The hyperglycemic activity of crustacean hyperglycemic hormone in the sakura shrimp Lucensosergia lucens

Abstract The pelagic shrimp Lucensosergia lucens , which is also known as “sakura shrimp,” is a small, swimming shrimp that reaches about 4–5 cm in length and is commercially caught mainly in Suruga Bay in Japan. Recently, its catches have declined dramatically, presumably owing to the increased water temperature, the increased predation pressure, and the meandering of the Kuroshio Current, although the substantial cause remains unclear. It is necessary to clarify the mechanism concerning reproductive physiology of this species to establish stable seedling production technology for stock recovery; however, no such study has been conducted. In decapod crustaceans, X-organ/sinus gland complex is a well-known endocrine system that secrets various neuropeptides, such as the crustacean hyperglycemic hormone (CHH)-superfamily peptides, regulating many physiological events such as growth, molting, sexual maturation, reproduction, and body-color change. In this study, we conducted the eyestalk ganglion RNA-seq analysis and revealed the repertoire of genes encoding the eyestalk-derived neuropeptides, including some CHH-family molecules in adult male and female L. lucens . Then, one of the CHH-family peptides was purified by reverse phase high-performance liquid chromatography (RP-HPLC) from the sinus glands of L. lucens , and finally, its hyperglycemic activity was validated. This study is the first report of CHH neuropeptide in Sergestoidea. Finally, a CHH neurohormone family-conserved domain was applied to extract CHH family-like genes from various crustacean genome sequences. The result of the phylogenetic analysis of these genes provides us with important information for further understanding the evolution of this neuropeptide family in Decapoda.