Swanson, C.A.: Positive effect of increasing egg mass size on juvenile success in the apple murex snail, Phyllonotus pomum

Packaging and placement of offspring is an important aspect of life history because it can directly affect fitness in terms of offspring survival. Previous studies addressing the effect of egg mass structure on embryo success suggest that, due to a lower oxygen diffusion coefficient in aquatic environments, increasing egg mass size without compensation for spacing, size, or number of embryos decreases embryo survival. Female apple murex snails, Phyllonotus pomum, exhibit communal egg-laying in which numerous females simultaneously lay clutches of egg capsules in a single mass. These masses can reach up to 2.3L. Because of the sheer size and 3-dimensional structure of these communal masses, I would expect to find a negative affect on juvenile success as mass size increases. Contrary to predictions based on empirical studies in other taxa, my data on Phyllonotus pomum show a trend of increasing juvenile number at time of hatching with increasing mass size. This suggests that larger mass sizes may actually provide protection for developing embryos in certain species.