Silverstone's Poison Frog

Diagnosis:Ameerega silverstonei can be distinguished from other members of the Dendrobatidae family by its large size and the lack of stripes in its orange-and-black or red-and-black coloration. Dendrobatids with uniformly colored bodies that superficially resemble Phyllobates bicolor, can be readily differentiated by observing the coarsely granular skin on the lower back that is smooth in P. bicolor (Myers and Daly 1979). Description:Male adults are large and have a maximum snout-vent length of 38.3 mm. Females are typically slightly larger than males with a maximum snout-vent length of 42.8 mm. The head is generally as wide as the body and is characterized with a sloping and rounded snout. Teeth are present on the maxillary arch. Adult males possess a shallow subgular sac and have well-developed vocal slits in the mouth. The tympanum is concealed post-dorsally. The skin of the lower body and hind limbs is coarsely granular, gradually smoothing out in the skin of the head, forelimbs and ventral surfaces. The fingers are appressed and have a relative length of 3>4≥1≥2, each terminating in small expanded discs. Hands and feet lack webbing (Myers and Daly 1979). Coloration:Adults have an orange or red head and body and may have heavy black spotting or marbling. Hind limbs are all or partly black, and may have a concealed calf spot. The undersides of the head and body of A. silverstonei are variably pigmented, ranging from black to uniformly pale orange. Palms and the undersides of the fingers also vary from gray to bright orange (Myers and Daly 1979). Tadpole Morphology: Tadpoles are grayish or blackish-brown, with a few smatterings of darker spotting. The beak of the tadpole is keratinized, but does not appear of considerable size. The mouth has delicately toothed edges, and the lower beak has a broad V-shape. They have a single row of pointed papillae. As they age, late tadpoles acquire dull yellow pigmentation on their forelimbs, snout, and upper eyelids. The dark brown of the larvae darkens to black as they become froglets and the yellow changes to light orange, and sometimes into red thereafter. The orange area expands over the head and torso. This pattern is developed within a month or so, and expansion of the orange-reddish areas occurs after twelve months (Myers and Daly 1979).Species Authority:A. silverstonei was discovered in the 1940’s during road construction in Cordillera Azul in the Peruvian Andes. John C. Pallister collected the first specimen in 1946 and Charles Myers and John Daly first described it in 1979 (Myers and Daly 1979).Synonymy/Taxonomy:Ameerega silverstonei was originally classified as the genus Phyllobates and species bicolor. In 1976, Philip A. Silverstone observed that P. bicolor was restricted to the northern Andes of Colombia and it was therefore highly unlikely that the Peruvian frog was related to the Colombian P. bicolor. In 1979, Charles Myers and John Daly proposed that the frog be named after Silverstone for making this distinction. The frog was first put in the genus Epipedobates and was known for some time as E. silverstonei. Presently, it is recognized as a member of the genus Ameerega and is now known as Ameerega silverstonei (Myers and Daly 1979).

Ameerega silverstonei is endemic to Cordillera Azul, a small mountain range that flanks the eastern side of the Andes in Peru. The climate in Cordillera Azul, Peru is typical of montane tropical rainforest and the frogs are generally found at an altitude of around 1330 m above sea level (Icochea et al. 2004).

While there have been no observations or records of courtship in A. silverstonei, there have been recordings of their calls, which have been described as “retarded trill” calls. When they reach sexual maturity, males begin the mating trills to attract females. Their call is a series of short, similar abrupt whistles, distinctly spaced and produced at 4-6 notes per second (Myers and Daly 1979). It is assumed that females lay eggs more than once a year, and possibly throughout the entire year due to the constantly wet climate in which they live. The female lays her eggs terrestrially in a closely packed single layer. Clutches are usually made up of about 30 eggs and have been observed on leaves. Males guard the eggs while the tadpoles develop and subsequently carry them to water on their backs. Males have not been observed to defend eggs when clutches were approached (Myers and Daly 1979). To defend against predators, skin secretions contain small amounts of pumiliotoxin-A alkaloids, a toxin found in the skin of poison frogs. However, the secretions lack the more potent batrachotoxin alkaloids. Despite lacking great potency, A. silverstonei has bright coloration which deters predators. In one observation, a frog-eating snake (Chironius sp.) of the Cordillera Azul area, seized and then immediately released a member of the species. Afterwards, the snake seemed disoriented and tried to rub out its mouth with branches, indicative of the toxic deterrent in the frog’s skin. However, the poison was not fatal and the snake seemed to recover fully. Not much more is known of the predators of A. silverstonei (Myers and Daly 1979).

This species is threatened by habitat destruction, accommodating the agricultural expansion of humans. Illegal trade may also be a threat to the conservation of this species that is collected by local people for dealers. The population status and trends of this species are unknown, as there is insufficient data for the species (Icochea et al. 2004).Although there is not enough data to determine population size and whether or not it is declining, it has been observed that these frogs have a preference for living in undisturbed forests (Myer and Daly 1979). This makes them vulnerable to agriculture, logging operations, and road constructions that border their habitat.

Illegal trade has been recorded and could be a possible threat to the species (Icochea et al. 2004).

Silverstone's poison frog (Ameerega silverstonei; formerly Epipedobates silverstonei) is a species of frog in the family Dendrobatidae endemic to Peru. Its natural habitats are subtropical or tropical moist lowland forests and rivers.