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Flesh-Eating Baby "Worm" Feasts on Mom's Skin

James Owen
for National Geographic News
April 12, 2006
 
The doting mom of a wormlike amphibian found in Africa lets her babies
devour her own flesh, scientists have found.

The tropical creature transforms its skin into a nourishing, fat-rich meal for its newborns to eat, researchers say.

This bizarre form of parental care was uncovered in Kenya (map), where a team of biologists observed the young of a caecilian, a type of limbless amphibian, feasting on their mother.

Furthermore, the youngsters' teeth appear to be specially designed for eating their mother's flesh.

The gruesome parenting method, described tomorrow in the journal Nature, has never before been seen in animals.

"There's nothing [in the animal kingdom] that peels off the skin and eats big chunks of it like these things are doing," said lead study author Mark Wilkinson, a zoologist at the Natural History Museum in London, England.

The team says the offspring of Boulengerula taitanus are entirely dependent on their parent's skin, which transforms into a kind of baby food that the study team likens to mother's milk in mammals.

The female's skin doubles in thickness during this period, the researchers found.

"You've got several layers of skin, and the outer layer is what they eat," Wilkinson said.

"When that's peeled off, the layer below matures into the next meal."

Spiked Points

The offspring were found to have special infant teeth, which they lose in adulthood, for gripping and stripping their mother's flesh.

"Some teeth are spoon-shaped, so they look good for scraping, while those with spiked points look good for perhaps piercing the outer skin layer," Wilkinson said.

Other teeth, he says, resemble grappling hooks.

Caecilian moms were found to lose about 14 percent of their body weight while raising their young this way. Yet they don't appear to be harmed.

"The mothers are losing weight because they're providing food for their babies, but otherwise they seem fine and are remarkably placid when the young are vigorously feeding on them," Wilkinson said.

Evolutionary Missing Link?

Caecilians are a poorly understood group of amphibians that lack arms or feet. With their tiny eyes and shiny skin they resemble giant earthworms.

Some 170 species have been documented, with the longest growing to almost 5 feet (2.4 meters) in length.

Found in tropical regions, they usually live in rain forests where they burrow through soil and leaf litter in search of beetles, frogs, lizards, and other prey.

Some species of caecilian lay eggs, while others give birth to live young. The species studied by Wilkinson's team lays eggs.

Previously it was thought that egg-laying caecilians guarded their offspring until they hatched but provided no parental care after that.

But this new discovery proves otherwise, and the team says the species could mark a key stage in the evolutionary transition from egg-laying caecilians to those that give birth to live young.

The young of some live-bearing species have likewise been found to feast on their mother's flesh while still inside the mother—also regarded by scientists as highly unusual behavior.

The study team says such live-born offspring are armed with teeth similar to those of the egg hatchlings.

These infant teeth are used to scrape fatty secretions and other nourishing substances from the female's reproductive organs.

"What we seem to have discovered is some kind of intermediate state, and that the [live-bearing] forms of caecilians have probably evolved from a skin-feeding, egg-laying form," Wilkinson said.

"So eating on the outside then becomes eating on the inside."

Lessons for Mammals

Wilkinson says caecilians may also help shed light on how parenting developed in other animals, including mammals.

"You can draw parallels between skin-feeding in these creatures and lactation in mammals," he added.

"Analogies between caecilians and mammals could be quite strong from an evolutionary perspective." Like mammals, he says, caecilians often invest a lot of time and energy in nurturing their young.

This isn't the case for many other amphibians, such as frog species that abandon their eggs after laying them.

"Caecilians are investing much more energy into each individual offspring, and that's a mammalian-like strategy," Wilkinson said.

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