title: The molecular evolution of visual pigments of freshwater crayfishes (Decapoda: Cambaridae).
abstract: This study examines the diverse maximum wavelength absorption (lambdamax) found in crayfishes (Decapoda: Cambaridae and Parastacidae) and the associated genetic variation in their opsin locus. We measured the wavelength absorption in the photoreceptors of six species that inhabit environments of different light intensities (i.e., burrows, streams, standing waters, and subterranean waters). Our results indicate that there is relatively little variation in lambdamax (522-530 nm) among species from different genera and families. The existing variation did not correlate with the habitat differences of the crayfishes studied. We simultaneously sequenced the rhodopsin gene to identify the amino acid replacements that affect shifts in maximum wavelength absorption. We then related these to changes that correlated with shifts in lambdamax by reconstructing ancestral character states using a maximum-likelihood approach. Using amino acid sequences obtained from five species (all were 301 amino acids in length), we identified a number of candidates for producing shifts of 4 to 8 nm in lambdamax. These amino acid replacements occurred in similar regions to those involved in spectral shifts in vertebrates.
authors.affiliation: Department of Zoology and Monte L. Bean Museum, 574 Widtsoe Building, Brigham Young University, Provo, UT 84602-5255, USA. kacranda@acd1.byu.edu
authors.forename: K A
authors.initials: KA
authors.lastname: Crandall
authors.forename: T W
authors.initials: TW
authors.lastname: Cronin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D019143:Evolution, Molecular; D005618:Fresh Water; D007448:Invertebrates / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012168:Retinal Pigments / Q000502:physiology*; D017299:Rod Opsins / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry
chemical_list: D012168:Retinal Pigments; D017299:Rod Opsins