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

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Tive; Euphausia superba; Homarus gammarus
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.525.7975; http://mbe.oxfordjournals.org/content/24/1/253.full.pdf

Investigations of opsin evolution outside of vertebrate systems have long been focused on insect visual pigments, whereas 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 1 opsin gene each from 6 previously uncharacterized crustacean species (Euphausia superba, Homarus gammarus, Archaeomysis grebnitzkii, Holmesimysis costata, Mysis diluviana, and Neomysis americana). Visual pigment spectral absorbancesweremeasuredusingmicrospectrophotometry for speciesnotpreviouslycharacterized (A.grebnitzkii5 496 nm, H. costata 5 512 nm, M. diluviana 5 501 nm, and N. americana 5 520 nm). These novel crustacean opsin se-quences 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 sensi-tive). Phylogenetic analyses indicate these novel crustacean opsins form a monophyletic clade with previously charac-terized 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 dN/dS ratio methods and more sensitive techniques investigating the amino acid property changes resulting from nonsynonymous replacements in a his-torical (i.e., phylogenetic) context. Although the conservative dN/dS methods did not detect any selection, 4 amino acid