Devils Hole pupfish

The rarest vertebrate in the world

Now, if I were to change careers and start my own romantic death metal band, my band’s name is obvious: Devils Hole Pupfish. The Devils Hole pupfish, Cyprinodon diabolis, is a tiny little creature with a tiny little population in a tiny little habitat located in the middle of a huge desert – it is found in only one location, Devils Hole, in Nevada. [RR1] The cave in which it lives is ironically part of the Death Valley National Park, although it is not inside the actual park’s borders – imagine opening a gig with ‘Hello, we are Devils Hole Pupfish from Death Valley!’. Is there anything more ‘metal’?. While there is plenty of room in that cave (it is more than 130m/400ft deep), the area which is suitable for pupfish life and reproduction is absurdly small: most breeding occurs on a shelf in shallow water only about the size of two ping-pong tables. That’s right, the world’s whole population of Devils Hole pupfish depends on a space smaller than most people’s garage for its survival. At least pupfish speed dating is easy to organize! [RR2] No wonder then that this spot is so well protected that its high security infrastructure looks more like Fort Knox than a national nature treasure. Needless[RR3] to say, these little critters now also face threats that cannot be kept at bay by fences and barbed wire – global climate change and draining of local ground water pose serious issues for the conservation of this species. But there are many great articles written on the topic of human interests clashing with the interests of our fellow species on this planet, and the Devils Hole pupfish has starred in plenty of them ever since it was chosen as one of the first ‘protected’ species in the US in 1967 alongside such national icons like the Grizzly and the Bald Eagle. So let us focus more on its biology, shall we?

One striking fact about these fish is that they live in waters that most other species would find intolerable. Now, when a fish finds water intolerable, that does not mean it wants the wall painted differently. It means it dies. It’s hard being a fish! And most fish would perish when thrown into 34°C/93°F hot water. Try it yourself, it is almost the temperature of a jacuzzi/hot tub. And now imagine breathing the jacuzzi water. Well, I guess humans would run into problems other than just the temperature, but you get the idea. So, Devils Hole pupfish belong to what is sometimes referred to as extremophiles, which are organisms that live in extreme environmental conditions. Another interesting biology fact about pupfish is their embrace of incest – with such a small population, they don't have much of a choice. This means that pupfish have apparent resilience to any form of inbreeding depression. That is the term biologists use when they try to say that marrying cousins (or worse: siblings; or even worse: parents and offspring) for several generations is not a great idea from a health and wellbeing perspective; it increases the risk of having genetic defects and diseases (not to mention devastatingly awkward family reunions). However, Devils Hole pupfish have been doing it for hundreds of years (or tens of thousands of years, there is still some debate over when the fish actually arrived in Devils Hole[RR4] [AJ5] ). And there probably have rarely been more than 500 individuals at any given time. In fact, there were less than 50 at one point during the period since they have been closely monitored. And now there are about 200 again, but without obvious signs of inbreeding depression. So how do Devils Hole pupfish manage to thrive despite generations of incestuous propagation? It is not exactly clear. What is clear, however, is that the Royal Houses of Europe are probably very interested to find out.[RR6]