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Wednesday, March 22, 2006


Black-spotted frog

* Japanese name: Tonosama-gaeru
* Scientific name: Rana nigromaculata
* Description: Males of this handsome frog grow to about 70-mm long, while females are slightly larger at 77 mm. They vary in color, from lime green to gray-brown, but they all have a pattern of black spots down the flanks of their body.
* Where to find them:In and around rice fields and streams in non-mountainous parts of Honshu and Kyushu. The frogs were introduced into Hokkaido and can also be found there. When adult, frogs are mainly terrestrial, returning to the water to mate and lay their eggs, and occasionally to feed. The eggs they lay are more "primitive" than those of reptiles, in that they lack a hard shell. This means that the eggs rely on the moisture of the surrounding water -- if the water dries up, so do the eggs, so it is important for the females to lay them in a reliably wet place. The tadpoles, of course, are completely aquatic, developing legs as they grow, gradually losing their tail and finally emerging onto land. The tadpoles also lose their internal gills that allow them to breathe underwater, and develop lungs.
* Food:These frogs are opportunist hunters, and eat whatever prey they come across, meaning that their diet changes with the seasons. They also take larger animals as they themselves grow, but generally they are not fussy eaters. They have a sticky tongue which helps them keep hold of struggling prey such as crickets and grasshoppers.
* Special features: The skin has anti-microbial properties. It contains several peptides (molecules made from amino acids) that give it a broad spectrum of protection against different sorts of potential attack. Thus bacteria, yeast and other microorganisms that settle on the frog can't grow and cause the animal health problems. The peptides work by busting open the cell membranes of the attacking microorganism, killing the cell. Interestingly, meanwhile, a frog discovered recently that lives by a noisy stream in China has been found to communicate ultrasonically. All frogs croak, but the deep croak noise doesn't transmit clearly over the noise of rushing water. The Chinese frogs -- and perhaps others that live in noisy water environments -- solve the problem by emitting ultrasonic squeaks, like dolphins and bats, to communicate with other frogs.


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