BYRNE, M; University of Sydney: Evo-Devo and the Asteroidea

The Asterinidae is a species-rich asteroid family in Australia with the full array of mating systems, larval types and developmental habitats seen in marine invertebrates. Using ““Patiriella and Cryptasterina as model systems, we use the comparative approach to determine what aspects of maternal provisioning and development are labile for change and what features are conserved. Although the lipid component of eggs can vary widely, there appears to be some conservation in provisioning of yolk protein. The ancestral-type ontogeny of these sea stars involved two developmental modules, the bipinnaria and brachiolaria larval forms. The evolution of lecithotrophy has resulted in complete loss of the feeding bipinnaria and its nervous system while the brachiolaria and neuronal architecture required for settlement are conserved. In the extreme case where a large egg is no longer needed due the evolution of brood cannibalism and where settlement is not relevant in the gonadal habitat, the brachiolaria stage is reduced or lost in viviparous species evolving towards complete direct development. Careful attention to the phenotypic expression of life history traits has revealed the presence of cryptic species and hitherto undetected biological diversity.