Parasitism increases offspring size in a damselfly: experimental evidence for parasite-mediated maternal effects.

The effects of parasites on host fitness and the fitness effects of maternal effects are widely discussed. In this study, I conducted an experiment linking both aspects. I manipulated the ectoparasite load (Acari: Arrenurus cuspidator) of damselflies, Coenagrion puella, and found that larvae from mothers with high parasite loads were larger (assessed by head width) than larvae from mothers with low parasite loads. Furthermore, there was a negative correlation between the number of eggs laid and parasite load. Parasitized mothers thus seemed to have fewer, but probably better, offspring. The ecological significance of these parasite-mediated maternal effects remains to be tested. However, size-dependent cannibalism almost certainly has important consequences for population dynamics. Copyright 1999 The Association for the Study of Animal Behaviour.