Expression of genes encoding photosensitive proteins and reflectins during cephalopod development


David Koller

MSc Student
Advisor: Tim Wollesen

Unit for Integrative Zoology, Department of Evolutionary Biology
University of Vienna


Vision and photoreception in cephalopods are of high interest due to the similarity of cephalopod and vertebrate eyes. Previous studies showed that genes such as pax6 or opsins are evolutionarily highly conserved and play similar roles during ontogenesis in remotely related bilaterians.

This master thesis explores genes encoding photosensitive proteins and reflectins. Via in situ hybridization the expression patterns of five candidate genes including r-opsin, xenopsin, retinochrome and two reflectins have been visualized in developing embryos of the pygmy squid Xipholeptos notoides.
ISH experiments revealed that r-opsin and xenopsin are not only expressed in the retina of X. notoides but also in the optic lobes and the associated optic glands, a cephalopod apomorphy. The reflectins are expressed in the cornea of the eyes, in the vicinity of the optic glands and in the mantle. These findings corroborate previous studies that found opsins in the transcriptomes of the eyes, the skin and the mantle of various cephalopods. Expression of r-opsin, xenopsin, retinochrome and the two reflectins in and around the optic glands is a finding that has not been described yet. In other organisms it has been shown that retinochrome is obligatorily associated with r-opsin as both molecules rely on each other for retinal isomerisation. Although retinochrome could not be detected in the eyes of X. notoides there is some expression in the optic gland region. Upcoming studies will highlight gene expression in yet unstudied developmental stages of X. notoides and may reveal hitherto unknown expression domains for these genes.