The filtering of light by water is contingent on depth, direction and clarity.
Consequently, fish must contend with a much more variable spectral world than
terrestrial species. The gene family responsible for light sensitivity, the opsins, has
expanded in fish. The duplication events responsible for large fish opsin gene repertoires
have been characterized as part of this thesis research. The four-eyed fish, Anableps
anableps, swims at the surface with its eyes at the waterline. Among many unusual
adaptations, these eyes have two pupils, one above and one below the surface, giving it
simultaneous access to broad spectrum aerial light and filtered aquatic light. It also has a
nine cone opsin genes including duplications in three of the four cone opsin subfamilies.
In situ hybridization was used to localize opsin transcripts in the retina. My data show
that A. anableps expresses SWS1, SWS2 and RH2 opsins and has broad spectral
sensitivity across its entire retina. In addition, I discovered that the region of the retina
exposed to aquatic light expresses LWS and is, therefore, additionally red sensitive to
match the longer wavelength available in cloudy water. By comparing this pattern with
its normal eyed sister species, Jenynsia onca, I found that this increased red sensitivity is
accomplished through the reduction of green sensitive pigments, which in A. anableps
(but not J. onca) are expressed only in the ventral region of the retina that is exposed to
aerial light. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3653 |
| Date | 03 November 2011 |
| Creators | Owens, Gregory Lawrence |
| Contributors | Taylor, John Stewart |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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