Meeting Abstract
Egg size and composition vary both within and across marine invertebrate taxa. Generally, smaller eggs contain fewer maternally provisioned biochemical constituents for developing larvae, whereas larger eggs may provide more of these materials and energy. Of these constituents, proteins are used primarily for morphogenesis, whereas lipids are used for both metabolism and morphogenesis. Larger eggs do not always correlate with increased maternal provisioning, however. In fact, how egg size, composition, and energy co-vary is not entirely understood. In some cases, larger eggs may have similar constituent amounts as smaller eggs, but greater volumes of seawater or energy-poor carbohydrates. Hybridized individuals of the sea star Asterias have been observed to produce two size classes of eggs. Hybrids may show more variation in egg size across reproductive females than within populations of purebred females, but whether this variation is due to differing amounts of biochemical constituents or seawater is unknown. We assayed the eggs of 12 suspected hybrid Asterias females collected from within a hybrid zone for protein composition. While none of the females we spawned produced two different size classes of eggs simultaneously, we did find that across females, the eggs we obtained fell into two different size classes: smaller eggs (egg volume <1.1 nL) and larger eggs (egg volume >1.1 nL). Colorimetric assays indicate that the protein amount of smaller eggs was not significantly less than in larger eggs and that protein density decreased as egg size increased. We are conducting additional assays for lipid and carbohydrate composition, which will provide a more complete understanding of maternal investment in the eggs of Asterias rubens and Asterias forbesi collected from within a hybrid zone.
