David Koller


Developmental Gene Expression in Cephalopod Eyes

MSc Student
Advisor: Tim Wollesen
Unit for Integrative Zoology, Department of Evolutionary BiologyUniversity of ViennaAbstract


The eyes of squids, octopuses, and cuttlefish are a textbook example for evolutionaryconvergence due to their striking similarity to those of vertebrates. For this reason, studies oncephalopod vision and photoreception are of importance for a broader audience. Previous studies showed that genes such as Pax6 or certain opsin-encoding genes are evolutionarily highly conserved and play similar roles during ontogenesis in remotely related bilaterians. In this Master thesis, genes are identified and characterized that encode photosensitive proteins and reflectins. Via in situ hybridization experiments the expression patterns of five candidate genes including Rhodopsin, Xenopsin, Retinochrome and two Reflectin-encoding genes have been visualized in developing embryos of the pygmy squid Xipholeptos notoides.In situ hybridization experiments revealed that Rhodopsin is not only expressed in the retina of X. notoides but also in the olfactory organ and the dorsal parolfactory vesicles, acephalopod apomorphy. The two Reflectin genes are expressed in the eyes and in the olfactory organ. These findings corroborate previous studies that found opsins in the transcriptomes of the eyes and several extra ocular tissues of various cephalopods. Expression of Rhodopsin, Xenopsin, Retinochrome and the two Reflectin genes in the olfactory organ is a finding that has not been described yet. In other organisms, it has been shown that retinochrome and rhodopsin proteins are obligatorily associated with each other as both molecules rely on each other for retinal isomerisation. In addition, Retinochrome wasdetected in the retina of X. notoides and in the olfactory organ. This study shows numerous new expression domains for opsin encoding genes in organs that have not been associated with photoreception before that suggest that either opsins may not only be involved in photoreception or organs such as the olfactory organ are involved in photoreception.