You’re probably all familiar with the slimy, jelly-like frogspawn from which tadpoles emerge; the vast majority of frogs reproduce this way, with females laying eggs which are then fertilized by males. But it turns out there is a species of frog out there that reproduces in a very different way, which is also completely new to science: the female gives birth to live tadpoles.
This frog, which is found in Indonesia, joins only around 10 other known species of anurans (toads and frogs) out of almost 6500 which display internal fertilization. Scientists have now described this intriguing frog for the first time in the open access journal PLOS ONE.
Anurans are known to display a remarkable variety of reproductive strategies and parental care methods. Most exhibit external fertilization, where the male embraces the female and fertilizes her eggs with his sperm as she lays them. Some species will then guard the eggs, whereas others carry them in pouches or depressions on their backs, or even in their mouths. Two frog species were even known to swallow their fertilized eggs, which then developed in the stomach before emerging from the mouth as froglets.
Despite this intriguing array of reproductive methods, only around 10-12 species have evolved ways to fertilize eggs inside the female. Furthermore, the mechanisms employed by the frogs to achieve internal fertilization are, in general, poorly understood. The exceptions are two species found in California which use a penis-like “tail” to facilitate the transfer of sperm. These frogs still lay eggs, although they are obviously fertilized, whereas the other documented species known to display internal fertilization give birth to froglets (immature frogs).
But the newly documented frog species displays a mode of reproduction that is unlike any of these previously described strategies, which is exciting. The discovery was made last summer as herpetologist Jim McGuire from the University of California, Berkeley, was scouring a rainforest in Sulawesi, Indonesia. The frog had actually first been spotted some years ago by McGuire’s colleague, but the species had not been described in the literature until now.
McGuire actually first caught what he believed to be a male, until it squirted a bunch of tadpoles all over his hands. The team had their suspicions that this particular species, which has been named Limnonectes larvaepartus, displayed this particular reproductive mode, but they had no proof prior to this trip. In total, McGuire and his colleagues either observed tadpoles in the oviducts of dissected frogs or direct birth of tadpoles 19 times throughout the expedition. They also saw several clutches of tadpoles in small pools, away from streams, which could be a strategy to avoid bigger frogs residing in these areas.
The newly described species is a type of fanged frog- one of potentially 25 residing in Sulawesi, although only four have been so far described. These frogs don’t actually have fangs, but have projections from the lower jaw which are used in fights. These frogs range in size from almost a kilogram (2 lbs) in weight to just a few grams. The tiny L. larvaepartus is around 5 grams (0.2 lbs) on average.
[Via University of California- Berkeley, PLOS ONE, Live Science and BBC News]
