All-female crayfish populations for biocontrol and sustainable aquaculture

Snail control in aquaculture and control of snail vectors implicated in animal and human diseases are global challenges. Potential biocontrol agents could be species of crayfish, which are known to be voracious predators of snails. However, at present, the use of crayfish as biocontrol agents is limited due to their invasive nature. A promising candidate biocontrol agent is the Australian redclaw crayfish, Cherax quadricarinatus, a key species in the aquaculture industry. However, the downside of using this species for biocontrol is that C. quadricarinatus aquaculture escapees - being highly robust, fast growing, and ferocious omnivores - have become invasive, establishing feral populations around the world. Here we suggest the production of monosex C. quadricarinatus populations that open two exciting biotechnology applications-as a possible sustainable solution for snail control and as a means to improve yields and management in crayfish aquaculture, without the inherent danger of establishing invasive populations of aquaculture escapees. In the first part of this study, C. quadricarinatus was tested as a snail eradicator. Both males and females were highly efficient in predation experiments, eliminating 89% and 98% of Thiara scabra snails, respectively. The superior efficiency of the females in the predation experiments and the possible advantage for aquaculture of all-female crayfish populations provided the rationale for the second part of the study-the development of an economically feasible and non-labor-intensive biotechnology for the production of all-female C. quadricarinatus populations. To this end, we leveraged the naturally occurring intersexuality in C. quadricarinatus populations to produce female-biased populations. Females bearing only the W sex chromosome isolated from such populations using W and Z-specific genomic markers were found to be reproductive when bred with WZ intersexuals. Resulting progenies from the above crosses were 100% female populations including 50% WW females, thus paving the way to the establishment of an all-female producing brood stock. We present a quantitative scheme that demonstrates how our approach, which does not include any genomic intervention, can be implemented both for sustainable aquaculture and to fight harmful snails damaging aquaculture, agriculture, and human health.