Description
The now exinct Rheobatrachus vitellinus was moderately large and squat with a length of 55.7 – 58mm (males) and 62.2 – 83mm (females). The species’ head was flattened and about as long as it is broad, with a blunt snout that was not very prominent. On the upper eyelids, there were large projections of skin present, and the eyes themselves were prominent. The pupil was noted to be vertical to vertically rhomboidal. The nostrils are directed upward and surrounded by a loose fleshy margin with small papillae at the posterior border. The space between the nostrils was about as wide as the space between the eyes and the nostrils, but the internarial space is larger. The canthus rostralis and the tympanum were not externally visible, but the supratympanic fold was very distinct. Additionally, there was a narrow dermal fold above the anterior third of the supratympanic fold. There is a moderately sized frontoparietal foramen present in adults. The maxillary teeth were present and ‘fang-like’, while the vomerine teeth were absent. The tongue of this species was broad and completely attached to the floor of the mouth. Male specimens had a vocal sac with paired apertures on the floor of their mouths that are outlined with fleshy margins. The dorsal surface was noted to be granular, while the ventral surfaces of the body and limbs were smooth. The cylindrical fingers of R. vitellinus were free, but the long toes were fully webbed. The relative finger length was III > IV > II > I, and finger II had a lateral fringe on its medial surface. There were poorly defined subarticular tubercles, but no palmar tubercles. Adult males had unpigmented nuptial pads covered in tiny spines only visible through scanning electro micrograph illustrations, on the medial and dorsal surfaces of finger I. The hind-limbs were noted to be short and without a tarsal fold. There were a small number of prominent tubercles on the posterior surface of the tarsus, but none on the flanks. The relative toe length was IV > III – V > II > I. On the toes there was a large flattened inner metatarsal tubercle, but none on the outside. There were also no supernumerary tubercles on the foot. All of the terminal phalanges had a broad apical knot, and the tips of the digits were slightly dilated, but more so in the toes than in the fingers. The anus had a fringe on its border (Mahony et al. 1984; Cogger 2000).

The snout-vent length of the young at birth is from 15.1 – 15.9 mm (Tyler 1983).

Rheobatrachus vitellinus (female snout-vent length: 62.2 – 68.9mm) can be distinguished from its smaller southern counterpart, R. silus (female snout-vent length: 44.5 – 53.9mm), by its dark brown coloring and the patches of bright yellow under its limbs and abdomen versus the lack of dark brown coloration and the paler yellow seen in R. silus. The two species have the same diploid chromosome number and relative chromosome lengths, but the centromere location and position of secondary constriction does vary. Where the centromere is submetacentric in pair 6 and acrocentric in pairs 9 and 10 in R. vitellinus, they are acrocentric and metacentric respectively in R. silus. The prominent secondary constriction present in pair 6 of R. vitellinus’ chromosomes is not present in R. silus (Mahoney et al. 1984).

In life, R. vitellinus had a pale brown dorsal surface with darker patches. The ventral surface was white or brown and the abdomen and undersides of the limbs were bright yellow to orange in color. In preservative, the light brown dorsum is mottled irregularly with dark brown and small patches of cream. The ventral surface is cream with a dense dark brown stippling on the throat and chest that becomes sparse toward the posterior. The back of the thighs was heavily covered in dark brown (Mahoney et al. 1984).

In some individuals, the ventral surface was dark brown instead of cream where it was not orange (Mahoney et al. 1984).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Australia

View distribution map in BerkeleyMapper.

Population and Distribution

Rheobatrachus vitellinus was discovered in January 1984 (Mahony et al. 1984) and was found exclusively in undisturbed rainforest in Eungella National Park, mid-costal Queensland at altitudes of 400 - 1000 m, with location coordinates 21°00’S, 148°35’E to 21°04’S, 148°41’E (Covacevich & McDonald 1993). The area of occurrence of R. vitellinus was less than 500 km² (map in McDonald 1990). The species was considered common across its range until January 1985 when the first signs of decline (reported by Winter and McDonald 1986) were observed at lower altitudes (ie. about 400 m) (McDonald 1990). At higher altitudes the frogs remained common until March 1985 but were absent in June of that year (McDonald 1990). Despite continued efforts to locate the species, Rheobatrachus vitellinus has not been recorded within Eungella National Park or any other locations since March 1985 (Ingram and McDonald 1993; McDonald and Alford 1999). Rheobatrachus vitellinus was formerly known from Eungella National Park and Mt Pelion State Forest (Tyler 1997) and was not recorded on private lands.

Habitat

Rheobatrachus vitellinus was recorded from pristine rainforest where the only form of human disturbance was a poorly defined walking trail (McDonald 1990). The species occurred in first- to third-order streams (McDonald 1990). Individuals were located in shallow, rocky, broken-water areas, in cascades, riffles and trickles, but were absent from the pools of water found between riffles (McDonald 1990). The water in these streams is cool and clear, and individuals hid away beneath or between boulders in the current or in backwaters (Tyler 1989).

Life History, Abundance, Activity, and Special Behaviors

Activity

Rheobatrachus vitellinus is mostly nocturnal. They are frequently found on rocks in and around streams during rainfall (McDonald 1990).

Reproduction

Rheobatrachus vitellinus brooded its young in the female’s stomach and gave birth through the mouth (McDonald and Tyler 1984; see Rheobatrachus silus for account of reproduction in similar species). It is not known whether the eggs are laid on land or in water prior to fertilization and the subsequent swallowing (McDonald 1990). The hormone, Prostaglandin E, was present in the jelly that surrounds the eggs, which inhibited the secretion of gastric acids in the brooding female, rendering her unable to feed (Tyler et al., 1985). There are no major structural changes to the stomach in R. vitellinus, contrary to R. silus, which suggests a dichotomy in the evolution of gastric brooding. The biochemical and physiological adaptations for gastric brooding in R. vitellinus remain unknown (Leong et al. 1986). The fully formed metamorphs are born via regurgitation in the months of January to February.

In the only documented case, 22 metamorphs were brooded in the stomach of one female. Upon collection the stomach of the female was reported to be greatly distended and during road transport the individual began to give birth. The birth lasted approximately 34 hours. The young were born underwater, though it is not known whether this underwater birth was a natural phenomenon or a consequence of the conditions in which the female was held (McDonald and Tyler 1984).

Feeding

This species was both an aquatic and stream edge feeder. The diet of R. vitellinus included small crayfish, caddisfly larvae, terrestrial and aquatic beetles and a sympatric frog species Taudactylus eungellensis (Winter and McDonald 1986).

Predators

Rheobatrachus vitellinus was a food source for higher trophic levels including birds, fish and other aquatic fauna (Winter and McDonald 1986).

Calling

Males were most frequently heard calling between September and December (Winter and McDonald 1986). The call consists of several staccato notes and is deeper than that of R. silus (McDonald 2005).

Trends and Threats
After the species was discovered in 1984, a monitoring program found R. vitellinus to be quite common across its range with up to six individuals being found in a 2 x 5m stream (McDonald 1990). However, despite continued efforts to locate the species, R. vitellinus has not been recorded within Eungella National Park or any other locations since March 1985 (Ingram and McDonald 1993; Richards et al. 1993; Hero et al. 1998; McDonald and Alford 1999). McDonald (1990) found no obvious evidence that seasonal rarity, over-collecting, predation, drought, floods, habitat destruction, disease, heavy parasite loads or stress due to handling for data collection were responsible for the population declines. It was thought that the decline observed in 1984-1985 may have been a natural population fluctuation and that residual individuals had retreated to hidden refuges (Winter and McDonald 1986; McDonald 1990). The extent of such population fluctuations is unknown, but there is evidence of large swings in numbers of other Australian frogs (McDonald 1990).

Recently, it has been determined that the most likely cause of extinction is infection by the chytrid fungus, Batrachochytrium dendrobatidis, resulting in chytridiomycosis. The Eungella torrent frog (Taudactylus eugellensis), which inhabited the same streams, was actively preyed upon by R. vitellinus (Winter and McDonald 1986) and suffered a steep population decline around the same time as R. vitellinus was discovered to have traces of infection from the chytrid fungus (McDonald 1990; Rettalick et al. 1997). Taudactylus eugellensis has been implicated as a host and reservoir for the chytrid fungus (Rettalick et al. 1997) so it is therefore very likely that transmission of the fungus occurred between these species.

Relation to Humans
Historical data suggests that it was unlikely that R. vitellinus was subject to trade, legal or illegal (McDonald, 1990).

Possible reasons for amphibian decline

Disease

Comments
The species authority on Rheobatrachus vitellinus is Mahony, M., Tyler, M.J., and Davies, M. (1984). ''A new species of the genus Rheobatrachus (Anura: Leptodactylidae) from Queensland.'' Transactions of the Royal Society of South Australia, 108(3), 155-162.

Rheobatrachus vitellinus has a sister species, Rheobatrachus silus, the southern gastric-brooding frog, which is also considered extinct (Richards et al. 1983). The last captive specimen of R. silus died in 1983 (Tyler and Davis 1985).

The name “vitellinus” comes from the Latin word for “of the yolk of an egg” and it refers to the yellow ventral coloration (Mahonet et al. 1984).

Rheobatrachus vitellinus had chromosomes with a diploid number of 2n = 24. The metacentric chromosomes include pair numbers 1, 5, 7 and 8, the submetacentric include pair numbers 3, 4 and 6, the subacrocentric consists of pair number 2 and the acrocentric includes pairs 9 – 12. Notably, a prominent secondary constriction is seen on the short arm of pair 6.

References

Cogger, H.G. (2014). Reptiles and Amphibians of Australia (7th ed.). CSIRO Publishing, Collingwood.

Covacevich, J.A. and McDonald, K.R. (1993). ''Distribution and conservation of frogs and reptiles of Queensland rainforests.'' Memoirs of the Queensland Museum, 34(1), 189-199.

Hero, J-M., Hines, H.B., Meyer, E., Morrison, C., and Streatfeild, C. (1999). ''New records of 'declining' frogs in Queensland (April 1999).'' Frogs in the Community – Proceedings of the Brisbane Conference 13–14 February 1999. R. Natrass, eds., Queensland Museum, Brisbane.

Hero, J.-M., Hines, H.B., Meyer, E., Morrison, C., Streatfeild, C., and Roberts, L. (1998). ''New records of 'declining' frogs in Queensland, Australia.'' Froglog, 29, 1-4.

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.

Mahony, M., Tyler, M.J., and Davies, M. (1984). ''A new species of the genus Rheobatrachus (Anura: Leptodactylidae) from Queensland.'' Transactions of the Royal Society of South Australia, 108(3), 155-162.

McDonald, K. and Alford, R. (1999). ''A review of declining frogs in northern Queensland.'' Declines and Disappearances of Australian Frogs. A. Campbell, eds., Environment Australia, Canberra. Available in .pdf format online.

McDonald, K.R. (1990). ''Rheobatrachus Liem and Taudactylus Straughan and Lee (Anura: Leptodactylidae) in Eungella National Park, Queensland: distribution and decline.'' Transactions of the Royal Society of South Australia, 114(4), 187-194.

McDonald, K.R. and Tyler, M.J. (1984). ''Evidence of gastric brooding in the Australian leptodactylid frog Rheobatrachus vitellinus.'' Transactions of the Royal Society of South Australia, 108, 226.

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. (1997). The Action Plan for Australian Frogs. Wildlife Australia, Canberra, ACT.

Winter, J. and McDonald, K. (1986). ''Eungella, the land of cloud.'' Australian Natural History, 22(1), 39-43.

Species Account Citation: AmphibiaWeb 2016 Rheobatrachus vitellinus: Northern Gastric Brooding Frog <https://amphibiaweb.org/species/3544> University of California, Berkeley, CA, USA. Accessed Dec 30, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 30 Dec 2024.

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