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

Thesis (Ph.D.)--University of Florida, 2005. / Typescript. Title from title page of source document. Document formatted into pages; contains 277 pages. Includes Vita. Includes bibliographical references.

This paper reports a phylogeny of the African killifishes (Genus Nothobranchius, Order Cyprinodontiformes) informed by five genetic markers (three nuclear, two mitochondrial) of 80 taxa (seven undescribed and 73 of the 92 recognized species). These short-lived annual fishes occupy seasonally wet habitats in central and eastern Africa, and their distribution coincides largely with the East African Rift System (EARS). The fossil dates of sister clades used to constrain a chronometric tree of all sampled Nothobranchius recovered the origin of the genus at ~13.27 Mya. It was followed by the radiations of six principal clades through the Neogene. An ancestral area estimation tested competing biogeographical hypotheses to constrain the ancestral origin of the genus to the Nilo-Sudan Ecoregion, which seeded a mid-Miocene dispersal event into the Coastal ecoregion, followed closely (~10 Mya) by dispersals southward across the Mozambique coastal plain into the Limpopo Ecoregion. Extending westwards across the Tanzanian plateau, a pulse of radiations through the Pliocene were associated with dispersals and fragmentation of wetlands across the Kalahari and Uganda Ecoregions. We interpret this congruence of drainage rearrangements with dispersals and cladogenic events of Nothobranchius to reflect congruent responses to recurrent uplift and rifting. The coevolution of these freshwater fishes and wetlands is attributed to ultimate control by tectonics, as the EARS extended southwards during the Neogene. Geobiological consilience of the combined evidence supports a tectonic hypothesis for the evolution of Nothobranchius.