Worldwide amphibian declines have reached crisis proportions. In many areas, habitat loss is the likely culprit but, in 1996, it was suggested that some unknown disease had spread through the populations. In 1998, the fungus Batrachochytrium dendrobatidis was identified from sick and dead frogs and, since then, several lines of laboratory based evidence have suggested that B. dendrobatidis is to blame for the dramatic frog declines. But with little information about how the disease impacts frogs in the wild, the causal role of this chytrid fungus remains unclear. In the open access journal PLoS Biology, Australian researchers Richard Retallick, Hamish McCallum and Rick Speare now "show unequivocally" that remaining populations of T. eungellensis, a rainforest frog listed as endangered, can persist in the wild with stable infections of this fungus.

To evaluate the effects of the fungus on frogs in their natural habitat, the authors focused on six species living in the high-elevation rainforest streams of Eungella National Park in Queensland, Australia, where frog losses were "particularly catastrophic". Two species vanished between 1985 and 1986: the Eungella Gastric-Brooding Frog (Rheobatrachus vitellinus), which is now thought extinct, and the Eungella Torrent Frog (Taudactylus eungellensis), which later reappeared in a few small populations. In the PLoS Biology study, Retallick et al. tested tissue samples taken from frogs between 1994 and 1998 - before the disease had been identified. The marked frogs were released back into the wild at the time the samples were collected. The authors found fungal infections in the samples of two species, including T. eungellensis. An analysis of tissue from recaptured frogs during the same period showed that the prevalence of infection did not vary from year to year, suggesting that the infection is now endemic. McCallum and colleagues also found no evidence that su
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Contact: Paul Ocampo
pocampo@plos.org
415-624-1224
Public Library of Science
4-Oct-2004

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