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Hairy marron (Cherax tenuimanus Smith) are critically endangered freshwater crayfish found only in a single river in south-west Australia. Conservation efforts have included a captive breeding program, which has been largely unsuccessful, despite the closely related smooth marron (Cherax cainii Austin) being successfully bred for aquaculture. Using an untargeted liquid chromatography-mass spectrometry (LC-MS) metabolomic approach we created a profile of the metabolites in the haemolymph for males and females of the two species of marron. A non-lethal method was used to collect haemolymph and 84 reproducible annotated metabolites were identified. Variation in the levels of some metabolites were detected between species and between sexes within species. Multivariate analyses clearly differentiated the congeneric species and univariate analyses identified differences between species, sex and for some metabolite interactions between species and sex. This study created a baseline metabolome dataset for the two species and began to investigate the biological significance of metabolites that varied between species. We have shown metabolomics could be used for targeted studies to potentially assist reproductive success. This approach will be beneficial for conservation and aquaculture practices with potential applications for other aquatic taxa worldwide.

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Hybridization and genetic introgression following the introduction of exotic species can pose a significant threat to the survival of geographically restricted species. A remnant population of the critically endangered freshwater crayfish Cherax tenuimanus in the upper reaches of the Margaret River in southwestern Australia is under threat following the introduction and spread of its congener Cherax cainii. Here, we examine the extent of hybridization and introgression between the two species using twelve polymorphic microsatellite loci. Our study reveals there are three times more C. cainii than C. tenuimanus at our study site in the upper reaches of the Margaret River. There is also evidence of hybridization and introgression between C. tenuimanus and C. cainii at this site, with F1, F2 and backcrossed individuals identified. While interbreeding was confirmed in this study, our simulations suggest that the levels of introgression are much lower than would be expected under random mating, indicating partial reproductive barriers exist. Nevertheless, it is apparent that hybridization and introgression with C. cainii pose a serious threat to C. tenuimanus and their survival in the wild will require active adaptive management and continued genetic monitoring to evaluate management effectiveness.

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