Testosterone and steroidogenic genes in the male blue crab Callinectes sapidus and their relationship with insulin-like androgenic gland factor (IAG) and crustacean female sex hormone (CFSH)

Abstract

The abundance of the blue crab, Callinectes sapidus, has been declining in the Chesapeake Bay, possibly due to reduced spawning stock and deteriorating habitat conditions. Callinectes female reproductive capacity, i.e., fertilization efficiency, may depend on the quality and number of sperm stored in the spermathecae. Understanding endocrine regulation in male development and reproduction is necessary. Sexual differentiation of decapod crustaceans is primarily regulated by the insulin-like androgenic gland factor (IAG) and crustacean female sex hormone (CFSH). This system contrasts with the vertebrates wherein testosterone (T) controls male reproduction, sexual differentiation, and sex-specific behavior and physiology. With earlier reports of T presence in some decapods, this work aimed to determine if the blue crab Callinectes sapidus males exhibit T and if the corresponding levels are related to IAG and CFSH transcripts. To this end, the IAG and CFSH transcripts are estimated in the androgenic glands (AG) and eyestalk ganglia of juvenile and adult males, respectively. The levels of IAG transcripts are significantly (p < 0.05) higher in adult AGs than in juveniles. However, this pattern contrasts with CFSH transcripts in the eyestalk ganglia with juveniles higher than adults. The levels of T in adult testis, posterior vas deferens, AG, and hemolymph are significantly (p < 0.05) higher than those in juveniles. The presence of authentic T is further confirmed by liquid chromatography with tandem mass spectrometry. The transcript levels of the following genes known to be involved in vertebrate steroidogenesis are determined: StAR-related lipid transfer protein 3 (StAR3); 3β-hydroxysteroid dehydrogenase (3βHSD); two isoforms of 17β-hydroxysteroid dehydrogenase 8 (17βHSD8); and, 5α-reductase (5α-red). StAR3 levels are significantly (p < 0.05) higher in adult testis, anterior vas deferens, and AG than in juveniles. In comparison, 5α-red levels in testis, anterior vas deferens, posterior vas deferens, and AG of adults are significantly (p < 0.05) lower than in juveniles. The 5α-red transcripts are localized in the spermatocytes and spermatids in the testis and AG cells in the AG using in situ hybridization. These results indicate that CFSH may suppress IAG expression; the levels of T may be related to the male reproductive activity; and a putative regulatory interaction among IAG, CFSH, and steroidogenic genes in T synthesis may present in decapod crustaceans.