A team of biologists has just named three new salamanders in the genus Thorius; the tiniest tailed tetrapods known to science. Smaller than a matchstick, these creatures are as strange as they are adorable, their miniaturised anatomy pushing the boundaries of what natural selection can produce. Tragically, all three species appear to be edging toward extinction.
Adult and juvenile Thorius troglodytes from montane cloud forest in Veracruz, Mexico. Adults of this species are about the name size as the three newly described species of Thorius. All images courtesy of James Hanken
Thorius pinicola, Thorius longicaudus and Thorius tlaxiacus are the subject of a new scientific paper published today in the open-access journal Peer-J. Found high in the montane cloud forests of Oaxaca, Mexico, the three new species join the ranks of 26 other members of the Thorius genus thanks to a decades-long study that included field surveys, DNA sequencing, digital imaging and statistical analysis of the wee critters' anatomy.
Thorius papaloae, a species from a montane cloud forest of northern Oaxaca, was described in 2001.
Thorius salamanders have exaggerated, almost absurd proportions. Like other New World tropical salamanders, they have enormous projectile tongues, which shoot out to a distance of up to half the length of the body to catch insects. To make way for the tongue, the rest of the creature's tiny head is extremely reduced in size, with some skull bones missing entirely.
Photomicrograph of Thorius pennatulus. Bones are stained red and cartilage stained blue. The entire head is 3mm long.
Thorius salamanders are also well-endowed in the reproductive department. As Harvard University biologist and study co-author James Hanken explained to Gizmodo, adults need to maintain a minimum size of ovaries and testes in order to produce enough eggs and sperm. "As a result, the gonads occupy a relatively large proportion of the total body volume," he wrote in an email. "In some females, much more than half the volume of the trunk is occupied by yolky eggs inside the oviducts; the rest of the visceral organs are pushed aside."
Because of their oversized tongues, ovaries and testes, biologists have affectionately nicknamed Thorius the "tongue-flipping gonad" of salamanders.
Unfortunately, even as we continue to discover new species of this remarkable genus, Thorius salamanders are rapidly disappearing, paralleling the global decline in amphibians of all shapes and sizes. "It's very hard to say definitively what's causing their decline," Hanken said, noting that habitat destruction, pesticide poisoning and climate change are all likely factors. We also can't rule out the possibility that the deadly chytrid fungus which has decimated other amphibian populations in central and south America has infected Thorius, too.
"There is no simple solution, but there are longterm solutions: Lessen and hopefully stop global warming and other climate change, preserve large tracts of forest, eliminate dangerous pesticides and herbicides," Hanken said.
Those are big challenges — but if the plight of these tiny salamanders doesn't make you want to help the planet, I don't know what will.
Thorius longicaudus, one of three newly described species.