The smallest vertebrates discovered so far are flea toads, which live at the limit of how small any vertebrate can get.
Science’s new flea toad, Brachycephalus dacnis, sits in the palm of a researcher. (Credit: Lucas … [+]
I have shared news about several species of extremely small frogs and toads, commonly known as flea toads or toads (read more here and here). These little amphibians are remarkable because they are LOT smaller than a human fingernail.
“These are small toads with all the characteristics of large toads, except for their size,” said Luís Felipe Toledo, who is the corresponding author of the recently published study and a professor at the Institute of Biology of the University of Campinas (IB- UNICAMP).
The recently discovered flea beetle to be described was given its scientific name, Brachycephalus dacnisin honor of the Dacnis Project, a conservation, research and education NGO that maintains private areas of the Atlantic rainforest, including the one in Ubatuba, on the coast of Brazil’s São Paulo state, where a Dacnis Project team discovered a new flea toad , which was classified into gender, Brachycephalus.
“This genus is different,” Professor Toledo explained. “During its evolution, it underwent what we biologists call ‘miniaturization,’ which includes the loss, reduction and/or fusion of bones, as well as fewer digits and the absence of other parts of its anatomy.”
This new species of flea toad is neither the first nor the second to be discovered and scientifically described. In fact, it is the seventh such species of flea toads described in the genus Brachycephalus until now.
This genus is known mainly for its small but brightly colored species of amphibians which are highly poisonous, most notably the bright orange gourds, B. rotenbergae, B. ephippium AND B. pitanga (more here).
Pumpkin legs are somewhat larger than their cousins, the toads, but surprisingly, pumpkin frogs lack some anatomical features that are present in other frogs and toads. For example, they lack a tympanic bone of the middle ear, which makes them unable to hear their vocalizations.
Another closely related group Brachycephalus species are flea toads, which are even smaller than pumpkin toads and are cryptically colored in shades of brown-yellow so they can blend in with the leaf litter they live on.
How did the researchers find such a small creature?
According to Professor Toledo, researchers first became aware that there might be a new species to find after hearing the distinctive vocalizations of adults while conducting sampling surveys between June 2021 and May 2022 in Ubatuba, on the coast of São Paulo state. in an area of the Atlantic rainforest (Figure 6b).
“Edelcio [Muscat] and his team at Projeto Dacnis, a private nature reserve, found the new species (Brachycephalus dacnis) in the same place as its sister species (already known Brachycephalus hermogenesi), after he recognized 2 different sounds,” Professor Toledo described in an email. “He then sent me the specimens, the sounds, and we performed DNA analysis, high-resolution CT-scans, anatomical studies and confirmed the finding. “
Figure 6: Geographic distribution, advertisement call sonograms and phylogeny. … [+]
DNA analysis revealed this B. dacnis is closely related to another similarly colored and yellow-brown marked toad, B. hermogenesis (Figure 6c). Both species are cryptic, closely matching the leaf litter where they live, and both occur in the same geographic area (Figure 6or). In fact, the resemblance between these two types of flea toads is so close that it is possible that B. dacnis it may have been discovered accidentally before.
“There may have been specimens belonging to new species among those that served as the basis for describing B. hermogenesis in 1998,” noted Professor Toledo.
Is this new species of flea toad smaller than a previously discovered and described flea toad, B. pulex (read more here)?
“One of the individuals measured 6.95 mm, which is currently the second smallest adult vertebrate ever described, only larger than another individual of another species. [belonging to the same genus B. pulex] species”, writes Professor Toledo and collaborators in the paper describing the new species.
However, both Brachycephalus species are extremely small.
“It’s just an individual B. pulex which is smaller than the smallest individual i B. dacnis,” Professor Toledo replied in the email. “Therefore, they are about the same size overall.”
What was the inspiration for the common name, “flea toad”?
“We know they FLY extremely far – hence the name ‘plea’, except they’re tiny,” Professor Toledo replied in the email.
How small can these – or any other – vertebrates get? Have toads-pleas reached the evolutionary limit of what small vertebrates can have?
“YES! this is the limit… if someone in the future finds an even smaller frog or vertebrate, it would be only a few decimal millimeters smaller (a trivial difference),” Professor Toledo replied in an email.
How do these small animals protect themselves from predators? Are they poisonous?
“[T]hey open your mouth to threaten their predators!” Professor Toledo responded by email.
“[But there’s] there is no evidence of poison,” added Professor Toledo.
The newly described flea toad, Brachycephalus dacnis, in a defensive position (Credit: Lucas Botelho.)
What else is known about flea toads?
“Since we just discovered this species, we don’t know much yet,” Professor Toledo said. “For example, who are the predators? how do women choose men? do they hybridize with sister species? how do such small internal organs work? (heart, liver, lungs, etc.)?”
What is the most surprising or interesting aspect of flea toads?
“Size, of course, but other than that, in my opinion, it will be their internal anatomy,” replied Professor Toledo. “For example, examining another Brachycephalus species (B. rotenbergae), we found that they have a ‘fish-like heart’ with only two cavities, instead of three, as in most amphibians – and this is information from one of the largest. Brachycephalus species – so how would it be in such a smaller species?”
Professor Toledo and colleagues also found that, unlike many frogs and toads, flea toads show direct development – bypassing the chick stage and emerging from their eggs as fully formed miniature versions of adults. In addition, they also discovered that flea toads produce only two eggs in a cycle, unlike many other frogs and toads that produce dozens, hundreds, or sometimes thousands of eggs at a time.
Since there are seven species of flea toads already described, how many more could be out there waiting to be discovered?
“The diversity of these miniature frogs may be much greater than we think,” said Professor Toledo. “Hence the importance of describing as many traits and features as possible, to speed up the description process and start conservation work as soon as possible.”
Source:
Luis Felipe Toledo,Lucas Machado Botelho, Andres Santiago Carrasco-Medina, Jaimi A. Gray, Julia R. Ernetti, Joana Moura Gama, Mariana Lucio Lyra, David C. Blackburn, Ivan Nunes, Edelcio Muscat (2024). Among the world’s smallest vertebrates: a new miniature flea toad (Brachycephalidae) from the Atlantic rainforest, PeerJ 12: e18265 | doi:10.7717/peerj.18265
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