Journal
MOLECULAR BIOLOGY AND EVOLUTION
Volume 29, Issue 10, Pages 3045-3060Publisher
OXFORD UNIV PRESS
DOI: 10.1093/molbev/mss115
Keywords
Crenicichla frenata; Poecilia reticulata; Crenicichla alta; opsins; d(N)d(S); visual ecology
Funding
- National Sciences and Engineering Research Council (NSERC)
- Government of Ontario Early Researcher Award
- National Science Foundation [IOS 0743990]
- NSERC Postgraduate Scholarship
- University of Toronto Vision Science Research Program Fellowship
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [0743990] Funding Source: National Science Foundation
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The Trinidadian pike cichlid (Crenicichla frenata) is a major predator of the guppy (Poecilia reticulata), a model system for visual ecology research, and visual predation by the pike cichlid is known to select for male guppies with reduced short-wavelength reflectance. However, an early study of the pike cichlid's visual system suggested a lack of short-wavelength-sensitive cone photoreceptors, a surprising finding as many African cichlids have highly developed short-wavelength vision. In this study, we found evidence for only four expressed cone opsins (LWS, RH2a, SWS2a, and SWS2b), plus one pseudogene (RH2b). Taken together with our microspectrophotometry data, which revealed the presence of three types of cone photoreceptor, including one sensitive to short-wavelength light, this would indicate a broader spectral capacity than previously believed from earlier visual studies of this fish. Relative to the highly diverse African cichlids, however, this Neotropical cichlid appears to have a greatly reduced opsin complement, reflecting both gene loss along the Neotropical lineage (lacking functional RH2b and, possibly, SWS1 opsins) and gene duplication within the African clade (which possesses paralogous RH2a alpha and RH2a beta opsins). Molecular evolutionary analyses show that positive selection has shaped the SWS2b and RH1 opsins along the Neotropical lineage, which may be indicative of adaptive evolution to alter nonspectral aspects of opsin biology. These results represent the first molecular evolutionary study of visual pigments in a Neotropical cichlid and thus provide a foundation for further study of a morphologically and ecologically diverse clade that has been understudied with respect to the link between visual ecology and diversification.
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