Credit: © 2014 Iskandar et al
One of the most incredible new vertebrates last year was the Sulawesi fanged frog, Limnonectes larvaepartus. Apart from 2 big teeth in the front of the jaw, the animal had internal fertilisation and was viviparous, in order to cope with unique conditions on the island. Hardly your typical frog. From the Institut Teknologi Bandung and the University of California in Berkeley, Djoko T. Iskandar, Ben J. Evans, and Jimmy A. McGuire presented their paper on New Year’s Eve on this
Novel Reproductive Mode in Plos One
Sulawesi has the kind of tropical rainforest we should all walk in, just to sample the sounds and the sights that are possible in this richest of all environments . Tiny, but totally evolutionarily biodiverse in its isolation, the islands fanged frogs first appeared to science in the 1990s. Although viviparous amphibians are known, this is the only live-bearing frog, but one of 15 species of the genus Limnonectes on this one island. The big species live in fast flowing rivers, weighing in at up to 900g (just 1oz under 2lb)The little ones live more on land, in streams and in leaf litter.
Among the anuran frogs, some look after their young and some don’t. Parental guards are quite common,
back-packing is also used and pouches are known from the so-called marsupial frog. Males also use the vocal sac for development and an extinct species developed in the stomach! Only this species has live young born directly however, which in itself is a type of parental care. Others simply plop out the developed eggs which promptly hatch.
Internal fertilisation, supposedly a feature of mammals, is found in birds, reptiles and fish, so there is no surprise in some anurans doing it.The African toads, Netophrynoides and Nimbaphynoides with another extinct species from Puerto Rico all combine internal fertilisation with live birth.
The new frog in found in the northern arm of Sulawesi and the west of the central part of the island. Disturbed and natural habitats are used, with other fanged frogs also present, including one of the large river-living species, which would readily eat it. Flying lizards and tarsiers are their companions in the rich forest there. It is only 3.7 to 4.0cm long and has well-webbed hind feet, unlike similar species. The paper gives you other species you might find if you are ever lucky enough to visit. 50-100 eggs can be incubated, with no jelly needed! Yolk is provided on tap in the oviduct and the birth can be delayed till the tadpole is well-developed (or possibly even a froglet) or brought forward, presumably in case of a maternity emergency!
I hope the authors enjoyed their investigation of adaptive radiation in a small group of frogs as much as we enjoyed the understanding of their unique situation in this rich ecosystem. It almost seems as if the larger species could rely on their smaller cousins if another food supply ran out! The South American Dendrobates’ fatherly behaviour reminds me of intraspecifcc predations, just like the wild African clawed toad, Xenopus laevis. Enough supposition though- I’ll leave that to the research that is bound to come after such discoveries. (Look at the female’s quivering abdomen in the paper’s video, S1, to experience some of the thrill of amphibian research.)