Understanding a crustacean's masculinity: Transcriptomics of the Eastern rock lobster

In the Eastern spiny lobster, Sagmariasus verreauxi, commercial importance and growing potential in aquaculture drive a need to better understand sexual development. As a crustacean of the class Malacostraca, male sexual-differentiation is governed by the male-specific androgenic gland (AG), which secretes the masculinising insulin-like AG hormone (IAG) but from here little else is known. Thus, using the de novo assembled S. verreauxi transcriptome, we aim to uncover the male sexual-development pathway (SDP). Starting with the endocrinology of Sv-IAG, we have identified a binding protein (Sv-IGFBP) and additional insulin-like peptides (Sv-ILP1, ILP2) and investigated their binding in silico. Moreover, we have identified a tyrosine kinase insulin receptor (Sv-TKIR) and provided proof-of-function using a recombinant-IAG activation assay. Nevertheless, IAG is not a sex-determining factor, so we have also focused on identifying upstream elements of the SDP. Through the use of phylogenetic analyses we have identified a class of highly conserved sex-determining factors, the DM-domains (Dmrts). With further investigation, one of the Sv-Dmrts was found to have two genetic variants, one of which is male-specific, hence we have termed it Sv-DMY. Therefore, we have identified a sex-linked, putative sex-determining Dmrt which have been sparsely identified in only four of the higher vertebrates (Y-linked DMY in Medaka, Z-linked Dmrt1 in chicken and flatfish and W-linked DM-W in frog). Moreover, this discovery has determined the chromosomal mechanism of sex-determination and provided a genomic sex-marker, both of which have significant application in aquaculture