Characterization and Comparison of Eye Development and Phototransduction Genes in Deep- and Shallow-Water Shrimp Alvinocaris longirostris and Palaemon carinicauda

Abstract

The investigations of the molecular components of eye development and phototransduction in deep-sea species are important to elucidate the mechanism of their adaptation to dim light. In this study, eye transcriptomes of the shrimp Alvinocaris longirostris from the deep-sea chemosynthetic ecosystem and the shallow-water shrimp Palaemon carinicauda were compared. Two Pax6 homologs with low expression levels were identified in both species, which are essential transcription factors in eye development. This finding implies that the development of the two shrimp eyes at early embryo–larvae stages might be similar. The multiple components of the phototransduction pathway were identified in both species. However, the number of phototransduction components was significantly reduced in A. longirostris, as well as expression level. Particularly, short-wavelength/UV-sensitive (SWS/UVS) opsins were absent in A. longirostris and only one putative middle-wavelength-sensitive (MWS) opsin was identified in this species. The conserved sites and structures of the putative LWS opsins were found between deep-sea and shallow-water decapods, indicating that the opsins in deep-sea crustaceans may also conserve their spectral absorption and signal transduction function. Phylogenetic analyses supported the monophyly of LWS opsins and SWS/UVS opsins in arthropods, while the MWS clade fell outside of the main arthropod LWS clade. The results are expected to provide baseline for study of visual adaptation in deep-sea shrimps.