New Zealand has 4 species1 of native frogs that are all endemic2. All 4 are threatened with extinction. A major focus of the amphibian3 research at the University of Otago is how to save these unique animals.
Professor Phil Bishop, along with colleagues and postgraduate4 students, is working on techniques to successfully keep and breed frogs in captivity. An important aspect of this work is the research into frog disease5.
Frog diseases
Phil’s frog disease research has 2 main strands – metabolic bone6 disease and chytrid fungus7.
Metabolic bone disease is affecting reptiles and amphibians throughout the world and is unusual because it only affects animals in captivity.
Chytrid fungus8 is an ancient type of fungus. Scientists think that it originated in Africa and was spread when people shipped a species of frog used for pregnancy testing around the world. The chytrid fungus causes chytridiomycosis, an infectious9 disease that has now affected almost every frog population10 in the world. Scientists are not sure about how the fungus works. They know that it attacks the skin, and this may affect the ability of frogs to stay hydrated. Some scientists believe that the fungus secretes a toxin11 that eventually poisons the frog.
Chytridiomycosis
Chytridiomycosis was first discovered in New Zealand frogs in 1999. It has affected the two known populations12 of Archey’s frogs. Fortunately, no other native13 frogs have tested positive at this stage. Scientists are not sure whether this is because they are resistant to the disease or whether they haven’t yet been exposed to it.
Chytridiomycosis is a difficult disease to diagnose. The fungus often causes some slight redness on the stomach14 and legs of infected frogs, but there are no obvious ulcers or lesions. The biggest impact is on the behaviour of the frogs, but even this is hard to spot unless you are an expert in frog behaviour. Scientists use swabs and DNA15 analysis in the lab to test for the disease.
Why worry about the chytrid fungus?
Chytridiomycosis kills frogs. Research into the treatment and transmission of the fungus is important internationally as chytridiomycosis is blamed for the decline16 and extinction17 of numerous species of frog around the world. It is also very important in New Zealand. Archey’s frog is critically endangered18. It is already vulnerable to introduced predators and loss of habitat19. There is also concern that the disease could spread to our other native frogs.
Finding a cure for chytrid
The frog research team at the University of Otago discovered that a common antibiotic20 (chloramphenicol) used for humans was able to kill samples of chytrid fungus in the lab. They decided to test this antibiotic on some Archey’s frogs that were infected with the disease. They found that they were able to cure the diseased frogs and keep them alive in the lab – an important breakthrough for this critically endangered21 species.
This antibiotic treatment is very useful in New Zealand. Phil has also been collaborating with scientists overseas to test the treatment of infected frogs with this same antibiotic. However, there are some problems. For example, even if the frog has a negative test for chytridiomycosis, the scientists are reluctant to put the animal back into the wild in case the result is a false negative. Additionally, this treatment only works in captivity, as it’s not possible to spray antibiotics in the wild.
However, one very positive aspect of this research is that, if a vulnerable population is infected in the wild, the scientists can at least cure them in captivity. The hope is that, in the near future, it may be possible to re-release these frogs as well as to develop alternative treatment options for wild populations.
Related content
Find out more about what is being done to help save our native reptiles and amphibians in New Zealand and discover some of the conservation22 management tools used, including captive management and translocation.
Threats to native reptiles and amphibians looks at the 3 most significant threats facing our remaining populations of reptiles and amphibians – introduced species23, habitat loss and disease.
Activity idea
The activity Observation: learning to see looks at the role of observation in science and gives students the opportunity to boost their observation skills.
Useful links
Visit the NZFrogs website to find out more about frog research in New Zealand.
Listen to an 2009 interview from National Radio with Phil Bishop talking about his research into frog disease.
- species: (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.
- endemic: Native to only one location. For example, species endemic to New Zealand naturally occur only in New Zealand but may have been introduced elsewhere in the world.
- amphibian: A class of animals that includes frogs, toads, salamanders and newts.
- postgraduate: A student who has obtained a first degree and is now working towards a higher degree such as master’s or PhD.
- diseases: 1. An abnormal condition of an organism that impairs bodily functions. 2. In plants, an abnormal condition that interferes with vital physiological processes.
- bone: A specialised form of connective tissue. The presence of the mineral hydroxyapatite helps to give bone its strength and density.
- chytrid fungus: A fungus that causes chytridiomycosis, an infectious disease that has now affected almost every frog population in the world.
- fungi: The Fungi are a kingdom separate from plants and animals. Like animals, a fungus (or fungi – plural) is an organism that cannot make its own food. It can be multicellular such as mushrooms and moulds, or unicellular such as yeasts. Fungi may be decomposers, parasites, or mutualists (helping plants to grow).
- infectious: An infection that quickly spreads.
- population: In biology, a population is a group of organisms of a species that live in the same place at a same time and that can interbreed.
- toxin: A poisonous substance that is a specific product of the metabolic activities of a living organism.
- population: In biology, a population is a group of organisms of a species that live in the same place at a same time and that can interbreed.
- native: A species that lives naturally in a country, as opposed to species that have been introduced by the activity of humans.
- stomach: An organ of digestion with a sac-like shape located between the oesophagus and the small intestine. It temporarily stores food, mixes and churns it with gastric juice and allows digestion of some of the protein content of food to take place.
- DNA: Deoxyribonucleic acid (DNA) is a molecule that contains the instructions needed for an organism to develop and function. These instructions are stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C) and thymine (T).
- decline: The gradual and continuous loss of something such as bird numbers or sea ice.
- extinction: In biology, the death of the last remaining individual of a species.
- critically endangered: Extremely high risk of extinction in the wild (International Union for Conservation of Nature ranking).
- habitat: The natural environment in which an organism lives.
- antibiotic: A substance produced by an organism that kills bacteria.
- endangered: A species that is possibly going to become extinct soon due to limited numbers of individuals alive or not enough habitat to live in.
- conservation: The protection, preservation and careful management of a species, habitat, artifact or taonga.
- introduced species: An animal or plant that has been transferred by humans, either on purpose or by accident, to somewhere it doesn’t live naturally.
