Mexico is in news for being home to six species of frogs some of them smaller than the diameter of a coin. Experts believe that these could be the world’s smallest vertebrates. Living among a variety of habitats in the country are the six new Craugastor species. These frogs are pill-sized and smaller than 13 millimeters. Scientists find the close association between them surprising and are in awe that they did not uncover the species until now. They published their findings on this species in the Herpetological Monographs.
World’s Smallest Frogs
Even though these frogs are tiny, they are not the smallest amphibians in the world. A few decades back, Brachycephalus didactylus, a Brazilian gold frog, was thought to be the smallest frog in the world. It was around 8.6 millimeters long and was the world’s smallest frog since its discovery in the 1970s. However, this was until 2012, that Paedophryne amanuensis was found in Papua New Guinea. The male frog measures only 7.7 millimeters long. The researchers came across frog noises and homed in on its unique call.
Why Are These Frogs So Small?
It still remains a mystery as to why some animals remain this small. Larger animals, where populations are quarantined in small environments shrink in size. This process is called insular miniaturization. Animals do this to reduce predation pressure and less availability of food. For animals that are already small in size like frogs, shrinking can push their body significantly. This results in the loss of bones, thinner skeletons, as well as the omission of some stages of the lifecycle. For example, several small frogs never become tadpoles. They emerge from the egg, completely formed through the process of direct development like Craugastor.
Advancing in the lifecycle and limiting growth might allow these small animals to come out more quickly compared to their larger counterparts and give them a push on reproduction. Moreover, being small allows these animals to make full use of various food resources and habitats, like the leaf litter occupied by P. amanuensis.
How were they discovered?
The Craugastor frogs of Mexico and Guatemala reside in leaf litter in various different forests, from mountain woodland to rainforest. They are found in a variety of different sizes and colors, with many species living together. This means that these tiny frog species might be mistaken to be the baby of larger relatives which led the scientists to reexamine these amphibians and discover how many species exist.
Around the world, frogs taken under the hold of natural history collections were studied to locate their characteristics and genetics. During this process, the team found an unusual method of inferring whether the small frog was in reality an adult or a child of the larger species. Overall, six new species were reported, making it a total of 12 frogs in this Mexican frog group. These include C. titanium.
One specie, C. portilloensis, was even smaller, just 11 millimeters long. This was a surprise to many of the researchers but since the specimens were not completely grown. It was difficult for the scientist to conclude how much bigger they could get. In reality, these small frogs are prone to larger threats. Some of them are positioned at the lowest level of conservation concern, the others are “endangered.” They face greater threats such as habitat fragmentation and chytridiomycosis. This is a fungal disease that wipes out the entire amphibian population around the world.
An Endangered Species
According to Tom Jameson, the lead author of the study, in the last era, most of their population was shrinking. Many of their bodies were very micro-endemic, not making it capable to disperse.
Researchers quite struggled to distinguish whether the frog is an adult or not, particularly if it has been kept in a Museum collection for a while. However, one characteristic of the anatomy is that males of almost all species have pigmented testes. They think all these six frogs should be termed as “Endangered” or at least enlisted as Data Deficient so that their preservation standing can be properly examined in the future. Their suggestion is two hotspots for Craugastor frogs, Central Guerrero, and southcentral Oaxaca will be beneficial for the creation of new protected areas.