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 materna l effects are widely discussed. In this study, I conducted an experiment li nking both aspects. I manipulated the ectoparasite load (Acari: Arrenurus c uspidator) of damselflies, Coenagrion puella, and found that larvae from mo thers with high parasite loads were larger (assessed by head width) than la rvae from mothers with low parasite loads. Furthermore, there was a negativ e correlation between the number of eggs laid and parasite load. Parasitize d mothers thus seemed to have fewer, but probably better, offspring. The ec ological significance of these parasite-mediated maternal effects remains t o be tested. However, size-dependent cannibalism almost certainly has impor tant consequences for population dynamics. (C) 1999 The Association for the Study of Animal Behaviour.