Meeting Abstract
Arthropod eye evolution is a dynamic process, with gain and loss prevalent throughout history. The genomics age has shown that opsin, a primary light-sensing protein in eyes, has an even more dynamic evolutionary history. A further layer of complexity is added when we include phylogenetically and ecologically distinct taxa into the study of opsin evolution, even if they lack eyes. We sequenced the transcriptome of a halocyprid ostracod crustacean, a lineage at least 380 MYA diverged from ostracods with characterized opsins. This lineage is ecologically distinct because it is eyeless, pelagic, and performs diel, vertical migrations. We found that this unique halocyprid expresses more diverse r-opsins than any previously characterized ostracod lineage, with or without eyes. We find that the halocyprid expresses the first ever oligostracan MW1-type opsin and the first ostracod SW-type opsin. Next, we find two copies of MW2-type opsins, similar to the median and lateral-eye specific opsins found in other myodocope ostracods, although halocyprids lack these tissues. These findings show that opsins have had even more losses than previously thought, and we hypothesize that further addition of these unique lineages will increase the estimate of losses even more. Lastly, we highlight the importance of including evolutionarily distinct taxa, even those that lack eyes, to teach us about opsin molecular evolution.
