30 June 2017

American Society of Parasitologists, Day 3

I brought my iPad, with one of those nice little keyboards, and all the keys were working except the space bar. Great. That rather slowed my plans for tweeting, blogging, and so on.

The day started with the presidential research symposium on parasite ecology, given by Celia Holland on Ascaris. She is talking about how parasites tend to aggregate:  the variance to mean ratio is almost always greater than one (higher numbers mean more aggregation). Ascaris infection is a very bad, neglected tropical disease – maybe one of the worst in terms on number of people infected world wide. A big chunk of her talk was about trying to develop a model for Ascaris infection. The only animal that Ascaris will go through its entire life cycle are pigs. Well, pigs are big, expensive, and tricky to house. So, can we do it in a mouse? Well, sort of. The Ascaris will do some of their life cycle in mice, and some mouse strains are better hosts than others.

Kim Jacobson talked about using parasites as tags for fisheries management. Artificial tags are often too big for commercially important fish, like anchovies. Parasites can tell you were fish have been, since they can only get infected in the parasite’s endemic range. They used parasites to try to figure out the migration of sardines.

Derek Zelmer (who apparently is the punchline for many jokes at ASP) talked about the synchrony of parasite populations in sunfish. Variance to mean ration of 1 is random, variance to mean ratio less than one is even. Over and over, he saw more synchrony between sites that were further away from each other. This can allow for “rescue effects”: if one population drops, another can replace it.

Notes from some of the regular contributed talks I saw:

Rachel Paseka showed carbon,nitrogen,and phosphorus ratios vary across species. This is mostly related to body size; growth needs phosphorus.

Sarah Bush gave one of my favourite talks so far. It was like the classic peppered moth story in evolution, except with lice and bird feathers instead of moths on blackened tree trunks. Feather lice are under strong selection pressure from host preening, and they evolve cryptic colouration to match feather colour quite quickly.

Martina Laidemitt: amplification or dilution effects. Coolest part of this talk was discussion of how one trematodes species can completely take over a host from competitor species.

Tim Anderson more snail parasites. Schistosomes parasites vary in Ho the time in when their cercaria are shed. Some species synchronize their release. In one case, the same species releases at different times depending on what host they have infected. Does this have a genetic bases? Oh yes. And they have tracked it down to chromosome 1, which affects lots of cercaria release traits.

Laura Eliuk: trematodes life cycles often have a three host life cycle. Not much research on mollusk (first intermediate) hosts. Parasites may alter mucus composition of first intermediate host, to make them more attractive to the second host. The moral of her talk was never trust sweet smelling snail snot (my summary, not hers).

Alyssa Gleischner: does parasite competition influence virulence? Related parasites should have reduced virulence, as per kin selection theory, since if host dies, it takes all kin with it. But if parasites are not related, there is direct competition, so you care less if competitors die. She tried answering this in schistosomes. Results were sometimes supportive of kin selection, sometimes not, depending on what you measure. Low virulence for intermediate hosts, high for definitive hosts. Stage in life cycle may also matter.

Frederick Chevalier: schistosomes were transported from Africa to South America. How are they adapting to new habitat? Quite well.

Erika Ebbs was supposed to be speaker, but Sara Brant ended up giving it instead. Watch the fun when a supervisor has to take over a student's talk. Duck ecology shapes influence microevolutionary changes of parasites. I think at one point she mentioned that one of her duck species was infected 98% of the time, and she couldn't remember seeing prevalence that high before. Heh. I got something that ties that; come to my poster tomorrow!

The afternoon ended with a student session about funding. People discussed NIH, NSF, and small society grants. I took over the session for a minute or two to talk about crowdfunding.

Then, I walked around. San Antonio is a very walkable city.

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