Meeting Abstract
Sessile marine invertebrate larvae commonly possess motile larval stages that make settlement decisions based on environmental sensory cues. Phototaxis, mobility toward or away from light, is a common feature of marine larvae for a diversity of taxa, but the behavioral and genetic details are only known from a few systems. Here we describe results from a study of wavelength sensitivity, preference and gene expression during the development of the colonial hydrozoan Hydractinia symbiolongicarpus. We monitored positive phototaxis to pure Red, Blue and Green light over the course of development and performed RNAseq experiments for selected developmental time points. We find that Hydractinia larvae are strongly phototactic to green light after the development of the sensory furrow upon larval day two of development and remain so until settlement. We find a significant, but weak response to pure blue light and no significant phototaxis response to red light. Analysis of RNAseq data taken from before and after the onset of phototaxis reveals a set of differentially expressed genes that are putatively involved in this photo response.
