RXwildlife Sightings

In one of the current herpetological investigations, across the country, fieldworkers are collecting samples of amphibians and retiring to a sheltered place to stroke their bottoms thighs and toes with an implement that looks like a cotton wool bud!  It’s all down to a new amphibian disease, Chytrid, that is raising concerns about global amphibian declines (as featured on the recent David Attenborough “Life in Cold Blood” series)

Chytrid has been recently linked with amphibian declines across the world, and was first discovered in the UK, in East Sussex, in 2004 in a population of introduced North American Bullfrogs Lithobates catesbeianus. There is a lot to be learnt about this fungus and investigations are ongoing, with rapid developments in our understanding of the disease. Just a few months ago it was thought to have originated in Africa and travelled around the world on that popular laboratory animal, the African clawed toad Xenopus laevis. Recent work now suggests that the disease originated in America, and has been spread with the bullfrog - another much introduced species, included in the list of the 100 worst invasive species by the IUCN.

The discovery of the disease emerged as the bullfrog population was being wiped out in East Sussex, but we don’t know how widespread the infection is, or whether it will be pathogenic or harmless. Which is why there is a current study ongoing to determine the extent of the disease in the UK. So last weekend Eleanor Banks and I collected a sample of amphibians from Northiam (where some of the bullfrogs are buried), and wiped sterile swipes, supplied by Ed Brede of the Institute of Zoology, across their pelvic patch, thighs and toes. Thirty more will be tested in the summer as the tadpoles metamorphose. We also aim to do Dungeness again, collecting a larger sample than previously.

Chytrid can infect the tadpoles, living in areas of skin with keratin, and is thought to be relatively harmless at this stage. When the tadpoles metamorphose, in some species, there can be serious mortality a few weeks after metamorphosis, leading to population declines. Because the animals are so small this problem usually goes un-noticed.

Chytrid is one of several amphibian diseases in the country that encourage the view that frog spawn should not be transfered from pond to pond for fear of spreading problems. It is best to allow your local population to colonise naturally if possible.

Posted in Reptiles and Amphibians | by Brian Banks