Overview

Comprehensive Description

Description

Rheobatrachus silus was a medium-sized frog with a snout-vent-length of 33-41 mm for males, and snout-vent-length of 44-54 mm for females. The skin was finely granular dorsally and smooth ventrally. The snout was round and blunt, and nostrils were directed upwards. The eyes, also directed upwards, were large and projected outwards. The eyes were close together and were located to the front of the head. The tympanum was hidden. The toes were fully webbed to the tip, but the fingers did not have webbing. All of the digits had small discs. The tadpoles were bulbous, pale, low-finned, and did not have keratinized mouthparts (CITES 2013). Rheobatrachus silus could be differentiated from its sister taxa by its distribution, color pattern, and mottled webbing. It was also smaller than R. vitellinus (CITES 2013).

The dorsal coloration ranged from olive to almost black and it had small light and dark patches scattered throughout. There was a dark streak that ran from the eye to the base of the forelimb. The limbs had dark crossbars and the digits and webbings had a variety of pale and dark patches. The white or cream ventral surface had yellow markings on the limbs. Tadpoles brooded in the stomach and initially lacked any pigmentation on their skin (Tyler and Davies 1983).

Species Authority: The species authority is Liem 1973.

Phylogenetic Relationships: Rheobatrachus silus was one of two gastric-brooding frogs, the other being its sister species R. vitellinus. R. vitellinus is also thought to be extinct; the last wild sighting was in 1985 (CITES 2013).

Etymology: The common name of this species refers to its eccentric reproductive behavior (see “Life History”).

This frog has been part of the Lazarus Project at the University of New South Wales whose goal is to bring the frog back to life. The Lazarus Project team has recovered cell nuclei from tissues from the 1970s and kept frozen for 40 years. Their goal is to clone the frog by implanting these cell nuclei into fresh eggs from another frog species. The researchers used a technique called somatic cell nuclear transfer to do this. They took the fresh eggs of the barred frog and destroyed the nucleus manually or with UV radiation. They replaced the egg nuclei with a dead nuclei from R. silus. Some of the eggs began to divide and grow to early embryo stage. As of March 2013, none of the embryos survived more than a few days, but researchers confirmed that the dividing cells contained genetic material from R. silus (Yong 2013).

  • CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora). Accessed November 25, 2013 from http://www.cites.org/eng/cop/16/prop/E-CoP16-Prop-40.pdf
  • Czechura, G.V. (1991). ''The Blackall-Conondale Ranges: frogs, reptiles and fauna conservation.'' The Rainforest Legacy, Australian National Rainforest Study, Volume 2. Flora and Fauna of the Rainforest. G. Werren and P. Kershaw, eds., Australian Government Publishing Service, Canberra, 311-324.
  • Czechura, G.V. and Ingram, G. (1990). ''Taudactylus diurnus and the case of the disappearing frogs.'' Memoirs of the Queensland Museum, 29(2), 361-365.
  • Hines, H., Mahony, M. and McDonald, K. (1999). ''An assessment of frog declines in wet subtropical Australia.'' Declines and Disappearances of Australian Frogs. A. Campbell, eds., Environment Australia, Canberra, 44-63.
  • Ingram, G. (1983). ''Natural history.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 16-35.
  • Ingram, G. J., and McDonald, K. R. (1993). ''An update on the decline of Queensland's frogs.'' Herpetology in Australia: A diverse discipline. D. Lunney and D. Ayers, eds., Transactions of the Royal Zoological Society of New South Wales, 297-303.
  • Ingram, G.J. (1990). ''The mystery of the disappearing frog.'' Wildlife Australia, 27(3), 6-7.
  • Ingram, G.J. (1991). ''The earliest records of the extinct Platypus Frog.'' Memoirs of the Queensland Museum, 30(3), 454.
  • Liem, D.S. (1973). ''A new genus of frog of the family Leptodactylidae from south-east Queensland, Australia.'' Memoirs of the Queensland Museum, 16(3), 459-470.
  • Meyer, E., Hines, H., and Hero, J.-M. (2001). ''Southern Gastric Brooding Frog, Rheobatrachus silus.'' Wet Forest Frogs of South-east Queensland. Griffith University, Gold Coast, 34-35.
  • Richards, S. J., McDonald, K. R., and Alford, R. A. (1993). ''Declines in populations of Australia's endemic rainforest frogs.'' Pacific Conservation Biology, 1, 66-77.
  • Tyler, M.J. (1989). Australian Frogs. Penguin Books Australia Ltd., Victoria.
  • Tyler, M.J. and Carter, D.B. (1982). ''Oral birth of the young of the gastric-brooding frog Rheobatrachus silus.'' Animal Behaviour, 29, 280-282.
  • Tyler, M.J. and Davies, M. (1983). ''Larval development.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 44-57.
  • Tyler, M.J. and Davies, M. (1983). ''Superficial features.'' The Gastric Brooding Frog. M.J Tyler, eds., Croom Helm, London, 5-15.
  • Tyler, M.J. and Davies, M. (1985). ''The Gastric Brooding Frog.'' Biology of Australasian Frogs and Reptiles. G. Grigg, R. Shine, and H. Ehmann, eds., Royal Zoological Society of New South Wales, Sydney, 469-470.
  • Tyler, M.J., Shearman, D.J.C., Franco, R., O'Brien, P., Seamark, R.F., and Kelly, R. (1983). ''Inhabitaion of gastric acid secretion in the Gastric Brooding Frog, Rheobatrachus silus.'' Science, 220, 609-610.
  • Yong, Ed. ''Resurrecting the Extinct Frog with a Stomach for a Womb.'' National Geographic. 15 March 2013. Web. 20 Feb. 2014.
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Distribution

Distribution and Habitat

Rheobatrachus silus was first discovered in 1972, although there was a possible sighting in 1914 in the Blackall Ranges of southeast Queensland in Australia. The species was restricted to an elevation of 350 - 800m above sea level and its geographic range was limited to 1,400 km2. The species was endemic to southeast Queensland and found in the Blackall and Cononale Ranges between Coonoon Gibber Creek and Kilcoy Creek. Found in Kondalilla and Conondale National Parks, Sunday Creek State Forest, State Forest 311, Kenilworth State Forest, and from private land not in these areas, it primarily inhabited the streams of Mary, Stanley, and Mooloolah Rivers (Hines et al. 1999). It inhabited rainforests, wet sclerophyll forests, and tall open forests that had a closed understory. The forests were closely associated with rocky mountain streams, rock pools, and soaks (Czechura 1991). The rock pools had to be deep enough that the frog could sit in the water with its head out and be able to submerge safely in it. The frog only sat fully exposed on the rocks if there was light rain (Ingram 1983). Although it was considered both a terrestrial and aquatic species, it preferred to live in mostly permanent water that only dried up in years of low rainfall and was never observed to be more than four meters from water. In spring and summer, the frogs were located in or at the edge of rock pools among the leaf litter, under or between stone, or in the crevices around the edge. Its winter habitat was unknown, but there is speculation that individuals hibernated in deep crevices in terrestrial or underwater rocks (Ingram 1983).

  • CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora). Accessed November 25, 2013 from http://www.cites.org/eng/cop/16/prop/E-CoP16-Prop-40.pdf
  • Czechura, G.V. (1991). ''The Blackall-Conondale Ranges: frogs, reptiles and fauna conservation.'' The Rainforest Legacy, Australian National Rainforest Study, Volume 2. Flora and Fauna of the Rainforest. G. Werren and P. Kershaw, eds., Australian Government Publishing Service, Canberra, 311-324.
  • Czechura, G.V. and Ingram, G. (1990). ''Taudactylus diurnus and the case of the disappearing frogs.'' Memoirs of the Queensland Museum, 29(2), 361-365.
  • Hines, H., Mahony, M. and McDonald, K. (1999). ''An assessment of frog declines in wet subtropical Australia.'' Declines and Disappearances of Australian Frogs. A. Campbell, eds., Environment Australia, Canberra, 44-63.
  • Ingram, G. (1983). ''Natural history.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 16-35.
  • Ingram, G. J., and McDonald, K. R. (1993). ''An update on the decline of Queensland's frogs.'' Herpetology in Australia: A diverse discipline. D. Lunney and D. Ayers, eds., Transactions of the Royal Zoological Society of New South Wales, 297-303.
  • Ingram, G.J. (1990). ''The mystery of the disappearing frog.'' Wildlife Australia, 27(3), 6-7.
  • Ingram, G.J. (1991). ''The earliest records of the extinct Platypus Frog.'' Memoirs of the Queensland Museum, 30(3), 454.
  • Liem, D.S. (1973). ''A new genus of frog of the family Leptodactylidae from south-east Queensland, Australia.'' Memoirs of the Queensland Museum, 16(3), 459-470.
  • Meyer, E., Hines, H., and Hero, J.-M. (2001). ''Southern Gastric Brooding Frog, Rheobatrachus silus.'' Wet Forest Frogs of South-east Queensland. Griffith University, Gold Coast, 34-35.
  • Richards, S. J., McDonald, K. R., and Alford, R. A. (1993). ''Declines in populations of Australia's endemic rainforest frogs.'' Pacific Conservation Biology, 1, 66-77.
  • Tyler, M.J. (1989). Australian Frogs. Penguin Books Australia Ltd., Victoria.
  • Tyler, M.J. and Carter, D.B. (1982). ''Oral birth of the young of the gastric-brooding frog Rheobatrachus silus.'' Animal Behaviour, 29, 280-282.
  • Tyler, M.J. and Davies, M. (1983). ''Larval development.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 44-57.
  • Tyler, M.J. and Davies, M. (1983). ''Superficial features.'' The Gastric Brooding Frog. M.J Tyler, eds., Croom Helm, London, 5-15.
  • Tyler, M.J. and Davies, M. (1985). ''The Gastric Brooding Frog.'' Biology of Australasian Frogs and Reptiles. G. Grigg, R. Shine, and H. Ehmann, eds., Royal Zoological Society of New South Wales, Sydney, 469-470.
  • Tyler, M.J., Shearman, D.J.C., Franco, R., O'Brien, P., Seamark, R.F., and Kelly, R. (1983). ''Inhabitaion of gastric acid secretion in the Gastric Brooding Frog, Rheobatrachus silus.'' Science, 220, 609-610.
  • Yong, Ed. ''Resurrecting the Extinct Frog with a Stomach for a Womb.'' National Geographic. 15 March 2013. Web. 20 Feb. 2014.
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Physical Description

Development

Gastric brooding in the recently extinct gastric-brooding frog Rheobatrachus silus not surprisingly involved major changes in the structure of the stomach (Corben et al. 1974; Tyler and Carter 1981; Fanning et al. 1982; Gibbins and Tyler 1983; Tyler et al. 1983). Remarkably, however, although the froglets of R. vitellinus, a second (also now extinct) gastric-brooding frog described by Mahoney et al. in 1984, were also clearly brooded in the stomach, in R. vitellinus no major changes were seen in the structure of the stomach of brooding individuals (McDonald and Tyler 1984; Leong et al. 1986). Sadly, both of these frogs are now extinct, making further physiological investigations impossible.

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Conservation

Life History, Abundance, Activity, and Special Behaviors

As the common name of Southern Gastric Brooding frog suggests, female R. silus brooded young within the stomach and gave birth through the mouth. The eggs averaged 5.1 mm in diameter and had large yolk sacs that nourished the embryos as they developed. Fertilized eggs or early stage larvae were presumably swallowed by the female and completed their development in the stomach (Tyler and Carter 1982). The production of hydrochloric acid in the stomach of the female ceased during brooding, which was caused by hormones produced by the young that altered the structure and physiology of the mother (Tyler et al. 1983). The number of eggs in gravid females (approximately 40) exceeded the number of juveniles found to occur in the stomach (21-26). It is not known whether the female ingested the excess eggs or if they were simply not swallowed (Tyler 1989). After 6-7 weeks, the females gave birth to up to 25 young (Tyler and Davies 1983a). In the brooding stage, the mother would cease eating until her juveniles were released after 36-43 days as fully formed metamorphs. They would exit the mother through her mouth (Ingram 1983). After the juveniles exit the mother, the digestive tract returned to normal and her feeding habits would return within four days of the young’s release (Tyler et al. 1983). The female probably would not have bred more than once per breeding season due to the duration of brooding (Ingram 1983).

Tadpoles developed in a manner similar to the aquatic tadpoles of other species, but lacked labial teeth, and formed the intestines at a later stage of development (Tyler 1989). Rheobatrachus silus has been observed to forage and take insects from both land and water (Ingram 1983). In an aquarium situation, Lepidoptera, Diptera and Neuroptera were eaten (Liem 1973). It was preyed upon by birds, fish, and other aquatic fauna (CITES 2013). Males, females and juveniles appeared to have limited home ranges, although juveniles and gravid females were particularly immobile (females carrying young tend to be sedentary). Adult males primarily inhabited deeper pools; the females and juveniles inhabited pools that were newly created after the rain, but only if the pools contained stones or leaf litter. Only two juveniles out of ten were found to have moved more than 3 m between observations. Juveniles were mobile in the sense that they would move to newly created pools, but once stationed there they usually remained in that area. During a breeding season, the home range of females and males was estimated to be 0-3.4 m (n=4) and 0-6.2 m (n=10) respectively (Ingram 1983). Ingram (1983) also reported the distance traveled along a stream by seven individuals between seasons. Four females moved 1.8-46 m, and the males moved 0.9-53 m. Only three individuals moved more than 5.5 m (46, 46, and 53 m respectively) and it would appear that they remained within the same pool or group of pools throughout the breeding season, only moving away during periods of high flow or flooding. Non-breeding winter habitat is unknown (Ingram 1983).

Breeding activity occurred between October and December, during the warmer months, and the breeding season appeared to be dependent on the summer rains. Males called from rock crevices above pools (Ingram 1983). The call had an upward inflection that lasted for about half a second and repeated every 6-7 seconds for 30-34 pulses up to 260-290 ms. The dominant frequency was 1000 Hz, but there were also calls at the frequencies of 500, 700, 1200, and 1400 Hz. The calls can be differentiated from the Northern Gastric-brooding frog, which has a shorter call with a deeper pitch and fewer repeats (CITES 2013; Tyler and Davies 1983).

  • CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora). Accessed November 25, 2013 from http://www.cites.org/eng/cop/16/prop/E-CoP16-Prop-40.pdf
  • Czechura, G.V. (1991). ''The Blackall-Conondale Ranges: frogs, reptiles and fauna conservation.'' The Rainforest Legacy, Australian National Rainforest Study, Volume 2. Flora and Fauna of the Rainforest. G. Werren and P. Kershaw, eds., Australian Government Publishing Service, Canberra, 311-324.
  • Czechura, G.V. and Ingram, G. (1990). ''Taudactylus diurnus and the case of the disappearing frogs.'' Memoirs of the Queensland Museum, 29(2), 361-365.
  • Hines, H., Mahony, M. and McDonald, K. (1999). ''An assessment of frog declines in wet subtropical Australia.'' Declines and Disappearances of Australian Frogs. A. Campbell, eds., Environment Australia, Canberra, 44-63.
  • Ingram, G. (1983). ''Natural history.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 16-35.
  • Ingram, G. J., and McDonald, K. R. (1993). ''An update on the decline of Queensland's frogs.'' Herpetology in Australia: A diverse discipline. D. Lunney and D. Ayers, eds., Transactions of the Royal Zoological Society of New South Wales, 297-303.
  • Ingram, G.J. (1990). ''The mystery of the disappearing frog.'' Wildlife Australia, 27(3), 6-7.
  • Ingram, G.J. (1991). ''The earliest records of the extinct Platypus Frog.'' Memoirs of the Queensland Museum, 30(3), 454.
  • Liem, D.S. (1973). ''A new genus of frog of the family Leptodactylidae from south-east Queensland, Australia.'' Memoirs of the Queensland Museum, 16(3), 459-470.
  • Meyer, E., Hines, H., and Hero, J.-M. (2001). ''Southern Gastric Brooding Frog, Rheobatrachus silus.'' Wet Forest Frogs of South-east Queensland. Griffith University, Gold Coast, 34-35.
  • Richards, S. J., McDonald, K. R., and Alford, R. A. (1993). ''Declines in populations of Australia's endemic rainforest frogs.'' Pacific Conservation Biology, 1, 66-77.
  • Tyler, M.J. (1989). Australian Frogs. Penguin Books Australia Ltd., Victoria.
  • Tyler, M.J. and Carter, D.B. (1982). ''Oral birth of the young of the gastric-brooding frog Rheobatrachus silus.'' Animal Behaviour, 29, 280-282.
  • Tyler, M.J. and Davies, M. (1983). ''Larval development.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 44-57.
  • Tyler, M.J. and Davies, M. (1983). ''Superficial features.'' The Gastric Brooding Frog. M.J Tyler, eds., Croom Helm, London, 5-15.
  • Tyler, M.J. and Davies, M. (1985). ''The Gastric Brooding Frog.'' Biology of Australasian Frogs and Reptiles. G. Grigg, R. Shine, and H. Ehmann, eds., Royal Zoological Society of New South Wales, Sydney, 469-470.
  • Tyler, M.J., Shearman, D.J.C., Franco, R., O'Brien, P., Seamark, R.F., and Kelly, R. (1983). ''Inhabitaion of gastric acid secretion in the Gastric Brooding Frog, Rheobatrachus silus.'' Science, 220, 609-610.
  • Yong, Ed. ''Resurrecting the Extinct Frog with a Stomach for a Womb.'' National Geographic. 15 March 2013. Web. 20 Feb. 2014.
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Threats

Life History, Abundance, Activity, and Special Behaviors

The species underwent a rapid decline in 1979 and was last sighted in the wild in September 1981 in Blackall Range. This occurred at the same time as a sympatric species, Taudactylus diurnus, commonly known as the southern day frog, went extinct (Czechura and Ingram 1990). The last specimen of R. silus in captivity died in November 1983 (Tyler and Davies 1985). In 1995, an intensive “frog search” occurred in Conondale Range, and over 50 surveys have been conducted in an attempt to find the species, but no frogs have been sighted. Since then, the species is believed to be extinct. The reason for the extinction of R. silus is unknown. There were stream catchments due to logging between 1972 and 1979 while R. silus inhabited the area (Hines et al. 1999). No studies have been done on the effects of logging on the populations, but the populations continued to persist through it (CITES 2013). There is a possibility that the chytrid fungus caused the decline in R. silus. This infectious disease, caused by the fungal pathogen Batrachochytrium dendrobatidis, has been the cause of the decline and extinction of at least 13 other rainforest frog species in Queensland, Australia that inhabited high elevations. Feral pigs, weed invasion (especially the mistflower Ageratina riparia), and altered stream flows threaten its potential habitat (CITES 2013; Hines et al. 1999).

  • CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora). Accessed November 25, 2013 from http://www.cites.org/eng/cop/16/prop/E-CoP16-Prop-40.pdf
  • Czechura, G.V. (1991). ''The Blackall-Conondale Ranges: frogs, reptiles and fauna conservation.'' The Rainforest Legacy, Australian National Rainforest Study, Volume 2. Flora and Fauna of the Rainforest. G. Werren and P. Kershaw, eds., Australian Government Publishing Service, Canberra, 311-324.
  • Czechura, G.V. and Ingram, G. (1990). ''Taudactylus diurnus and the case of the disappearing frogs.'' Memoirs of the Queensland Museum, 29(2), 361-365.
  • Hines, H., Mahony, M. and McDonald, K. (1999). ''An assessment of frog declines in wet subtropical Australia.'' Declines and Disappearances of Australian Frogs. A. Campbell, eds., Environment Australia, Canberra, 44-63.
  • Ingram, G. (1983). ''Natural history.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 16-35.
  • Ingram, G. J., and McDonald, K. R. (1993). ''An update on the decline of Queensland's frogs.'' Herpetology in Australia: A diverse discipline. D. Lunney and D. Ayers, eds., Transactions of the Royal Zoological Society of New South Wales, 297-303.
  • Ingram, G.J. (1990). ''The mystery of the disappearing frog.'' Wildlife Australia, 27(3), 6-7.
  • Ingram, G.J. (1991). ''The earliest records of the extinct Platypus Frog.'' Memoirs of the Queensland Museum, 30(3), 454.
  • Liem, D.S. (1973). ''A new genus of frog of the family Leptodactylidae from south-east Queensland, Australia.'' Memoirs of the Queensland Museum, 16(3), 459-470.
  • Meyer, E., Hines, H., and Hero, J.-M. (2001). ''Southern Gastric Brooding Frog, Rheobatrachus silus.'' Wet Forest Frogs of South-east Queensland. Griffith University, Gold Coast, 34-35.
  • Richards, S. J., McDonald, K. R., and Alford, R. A. (1993). ''Declines in populations of Australia's endemic rainforest frogs.'' Pacific Conservation Biology, 1, 66-77.
  • Tyler, M.J. (1989). Australian Frogs. Penguin Books Australia Ltd., Victoria.
  • Tyler, M.J. and Carter, D.B. (1982). ''Oral birth of the young of the gastric-brooding frog Rheobatrachus silus.'' Animal Behaviour, 29, 280-282.
  • Tyler, M.J. and Davies, M. (1983). ''Larval development.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 44-57.
  • Tyler, M.J. and Davies, M. (1983). ''Superficial features.'' The Gastric Brooding Frog. M.J Tyler, eds., Croom Helm, London, 5-15.
  • Tyler, M.J. and Davies, M. (1985). ''The Gastric Brooding Frog.'' Biology of Australasian Frogs and Reptiles. G. Grigg, R. Shine, and H. Ehmann, eds., Royal Zoological Society of New South Wales, Sydney, 469-470.
  • Tyler, M.J., Shearman, D.J.C., Franco, R., O'Brien, P., Seamark, R.F., and Kelly, R. (1983). ''Inhabitaion of gastric acid secretion in the Gastric Brooding Frog, Rheobatrachus silus.'' Science, 220, 609-610.
  • Yong, Ed. ''Resurrecting the Extinct Frog with a Stomach for a Womb.'' National Geographic. 15 March 2013. Web. 20 Feb. 2014.
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Relevance to Humans and Ecosystems

Risks

Relation to Humans

If the frog had not disappeared so quickly, the medical community was interested in studying how the frog was able to stop making acid in its stomach to brood its young. These studies could have led to new treatments for stomach ulcers or faster healing treatments for people who underwent stomach surgery (Yong 2013).

  • CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora). Accessed November 25, 2013 from http://www.cites.org/eng/cop/16/prop/E-CoP16-Prop-40.pdf
  • Czechura, G.V. (1991). ''The Blackall-Conondale Ranges: frogs, reptiles and fauna conservation.'' The Rainforest Legacy, Australian National Rainforest Study, Volume 2. Flora and Fauna of the Rainforest. G. Werren and P. Kershaw, eds., Australian Government Publishing Service, Canberra, 311-324.
  • Czechura, G.V. and Ingram, G. (1990). ''Taudactylus diurnus and the case of the disappearing frogs.'' Memoirs of the Queensland Museum, 29(2), 361-365.
  • Hines, H., Mahony, M. and McDonald, K. (1999). ''An assessment of frog declines in wet subtropical Australia.'' Declines and Disappearances of Australian Frogs. A. Campbell, eds., Environment Australia, Canberra, 44-63.
  • Ingram, G. (1983). ''Natural history.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 16-35.
  • Ingram, G. J., and McDonald, K. R. (1993). ''An update on the decline of Queensland's frogs.'' Herpetology in Australia: A diverse discipline. D. Lunney and D. Ayers, eds., Transactions of the Royal Zoological Society of New South Wales, 297-303.
  • Ingram, G.J. (1990). ''The mystery of the disappearing frog.'' Wildlife Australia, 27(3), 6-7.
  • Ingram, G.J. (1991). ''The earliest records of the extinct Platypus Frog.'' Memoirs of the Queensland Museum, 30(3), 454.
  • Liem, D.S. (1973). ''A new genus of frog of the family Leptodactylidae from south-east Queensland, Australia.'' Memoirs of the Queensland Museum, 16(3), 459-470.
  • Meyer, E., Hines, H., and Hero, J.-M. (2001). ''Southern Gastric Brooding Frog, Rheobatrachus silus.'' Wet Forest Frogs of South-east Queensland. Griffith University, Gold Coast, 34-35.
  • Richards, S. J., McDonald, K. R., and Alford, R. A. (1993). ''Declines in populations of Australia's endemic rainforest frogs.'' Pacific Conservation Biology, 1, 66-77.
  • Tyler, M.J. (1989). Australian Frogs. Penguin Books Australia Ltd., Victoria.
  • Tyler, M.J. and Carter, D.B. (1982). ''Oral birth of the young of the gastric-brooding frog Rheobatrachus silus.'' Animal Behaviour, 29, 280-282.
  • Tyler, M.J. and Davies, M. (1983). ''Larval development.'' The Gastric Brooding Frog. M.J. Tyler, eds., Croom Helm, London, 44-57.
  • Tyler, M.J. and Davies, M. (1983). ''Superficial features.'' The Gastric Brooding Frog. M.J Tyler, eds., Croom Helm, London, 5-15.
  • Tyler, M.J. and Davies, M. (1985). ''The Gastric Brooding Frog.'' Biology of Australasian Frogs and Reptiles. G. Grigg, R. Shine, and H. Ehmann, eds., Royal Zoological Society of New South Wales, Sydney, 469-470.
  • Tyler, M.J., Shearman, D.J.C., Franco, R., O'Brien, P., Seamark, R.F., and Kelly, R. (1983). ''Inhabitaion of gastric acid secretion in the Gastric Brooding Frog, Rheobatrachus silus.'' Science, 220, 609-610.
  • Yong, Ed. ''Resurrecting the Extinct Frog with a Stomach for a Womb.'' National Geographic. 15 March 2013. Web. 20 Feb. 2014.
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Wikipedia

Gastric-brooding frog

The gastric-brooding frogs or platypus frogs (Rheobatrachus) were a genus of ground-dwelling frogs native to Queensland in eastern Australia. The genus consisted of only two species, both of which became extinct in the mid-1980s. The genus was unique because it contained the only two known frog species that incubated the prejuvenile stages of their offspring in the stomach of the mother.[3]

The combined ranges of the gastric-brooding frogs comprised less than 2,000 square kilometres (770 sq mi). Both species were associated with creek systems in rainforests at elevations of between 350 metres (1,150 ft) and 1,400 metres (4,600 ft). The causes of the gastric-brooding frogs' extinction are not clearly understood, but habitat loss and degradation, pollution, and some diseases may have contributed.

The assignment of the genus to a taxonomic family is hotly debated. Some biologists class them within Myobatrachidae under the subfamily Rheobatrachinae, but others place them in their own family, Rheobatrachidae.[4]

Scientists at the University of Newcastle and University of New South Wales announced in March 2013 that the frog would be the subject of a cloning attempt, referred to as the ”Lazarus Project”, to resurrect the species. Embryos were successfully cloned.[5][6]

The southern gastric brooding frog has been listed as Extinct by the IUCN because it has not been recorded in the wild since 1981, and extensive searches over the last 25 years have failed to locate this species.


Taxonomy[edit]

Rheobatrachus was first described in 1973 by David Liem and since has not undergone any scientific classification changes; however the placement of this genus within a family has been controversial. It has been placed in a distinct subfamily of Myobatrachidae, Rheobatrachinae, in a separate family, Rheobatrachidae, placed as the sister taxon of Limnodynastinae and Rheobatrachinae has been synonymized with Limnodynastinae. In 2006, D. R. Frost and colleagues found Rheobatrachus, on the basis of molecular evidence, to be the sister taxon of Mixophyes and placed it within Myobatrachidae.[7][8]

Both species of gastric-brooding frogs were very different in appearance and behaviour to other Australian frog species. Their large protruding eyes and short, blunt snout along with complete webbing and slimy bodies differentiated them from all other Australian frogs. The largely aquatic behaviour exhibited by both species was only shared (in Australia) with the Dahl's Aquatic Frog and their ability to raise their young in the mother's stomach was unique among all frogs.

Common names[edit]

The common names, "gastric-brooding frog" and "platypus frog", are used to describe the two species. "Gastric-brooding" described the unique way the female raised the young and "platypus" describes their largely aquatic nature.

Southern gastric-brooding frog (R. silus)[edit]

Distribution[edit]

The southern gastric-brooding frog (Rheobatrachus silus) was discovered in 1972 and described in 1973, however, there is one publication suggesting that the species was discovered in 1914 (from the Blackall Range).[9] Rheobatrachus silus was restricted to the Blackall Range and Conondale Ranges in southeast Queensland, north of Brisbane, between elevations of 350 and 800 metres (1,150 and 2,620 ft) above sea level.[10] The areas of rainforest, wet sclerophyll forest and riverine gallery open forest that it inhabited was limited to less than 1,400 km2 (540 sq mi). They were recorded in streams in the catchments of the Mary, Stanley and Mooloolah Rivers.[11] Depending on the source, the last specimen seen in the wild was in 1979 in the Conondale Range, or in 1981 in the Blackall Ranges. The last captive specimen died in 1983. This species is believed to be extinct.

Physical description[edit]

The southern gastric-brooding frog was a medium sized species of dull colouration, with large protruding eyes positioned close together and a short, blunt snout. Its skin was moist and coated with mucus. The fingers were long, slender, pointed and unwebbed and the toes were fully webbed. The arms and legs were large in comparison to the body. In both species the females were larger than the males.

The southern gastric-brooding frog was a dull grey to slate coloured frog that had small patches, both darker and lighter than the background colouration, scattered over dorsal surface (back). The ventral surface was white or cream, occasionally with yellow blotches. The arms and legs had darker brown barring above and were yellow underneath. There was a dark stripe that ran from the eye to the base of the forelimb. The ventral surface (belly) was white with large patches of cream or pale yellow. The toes and fingers were light brown with pale brown flecking. The end of each digit had a small disc and the iris was dark brown. The skin was finely granular and the tympanum was hidden. The male Southern Gastric Brooding Frog was 33 millimetres (1.3 in) to 41 millimetres (1.6 in) in length and the female 44 millimetres (1.7 in) to 54 millimetres (2.1 in) in length.

Ecology and behaviour[edit]

The southern gastric-brooding frog lived in areas of rainforest, wet sclerophyll forest and riverine gallery open forest. They were a predominately aquatic species closely associated with watercourses and adjacent rock pools and soaks. Streams that the southern gastric-brooding frog were found in were mostly permanent and only ceased to flow during years of very low rainfall.[12] Sites where southern gastric-brooding frogs were found usually consisted of closed forests with emergent eucalypts, however there was sites where open forest and grassy ground cover were the predominate vegetation. There is no record for this species occurring in cleared riparian habitat. Searches during spring and summer showed that the favored diurnal habitat was at the edge of rock pools, either amongst leaf litter, under or between stones or in rock crevices. They were also found under rocks in shallow water. Winter surveys of sites where southern gastric-brooding frogs were common only recovered two specimens, and it is assumed that they hibernated during the colder months. Adult males preferred deeper pools than the juveniles and females which tended to inhabit shallower, newly created (after rain) pools that contained stones and/or leaf litter. Individuals only left themselves fully exposed while sitting on rocks during light rain.[11]

The call of the southern gastric-brooding frog has been described as an "eeeehm...eeeehm" with an upward inflection. It lasts for around 0.5 s and was repeated every 6–7 seconds.

Southern gastric-brooding frogs have been observed feeding on insects from the land and water. In aquarium situations Lepidoptera, Diptera and Neuroptera were eaten.[13]

Being a largely aquatic species the southern gastric-brooding frog was never recorded more than 4 m (13 ft) from water. Studies by Glen Ingram showed that the movements of this species were very restricted. Of ten juvenile frogs, only two moved more than 3 metres between observations. Ingram also recorded the distance moved along a stream by seven adult frogs between seasons (periods of increased activity, usually during summer). Four females moved between 1.8–46 metres (5 ft 11 in–150 ft 11 in) and three males covered 0.9–53 m (2 ft 11 in–173 ft 11 in). Only three individuals moved more than 5.5 m (18 ft) (46 m, 46 m and 53 m). It appeared that throughout the breeding season adult frogs would remain in the same pools or cluster of pools, only moving out during periods of flooding or increased flow.[11]

Northern gastric-brooding frog (R. vitellinus)[edit]

Distribution[edit]

The northern gastric-brooding frog (Rheobatrachus vitellinus) was discovered in 1984 by Michael Mahony.[14] It was restricted to the rainforest areas of the Clarke Range in Eungella National Park and the adjacent Pelion State Forest in central eastern Queensland. This species, too, was confined to a small area – less than 500 km2 (190 sq mi),[15] at altitudes of 400–1,000 m (1,300–3,300 ft) in altitude.[16] Only a year after its discovery, it was never seen again despite extensive efforts to locate it. This species is considered to be extinct.

Physical description[edit]

The northern gastric-brooding frog was a much larger species than the southern gastric-brooding frog. Males reached 50–53 mm (2.0–2.1 in) in length, and females 66–79 mm (2.6–3.1 in) in length. This species was also much darker in colour, usually pale brown, and like the southern gastric-brooding frogs its skin was bumpy and had a slimy mucus coating. There were vivid yellow blotches on the abdomen and the underside of the arms and legs. The rest of the belly was white or grey in colour. The tympanum was hidden and the iris was dark brown. The body shape of the northern gastric-brooding frog was very similar to the southern species.

Ecology and behaviour[edit]

The northern gastric-brooding frog was only recorded in pristine rainforests where the only form of human disturbance was poorly defined walking tracks. As with the southern gastric-brooding frog, the northern gastric-brooding frog was also a largely aquatic species. They were found in and around the shallow sections of fast flowing creeks and streams where individuals were located in shallow, rocky, broken-water areas, in cascades, riffles and trickles.[15] The water in these streams was cool and clear, and the frogs hid away beneath or between boulders in the current or in backwaters.

Male northern gastric-brooding frogs call from the water's edge during summer. The call was loud, consisting of several staccato notes. It is similar to the southern gastric-brooding frog's call although deeper, shorter and repeated less often.

The northern gastric-brooding frog was observed feeding on small crayfish, caddisfly larvae and terrestrial and aquatic beetles as well as the Eungella torrent frog (Taudactylus eungellensis).[17]

Reproduction[edit]

What makes these frogs unique among all frog species is their form of parental care. Following external fertilization by the male, the female would take the eggs into her mouth and swallow them. It is not clear whether the eggs were laid on the land or in the water, as it was never observed before their extinction.

Eggs found in females measured up to 5.1 mm in diameter and had large yolk supplies. These large supplies are common among species that live entirely off yolk during their development. Most female frogs had around 40 ripe eggs, almost double that of the number of juveniles ever found in the stomach (21–26). This means one of two things, that the female fails to swallow all the eggs or the first few eggs to be swallowed are digested.

At the time the female swallowed the fertilized eggs her stomach was no different from that of any other frog species. In the jelly around each egg was a substance called prostaglandin E2 (PGE2), which could turn off production of hydrochloric acid in the stomach. This source of PGE2 was enough to cease the production of acid during the embryonic stages of the developing eggs. When the eggs had hatched the tadpoles created PGE2. The mucus excreted from the tadpoles' gills contained the PGE2 necessary to keep the stomach in a non-functional state. These mucus excretions do not occur in tadpoles of most other species. Tadpoles that don't live entirely off a yolk supply still produce mucus cord, but the mucus along with small food particles travels down the oesophagus into the gut. With Rheobatrachus (and several other species) there is no opening to the gut and the mucus cords are excreted. During the period that the offspring were present in the stomach the frog would not eat.

Information on tadpole development was observed by a group that was regurgitated by the mother and successfully raised in shallow water. During the early stages of development tadpoles lacked pigmentation, but as they aged they progressively develop adult colouration. Tadpole development took at least six weeks, during this time the size of the mother’s stomach continued to increase until it largely filled the body cavity. The lungs deflated and breathing relied more upon gas exchange through the skin. Despite the mother's increasing size she still remained active.

The birth process was widely spaced and may have occurred over a period of as long as a week. However, if disturbed the female may regurgitate all the young frogs in a single act of propulsive vomiting. The offspring were completely developed when expelled and there was little variation in colour and length of a single clutch.[18]

Cause of extinction[edit]

The cause for the gastric-brooding frogs' extinction is due to human introduction of pathogenic fungi into their native range. Populations of Southern Gastric-brooding Frogs were present in logged catchments between 1972 and 1979. The effects of such logging activities upon Southern Gastric-brooding Frogs was not investigated but the species did continue to inhabit streams in the logged catchments. The habitat that the Southern Gastric-brooding Frog once inhabited is now threatened by feral pigs, the invasion of weeds, altered flow and water quality problems caused by upstream disturbances.[10] Despite intensive searching, the species has not been located since 1979 or 1981 (depending on the source).

The Eungella National Park, where the northern gastric-brooding frog was once found, was under threat from bushfires and weed invasion. Continual fires may have destroyed or fragmented sections of the forest.[17] The outskirts of the park are still subject to weed invasion and chytrid fungus has been located within several rainforest creeks within the park. It was thought that the declines of the northern gastric-brooding frog during 1984 and 1985 were possibly normal population fluctuations.[15] Eight months after the initial discovery of the northern gastric-brooding frog, sick and dead Eungella Torrent Frogs, which cohabitat the streams with gastric brooding frogs, were observed in streams in Pelion State Forest.[19] Given the more recent understanding of the role of the amphibian disease in the decline and disappearance of amphibians, combined with the temporal and spatial pattern of the spread of the pathogen in Australia, it appears most likely that the disease was responsible for the decline and disappearance of the gastric-brooding frogs. Despite continued efforts to locate the northern gastric-brooding frog it has not been found. The last reported wild specimen was seen in the 1980s. In August 2010 a search organised by the Amphibian Specialist Group of the International Union for Conservation of Nature set out to look for various species of frogs thought to be extinct in the wild, including the gastric-brooding frog.[20]

Conservation status[edit]

Both species are listed as Extinct under both the IUCN Red List and under Australia's Environment Protection and Biodiversity Conservation Act 1999; however, they are still listed as Endangered under Queensland's Nature Conservation Act 1992.

De-extinction attempt[edit]

Scientists are making progress in their efforts to bring the gastric-brooding frog species back to life using somatic-cell nuclear transfer (SCNT), a method of cloning.[21]

In March 2013, Australian scientists successfully created a living embryo from non-living preserved genetic material. These scientists from the University of Newcastle Australia led by Prof Michael Mahony, who was the scientist who first discovered the Northern Gastric-brooding frog, and Prof Mike Archer from the University of New South Wales hope to continue using somatic-cell nuclear transfer methods to produce an embryo that can survive to the tadpole stage. "We do expect to get this guy hopping again," says UNSW researcher Mike Archer.[22]

The scientists from the University of Newcastle have also reported successful freezing and thawing (cryopreservation) of totipotent amphibian embyonic cells,[23] which along with sperm cyopreservation [24] provides the essential "proof of concept" for the use of cyostorage as a genome bank for threatened amphibians and also other animals.

References[edit]

  1. ^ Meyer, Ed et al. (2004). Rheobatrachus silus. The IUCN Red List of Threatened Species. Version 2014.2
  2. ^ Hero, Jean-Marc et al. (2004). Rheobatrachus vitellinus. The IUCN Red List of Threatened Species. Version 2014.2
  3. ^ Barker, J.; Grigg, G. C. & Tyler, M. J. (1995). A Field Guide to Australian Frogs. Surrey Beatty & Sons. p. 350. ISBN 0-949324-61-2. 
  4. ^ Heyer, W. Ronald; Liem, David S. (1976). "Analysis of the inter-generic relationships of the Australian frog family Myobatrachidae" (PDF). Smithsonian Contributions to Zoology 233 (233): 1–29. doi:10.5479/si.00810282.233. 
  5. ^ Yong, Ed (15 March 2013). "Resurrecting the Extinct Frog with a Stomach for a Womb". National Geographic. Retrieved 15 March 2013. 
  6. ^ Dolak, Kevin (20 March 2013). "Frog That Gives Birth Through Mouth to be Brought Back From Extinction". ABC News. 
  7. ^ Amphibian Species of the World – Rheobatrahus (under "Comments"). research.amnh.org
  8. ^ Frost, Darrel R.; Grant, Taran; Faivovich, Julián; Bain, Raoul H.; Haas, Alexander; Haddad, Célio F.B.; De Sá, Rafael O.; Channing, Alan; Wilkinson, Mark; Donnellan, Stephen C.; Raxworthy, Christopher J.; Campbell, Jonathan A.; Blotto, Boris L.; Moler, Paul; Drewes, Robert C.; Nussbaum, Ronald A.; Lynch, John D.; Green, David M.; Wheeler, Ward C. (2006). "The amphibian tree of life". Bulletin of the American Museum of Natural History 297: 1–370. doi:10.1206/0003-0090(2006)297[0001:TATOL]2.0.CO;2. 
  9. ^ Ingram, G. J. (1991). "The earliest records of the extinct platypus frog". Memoirs of the Queensland Museum 30 (3): 454. 
  10. ^ a b Hines, H., Mahony, M. and McDonald, K. 1999. An assessment of frog declines in Wet Subtropical Australia. In: A. Campbell (ed.), Declines and Disappearances of Australian Frogs. Environment Australia.
  11. ^ a b c Ingram, G. J. (1983). "Natural History". In: M. J. Tyler (ed.), The Gastric Brooding Frog, pp. 16–35. Croom Helm, London.
  12. ^ Meyer, E., Hines, H. and Hero, J.-M. (2001). "Southern Gastric-brooding Frog, Rheobatrachus silus". In: Wet Forest Frogs of South-east Queensland, pp. 34–35. Griffith University, Gold Coast.
  13. ^ Liem, David S. (1973). "A new genus of frog of the family Leptodactylidae from S. E. Queensland, Australia". Memoirs of the Queensland Museum 16 (3): 459–470. 
  14. ^ Mahony, Michael; Tyler, Davies (1984). "A new species of the genus Rheobatrachus (Anura: Leptodactylidae) from Queensland". Transactions of the Royal Society of South Australia 108 (3): 155–162. 
  15. ^ a b c McDonald, K.R. (1990). "Rheobatrachus Liem and Taudactylus Straughan & Lee (Anura: Leptodactylidae) in Eungella National Park, Queensland: distribution and decline". Transactions of the Royal Society of South Australia 114 (4): 187–194. 
  16. ^ Covacevich, J.A.; McDonald, K. R. (1993). "Distribution and conservation of frogs and reptiles of Queensland rainforests". Memoirs of the Queensland Museum 34 (1): 189–199. 
  17. ^ a b Winter, J.; McDonald, K. (1986). "Eungella, the land of cloud". Australian Natural History 22 (1): 39–43. 
  18. ^ Tyler, M. J. (1994). Chapter 12, "Gastric Brooding Frogs", pp. 135–140 in Australian Frogs A Natural History. Reed Books
  19. ^ Mahony, Michael. "Report to Queensland National Park on status of stream frogs in Pelion State Forest". 
  20. ^ Black, Richard (9 August 2010). "Global hunt begins for 'extinct' species of frogs". BBC. Retrieved 9 August 2010. 
  21. ^ Nosowitz, Dan (15 March 2013) Scientists Resurrect Bonkers Extinct Frog That Gives Birth Through Its Mouth. popsci.com
  22. ^ Messenger, Stephen (15 March 2013) Scientists successfully create living embryo of an extinct species. treehugger.com
  23. ^ Lawson, Bianca; Clulow S; Mahony M; Clulow J (2013). Moreira, Nei, ed. "2 Lawson B, Clulow S, Mahony MJ, Clulow J (2013) Towards Gene Banking Amphibian Maternal Germ Lines: Short-Term Incubation, Cryoprotectant Tolerance and Cryopreservation of Embryonic Cells of the Frog, Limnodynastes peronii". PLoS ONE 8 (4): e60760. doi:10.1371/journal.pone.0060760. PMC 3618038. PMID 23577155. 
  24. ^ Browne, Robert; Mahony, Clulow (2002). "A comparison of sucrose, saline, and saline with egg-yolk diluents on the cryopreservation of cane toad (Bufo marinus) sperm". Cryobiology 44 (251–157): 251. doi:10.1016/S0011-2240(02)00031-7. 

Further reading[edit]

  • Barker, J.; Grigg, G. C.; Tyler, M. J. (1995): A Field Guide to Australian Frogs. Surrey Beatty & Sons.
  • Pough, F. H.; Andrews, R. M.; Cadle, J. E.; Crump, M.; Savitsky, A. H. & Wells, K. D. (2003): Herpetology (3rd ed.). Pearson Prentice Hall, Upper Saddle River, New Jersey.
  • Ryan, M. (ed.) (2003): Wildlife of Greater Brisbane. Queensland Museum, Brisbane.
  • Ryan, M. & Burwell, C. (eds.) (2003): Wildlife of Tropical North Queensland. Queensland Museum, Brisbane.
  • Tyler, M. J. (1984): There's a frog in my throat/stomach. William Collins Pty Ltd, Sydney. ISBN 0-00-217321-2
  • Tyler, M. J. (1994): Australian Frogs – A Natural History. Reed Books.
  • Zug, G. E.; Vitt, L. J. & Caldwell, J. P. (2001): Herpetology (2nd ed.). Academic Press, San Diego, California.
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