Many decapod crustaceans with sexual dimorphism in body size are economically significant species for fisheries and aquaculture, making monosex culture a desirable practice to increase farmers' yield and profits. It is well established that the male‐specific androgenic gland (AG) mediates masculinization in decapods by producing and secreting the insulin‐like AG hormone (IAG). However, IAG is not a sex‐determining factor; hence, iag silencing in decapods does not always lead to successful sex change. Since the establishment of monosex populations in the giant freshwater prawn Macrobrachium rosenbergii, the same AG/iag manipulation approach has been attempted in economically significant penaeid shrimps, crabs, crayfish and spiny lobsters, to no avail. There are many factors at play with species‐specific intricacies which require close examination when addressing monosex production. This review provides a refined roadmap to successful sexual manipulation in decapod crustaceans, highlighting the key caveats to be considered and critical gaps in knowledge such as the timing of iag expression compared to the development of sexual characteristics, the relationship between iag and a master regulator, as well as silencing capacity. Lastly, this review examines what the future might hold for monosex aquaculture in decapods, taking into consideration novel technologies such as gene editing.

Understanding the mechanisms of sexual development would pave the way for producing mono-sex populations to aid the aquaculture industry. This study investigates the functions of the Y-linked iDmrt1 paralogue (Po-iDMY) and insulin-like androgenic gland hormone (Po-IAG) in the process of sexual development in the tropical rock lobster, Panulirus ornatus (TRL). Previously, we identified that Po-iDMY, a male-specific heterogametic (Y-linked) paralogue of the autosomal Po-iDmrt1 found in TRL, is a second sex-linked iDmrt gene identified in invertebrates. Using 5′ and 3′ rapid amplification of cDNA ends and data from a draft male genome (with an assembly genome size of approximately 2.446 Gbp and 87% BUSCO completeness), we obtained the full-length Po-iDMY gene (encoding a protein of 312 amino acids). A 411 bp male-specific sequence located at the 3′ untranslated region of Po-iDMY mRNA was used as a sex marker, which was reported for the first time in our draft genome. However, Po-iDMY is not a master sex-determining factor since it was not expressed across developmental stages of embryos, juveniles and adults. Instead, we silenced Po-IAG at an early juvenile stage, generating two potential neo-females, implying that sexual manipulation could be a promising technique in TRL.

The slipper lobster ( Thenus australiensis ) is rapidly emerging as a high-potential species for commercial aquaculture. Because females exhibit superior growth characteristics due to less frequent moulting after sexual maturity, developing monosex breeding strategies is highly desirable for industry profitability. However, the lack of genomic resources and early sex-identification tools has hindered this development. Here, we report the first draft male genome assembly for T. australiensis , generated using a combination of whole-genome shotgun sequencing, DArT-seq, and multi-tissue transcriptomics. The curated assembly spans 0.913 Gbp with high functional completeness (93.0% BUSCO), providing a robust repertoire of 30,100 protein-coding genes. Through k-mer subtraction and population-level DArT-seq genotyping, we provide definitive evidence that T. australiensis utilizes an XX/XY sex-determination system. Crucially, by identifying male-specific structural variations within a neo-Y locus, we developed a diagnostic PCR assay targeting a male-exclusive sequence. This 171 bp marker achieved 100% accuracy in phenotypic sex identification across wild-caught populations. Ultimately, these foundational genomic resources, combined with a highly reliable molecular sexing tool, provide the critical framework necessary for early sex sorting, broodstock management, and the commercial advancement of monosex slipper lobster farming. Highlights: First draft genome of slipper lobster (0.913 Gbp) assembled. Multi-omics approach confirms an XX/XY sex-determination system. Developed a 171 bp diagnostic PCR sex marker with 100% accuracy. Facilitates early sex sorting for profitable monosex aquaculture.