The Pupfish family – Cyprinodontidae

Fish (almost) out of water:  iridescent desert-dwellers which flourish in extreme conditions

The desert pupfish: a minute, ultramarine marvel which survives volatile conditions. Image: John M Lynch, scienceblogs.com

The deserts of the southern United States and Mexico aren’t where you’d typically imagine finding populations of fish species.  However, one remarkable family of fish species tolerate extreme temperatures and water with little oxygen and higher salinity (salt content) than the sea, to thrive where other species cannot.  The pupfish family (Cyprinodontidae) contains over 100 species (see FishBase)  – most of which have very short life spans (often less than a year), and are extremely small (most less than 10cm) and iridescently colourful. The disappearance of huge lakes across Central America at the end of the last Ice Age (10-12,000 years ago) left isolated populations of pupfish in desert pools, which then evolved to adapt to their challenging environment, creating new and distinct species.

The desert pupfish (see FishBase) can tolerate temperatures of up to 45˚C in the hot springs of Mexico and southern USA (Death Valley, see here for a map)– that’s as hot as bath water! However, the freezing nights in many deserts mean the pupfish must withstand large water temperature fluctuations – truly a remarkably resilient family of tiny fish!

Living in such extreme conditions benefits the pupfish, because other species which may predate or out-compete it are unable to tolerate the extremities of temperature and salinity. However, any freshwater habitat in a desert environment is likely to be vulnerable to water abstraction, pollution and extreme weather or geological events.

‘Life in death valley’ – a PBS Nature video about the remarkable Devil’s Hole pupfish:

Death Valley, Nevada, USA: phenomenally, pupfish survive here in desert pools. Image: Wiki Commons

Amazingly, in April 2010 the entire population of tiny Devil’s Hole pupfish in Nevada, USA survived an earthquake (read more) which created a veritable tsunami in their miniscule habitat (the whole population breed and feed on a tiny shelf of shallow water 15 metres by 3 metres – smaller than some garden ponds!) – shown in this video.

The impact of water abstraction and pollution on the fragile Mexican desert freshwater habitat has driven the La Palma pupfish to extinction in the wild (read more on Fishbase).  However – as you can see in the video below – breeding populations of this chrome-coloured curiosity have been established at London Zoo in the UK. There is hope that populations may one day be reintroduced in the wild.

Where can I find out more?

Two La Palma pupfish, currently being bred back from the verge of extinction at London Zoo. Image: Heiko Kaerst, ZSL.org

Two La Palma pupfish, currently being bred back from the verge of extinction at London Zoo. Image: Heiko Kaerst, ZSL.org

The Zoological Society of London has managed to establish breeding populations of the La Palma pupfish, which is extinct in the wild:  watch video

Fishnet is a freshwater biodiversity conservation project run by the Zoological Society of London, focussed on killifish, the family to which pupfish belong.  Interestingly, the word ‘killifish’ derives from the Dutch word ‘kilde’, meaning puddle – literally puddle-fish!

Bristol Zoo, UK has established a breeding population of Potosí pupfish – extinct in its native Mexico.

Arkive – contains more images of various pupfish species

 

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