Seasonal changes in the expression of insulin-like androgenic hormone (IAG) in the androgenic gland of the Jonah crab, Cancer borealis

Abstract

Harvesting the adult male Jonah crab, Cancer borealis, mainly based on the size, has become an economically significant fishery, particularly in the Southern New England region of the US since 2000. Many decapod crustacean fisheries including C. borealis rely on harvesting adult males. Understanding the size related-sexual maturity and the seasonal changes in male reproductive activity is critical for sustainable management. In other decapods, an insulin-like hormone produced by the male-specific androgenic gland (AG), called insulin-like androgenic gland factor (IAG), plays an essential role in sexual maturity. Specifically IAG is involved in developing male primary and secondary sexual characteristics including spermatogenesis. This study aimed first to identify the IAG, then examine if season influences IAG expression in C. borealis males. Finally, the AG transcriptome was used to test if eyestalk neuropeptides regulate IAG levels via an endocrine axis between the two endocrine tissues as established in other crustaceans. The full-length CabIAG sequence is 928 nucleotides long, encoding a 151 amino acid deduced sequence. The CabIAG identified from the AG transcriptome after eyestalk ablation was the most highly expressed gene and accounted for up to 25% of transcripts, further confirming the presence of an endocrine axis between the androgenic gland and eyestalk ganglia. This gene expression was exclusive in male C. borealis AG. The transcriptomic analysis also revealed strong upregulation of the PPOAE transcript and downregulation of proteolytic enzymes. The CabIAG levels differ by season, increasing AG activity in fall and possibly coinciding with high mating activity. The timing of increased AG activity correlating to mating with females should be considered for better stock management for the C. borealis population.