36.4 Thursday, Jan. 5 Maternal size effects on reproduction and development in the mud snail, Ilyanassa obsoleta SCHWAB, DB*; ALLEN, JD; College of William and Mary email@example.com
A maternal effect occurs when the phenotype of an organism is influenced by the phenotype of its mother. When the maternal environment is an accurate predictor of the offspring’s environment, maternal effects can play an important role in enhancing offspring fitness. Maternal investment (e.g. egg size), which is often a function of maternal size, is one mechanism for the transmission of maternal effects. We use the mudsnail, Ilyanassa obsoleta, as a model system for examining the effects of maternal size on offspring phenotypes. Females deposit egg capsules on blades of eel grass, and exhibit high variability in the number of egg capsules laid and the number of eggs per capsule. During their development, encapsulated embryos suffer high levels of predation. To test for the presence of inducible maternal effects, we investigated how egg capsule deposition and embryonic development are mediated by maternal size in the presence of a predator (the green crab, Carcinus maenas) by exposing small (15 – 19 mm) and large (21 – 25 mm) adult mud snails to C. maenas cue and measuring egg size, egg number, egg capsule number, and egg capsule morphology. Additionally, we measured larvae at hatching to test for effects of predator cues on intracapsule development. We found that large snails lay more egg capsules and eggs per capsule, but that egg size does not vary with female size. In the presence of a predator, egg capsules were wider and possessed significantly longer defensive spines. Larval size at hatching did not vary significantly with either maternal size or predator presence/absence. Overall, our results suggest that maternal effects in I. obsoleta may play an important role in defending embryos from predators during early development, but may not persist post-hatching when the environment is less predictable.