That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

Harvard biologist David Blachurn knew he was onto something unusual when a benign-looking frog he was examining in Cameroon, West Africa kicked out and left him with a bleeding cut.  Unusual indeed – an article  (23 August 2008) in Biology Letters describes the hidden claws of Perret’s night frog as the only vertebrate claws known to break through the skin in order to become functional.  Some, or possibly all, of the other 10 frogs within the genus Astylosternus are also equipped with skin-covered claws on their toes (the fingers are clawless).

The frog’s sharp, curved claw is actually the last bone of the toe, and pierces the toe’s skin when a specific tendon is flexed.  It is assumed that the claw retracts after use and the skin heals, but further study is needed.  Other amphibians that experience “self-inflicted” wounds include the Surinam toads, Pipa spp., whose young push through the skin of the female’s back when ready to swim off on their own and the ribbed newt, Pleurodeles waltl.  The ribs of this newt pierce the skin of the back, carrying toxins with them, when the animal is threatened.

Despite the massive trauma caused by the emergence of 80+ fully formed little frogs, the skin of breeding Surinam toads (P. pipa) under my care appeared well-healed within 24 hours.  I’m sure there are some compounds that may be of medical use to people hidden in the body chemistry of this and other amphibian species.

Of course, people living within the habitat of Perret’s night frog have long known of its odd defense and even utilize specially-constructed spears when hunting it, to avoid being injured.

The only other frogs known to have claws are members of the family Pipidae – the various African clawed and dwarf African clawed frogs.  I have observed both putting their claws, which are always exposed, to interesting uses (more to come in future articles).

You can read more about this frog and related species at:
http://research.amnh.org/herpetology/amphibia/references.php?id=1191

An article to be published later this month (Zootaxa; August, 2008) will announce that a newly described Thread Snake from the Caribbean island of Barbados is the smallest of the world’s 3,100+ snake species.  The Barbados Thread Snake grows to a mere 4 inches in length, is no thicker than a strand of spaghetti, and can coil comfortably atop a quarter.  It subsists largely upon ant and termite larvae, and may be threatened by habitat loss.  A relatively large hatchling – ½ of the adult size – emerges from the single egg laid by the female (perhaps there is no prey species tiny enough to support a larger brood of smaller-sized young).

A related snake, nearly as tiny, has been discovered on nearby St. Lucia.  Two snakes within the genus dwell in the southwestern USA – the other 103 species are found in Mexico, Central and South America, the Caribbean, Africa, India and Pakistan.

The Penn State biologist who discovered the snake, Blair Hedges, seems to have a quite a flair for his work – he and his colleagues have named 65 new amphibian and reptile species on Caribbean islands, including the world’s smallest lizard and smallest frog.

Islands and other isolated habitats are often home to the largest (Komodo Dragons, Aldabra and Galapagos Tortoises) and smallest animals within a group.  Islands are difficult for many animals to reach, so those that do arrive often evolve into a variety of forms (and, eventually, species) to fill the many empty niches (specialized roles within a habitat) – in fact, Darwin’s theory of evolution was sparked by his observations of this process among finches on the Galapagos Islands.  Caribbean Thread Snakes, Australia’s monitor lizards and the African Rift Lake cichlids are likely examples of this phenomenon.

You can read more about other species of Thread Snakes at:
http://www.tigr.org/reptiles/families/Leptotyphlopidae.html

Indonesia’s Kalimantan jungle toad (aka Bornean flat-headed frog), Barboula kalimantenensis, has been declared the only frog known to lack lungs. The frog itself was not collected and described until 1978. The fact that it is lung-less was released on April 10, 2008, by Dr. David Bickford of the National University of Singapore. The picture listed here is courtesy of Dr. Bickford.

This aquatic frog, known only from the Kapaus River Basin in West Kalimantan, Borneo, relies upon its skin when breathing in its habitat’s cold, highly-oxygenated waters. Its flat shape may increase the surface available for oxygen absorption, but little else is known about its natural history. Since lungs increase buoyancy, their loss may be an adaptation to life in fast-moving waters (the frog might more easily remain stable at the stream’s bottom).

Many salamanders (i.e. North America’s red-backed salamander, Plethodon cinereus) and I species of caecilian (legless amphibians) are lung-less. Most frogs, especially aquatic species such as the African clawed frog, Xenopus laevis, a popular pet, use cutaneous respiration on occasion. Others have unusual means of assisting their lungs – the Lake Titicaca frog, Telmatobius culeus, does “push-ups” to increase water flow to its oxygen-absorbing skin folds, and male West African hairy frogs, Trichobatrachus robustus, obtain oxygen via hair-like skin projections.

Logging and mining are degrading water quality in the Kalimantan jungle toad’s streams, and threaten its continued existence.

You can read more about the frogs mentioned here at:
www.globalamphibians.org