Freaky Frogs/Lost Forever

Gastric-Brooding Frog

In this special Freaky Frog/Lost Forever crossover, we’ll be looking at a species that, until relatively recently, exhibited one of the most extreme forms of parental care seen in any frog. Known as the gastric-brooding frog (or platypus frog due to its largely aquatic nature), it lived only in Queensland, Australia. The female, after laying her eggs, swallowed them – just like Darwin’s frog, which we mentioned last time. But, once again, this was not cannibalism; it was a highly unconventional child-rearing technique.

As the name suggests, the female gastric-brooding frog safeguarded her offspring inside her own stomach. A hormone secreted by the eggs (and later the tadpoles) deactivated production of the hydrochloric acid that the mother normally used to digest her food, and also halted the wave of muscular contractions that would have moved food through the stomach into the guts. It seems likely that the first few eggs to arrive were dissolved before this digestive inhibitor could take effect, but by the time later eggs were swallowed, the frog’s stomach had effectively become a nice, cosy womb, able to accommodate around 20-25 tadpoles.

The developing young within the mother frog, now safe from being digested, were nourished on the yolk from their eggs. As they grew older and made the transition from tadpole to froglet, the stomach of the female greatly expanded and took up much of her body cavity, forcing her lungs to deflate. Now unable to use them to breathe, the mother frog, during the last stages of pregnancy, relied entirely upon absorbing oxygen through her skin. She also wasn’t able to eat during the incubation period because she couldn’t produce any stomach acid, so she was forced to fast for at least six weeks. Eventually, she regurgitated the young frogs from within her bloated stomach into the outside world. This process often took several days, but, if disturbed, she was able to expel them all at once in a single act of propulsive vomiting.

Unfortunately, herpetologists didn’t have much time to study this frog and its remarkable behaviour. When it was first discovered in 1973, it was considered relatively common, but, by the end of the decade, it was already extinct in the wild. The last captive specimen died in 1983. A very similar species, the northern gastric-brooding frog, which employed the same form of internal brooding as its southerly cousin, was discovered in 1984. But only a year later, it, too, had vanished. It has not been seen since, despite extensive efforts to locate it. Exactly what happened to these two unique species of frog remains unclear. Possible culprits include logging, water pollution, and the pathogenic chytrid fungus mentioned in our last Freaky Frogs post.

There is, however, a slim possibility that we have not seen the last of these extraordinary frogs. In 2013, Australian scientists managed to create gastric-brooding frog embryos by combining frozen tissue samples with eggs from the related great barred frog. The embryos only survived a few days, but the cloning experiment was deemed a huge leap forward in the field of de-extinction. If the Australian scientists achieve their goal, perhaps the gastric-brooding frog will become the first extinct species that isn’t lost forever. Perhaps, one day, this amazing frog will return to the world to throw up its young once again.

Surely we can’t get any freakier than a frog raising its offspring inside its stomach! But how about one that raises its young inside its own skin? Next time, we look at the truly bizarre Surinam toad.