 3rd ed. Kluwer Academic Publishers, (ISBN 1-4020-0651-9) (2002) Chapters 1 & 2.
  15. ^ Downward Causation
  16. ^ J.O. Berger, Statistical Decision Theory and Bayesian Analysis. Springer-Verlag 2nd ed. (1985) ch. 2. (ISBN 3540960988)

Further reading

  • Dawkins, R. (1976) The Selfish Gene. Oxford University Press; 2nd edition, December 1989 ISBN 0-19-217773-7.
  • Descartes (1637) Discourses Part V
  • Dupre, J. (1993) The Disorder of Things. Harvard University Press.
  • Jones, Richard H. Reductionism: Analysis and the Fullness of Reality. Bucknell University Press. (For the general reader.)
  • Nagel, E. (1961) The Structure of Science. New York.
  • Ruse, M. (1988) Philosophy of Biology. Albany, NY.
  • Dennett, Daniel. (1995) Darwin’s Dangerous Idea. Simon & Schuster. ISBN 0-684-82471-X.
  • Fritjof Capra. (1982) The Turning Point.
  • Alexander Rosenberg (2006) Darwinian Reductionism or How to Stop Worrying and Love Molecular Biology. University of Chicago Press.
  • Steven Pinker (2002) The Blank Slate: The Modern Denial of Human Nature . Viking Penguin.
  • Steven Weinberg (2002) describes what he terms the culture war among physicists in his review of A New Kind of Science
  • Eric Scerri
    The reduction of chemistry to physics has become a central aspect of
    the philosophy of chemistry. See several articles by this author.

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