Comprehensive DescriptionRead full entry
Allobates chalcopis is a small, slender-bodied frog with a snout-vent-length of 17.4 mm for males, and 16.1-18.4 mm for females. The head is a little bit wider than it is long. The snout is short and bluntly round in dorsal view and truncate in profile. The eye diameter is 2.9 mm. The diameter of the tympanum is 40% that of the eye. The diffused, weakly defined supratympanic fold obscures the posterodorsal part of the tympanum. The loreal region is slightly concave and the nostrils weakly project laterally. The dorsum, flanks, and ventral skin are all smooth, with some poorly defined tubercles located anterior to the anal opening, which is directed posteroventrally. Dorsolateral stripe, oblique lateral stripe, and ventrolateral stripe are absent. The forelimbs are slender and relatively long with unwebbed fingers lacking fringes. The first finger is barely shorter than the second, or equal in length. The terminal discs are somewhat expanded, with the disc on finger 3 being 1.4 times larger than the discs on the adjacent phalanges. The subarticular tubercles are oval-shaped and low. The thenar tubercles are large and round but the palmar tubercles are twice the size and are somewhat rounded. The hind limbs are moderately slender. The proximal half of the tarsus has a low, small tubercle. Inner and outer tarsal folds are absent. The outer metatarsal tubercle is rounded, elliptical, and three-fourths the size of the round, inner metatarsal tubercle. The toes lack lateral fringes. Some remnant, skin-like webbing is barely visible. The discs on the toes are slightly expanded. Toes 1-5 have 1-1-2-3-2 subarticular tubercles, respectively. The tubercles on the toes are small and rounded. Vocal slits are present. The dentigerous processes of the vomers are absent (Kaiser et al. 1994).
At the type locality, Allobates chalcopis can be potentially confused with Eleutherodactylus johnstonei and Eleutherodactylus martinicesis. The juveniles of these species are very similar in coloration to the juvenilles of Allobates chalcopis, which have not yet developed their ventral coloration. The presence of digital scutes quickly allows for differentiation. Also, the snout of Eleutherodactylus is more elongate. Other diagnostic characteristics of Allobates chalcopis include: disc of Finger 3 is expanded, Finger 1 same length or barely shorter than Finger 2, vestigial toe webbing that is barely visible, absence of dorsolateral, oblique lateral, and ventrolateral stripes, absence of outer tarsal fold, disc on toe 3 is expanded, some individuals have markings on the chest and throat, light orange belly, males have dark pigmentation on throat that cover the entire hyoid region, endotrophic, nidicolous larvae, and the finger III is not swollen (Kaiser et al. 1994).
In life, the dorsum is a pale brown with some darker brown markings. There is a triangle mark in between the eyes, but this character is not well defined in many of the paratopotypes. There is also a "u"-shaped marking on the snout, which was also indistinctive in some of the paratopotypes. Males have a dark, black, throat coloration, which fades into a dark gray anteriorly, and a black collar which covers the hyoid region. Females do not have such coloration of throats or hyoid regions and instead, have a homogenous pale orange throat and venter. Males also have a light orange venter. The eye is a brown with the upper portion of the iris being a copper hue. When preserved, the brown and dark brown markings on the dorsal side become gray and dark gray, respectively. The "u"-shaped marking between the nostrils is dark, the bottom on this marking being on the upper lip. The triangle in between the eyes has its apex region pointing posteriorly. The head has a strong strip along the canthus rostralis from eyes to nostril. There is an additional line, not as defined, which goes along the upper lip, parallel to the canthus rostralis. There is a dark supratympanic stipe that extends from the eye just past the tympanum that connects to a dark wedge. At the scapular level, there are two small, dark bilateral marks with pale centers. There are two more bilateral black spots at the posterior lateral sacral regions. On the anterior sacral region, there is an expansive dark mark. A diffuse pale band that stretches transversally across the thighs surrounds the dark brown anal region. The gray flanks have two dark brown bands; one of these bands is posterior to the forelimbs while the other band is anterior, obscuring the upper portion of the tympanic region. The forelimbs are light brown on the dorsal surface; the upper arm has some gray shading, diffused dark longitudinal stripes both anteriorly and posteriorly. There are also two dark stripes across the lower arm and lighter ones across the fingers. The digital discs of Fingers 1 and 2 are white while those of Fingers 3 and 4 are a little darker. The hind limbs are light brown on the dorsal side with dark bars across the entire length. Each limb has four narrow bars: one on the thighs, one on the shanks, one of the tarsus, and on across the base of toes. The toe pads and scutes have color to them while the throat is a homogenous gray with a black collar decorating the hyoid region. The chest and the abdomen have lost their pale orange coloration and are instead a pale gray with a light reticulated pattern on the abdomen. The limbs are grayish white ventrally (Kaiser et al. 1994).
Allobates chalcopis is the only known oceanic dendrobatid. Most of the native amphibians known from the Lesser Antilles are from the genus Eleutherodactylus but others include Leptodactylus fallax, Prisimantis euphronides, Pristimantis shrevei, and Allobates chalcopis (Fouquet et al., 2013).