Description
Bolitoglossa pygmaea is a small salamander, with males ranging from 23.6 to 32.6 mm and females from 23.6 to 36.8 mm in standard length. Tails are relatively short and do not exceed standard length. The head is somewhat broad with a rounded snout bearing large nostrils. Nasolabial protuberances are more visible in males but are small in both sexes. Eyes are large and protrude beyond the margins of the head. No sublingual fold is present. When limbs are adpressed to the body, the number of costal grooves visible (limb interval) is approximately 2.5. Limbs are relatively short. The hands and feet are relatively large with basally fused and broadly pointed digits, giving the appearance of webbing. Finger I and toes I and V are reduced in size. In order of decreasing length, fingers are 3>4>2>1; toes are 3>4>2>5>1. Postiliac glands are indistinct; however, collections of unicellular glands are noticeable on the lateral sides of the body, between the hindlimbs and the vent.

Teeth are relatively large and well developed, with a range of 3-6 premaxillary teeth, 18-60 maxillary teeth, and 15-25 vomerine teeth found in females. For males, the number of premaxillary teeth vary from 2-3, 27-44 for maxillary teeth, and 14-20 for vomerine teeth.

In alcohol, specimens are a very pale brown and appear translucent, except for a strikingly conspicuous black patch of internal pigment visible on the posterior venter. This black patch covers the peritoneal area (posterior abdomen) and stomach, as well as the testes in males, and can be seen through the ventral and lateral body wall. A brown line extends from the snout through each eye and past each shoulder, continuing as a poorly-defined stripe to the pelvic region. These lines then diffuse into a pair of weak stripes running the length of the tail. Transparent gland openings appear as silver circles between the hindlegs and on the ventral surface of the tail. A few melanophores are visible on the ventral surfaces. The iris is dark brownish-black.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Panama

View distribution map in BerkeleyMapper.

This species is endemic to Panamá, in the Provincia de Bocas del Toro, near the Costa Rican border. It has only been found on the Fábrega Massif, a plateau with a mean elevation above 3000 meters. Salamanders were found in grass tussocks, in an open area on the plateau.

Life History, Abundance, Activity, and Special Behaviors
The function of the ventral pigmentation is unknown. These salamanders are active by day at high elevations, where it is quite cool. Perhaps the pigmentation may serve to increase the stomach temperature and thereby the rate of digestion.

Comments
Bolitoglossa pygmaea is a member of the Bolitoglossa subpalmata group, subgenus Eladinea.

The specific epithet is derived from the Latin word pygmaeus, or pygmy, and the Greek word pygmaios, meaning dwarfish. It is currently the smallest salamander in the genus Bolitoglossa, smaller than B. minutula.

This species is thought to be miniaturized rather than paedomorphic, since its only paedomorphic trait is the lack of prefrontal bones (which are absent from many species of Bolitoglossa). Paedomorphic traits of small congeners such as B. occidentalis and B. rufescens include a less well-formed skull with an open dorsal fontanelle, the lack of vomerine teeth and mesopedial fusions in the limbs. These characters are not present in B. pygmaea. See Wake (1991) for a further discussion of miniaturization vs. paedomorphism.

References

Bolaños, F. and Wake, D. B. (2009). ''Two new species of montane web-footed salamanders (Plethodontidae: Bolitoglossa) from the Costa Rica-Panamá border region.'' Zootaxa, 1981, 57-68.

Wake, D. B. (1991). ''Homoplasy: the result of natural selection, or evidence of design limitations?'' American Naturalist, 138, 543-567.

Species Account Citation: AmphibiaWeb 2018 Bolitoglossa pygmaea: Pygmy Web-footed Salamander <https://amphibiaweb.org/species/7248> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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