Meeting Abstract

S10-1.3  Monday, Jan. 7  Opsins in brachiopod embryos and larvae PASSAMANECK, Y.J.*; MARTINDALE, M.Q.; University of Hawaii; University of Hawaii yale@hawaii.edu

In the larvae of most protostome invertebrates, detection of directional light is facilitated by simple pigmented eyes containing rhabdomeric photoreceptor cells. To extend the understanding of protostome eye evolution, we have investigated photoreceptor morphology, opsin expression, and photoresponse behavior in the articulate brachiopod Terebratalia transversa. Terebratalia develops as a distinctive, free-swimming trilobed larva with multiple pigmented eye spots, before metamorphosing into the sessile benthic adult form. Our analysis of the cells of the Terebratalia larva eyes has shown that they have the morphology of ciliary photoreceptors, distinct from the rhabdomeric photoreceptors in the eyes of most other protostomes. Consistent with this, we have also found that a ciliary opsin gene is expressed in these cells. In addition, both the ciliary opsin gene and a Go opsin gene are expressed early on in embryonic development, before neural differentiation is observed. This early expression is associated with a positive photoresponse by the embryo, suggesting this behavior may be mediated by a cell-autonomous modification of ciliary beating in response to light. These finding provide novel models for understanding the increase in complexity during the course of eye evolution.