IUCN threat status:

Endangered (EN)

Comprehensive Description

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Description

Phyllobates vittatus is a small frog, with males reaching 26 mm in SVL and females measuring up to 31 mm in SVL (Leenders 2001). The skin on the dorsal surfaces is slightly granular or shagreened, with tiny bumps (Silverstone, 1976). Skin is also slightly granular on the belly and the ventral surfaces of the thighs, but smooth on the rest of the ventral surfaces (Silverstone 1976). Both maxillary and premaxillary teeth are present (Silverstone 1976). Finger I is longer than finger II. The toes lack webbing (Silverstone 1976).

The back and head are generally solid black, although in some individuals there is an interrupted yellow median dorsal stripe. A wide gold, red-orange or orange dorsolateral stripe runs from each side of the snout over the eyes and back, down to the base of the thigh. A single white line projects from the shoulder, at the insertion of the upper arm, and runs along the lip to just under the eye. The dorsal surfaces of the limbs show dense blue-green speckling on a black background, while the venter and ventral surfaces of the limbs are marbled with white or pale blue-green on black. Each flank has a white or pale blue-green stripe running ventrolaterally (Silverstone 1976).

The tadpole coloration is uniformly dark brown on the dorsal side of the body, tail, and fins, with the venter being a lighter brown (Savage 2002). Tadpoles develop the paired bright-orange stripes characteristic of the adults about two months after hatching, near the time of metamorphosis (Leenders 2001). Larvae reach 30 mm in total length (Savage 2002). The body is depressed (Savage 2002). Nostrils and eyes are located dorsally, while the mouth is ventral (Savage 2002). The oral disc is small and emarginate, with serrated beaks and 2/3 rows of denticles; the row of denticles just above the beaks shows a gap in the middle (Savage 2002). Papillae are present both above and below the mouth but those above the mouth are not continuous (Savage 2002).

Phyllobates vittatus secretes batrachotoxins, which are lipophilic alkaloids that act as extremely potent cardiotoxins (Myers et al. 1978). Batrachotoxins bind to voltage-gated sodium channels and force them to remain open, with the resulting influx of sodium ions causing irreversible depolarization of nerve and muscle cells. This in turn leads to arrhythmias, fibrillation and eventually cardiac failure (Albuquerque and Daly 1977). These compounds are known to be secreted in high quantitities in several South American Phyllobates (P. terribilis, P. bicolor and P. aurotaenia), and in low quantities in the Central American Phyllobates vittatus and P. lugubris (Myers et al. 1978). The South American Phyllobates have all been documented to be used to poison darts, unlike the Central American Phyllobates (P. vittatus and P. lugubris), which are far less toxic (Myers et al. 1978).

Like other dendrobatid frogs, Phyllobates species are thought to acquire their toxins from dietary sources (Daly et al. 1980; Daly et al. 1992; Dumbacher et al. 2004). One source for batrachotoxin may be melyrid beetles, which have been shown to contain high levels of this toxin (Dumbacher et al. 2004). Melyrid beetles may also be the dietary source for batrachotoxin in the toxic New Guinea passerine bird genera Pitohui and Ifrita (Dumbacher et al. 2004).

Despite the fact that P. vittatus contains small quantities of batrachotoxins when compared to the far more toxic South American Phyllobates terribilis, P. bicolor, and P.aurotaenia, Myers et al. (1978) report that tasting a wild-caught P. vittatus resulted in a "lingering, almost numb sensation on the tongue, followed by a disagreeable tightening sensation in the throat". A captive snake (Rhadinaea taeniata aemula, from Mexico, which presumably had never encountered frogs with batrachotoxins) exhibited considerable distress for some hours after seizing and releasing a P. vittatus (Myers et al. 1978). Initially the snake gaped and attempted to rub its mouth on the substrate; half an hour later the snake was also slowly contorting its body, as well as expanding its thorax, after which it laid motionless for four hours (Myers et al. 1978). Recovery was complete by the next morning (Myers et al. 1978).

A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).

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