The marbled crayfi sh Procambarus fallax (Hagen, 1870) f. virginalis (Martin et al. 2010a) is actually a rather inconspicuous crustacean. With its small to medium body size, it is economically unattractive as food, and only because of the beautiful marbling of its carapace did the otherwise relatively unglamorously coloured crayfi sh gain some popularity in the aquarium trade. In science, however, this cambarid developed into an emerging model organism, which has been highlighted in several dozen papers about the marbled crayfi sh since its fi rst discovery just 20 years ago. The reason why it moved into the focus of research is its unusual form of reproduction. Out of approximately 10,000 decapod crustacean species, the marbled crayfi sh is the only species known to date which exclusively propagates parthenogenetically, i.e., without mating with a male (Scholtz et al. 2003).