Facts About the Gastric-brooding Frog

Scientists working in the 'Lazarus Project' created a living embryo of a gastric-brooding frog from preserved genetic material. However, the embryo survived only for a few days.

The gastric-brooding frog, also known as the 'platypus frog', was a genus that included two extraordinary species of frogs. Both the species were confined to the rainforests of Queensland, Australia, and became extinct in the mid-1980s, a few years after their discovery. Presently, scientists are trying to resurrect these frogs with the help of cloning technology.

Gastric-brooding frogs were no ordinary frogs, and this is the reason why they have been studied so extensively. What makes these frogs so unique was their ability to incubate their young in their stomach. The sight of young froglets coming out of their mother's mouth may seem quite incredulous, but that was the way gastric-brooding frogs gave birth to their young. The young ones remained in their mother's stomach till they passed the tadpole stage.

♣ There were two species of gastric-brooding frogs, the southern gastric-brooding frog (Rheobatrachus silus) and the northern gastric-brooding frog (Rheobatrachus vitellinus).

♣ The southern gastric-brooding frog was a medium-sized frog with a brown or olive-brown to black dorsal surface. Dark blotches were also found on the back. The northern gastric-brooding frog, on the other hand, was much larger than the southern species. It was pale brown in color, with a white or gray abdomen having striking yellow or cream-colored blotches. These yellow blotches were also found on the underside of the legs and arms.

♣ The skin of both the species was moist and coated with slimy mucus. The eyes were large and prominent, and the iris was dark brown in color. The tympanum was hidden in both, southern and northern gastric-brooding frogs.

♣ The fingers of gastric-brooding frogs were long and slender. Though the fingers of both the species lacked webbing, their toes were fully webbed. A small disc was also present at the end of each digit.

♣ Female gastric-brooding frogs were larger than males. The male southern gastric-brooding frog used to reach a size of 33 - 41 mm, while the female of the species grew to 44 - 54 mm. The male northern gastric-brooding frog, on the other hand, was typically 50 - 53 mm in size, while the female grew to 66 - 79 mm.

♣ Both species of gastric-brooding frogs were restricted to the rainforests of Queensland. Southern gastric-brooding frogs were mainly found in the Blackall and Conondale Ranges in southeast Queensland, between 350 and 800 meters of elevation.

♣ Southern gastric-brooding frogs were noticed in streams in the catchments of rivers like Stanley, Mooloolah, and Mary. Wet sclerophyll forests, riverine gallery open forests, and rock pools were the main habitats of this species. The male of the species preferred to inhabit deeper pools, while the females and juveniles were usually found in shallower pools.

♣ Northern gastric-brooding frogs were confined to the pristine rainforests of Clarke Range in Eungella National Park, between an altitude of 400 to 1000 meters. They were mainly noticed in the shallow sections of streams and creeks. Eungella National Park is located in central eastern Queensland.

♣ Like other frogs, gastric-brooding frogs also exhibited external fertilization. But what set them apart from other frogs was the type of parental care. The breeding activity in these frogs was observed to start between October and December.

♣ The female gastric-brooding frog was known to swallow her fertilized eggs, which were usually 5.1 mm in diameter. Soon after swallowing the eggs, the production of hydrochloric acid was turned off in her stomach, to prevent the digestion of the young ones. In this way, the female gastric-brooding frog transformed her stomach into a womb, where the fertilized eggs could develop.

♣ The larval development was entirely dependent on the yolk reserves. Therefore, eggs of gastric-brooding frogs had large yolk supplies.

♣ The tadpoles hatched inside their mother's stomach and developed into young froglets within 6 to 7 weeks. During this period, neither the mother nor the tadpoles ate anything. The tadpoles did not possess tooth rows, and could not feed. The mother also did not eat anything as its entire digestive system was shut down due to the absence of hydrochloric acid.

♣ Finally, when the tadpoles metamorphosed into young froglets, they were expelled by the mother through the mouth. Sometimes, the birth process took almost a week. But if the female frog was disturbed, she used to regurgitate all the froglets at once. The term 'propulsive vomiting' is generally used to describe the process in which the mother first propelled the froglets from her stomach to the mouth and then spewed them.

♣ The gastric-brooding frog's ability to block the production of hydrochloric acid is attributed to chemicals found in the egg jelly. It was observed that the jelly present in the eggs contained a substance called prostaglandin E2, which stopped the production of hydrochloric acid during embryonic development. Later on, this chemical was secreted by the tadpoles in order to keep the mother's digestive system in a non-functional state.

♣ The female gastric-brooding frog's stomach continued to increase in size when the tadpoles were growing inside. Eventually, the stomach bloated so much that it occupied a large part of the entire body cavity. As a result, the mother could not inflate the lungs, and had to breathe through the skin during this period.

♣ After the birth of the froglets, the mother's digestive tract returned to its normal state as the production of hydrochloric acid resumed. The female gastric-brooding frog began feeding within four days of releasing the young ones.

♣ The southern gastric-brooding frog was discovered in 1972, but was first described in 1973. The last captive specimen of this frog died in 1983, and since then the species has been believed to be extinct.

♣ Though the southern gastric-brooding frog was discovered in 1972, it captured public attention in 1974, when Mike Tyler, an Associate Professor of the University of Adelaide, Australia, discovered the unique way in which it reproduced.

♣ The northern gastric-brooding frog was discovered in 1984, but unfortunately it disappeared a year after its discovery.

♣ The gastric-brooding frog was observed to eat small insects and crayfish, larvae of caddishfish, and both terrestrial and aquatic beetles.

♣ White-faced herons and eels were
the main predators of gastric-brooding frogs. These frogs used to hide beneath the leaves of eucalyptus trees and stones to avoid predators. Sometimes, they spewed a coat of mucus in order to slip away and escape from their predators.

♣ The northern, as well as the southern gastric-brooding frogs used to call during summer. The call of the northern species was louder as compared to the southern species. The southern gastric-brooding frog's call was shorter and deeper.

♣ Both, the IUCN (International Union for Conservation of Nature) and Australia's Environment Protection and Biodiversity Conservation Act, 1999, have enlisted gastric-brooding frogs as extinct.

♣ The factors that led to the extinction of these frogs are still not known with certainty. However, loss or degradation of habitat and breeding sites, pollution, drought, pathogens, and parasites were some of the speculated reasons behind the extinction of gastric-brooding frogs.

♣ The growth of the chytrid fungus may also be associated with the extinction of gastric-brooding frogs. This fungus can infect most amphibians and cause chytridiomycosis. This disease has been linked to population decline and species extinction.

In March 2013, scientists at the University of New South Wales, Australia, announced that they would try to resurrect the amazing gastric-brooding frog with the help of cloning technology. This project is named as the 'Lazarus Project'. The medical community is also interested in studying this frog, mainly due to its ability to shut down the production of hydrochloric acid in the stomach. They believe that this frog may help find new treatment options for stomach ulcers.