Is there a trade-off between fecundity and egg volume in the parasitic copepod Lernanthropus cynoscicola?

Negative relationships between egg number and egg size are commonly seen in many animal taxa, supporting the idea that there is a trade-off between egg number and egg size resulting from the allocation of resources to either one or the other. In parasites, where availability of resources is presumably very high, there may be fewer energetic constraints acting on allocation strategies, and the trade-off may be weakened. We investigated the association between egg number and egg volume among females of the copepod Lernanthropus cynoscicola Timi and Etchegoin, 1996, parasitic on the fish Cynoscion guatucupa (Cuvier). Both egg number and egg volume were strongly correlated with female body size. After controlling for the effects of body size, we found absolutely no evidence of a trade-off, i.e. no negative relationship, between egg number and egg volume. For a given body length, females that produce many eggs do not tend to produce relatively small eggs, and vice versa. In contrast, under conditions in which resources are plentiful, large females produce large quantities of high-quality eggs, and have a marked fitness advantage over small females.