Bd is also strongly suspected in the extinction of the gastric brooding frogs, Rheobatrachus vitellinus and Rheobatrachus silus, as well as the Southern day frog, Taudactylus diurnus (Laurance et al. In coastal Queensland the rate of advance of the pathogen has been estimated at 100 km per year (Laurance et al. In Tasmania declines also began in the late 1970s (Fearn et al. Declines were first noticed in the late 1970s and early 1980s in the D'Aguilar, Blackall, and Conondale subcoastal mountain ranges near Brisbane, southeast Queensland (Laurance et al. Taudactylus diurnus, the Southern day frog, vanished over a period of three to four years, disappearing from the DíAguilar Range in late 1975, then from the Blackall Range in late 1978 and finally from the Conondale Range in early 1979 (Czechura and Ingram 1990).
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Declines were seen first in lower-elevation populations (400 m above sea level) of both species in January 1985 (Winter and Mc Donald 1986).
Despite the declines in lower-elevation populations, both species were still common at higher elevations in March 1985.
During metamorphosis the skin of the body become increasingly keratinized and the fungal infection is then able to spread over the skin in froglets (and adults) of susceptible species (Marantelli et al. In juveniles and adults Bd infects and encysts within skin cells particularly on the belly, digits, and pelvic "drink patch" (Berger et al. As infection proceeds the skin becomes much thicker (hyperkeratosis) and sloughs off (Berger et al. Osmotic regulation is increasingly compromised and electrolyte blood levels drop, leading to death from cardiac arrest (Voyles et al. Mortality rate and time to death post-exposure depend on a number of factors, such as pathogen dose, temperature, age and lifestage, species, and Bd strain (Berger et al. Infection intensity appears to be a key factor; death ensues in adult frogs and salamanders once the individual has reached an infection load of about 10,000 fungal zoospores (Vredenburg et al. 2007; see section VI below for further discussion of anuran species that can act as carriers of Bd).
1999, 2004; Lamirande and Nichols 2002; Woodhams et al. In salamanders, some species appear to resist, persist with or clear Bd infections to a greater extent than do frogs (Davidson et al. Changes in stream primary producer communities resulting from large-scale catastrophic amphibian declines: can small-scale experiments predict effects of tadpole loss?
From 1989-1996, several studies reported further declines in Queensland, with two species (Litoria nyakalensis, the mountain mistfrog, and Taudactylus rheophilus, the tinkling frog) gone from their upland rainforest habitat, one species missing from most of the surveyed upland sites (Taudactylus acutirostris, the sharp-snouted torrent frog) and other species missing from most of the surveyed upland sites but persisting at lowland sites (Litoria nannotis, the waterfall frog; Litoria rheocola, the common mistfrog; and Nyctimystes dayi, the lace-eyed tree frog) (Richards et al. Subsequently it was proposed by Laurance and colleagues that a pathogen, perhaps a water-borne virus, might be the cause of these amphibian extirpations, with at least fourteen species of endemic Australian rainforest frogs affected (Laurance et al. Declines were selective, with some species persisting and others not (Laurance et al. Because pathogens do not typically drive their hosts to extinction, this hypothesis was not initially accepted. Retrospective examination of preserved museum specimens showed that Bd infection was not present in specimens collected in south Queensland until 1978, after which it spread north and south along the coast (Skerratt et al. In western Australia, chytridiomycosis was first detected in 1985 at a site south of Perth, and spread in all directions from the initial site of detection (Skerratt et al. In Tasmania, the first amphibian declines occurred in the late 1970's, according to retrospective accounts from individuals living in the Launceston area, who noted a steep drop in abundance in Litoria raniformis, the southern bell frog (Fearn et al. PCR-based surveys for chytridiomycosis were first conducted in 2004, specifically testing tadpoles from a number of different species (Obendorf 2005; Obendorf and Dalton 2006).
However, examination of dead frogs from the 1993 Big Tableland die-off revealed a parasitic infection of the skin; subsequently the parasite was identified as a chytrid fungus and tests confirmed its involvement in amphibian deaths (Berger et al. By that time declines had also been noted in an endemic Tasmanian species, the Tasmanian tree frog (Litoria burrowsae), and mass mortality events had been reported in suburban populations of juvenile Litoria ewingi, the whistling tree frog (Obendorf 2005). Strategies for Batrachochytrium dendrobatidis survival and pathogenesis, Part 2.
However, surveys in June 1985 (just three months later) looking for higher-elevation populations of Rheobatrachus vitellinus revealed no trace of this species (Mc Donald 1990). Batrachochytrium dendrobatidis and the collapse of anuran species richness and abundance in the upper Manu National Park, southeastern Peru.
Rheobatrachus vitellinus has not been recorded since March 1985; Taudactylus eungellensis has not been seen since June of 1986 (Mc Donald 1990). In 1993, amphibian populations at Big Tableland (near Cookstown in north Queensland) suffered mass mortality and crashed suddenly, and this time amphibian biologists were able to collect dead frogs rather than simply noting that numbers had declined. In some species, lowland populations were able to persist while high-elevation populations vanished.
The earliest museum specimen in each zone with signs of Bd infection dates to December 1978 for the east coast (Conondale Range, southern Queensland), October 1985 for the southwest, May 1996 for Adelaide, and 2004 for Tasmania (Obendorf 2005). The biology and recent history of the Critically Endangered Kihansi Spray Toad in Tanzania.
At least one Australian frog species, the sharp-snouted torrent frog (Taudactylus acutirostris) is known to have been driven to extinction by Bd, with the last wild population crashing in September 1993 and the last captive animal dying from Bd in the Melbourne Zoo in 1995 (Speare and Berger 2005). Rapid amphibian declines in mainland Australia began in the late 1970s in southern Queensland, near Brisbane (Czechura and Ingram 1990) and continued northward to central eastern Queensland in the mid-1980s. Journal of East African Natural History 95: 117-138.
In particular, Bd infection was found most frequently in habitats that were close to major cities and towns (Obendorf and Dalton 2006), and to be much less prevalent in remote areas of the Tasmanian Wilderness World Heritage Area (TWWHA) (Pauza and Driessen 2008). It is thought that Bd was introduced to Santa Clara County, in northern California, in the late 1950's or early 1960's; one possible vector might have been Xenopus laevis, which is known to be a carrier of Bd and which was first shipped to the United States in 1949, perhaps to Stanford University (Padgett-Flohr and Hopkins 2009). 2006) and is continuing into South America, at a rate of about 17 km/year (Lips et al. The best-known case occurred in 1988 when the golden toad (Bufo periglenes) vanished from its remote, pristine mountainous habitat in a Costa Rican preserve, with the last golden toad seen in 1989.