Parthenogenetic marmokrebs has sex on its own

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A species of crayfish known only from the aquarium trade has been providing scientists with an opportunity to study the rare reproductive processes of parthenogenicity.

Known as "marmokrebs", which is German for marbled crayfish, the new decapod is a member of the Cambaridae family but it's not known where it's come from, or what species it is.

Interestingly, the crayfish is capable of breeding on its own, and in some areas where it has been illegally released into the wild, it has undergone population explosions.

A team of scientists from the Department of Zoology at The University og Heidelberg in Germany will report the findings of their study into its reproduction in the Journal of Morphology in September.

The team diseccted 100 specimens and examined their anatomy using both light and high-powered electron microscopy (EM) to determine how the reproductive system changes from the larval stage to the adult form.

The results showed that the external sexual differences and the gonads of marbled crayfish are purely female. Male sexual tissues, such as ovotestes, male gonoducts, or gonopods, weren't found in any specimens, proving that the species is indeed parthenogenetic.

The scientists reckon that parthenogeneticity might have arisen by either interspecific competition with other species of crayfish in their native environment, or by a spontaneous evolutionary change.

Microorganisms which can feminise animals, such as Wolbachia, weren't found in the crayfish, so it appears that they've certainly evolved the trait.

The marbled crayfish was also found to be carrying diseases which may transfer to other species of native crayfish. This highlights the importance of keeping aquarium specimens in the aquarium and not releasing them illegally into the wild.

For more details on the legality of keeping crayfish in the UK, please see our Legal FAQs.

For more details read the paper: Vogt, G., Tolley, L. and Scholtz, G. (2004) - Life stages and reproductive components of the marmokrebs (marbled crayfish), the first parthenogenetic decapod crustacean. Journal of Morphology, 2004, Sep, 261 (3) 286-311.