Tribbles and Crayfish by William V. Raszka MD, Associate Editor, Pediatrics The New York Times: This Mutant Crayfish Clones Itself, and It's Taking Over Europe I recently again saw the classic Star Trek episode "The Trouble with Tribbles". In this episode, tribbles, depicted as small, furry, gentle aliens, reproduce at a fantastic rate. After a crew member brings a single tribble onto the starship, tribble numbers quickly expand and soon they are everywhere. In the Star Trek universe, many societies consider these slow-moving and cuddly creatures one of the most dangerous creatures in the entire universe- simply because they reproduce so quickly. "The Trouble with Tribbles" is not my favorite Star Trek episode. However, it did make me think of the potential benefits and consequences of rapid expansion of a population. Interestingly, a somewhat similar situation is unfolding before our eyes. As reported inThe New York Times, the marbled crayfish, a brand new species, is reproducing at a fantastic rate and successfully invading habitats from South Asia to Central Europe. According to scientists who sequenced the marbled crayfish genome, the species is less than a quarter century old and is the outcome of two slough crayfish mating. One of the crayfish evidently harbored a mutation that gave rise to a gametocyte containing two copies of the genome. The outcome was an apparently normal female crayfish that had three copies of each chromosome. Not only was this female able to survive chromosomal excess, she was able to induce her own eggs to start dividing into embryos. Each offspring was therefore female, had three copies of each chromosome, and was a clone of the parent. The consequence is that all marbled crayfish are identical, fecund females. Because the females can survive in many environments and each female can make hundreds of eggs, the population of the marbled crayfish has exploded. Asexual reproduction is rare in the animal world, mostly likely because while there are short-term benefits, any insult that kills one individual can potentially kill all members of the species. I am not sure if the marbled crayfish is currently under threat by a pathogen, but similar to the administrative leaders in the Star Trek universe, I would be very wary of the marbled crayfish and would certainly not transport it. ● Facebook ● Instagram Copyright © 2018 American Academy of Pediatrics.