Tuesday, January 17, 2012

Animal of the Week January 16, 2012 -- world's smallest frog

P amauensis on a US dime
This week's animal of the week (and I bet the email out it gets blocked by a few oversensitive filters) Paedophryne amauensis is a newly described species of frog that is not only the world's smallest frog, but actually the world's smallest vertebrate.

First discovered in Papua New Guinea in 2009 by researchers scooping up handfuls of leaf litter whence they could hear the frogs calling from, the species was formally described last week in a paper in the journal PLoS One. The frog, with an average adult size of 7.7 mm in length, steals the smallest vertebrate crown from the small Indonesian fish Paedocypris progenetica of the carp family. The frog is one of several species in the genus Paedophryne, all from Papua New Guinea, and all of pretty diminutive size. Such extreme small size has evolved several times in the frogs and toads, but nearly always in wet tropical forests and nearly always among frogs that develop straight into small frogs in their eggs rather than going through a free-living tadpole stage.

Other notable small animals include the smallest lizards, two gecko species from the Caribbean, about 15-18 mm long (not including tails), and miniature chameleons from Madagascar of about the same size. Perhaps the most famous small animal is the bee hummingbird, which at 5 cm and less than 2 g in weight is scarcely bigger than a large bee; this species is also from the Caribbean, hailing from Cuba. This weekend, while watching Great Barrier Reef -- a highly entertaining BBC series available on iPlayer -- I was introduced to the pygmy seahorse, a quite exquisitely camouflaged 2 cm beauty. The position of smallest mammal is contested by the bumblebee bat from Thailand and Burma, which is about 3 cm in length and weighs about 2 g and the Etruscan shrew, which is about 3.5-5 cm long (tail excluded) but weighs less than the bat at about 1.5 g; these shrews are widely distibuted from southwest Iberia to Malaysia.

But all of these animals positively dwarf our tiny champion, this weeks animal of the week Paedophryne amauensis.