The 2011 UK Chytrid Survey
(A ZSL/DEFRA/ARG-UK partnership)
Amphibians in some parts of the world are declining because of amphibian disease. Whilst a number of diseases cause mortality and incapacity in amphibians, the disease thought to be of most serious conservation concern is chytridiomycosis.
Chytridiomycosis has apparently been responsible for catastrophic declines in some Australian, North American, Central American, South American and Caribbean species. The situation in Europe is less clear, although some species have seriously declined in upland areas of Spain.
The pathogen which causes this disease has already reached the UK. Thanks to a survey conducted in 2008 we know that it can be found widespread in England and also in Scotland and Wales.
We also know that infection can be carried in all native species. This survey was coordinated by ZSL with funding from Natural England, Countryside Council for Wales and Scottish Natural Heritage.
It is not yet clear whether it is having a negative impact on our native amphibians, although a number of more population-focussed research projects are working on this question.
In the meantime we are keen to learn as much as possible about its whereabouts, including how distribution of infection is changing over time.
To answer these questions, a second national chytrid survey (aka the Big Swab!) is taking place during the spring and summer of this year (2011). This survey, coordinated by ZSL, is funded by DEFRA. As with the 2008 survey, the field work will be carried out by volunteers, recruited mainly via the Amphibian and Reptile Groups of the UK (ARG-UK).
NOTE: The chytrid fungus only infects amphibians and poses no risk to humans.
What is Chytridiomycosis?
Chytridiomycosis is a disease that gained attention in late 90s as an explanation for wild and captive population die-offs (Berger, Speare et al. 1998) and is recognized as a global pathogen of amphibians causing declines and species extinctions.
The disease is caused by a fungus (Batrachochytrium dendrobatidis) that infects the skin of adult amphibians and the mouthparts of tadpoles (Longcore, Pessier et al. 1999).
Batrachochytrium dendrobatidis has two life stages, an intra-cellular sporangium and a free swimming zoospore.
How does it kill the amphibian?
This question puzzled scientists for many years, not least because the fungus is limited to infecting amphibian skin and cannot move into deeper tissue.
However, amphibians are rather special creatures and use their skin for the transfer of not only water and gases, but also salts (electrolytes).
What we now believe to happen is that infection with the fungus causes skin thickening, reducing the efficiency with which salts can be moved into and out of the body.
This leads to electrolyte imbalance, ultimately resulting in cardiac arrest!
Infected skin as seen under a microscope
So how can I help?
You can help by getting involved with the 2011 UK Chytrid Survey! Also known as the Big Swab, this survey will see volunteers returning to sites sampled in 2008, in order to see if there has been any change in the distribution of infection.
We are also recruiting newt sites (previously unsampled) in areas of the UK which were less well represented in 2008.
How are samples collected?
Surveyors have been asked to catch and sample 30 amphibians per site. Amphibians are checked for the presence of Batrachochytrium dendrobatidis by swabbing their skin.
This is a quick procedure, with the amphibian being released unharmed straight afterwards at the exact site where it was found.
The swab is then sent to the Institute of Zoology where it is screened for the presence of Batrachochytrium dendrobatidis DNA.
How can I get involved?
If you would like to get involved, the best starting point is to get in touch with you local Amphibian and Reptile Group to see if there is any surveying already going on in your area.
You can also have a look at the Big Swab project page on the AGR-UK website for more information about whereabouts additional sites are needed.
Alternatively, please feel free to get in touch with the project directly by emailing Freya Smith at freya.smith@ioz.ac.uk .
In partnership with:
References:
Berger, L., R. Speare, et al. (1998). "Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America." Proc Natl Acad Sci USA 95(15): 9031-9036.
Longcore, J. E., A. P. Pessier, et al. (1999). "Batrachochytrium dendrobatidis gen et sp nov, a chytrid pathogenic to amphibians." Mycologia 91(2): 219-227.
Want to know more?
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