Understanding the mode of crustacean female sex hormone (CFSH) action in sex differentiation of the blue crab, Callinectes sapidus

Abstract

Crustacean female sex hormone (CFSH), identified from the eyestalk of the female blue crab Callinectes sapidus, regulates developing adult-female-specific reproductive phenotypes of ovigerous setae for embryo brooding and gonopores for mating at the puberty-terminal molting. However, the mode of CFSH action is unknown in these adult-female-specific tissues. With earlier reports of vertebrate-type sex steroids present in some decapods, it is hypothesized that CFSH may exert its function in female sex differentiation via sex steroid hormones. On the other hand, male sex differentiation of decapod crustaceans is primarily regulated by the insulin-like androgenic gland factor (IAG). The expression of IAG induces masculinization, while RNA interference (RNAi)-mediated reduced IAG transcripts results in testicular degeneration and feminization. The inhibitory feedback between CFSH and IAG is supported by results obtained from RNAi studies and in vitro bioassay, but the inhibitory mechanism remains to be unveiled. This dissertation aimed to 1) clarify if the mode of CFSH action involves 17?-estradiol (E2) in females of the blue crab; 2) determine if males of the blue crab exhibit testosterone (T) and if the corresponding levels are related to IAG and CFSH transcripts; 3) identify the genes associated with ovigerous setae development using transcriptomic analysis. The significantly decreased E2 amounts and steroidogenic gene expressions in the adult-female-specific tissues following long-term CFSH knockdown suggest the potential involvement of E2 in the mode of CFSH action. The increase in T levels and IAG expression during male development and the opposite expression pattern between CFSH and IAG transcripts provide evidence for the presence of a putative regulatory interaction among IAG, CFSH, and T in decapods. Moreover, cuticle and tubulin transcripts, essential for developing ovigerous hairs located on ovigerous setae are identified, together with the genes involved in the wingless-type MMTV integration site family signaling and cell cycle pathways. These findings are formulated in a model, describing a putative mode of CFSH action in developing ovigerous setae, which may facilitate future research into decapod reproduction and sex differentiation.