During its life, a great crested newt will breathe in three distinct ways. For the first four or five months, it is entirely aquatic, breathing through gills that it wears in a froth around its neck like a feather boa. As autumn approaches, the juvenile ‘eft’ emerges from the water, sheds its gills and begins to breathe with its lungs. It then lives exclusively on land until it reaches sexual maturity at around the age of three, when it returns to its natal pond to spawn. The adult newt is a true amphibian – a creature of both (amphi) worlds (bios) – slipping easily between the elements, breathing underwater through its skin and above through its mouth.
Like other frogs, toads and salamanders, a newt’s skin is a sensitive, receptive and responsive organ, far more open to water- and airborne chemicals than ours. Under a microscope, its skin looks lacy and netted, and it is this very porousness that makes these creatures so vulnerable. To watch a newt hang, arms akimbo, in a column of pond water is to witness a fine balance – its skin is strong and supple enough to hold the creature’s shape, yet so delicate that it offers minimal resistance to the cloudy soup of nutrients in which it is suspended. The animal and its surroundings are enmeshed, inseparable parts of a single system.
A third of the world’s amphibian species are in imminent danger of extinction. These creatures, like all the rest, are suffering from habitat loss, pollution and climate change. But the amphibians have a specially hellish fourth horseman to contend with: a fungal pathogen called Batrachochytrium dendrobatidis, or Bd for short.
Bd attacks the keratin in the adult animal’s skin, causing chytridiomycosis, or chytrid, a highly infectious disease. A report on its global impact, compiled by no fewer than forty-one scientists from seventeen countries, was published in Science in March 2019. It concludes that since the fungus was first identified two decades ago, chytrid has been responsible for the catastrophic decline of 501 known species and the extinction of at least ninety, representing ‘the greatest recorded loss of biodiversity attributable to a disease’ in history.
Death by chytrid is a slow and cruel affair. As the animal’s outer membrane hardens to become an impenetrable barrier, all exchange ceases between the internal organs and the outer world. Osmosis slows and then stops. The circulation of ionic salts grinds to a halt. Oxygen cannot be absorbed nor carbon dioxide expelled. The vital organs shut down – and the animal finally suffocates, hermetically sealed inside its own skin.
Published in Granta issue no 151, spring 2020