Characterization of a crustacean hyperglycemic hormone of the horsehair crab Erimacrus isenbeckii

Abstract

The horsehair crab Erimacrus isenbeckii is widely distributed from Alaska and the Bering Sea through Southern Sakhalin, and in Japan from the coastal areas of Hokkaido to the Sea of Japan. In the Hokkaido area, although strict resource management has been promoted by setting an allowable catch limit, the catch amount has remained at a low level. While knowledge on larval rearing methods is accumulating in relation to seedling production techniques, information on adult growth and molting is limited, due to a deep-sea species that requires a long period for growth. In decapod crustaceans, the sinus-gland/X-organ complex in the eyestalk ganglion synthesizes and secrets various neuropeptides such as crustacean hyperglycemic hormone (CHH) to regulate the homeostasis of haemolymph glucose levels. In this study, combined isolation of sinus gland peptides by reverse-phase high-performance liquid chromatography (RP-HPLC) and amino acid sequencing, and transcriptome analyses using male and female eyestalk ganglion has been successfully identified EiCHHa. In adult male E. isenbeckii, no decrease in haemolymph glucose levels was observed following bilateral eyestalk ablation, indicating that this treatment does not affect glucose homeostasis in this species. Therefore, the in vivo assays of EiCHHa using the blue swimming crab Portunus pelagicus revealed EiCHHa has a hyperglycemic effect, as well as CHHs in other decapod crustaceans. On the other hand, EiCHHa-injected red swamp crayfish Procambarus clarkii with bilateral eyestalk ablation showed no significant increase in hemolymph glucose levels. Additionally, we successfully demonstrated the sexual differences in the transcriptomic profiles between males and females. Especially, two sinus gland-derived neuropeptides (EiCHHb and a crustacean female sex hormone (EiCFSH)) were isolated as female-biased transcripts, suggesting that both hormones may have female-specific roles such as the development of female characteristics and reproduction.