The hard life of the Brazilian microfrog, which is the smallest known vertebrate – 03/04/2024 – Science

Scientists believe they have identified the world’s smallest vertebrate: a tiny, pea-sized Brazilian frog called Brachycephalus pulex (or flea thrush), according to recent research.

In 2011, Mirco Solé, a researcher at the State University of Santa Cruz, in Bahia, was the first to analyze the size of this species in comparison with that of other similar frogs.

The sample wasn’t large enough at the time to be conclusive, but the more recent research, in which Solé and his team measured the body lengths of 46 flea frogs, is more comprehensive.

It turned out that male frogs B. pulex they measured just over 7 mm and females were slightly larger, measuring just over 8 mm.

The team also confirmed the maturity and sex of the frogs by examining their gonads and checking for the presence of vocal slits in the throat, which only males have.

As the smallest extant vertebrates, frogs B. pulex face their own challenges — as well as being difficult to monitor accurately. They have trouble doing something frogs are supposed to be inherently good at: jumping.

In fact, 2022 research found that these vertebrates lose their balance when they leave the ground.

They are simply so small that they cannot make proper use of their vestibular systems, which help control stabilization.

‘Competition’ open

Mark D. Scherz, curator of herpetology at the Natural History Museum of Denmark, says that this “impressively small” frog species most likely holds the title of smallest vertebrate in the world, and that the claim “is based on a remarkable and large data set.”

Still, he says that although there is a lot of evidence, it is not possible to know what is coming in terms of new discoveries.

“It’s definitely possible that the cap continues to fall,” says Scherz.

After all, this has been the standard.

The record of tiny species has continually evolved, reaching smaller and smaller sizes as more research is done.

“In the last 30 years,” notes Scherz, “the record has gone from about 10 mm (Eleutherodactylus iberia) to 6.45-8.87 mm”.

This represents a reduction of more than 10% in length.

Sherz says that while there are likely to be likely contenders for the title of smallest vertebrate in the coming years, this classification as “small” depends on how the species is being measured.

“If we take this as a linear measure, frogs are currently the winners,” he explains. “But if we consider mass or volume, then fish would probably claim the title, as they are very narrow and slender, while frogs are quite round.”

He imagines that there are some small “planktonic fish” that have not yet been discovered.

These discoveries, and subsequent research to understand what makes these species unique and interesting beyond their size, have their challenges when it comes to very small species.

Scientists have already created tiny pants and mini-belts to put on tiny vertebrates so researchers can understand how these animals move.

Luci Kirkpatrick, professor at the School of Environmental and Natural Sciences at Bangor University in Wales, understands these challenges well.

It has developed tracking devices that fit some smaller animals. She says they are typically difficult to track, but argues that this task is extremely important for conservation.

Although tiny, these animals are like “ecosystem engineers” who, she says, are “fundamental to ensuring the food chain functions correctly.”

“These populations can change quickly and react to changes in the environment,” which can be extremely positive, she explains.

But a disease outbreak could be catastrophic if not monitored, says the scientist.

“If you want to conserve an animal, you need to know what it’s doing,” explains Kirkpatrick.

Read the original version of this report (in English) on the BBC Future website