WHO’S YOUR CRAWDADDY? The highly invasive marbled crayfish, pictured here in Madagascar, might trace its origins to a German aquarium.RANJA ANDRIANTSOAAt first glance, the marbled crayfish (Procambarus virginalis), a medium-size decapod crustacean with a speckled brownish-green shell, seems rather unexceptional. But since it first appeared on the German hobby-aquarium scene around two decades ago, the creature has been making waves. The clonally reproducing, all-female animals have been spotted in numerous freshwater habitats across Europe, and, according to a recent analysis, they’re spreading swiftly through the island nation of Madagascar. While this rapid expansion has alarmed scientists due to the crayfish’s ability to alter aquatic ecosystems by outcompeting native species, the organism captured the attention of some researchers for another reason: the mystery of its origin.
The first scientific description of the marbled crayfish was published in the early 2000s. Shortly before that, rumors about an “enigmatic animal able to reproduce without a male” had started to circulate among the internet community of hobby aquarists, says Gerhard Scholtz, a zoologist at Humboldt University in Germany. These rumors piqued the interest of Scholtz and his colleagues, who obtained some of the mysterious creatures for analysis in the lab. As advertised, the crustaceans, when placed in isolation, reproduced without males—a phenomenon known as parthenogenesis—and all the offspring had female gonads. The team named the newly identified organism the marbled crayfish, or Marmorkrebs in German, due to the patterning on its shell (Nature, 421:806, 2003).
Although parthenogenesis is prevalent among crustaceans, this was the ...
