Sunday, December 14, 2008

Many parasites have complex life cycles in which they require their current host to be eaten by the next host, e.g. a tapeworm cyst in an undercooked sausage. To facilitate transmission between hosts, parasites often alter the behavior of their hosts. For example, an infected host may not hide as often uninfected hosts or they may not act afraid of predator odors. These behavioral modifications presumably increase the parasite’s chances at getting eaten by the next host in its life cycle. There are a lot of examples of this phenomenon, and besides making for good cocktail party conversation, this is a fascinating and active area of research in parasite evolutionary ecology. All 3 of the papers I published in 2008 deal with host manipulation. I’ve been working in this field since I got into professional science; my undergrad thesis was on the photic behavior of amphipods infected with duck acanthocephalans. For my stay in Finland, I did not plan to do any work on host manipulation. I intended to learn how to make molecular phylogenies. I did a bit of work in this direction, but the endless pipetting associated with DNA work bored me somewhat. With the blessing of my advisor Tellervo and the urging of my collaborator Otto Seppälä, I planned some small experiments dealing with host manipulation. Those initial experiments snowballed and eventually became a major component of my PhD thesis. We somehow squeezed 4 manuscripts out of that work (2 published this year, 1 coming out next year, and a fourth hopefully next year too). While I am proud of this work, I think that I am sick of host manipulation. Maybe it was the painful peer-review process that did it to me, but maybe it is simply time for something new. I have worked on host manipulation on and off since I started in science 5 years ago. Next year, I want to focus on a whole new direction. Lately, I have been trying to understand the evolutionary forces acting on larval parasite growth and development. This is extremely interesting, but it is actually quite similar to the whole manipulation business, i.e. host manipulation usually only begins when parasite’s reach a particular developmental stage. The new field that I intend to delve into is the evolution of mixed mating in hermaphrodites. All tapeworms have both male and female sexual organs, and can thus fertilize their own eggs or accept sperm from other worms. Fertilizing one’s own eggs is generally a bad idea, because it represents an extreme form of inbreeding. In the tapeworm I am working with, it has been shown that inbreeding is costly; inbred worm eggs hatch very poorly. Thus, worms should avoid fertilizing their own eggs. They don’t, however. Even when a partner is present, worms still self-fertilize a small portion of their eggs. This seems wasteful, so it is puzzling why they do it. Starting next year, I intend to work towards an explanation for this paradox. Consider it a nerdy new year’s resolution.

1 comment:

Anonymous said...

Ines and Dan!!

Have a VERY MERRY XMAS!!!

-Ari