Order: Caudata

Although rare to see, salamanders inhabit the rainforest undergrowth of Costa Rica's Osa Peninsula. They are very easily distinguished from all other amphibians by their long tail.  Despite the very rich variety of frog families represented in Costa Rica, there is only one salamander family: Plethodontidae. Plethodontidae is the world's largest salamander family containing about 240 species. This is about 60 percent of all known salamanders.

Forty-three species have been recorded in Costa Rica so far and diversity is greatest in the highlands. In January 2008 three species of salamander new to science were discovered in La Amistad International Park. La Amistad is Costa Rica's largest National Park and is also a UNESCO World Heritage Site. Four species of salamander are known from the Osa Peninsula, two of which are featured on this page.

 The two species pictured here, Oedipina alleni and Oedipina pacificensis, are know as worm salamanders. Why they are called worm salamanders is strikingly obvious when looking at one. With their very narrow build, long tail, tiny legs and feet, these salamanders resemble earthworms at first glance. They will also quickly squirm for cover like little worms when startled. Finding these exceptional creatures on the Night Tour is always a very lucky encounter. They spend most of their lives on the forest floor underneath the leaf litter or hiding under logs and rocks. Given their small size and cryptic coloration, a run in with a salamander is always an exciting and uncommon event. It seems they are more easily encountered moving about in the open during or after a heavy rain.

Salamanders are an extraordinary group. Worldwide, there are many variations in their lifestyles, reproductive habits, and development. Most salamanders inhabit the Northern Hemisphere with only a handful of species drifting south of the Equator. On this page, we will concentrate solely on Costa Rican salamanders.

All Costa Rican salamanders are lungless and gas exchange is believed to take place through their very thin skin membrane, as well as mucous membranes in the mouth and throat. Also, Costa Rican Salamanders have interesting receptors called nasolabial grooves. These little grooves run from the salamander's nostril to their upper lip and are believed to pick up chemical cues from their surroundings. A salamander may use this "sixth sense" in order to find a mate, avoid predators, or locate food.

Another weapon Costa Rican Salamanders employ while hunting is their very long projectile tongue. In some species the tongue may measure up to 80 percent of the salamander's body length and its tip is designed for gripping, almost like a hand. It only takes about ten milliseconds for salamanders to shoot their tongue out and snatch their unsuspecting prey!

When not in use, the tongue is rolled up and stored in the same cavity where the salamanders originally kept their lungs, which they have lost through evolution. A worm salamander's tiny legs and feet are another feature believed to have been brought about by evolution, to enhance their fossorial lifestyle.

The two worm salamanders featured here, Oedipina alleni and Oedipina pacificensis, are closely related. Adults normally measure between 108 and 175 millimeters, with Oedipina pacificensis being slightly longer. They are mainly fossorial and spend much of their time burrowing. For such small animals, salamanders are extremely long lived.

In Costa Rica, individuals have lived as long as 20 years. In one study group, males did not even reach sexual maturity until they were six years old and females at twelve years of age! This is remarkable for such small, delicate animals. Although, most species of lungless salamanders are able to breed within six months to three and a half years of hatching.

During their breeding season, male salamanders will go through complex courtship rituals to attract females. Male salamanders don't call in an attempt to attract a mate, so courtship is a proactive venture. This may include pursuit of the female, ritualistic dances, and caressing of the female by the male. Each species of salamander has its own unique mating dance.

The male will also make a small incision on the female's skin where he will rub her with his "mental gland". This gland is located underneath the male's chin and secretes pheromones designed to entice her to mate. Once she has been induced to mate, the male will lay his cone-shaped sperm packet, called a spermatophore,  on the ground and she will pick it up with her cloaca.

The female can store this sperm packet internally for up to two months. When she decides to lay her eggs they will be fertilized internally, as they leave the cloaca. Generally, females will lay from 9 to 37 eggs individually in a moist area on the ground. In some species the mother will curl around the eggs and guard her offspring. Parental care has never been recorded among the two species pictured here.

With every Costa Rican salamander, all of the larval development takes place inside the egg and the little salamander that hatches out is a miniature version of the adult. No metamorphosis takes place after hatching. Costa Rican salamanders are fully terrestrial and don't ever have an aquatic phase.

But perhaps their most incredible attribute is their ability for regeneration. As with many lizards, a salamander will drop its tail when gripped by it in order to escape a predator. But unlike lizards, salamanders will regenerate their tail complete with all its vertebrae!

Still not fully understood by science, this amazing skill is currently under heavy scrutiny by researchers. If one day scientists are able to solve this puzzle, could that mean a cure for severe spinal injuries in humans?

Oedipina alleni and Oedipina pacificensis are only known from southwestern Costa Rica and adjoining western Panama. The other two species of salamander living on the Osa Peninsula, which are not pictured here, are Bolitoglossa colonnea and Bolitoglossa lignicolor.

References:

Janzen, D.  1983  Costa Rican Natural History  University of Chicago Press

Leenders, T.  2001  A Guide to Amphibians and Reptiles of Costa Rica  Zona Tropical

Savage, J.  2002  The Amphibians and Reptiles of Costa Rica   University of Chicago Press