Molecular Characterization of Crustacean Visual Pigments and the Evolution of Pancrustacean Opsins

• Published in: Molecular Biology and Evolution
• Main Authors: Porter, Megan L., Cronin, Thomas W., McClellan, David A., Crandall, Keith A.
• Format: Text
• Language: English
• Published: Oxford University Press 2006
• Subjects: Research Article; Euphausia superba; Homarus gammarus
• Online Access: http://mbe.oxfordjournals.org/cgi/content/short/msl152v1; https://doi.org/10.1093/molbev/msl152

Investigations of opsin evolution outside of vertebrate systems have long been focused on insect visual pigments while other groups have received little attention. Furthermore, few studies have explicitly investigated the selective influences across all the currently characterized arthropod opsins. In this study, we contribute to the knowledge of crustacean opsins by sequencing one opsin gene each from six previously uncharacterized crustacean species ( Euphausia superba , Homarus gammarus , Archaeomysis grebnitzkii , Holmesimysis costata , Mysis diluviana , and Neomysis americana ). Visual pigment spectral absorbances were measured using microspectrophotometry for species not previously characterized ( A. grebnitzkii = 496 nm, H. costata = 512 nm, M. diluviana = 501 nm, and N. americana = 520 nm). These novel crustacean opsin sequences were included in a phylogenetic analysis with previously characterized arthropod opsin sequences to determine the evolutionary placement relative to the well-established insect spectral clades (long-/middle-/short-wavelength sensitive). Phylogenetic analyses indicate these novel crustacean opsins form a monophyletic clade with previously characterized crayfish opsin sequences, and form a sister-group to insect middle-/long-wavelength sensitive opsins. The reconstructed opsin phylogeny and the corresponding spectral data for each sequence were used to investigate selective influences within arthropod, and mainly ‘pancrustacean’, opsin evolution using standard d N / d S ratio methods and more sensitive techniques investigating the amino acid property changes resulting from nonsynonymous replacements in a historical (i.e. phylogenetic) context. While the conservative d N / d S methods did not detect any selection, four amino acid properties (coil tendencies, compressibility, power to be at the middle of an α -helix, and refractive index) were found to be influenced by destabilizing positive selection. Ten amino acid sites relating to these properties were found to face the binding ...