To keep their pools clean, some tadpoles don’t poop for weeks
Baby Eiffinger’s tree frogs store their solid waste in an intestinal pouch
The tiny Eiffinger’s tree frogs live in Japan and Taiwan. They reach an adult size of only about 3 to 4 centimeters (1 to 1.5 inch) long.
Bun Ito
Some tadpoles seem to have a unique way to keep their watery cribs clean: They don’t poop for weeks!
These baby Eiffinger’s tree frogs live in Taiwan and on the Japanese islands of Ishigaki and Iriomote. Even as adults, they’re tiny — just 3 to 4 centimeters (1 to 1.5 inch) long. When these itty-bitty amphibians lay their eggs, they do it in puny puddles. Often, these small pools are nestled in plant stems, tree hollows or bamboo stumps.
On hatching, the tadpoles spend their early lives in these puddles. But in such small pools of water, there’s not a lot of liquid to dilute ammonia. These animals release that toxic chemical in their pee and poop. So why don’t the pools quickly turn poisonous?
The tadpoles’ secret to keeping their pools clean, Bun Ito and Yasukazu Okada have now discovered, is constipation. Baby Eiffinger’s tree frogs store their poop in an intestinal pouch. And they don’t release it until they start to turn into full-fledged frogs.
Ito and Okada are biologists at Nagoya University in Japan. They shared their findings September 22 in Ecology.
Tidy tadpoles
The pair raised tadpoles from four different frog species in makeshift nurseries: Eiffinger’s tree frogs, Japanese tree frogs, Montane brown frogs and forest green tree frogs. Once their experiment began, Ito and Okada moved the tadpoles to smaller cribs. These were plastic cases, each holding a little more than a tablespoon (15 cubic centimeters) of water.
The team measured and compared how much ammonia each frog species released. They also measured how much of the chemical each species had stored in their guts.
Eiffinger’s tree frog tadpoles released less than half as much ammonia, on average, than the forest green tree frog — the species that released the most. They also kept more ammonia in their guts compared with Japanese tree frogs and Montane brown frogs.
Unlike the Eiffinger’s frogs, the other three species typically lay their eggs in open ponds. There, ammonia would be easily diluted. That may explain why those others haven’t evolved a way to hold their ammonia in, as Eiffinger’s tree frogs do.
The behavior of these tadpoles “likely serves to prevent contamination of small water bodies,” Ito says. Some ammonia still seeped into the Eiffinger’s tree frogs’ water. It might have come from their pee.
The tadpoles of Eiffinger’s tree frogs have another superpower, too. They can survive in higher levels of ammonia than the Japanese tree frog, the experiments showed.
That might seem strange, since Eiffinger’s tree frog tadpoles take such pains not to poop. But Ito notes that sometimes the tadpoles share their cribs with other animals, such as mosquito larvae. Those critters release ammonia, too.
“The tadpoles [may] have developed a tolerance to ammonia as a dual defense,” says Ito. It would shield them against ammonia produced by other creatures — and the waste they make themselves.
