IUCN threat status:

Least Concern (LC)

Comprehensive Description

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Description

Bolitoglossa occidentalis has a snout-to-vent length ranging from 28 – 41 millimeters, with a mean snout-to-vent length of 35.3 millimeters. It has a relatively flat head that is wider than its body. The skin on its head has rudimentary indentations, and the length of its eye is about the same as the length of its snout. The rear part of its eyelids end in a diagonal fold, and there is a groove that starts from the eye and runs down its back. It has grooves on its throat that go a short distance up its neck. The skin on its neck and back is smooth, whereas the skin on its sides is wrinkled. Its body is relatively short, and it has 13 costal grooves which are very faint and do not reach the ventral side. Its digits are fully webbed, and it lacks subdigital pads. The ratio of its tail length to its snout-to-vent length is 0.80 +/- 0.2mm, and it has trace lateral grooves that run down its tail (Alberch and Alberch 1981, Alberch 1983, Green and Alberch 1981, Larson 1983, Taylor 1941).

Bolitoglossa occidentalis individuals are characterized by small body size, fully webbed hands and feet, fusion of the tarsals and carpals, the absence of prefrontal bones, the reduction of phalangeal elements, a relatively short tail, and a reduction in skull ossification (Alberch and Alberch 1981).

The prefrontal bone does not form in Bolitoglossa occidentalis (smaller size permits this), unlike in related species, B. rostrata and B. subpalmata. Similarly, the third phalanx of the fourth digit does not exist in Bolitoglossa occidentalis as it does the two previously mentioned species. The tail of B. occidentalis appears shorter than in other Bolitoglossa because it has a relatively bulkier body (Alberch and Alberch 1981).

The allometric patterns in the rate of increase in foot surface area compared to body weight are analogous for the three species B. rostrata, B. subpalmata and B. occidentalis, despite major variation in foot shape. However, truncation occurs early in development of B. occidentalis, accounting for the webbed condition found in this species (Alberch and Alberch 1981).

In life, the dorsal coloration can range from gray to dull brown with dark lavender-brown markings present above the eyes and crossing the neck. The lower half of its body and its tail are streaked with cream and light brown spots. The sides of the head, body and tail region are the same as dorsal coloration. The ventral surfaces are generally lighter in color, and may be punctuated by tiny spots of pigment (Taylor 1941).

Color patterns vary considerably, however lines above the eyes and neck are typically distinct. The backsides of the neck and base of tail are generally lighter than the rest of the back. Some individuals may have a darker vent with noticeably lighter flecks (Taylor 1941).

The species authority is: Taylor, E. H. 1941. New Amphibians From the Hobart M. Smith Mexican Collections. The University of Kansas Science Bulletin 27:141-167.

Bolitoglossa occidentalis is a sister species to B. rufescens; both are characterized by an inflated nasal region, the absence of folds under the tongue, and webbed hands and feet (caused by the absence of the gene that causes apoptosis in salamander toes). However, they do differ somewhat in general coloration and the presence of maxillary teeth (Taylor 1941).

“Bolito” is derived from the Latin term “boletus” meaning mushroom, ultimately stemming from the ancient Greek word “bolos” -- a lump or clod. “Glossa” stems from the Greek word “glosso”, meaning tongue. “Occidentalis” is a Latin adjective mean “western” (Online Etymology Dictionary).

The partial fusion of the ascending processes of the premaxilla was observed in one specimen of Bolitoglossa occidentalis in 1983. This type of fusion is not typical for Bolitoglossa, but is present in other plethodontid genera. It is unable to move its digits independently, and instead the entire foot acts as one fused “plate” (Alberch 1983, Alberch and Alberch 1981).

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