Meeting Abstract
The evolution of feeding and non-feeding larval types has occurred repeatedly in both terrestrial and marine phyla, however we lack a detailed understanding of how such shifts occur. We analyzed development and gene expression in two seabiscuit species with alternate larval types and their hybrid offspring in order to investigate the evolution of larval type. Clypeaster subdepressus develops via a typical, obligately feeding, pluteus, which must feed in order to reach metamorphosis. However, Clypeaster rosaceus larvae develop via a rare intermediate mode—facultative planktotrophy—where they can feed but do not need to feed during their larval period. This intermediate larval type is presumed to be the one of the first steps in the transition to non-feeding development. In our crosses between these species, both reciprocal hybrids developed via the feeding mode of their maternal species rather than displaying a unique phenotype. In order to investigate the genetic basis of the developmental patterns we observed, we assembled developmental transcriptomes for both species using the program Trinity. We then analyzed gene expression patterns throughout development in both parental species and each reciprocal hybrid cross in order to identify gene expression patterns associated with each life history. We found differences in the timing and developmental stage at which genes were expressed in each cross. Our results suggest that accelerated gene expression may be an important initial step in the evolution of non-feeding larval development.
