CHH family peptides from an ‘eyeless’ deep-sea hydrothermal vent shrimp, Rimicaris kairei: Characterization and sequence analysis

The crustacean eyestalk synthesizes and secretes several structurally-related peptides belonging to the crustacean hyperglycemic hormone (CHH) family, which are considered major physiological regulators during the crustacean life cycle. However, it is intriguing that eyestalks of many hydrothermal vent crustaceans prove to have varying degrees of reduction. In the present study, we characterized full-length cDNAs encoding two important eyestalk hormones of the CHH family, CHH and VIH (vitellogenesis-inhibiting hormone), from the ‘eyeless’ hydrothermal vent shrimp Rimicaris kairei. The two isoforms of Chh cDNA were 1027 and 1877 bp in length, respectively, and the deduced preprohormones contained 137 and 138 aa, respectively. The Vih cDNA was 907 bp in length, encoding a putative preprohormone of 113 aa. When compared with other known protein sequences of CHHs and VIHs, these polypeptides from hydrothermal vents show high similarity with their non-vent counterparts. These results may provide evidence for the mechanisms of eyestalk reduction and vent-adapting evolution of crustaceans. The hydrothermal vent shrimp with reduced eyestalks may take a different evolutionary pathway than eyestalk-holding crustaceans, and the reduced eyestalks can be considered a good example for the investigation of the diversity of crustacean evolution in different environments.