Meeting Abstract

P1.70  Tuesday, Jan. 4  The effect of maternal size on egg deposition in the mud snail, Ilyanassa obsoleta SCHWAB, DB*; ALLEN, JD; College of William and Mary; College of William and Mary dbschwab@email.wm.edu

During the reproductive season, the mud snail, Ilyanassa obsoleta, deposits egg capsules on blades of eel grass along coastal mud flats. Female I. obsoleta show high variability in reproductive traits, including egg size, the number of eggs per capsule, and the number of egg capsules they deposit. Prior studies have shown that, in the presence of chemically mediated predator cues, females increase the amount of eggs they deposit per egg capsule. To test how maternal size (MS) might influence egg deposition, we defined MS as shell length, and determined that MS is positively correlated with soft tissue wet weight (R2 = 0.6022) and presumably with the energy available for reproduction. We then conducted two studies, testing (1) how variation in MS affects egg capsule deposition and (2) how variation in MS affects egg laying responses to the scent of a green crab (Carcinus maenas) predator. In the first experiment, we found a positive correlation between MS and the number of egg capsules deposited, but no correlation between MS and the number of eggs laid per egg capsule. We also found a significant difference between the egg capsule size of small snails (14.5 – 18.0 mm) and those of medium (18.1 – 21.0 mm) and large (21.1 – 26.0 mm) snails. In the second experiment, we found limited response to crab predators by large snails, although medium-sized snails responded both by depositing fewer eggs per egg capsule and by extending the length of a spine found on those egg capsules. Future studies will investigate how egg size varies with MS, as well as how predation ultimately affects trade-offs in survival and reproduction in I. obsoleta.