Harlequin Frog

Atelopus limosus males have a snout-vent length of 26.5 - 30.7 mm while females have a snout-vent length of 38.9 - 40.2 mm. The species’ head is narrower than the body and is slightly wider than it is long. Males possess a small vocal sac. The pupils are horizontal and elliptical. It has a tapered snout, and lacks a tympanum. Prominent thick supratympanic crests are present, as are small but defined parotids. The dorsal skin appears smooth, and the ventral skin appears cracked; however, the skin is revealed to be finely granular under low magnification. The granules are most conical and elevated on the front legs. Folds are present on the knees, though tarsal folds and ulnar folds are absent. In males, forearms are robust and considerably more robust than the arm; in females, both parts of the arm are similarly robust. No information is available regarding the relative lengths of all the digits. On the hand, digits II-IV are thin and slightly expanded at the tips. Digit II of the hand is significantly longer than digit I, which has a keratinized pad. The toe tips range from round to oval, and vestigial webbing is present between digits. The webbing is especially prominent between digits II and III. The inner metatarsal, which is long and oval, is 2.5 times larger than the outer metatarsal, which is prominent and round (Ibáñez et al. 1995).Atelopus limosus can be distinguished from other Atelopus species by a combination of the following characters: pointed snout, small defined parotids, absent tympanum, smooth dorsal skin, cracked ventral skin, vestigial webbing on the hands, slender fingers except the thumb, moderate webbing on the feet, absent tarsal fold, heel reaching the posterior border of the orbit when limb extended along body, typically dark green dorsal coloring which may be olive brown in females, males with a black lateral line dividing the back and underside, typically white ventral coloring with small black spots on males and partial to complete orange ventral coloration in females. Furthermore, A. limosus can be distinguished from A. certus, A. chiriquiensis, A. glyphus, A. senex, A. varius, and A. zeteki by its dark green or olive brown back with no spots, and the males have a black line running down the sides of its chest (Ibáñez et al. 1995).In life, this species usually has a solid dark green black that may be olive brown in females. Males have a black line dividing the underside and back, which may be thin, irregular or thick. The underside of males is typically white with small black spots, particularly on the throat. The posterior end of the underside may be orange in some males. The underside of females is completely or partially orange, but some white coloration and yellow and green spots may also be present. The thighs may be grayish yellow, the arms are white, and palms and fingertips are yellow. The iris is green. In preservative, the back is dark gray. The flank is gray with a dark line separating the back from the underside, which is white with scattered black spots (Ibáñez et al. 1995).There are two varieties of this species: the lowland variety may be brown with yellow nostrils and fingertips, whereas the highland variety may be green and yellow with a black V-shaped pattern on its body (Wilson 2014).The species authority is: Ibáñez, R. D., Jaramillo, C. A., & Solís, F. A. (1995). Una especie nueva de Atelopus (Amphibia: Bufonidae) de Panama. Carribean Journal of Science 31, 57-64.

Atelopus limosus occurs in central Panama at elevations of 10 m to 730 m asl. It has been recorded in Parque Nacional Chagres. It inhabits tropical lowland forests where there are tall trees with a shrub understory. During breeding, it is found in nearby permanent forest streams (Ibáñez et al.1995, La Marca et al. 2005, Stuart et al. 2008).

This species is diurnal and typically found on the slopes and banks of narrow rocky streams in primary forests. It has never been found residing in areas far away from said moderately flowing streams. The silt in these streams matches the frogs’ color; thus, the frogs are inconspicuous on the surface (Ibáñez et al.1995).A mating pair was observed one November (during the rainy season); in this instance, the frogs were engaged in axillary amplexus on a rock jutting out over a stream (Ibáñez et al.1995).Embryos hatch as free-living larvae, and they use their ventral suction disks to cling to rocks in flowing streams. More than 50 tadpoles may hatch per clutch, and highland tadpoles are nocturnal (Amphibian Ark 2009a, Amphibian Ark 2009b).Atelopus limosus males call. Two call types have been noted: the advertisement call and the short call. The advertisement call occurs at average ambient temperatures of 26°C and lasts 260 ± 30 milliseconds at a dominant frequency of 2689 Hz. This call is described as sharp soft trill with pulses that gradually increase in amplitude and frequency and then decrease in amplitude. The call is similar to that of A. varius and A. zeteki, though it is of a shorter duration, consists of more pulses per second and is a higher frequency. Between advertisement calls at the edge of a stream, a male was observed to move in a < 50 cm radius while occasionally waving his left arm and extending both rear limbs in a motion described as a horse kick. Both these limb movements displayed the yellow areas on the palms and toe tips (Ibáñez et al. 1995).The short call occurs at average ambient temperatures of 21°C and lasts 10 ± 3 milliseconds at a dominant frequency of 2082 ± 44 Hz. This call occurs when the male is handled, and it is described as a soft cheeping sound. The short call of A. limosus is similar to that of A. zeteki but is of shorter duration and higher frequency (Ibáñez et al. 1995).

The population size was noted to be stable and reasonably common up till 2009 but is now declining dramatically, and it is predicted that the entire Atelopus genus will soon be extinct. These dramatic declines are largely attributed to decreases in the extent and quality of its forest habitat due to agriculture and infrastructure development. Other habitat threats include water pollution from domestic and urban wastewater, erosion, stream sedimentation, and mining and quarrying activities. Gold mining has been particularly damaging to local habitats, and this has been suggested as a threat especially to egg and larval development (Ibáñez et al. 1995, Luger et al. 2009, Stuart et al. 2008).Though other members of Atelopus have been severely affected by chytridiomycosis, some scientists postulate that A. limosus occurs at a low enough altitude where the disease is less impactful. Studies have shown that lowland frogs are able to inhibit the growth of chytrid fungus on their skin due to increased ambient temperatures. Bacteria found on the skin of A. limosus may also play a role in its protection from the fungus, though this is not entirely certain (Flechas et al. 2012, Stuart et al. 2008).As a result of its endangered status, the Panama Amphibian Rescue and Conservation Project has a captive-breeding project for Atelopus limosus (Wilson 2014).

Atelopus limosus is not typically collected by humans except in limited numbers for conservation and captive-breeding efforts (Pessier et al. 2014).

Atelopus limosus, the limosa harlequin frog (Spanish: sapo limoso) is an endangered species of toad in the family Bufonidae endemic to Panama. Its natural habitats are stream banks in tropical moist lowland forests and rivers of the Chagres watershed in central Panama.