3. Field TRIP,
1:30 - 4:00, 1 May

4. Field TRIP,
1:30 - 4:00, 1 May
Collect snails/shed
Environment/animals
Snail families/genera
Parasites
Prevalence of patent infection
Wear water/mud-suitable attire
Collect snails,
not devastate the property

5. Freshwater pulmonate snail family-level identification based on shell morphology
Lymnaeid
Physid
Planorbid
Planorbella sp.
Gyraulus sp.
dextral
sinistral
For shells with spire, check aperture right (dextral) or left (sinistral)
Planorbids have a sinistral shell, coiled in one plane, sunken spire
New Mexico has several species each of Lymnaeids and Physids
Shell length: Lymnaeids ≤ 2.5 cm, Physids ≤ 1 cm
Planorbids include Gyraulus spp. (adults < 5 mm shell diameter) and
Planorbella (Helisoma) duryi, P. (H) trivolvis (large shells)
For additional info see:

7. TO THE NEXT HOST Parasites move through lifecycles:
                                                                                    
TO THE NEXT HOST
Parasites move through lifecycles:
Rely on host behavior
favorite food/prey
Modify host behavior or the host
(extended phenotype)
EXTENDED PHENOTYPE (Richard Dawkins, 1982)
Phenotype not limited to biological processes, includes all effects that a gene has on its environment, inside or outside of the body of the individual organism. Parasite genes have effects in the body of their hosts

8. Reliance on host behavior favorite food/prey

9. Dicrocoelium dendriticum

18. Dicrocoelium dendriticum (NO WATER)18

19. Caption: Brown ant. Coloured Scanning Electron Micrograph (SEM) of a brown ant, Formica sp., biting a blade of grass. A parasitic Dicrocoelium dendriticum fluke has infected the ant. The fluke has formed an encysted stage (metacercaria) within the ant and is ready to infect a larger animal. The parasite causes cramp in the ant's mouthparts (mandibles), clamping it to the grass blade for many hours. During this time the ant may be consumed when the grass is eaten by a grazing animal such as a cow or sheep. The fluke will then infect its new host's gall bladder and bile duct. Dicrocoelium sp. flukes are found world-wide. Magnification: x17 at 5x7cm size. Magnification: x28 at 4x5 inch size.

20. PARASITE-MODIFIED HOSTS
1. Altered morphology
Coloration / size
2. Altered feeding
Time budgets / competitive ability
3. Altered locomotion
Reduced performance / conspicuous locomotion
4. Altered habitat selection
Horizontal / vertical / cover preferences
5. Altered anti-predator behavior
Susceptibility to encounter / detection / capture
6. Altered reproduction

21. The EXTENDED PHENOTYPE
‘When infections cause changes in host behavior…a parasite’s genes find phenotypic expression in the behavior of the host’
(1)
Acanthocephalon parasite causes phenotypic change in termites, increased chance of predation

22. (2)

23. (3)
Fundulus parvipinnis
Euhaplorchis californiensis
Cerithidea californica
Euhaplorchis californiensis
3) Altered Behavior of Parasitized Killifish Increases Susceptibility to Predation by Bird Final Hosts
Kevin D. Lafferty, A. Kimo Morris
Ecology, Vol. 77, No. 5 (Jul., 1996), pp

24. Infected killifish exhibited altered behaviour
Uninfected
Infected fish performed many more ‘conspicuous’ behaviours 25 15 5 10 20 30
Number of parasites
Conspicuous behaviours
in 30min
500
1000
2500
2000
1500
Include ‘flashing’, jerking and ‘surfacing’
Lafferty & Morris 1996 (Ecology 77, )

25. Birds selectively caught infected fish
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9 1
Uninfected
<1400 cysts
>1400 cysts
Parasite intensity
Proportion eaten by birds
Lafferty & Morris 1996 (Ecology 77, )

26. Diplostomum (Digenea) in the eye
Infected trout
Suffer from ‘parasitic cataract disease’ as a result of heavy infections
This means that lenses become clouded as a result of the invasion of large numbers of parasites
Economic consequences?
Moody & Gaten (1982) Hydrobiologia 88,

27. (4)
Plagiorhynchus cylindraceus
Altered habitat preference in isopods

29. OTHER EXAMPLES

31. Modify host behavior or the host (extended phenotype)
(5)
Modify host behavior or the host (extended phenotype)
Behavioral changes induced by Toxoplasma infection of rodents are highly specific to aversion of cat odors. Ajai Vyas*,, Seon-Kyeong Kim, Nicholas Giacomini*, John C. Boothroyd, and Robert M. Sapolsky* PNAS | April 10, 2007 | vol. 104 | no. 15 |
The "behavioral manipulation" hypothesis postulates that a parasite will specifically manipulate ONLY host behaviors essential for enhancing its own transmission

32. Biomphalaria glabrata/Schistosoma mansoni
(6)
Biomphalaria glabrata/Schistosoma mansoni
“CUCKOO?”

33. Direct and indirect manipulation
from Milinski (1990)
Direct (e.g. secretion of a chemical message)
Indirect (e.g. via alterations in nutrition)

34. Mechanisms of manipulation
DIRECT
Interaction with host CNS or muscle: Secretion/excretion of neuroactive substance that can stimulate host release of neurotransmitters or mimic host´s neurotransmitters.
INDIRECT
Presence of parasites in tissues other than CNS and muscles can influence host´s development, metabolism and/or immunity.

35. ALTERNATIVE EXPLANATIONS
Side effects of infection.
A heavy load of parasites, their location, interferes with normal physiological functioning.
Coincidental benefits for the parasite.
Infected leads to higher energetic needs. Increased time spent feeding/foraging yields an increasing risk of predation.
Fortuitous payoffs of other adaptations.
Locating to the CNS (immune privileged site) may really only be an adaptation to escape the host´s immune system

36. Anisakis nematodes in cod (Gadus morhua)
Anisakis nematodes require fish intermediate hosts to be eaten by marine mammals
Encyst in the musculature of the body wall
Waste products include alcohols and ketones
These have an anaesthetic (direct) effect on muscle and impair swimming
Ackman & Gjelstad (1975) Anal. Biochem. 67,