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.

The Australian red claw crayfish Cherax quadricarinatus, an emerging species within the freshwater aquaculture trade, is not only an ideal species for commercial production due to its high fecundity, fast growth, and physiological robustness but also notoriously invasive. Investigating the reproductive axis of this species has been of great interest to farmers, geneticists, and conservationists alike for many decades; however, aside from the characterisation of the key masculinising insulin-like androgenic gland hormone (IAG) produced by the male-specific androgenic gland (AG), little remains known about this system and the downstream signalling cascade involved. This investigation used RNA interference to silence IAG in adult intersex C. quadricarinatus (Cq-IAG), known to be functionally male but genotypically female, successfully inducing sexual redifferentiation in all individuals. To investigate the downstream effects of Cq-IAG knockdown, a comprehensive transcriptomic library was constructed, comprised of three tissues within the male reproductive axis. Several factors known to be involved in the IAG signal transduction pathway, including a receptor, binding factor, and additional insulin-like peptide, were found to not be differentially expressed in response to Cq-IAG silencing, suggesting that the phenotypic changes observed may have occurred through post-transcriptional modifications. Many downstream factors displayed differential expression on a transcriptomic level, most notably related to stress, cell repair, apoptosis, and cell proliferation. These results suggest that IAG is required for sperm maturation, with necrosis of arrested tissue occurring in its absence. These results and the construction of a transcriptomic library for this species will inform future research involving reproductive pathways as well as biotechnological developments in this commercially and ecologically significant species.

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