Ocular and extraocular expression of opsins in the rhopalium of Tripedalia cystophora (Cnidaria: Cubozoa)

PLoS One. 2014 Jun 5;9(6):e98870. doi: 10.1371/journal.pone.0098870. eCollection 2014.

Abstract

A growing body of work on the neuroethology of cubozoans is based largely on the capabilities of the photoreceptive tissues, and it is important to determine the molecular basis of their light sensitivity. The cubozoans rely on 24 special purpose eyes to extract specific information from a complex visual scene to guide their behavior in the habitat. The lens eyes are the most studied photoreceptive structures, and the phototransduction in the photoreceptor cells is based on light sensitive opsin molecules. Opsins are photosensitive transmembrane proteins associated with photoreceptors in eyes, and the amino acid sequence of the opsins determines the spectral properties of the photoreceptors. Here we show that two distinct opsins (Tripedalia cystophora-lens eye expressed opsin and Tripedalia cystophora-neuropil expressed opsin, or Tc-leo and Tc-neo) are expressed in the Tripedalia cystophora rhopalium. Quantitative PCR determined the level of expression of the two opsins, and we found Tc-leo to have a higher amount of expression than Tc-neo. In situ hybridization located Tc-leo expression in the retinal photoreceptors of the lens eyes where the opsin is involved in image formation. Tc-neo is expressed in a confined part of the neuropil and is probably involved in extraocular light sensation, presumably in relation to diurnal activity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cnidaria / classification
  • Cnidaria / genetics*
  • Eye / metabolism*
  • Eye / ultrastructure
  • Female
  • Gene Expression*
  • Opsins / genetics*
  • Photoreceptor Cells, Invertebrate / metabolism
  • Phylogeny

Substances

  • Opsins

Grants and funding

The study was funded by a travel grant from Journal of Experimental Biology and Danish Independent Research Council grant DFF132500146 awarded to JB, Villum-Kahn Rasmussen grant VKR022166 to AG and National Science Foundation grant ISO-1045257 to THO. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.