Two Homogametic Genotypes – One Crayfish: On the Consequences of Intersexuality

In the Australian redclaw crayfish, Cherax quadricarinatus (WZ/ZZ system), intersexuals, although exhibiting both male and female gonopores, are functional males bearing a female genotype (WZ males). Therefore, the occurrence of the unusual homogametic WW females in nature is plausible. We developed W/Z genomic sex markers and used them to investigate the genotypic structure of experimental and native C. quadricarinatus populations in Australia. We discovered, for the first time, the natural occurrence of WW females in crustacean populations. By modeling population dynamics, we found that intersexuals contribute to the growth rate of crayfish populations in the short term. Given the vastly fragmented C. quadricarinatus habitat, which is characterized by drought-flood cycles, we speculate that intersexuals contribute to the fitness of this species since they lead to occasional increment in the population growth rate which potentially supports crayfish population restoration and establishment under extinction threats or colonization events.