Meeting Abstract

P1.8  Monday, Jan. 4  Predator induced plasticity in maternal investment of the mud snail Ilyanassa obsoleta SANTONI, AM*; ALLEN, JD; Randolph-Macon College; College of William and Mary amandasantoni@students.rmc.edu

Phenotypic plasticity occurs in various organisms including marine gastropods. In many instances plasticity is a defensive response to predator cues in the environment. In addition to a morphological response to predator cues (e.g. increasing shell thickness), gastropods can also respond behaviorally by changing their investment in reproduction. While plasticity in gastropods has been demonstrated in adult and larval stages, our understanding of plasticity in reproductive investment is poor. Our study tested whether the presence of predators can induce changes in the maternal investment of the mud snail Ilyanassa obsoleta. We exposed mud snails and their egg capsules to the marine predators Carcinus maenas, Pagurus longicarpus, and Littorina littorea, as well as a no predator treatment. As a positive control, I obsoleta were also exposed to the urchin Strongylocentrotus droebachiensis which are not known to prey on mud snails or their egg capsules. In order to distinguish between responses of adults and responses of embryos, snails were exposed to predator treatments either throughout the entire experiment, only when laying, or only as encapsulated embryos. Because of the complex life cycle of I. obsoleta (intracapsular development, followed by a free-swimming larval stage), it was expected that egg size would decrease, hatching times would also decrease and therefore larvae would escape benthic predation by entering the water column sooner. Adult I. obsoleta responded to cues from C. maenas by increasing the number of eggs allotted per egg capsule. However, egg size was not affected by the presence of predators. We will also discuss the effects of predator exposure on egg capsule morphology, time to laying and time to hatching.