Frogs of the United States and Canada, 2-vol. set

Family Leptodactylidae

Family Leptodactylidae Leptodactylus fragilis (Brocchi, 1877) Mexican White-lipped Frog ETYMOLOGY fragilis: from the Latin frag meaning ‘brittle.’ The meaning of the name in relation to the frog is unknown. NOMENCLATURE Synonyms: Cystignathus caliginosus, Cystignathus fragilis, Leptodactylus albilebris, Leptodactylus caliginosus, Leptodactylus gracilis, Leptodactylus labialis [in part], Leptodactylus melanotus, Leptodactylus mystaceus There is some discussion in the literature as to which specific epithet, fragilis or labialis, has priority for this species. I follow the nomenclature recommended by Heyer (2002), Heyer et al. (2006), and Crother (2008) in using fragilis. Heyer (2002) and Heyer et al. (2006) discussed the nomenclatural history in detail and provided a synonymy. IDENTIFICATION Adults. This is a very streamlined frog with a pointed snout. The ground coloration is olive yellow, olive, brown, or reddish brown, with dark dorsal irregular spots. These spots may or may not be circled in white. There is a distinctive white or cream stripe on the upper jaw and a dark stripe from the nostril to the tympanum. Dorsolateral and lateral folds are present. There is no webbing on the long fingers and toes, and there are no terminal disks on the digits. There is a distinct disk on the belly. Sexual dimorphism is not present. Males are 27–43 mm SUL and females are 30–44 mm SUL (Heyer et al., 2006). Larvae. At hatching, tadpoles are nearly invisible except for their yolk sac. After several hours, they begin to attain a light brown coloration. Mature tadpoles are dark brown with an elongate snout. Nostrils are nearer the eyes than the snout. Tails are long, ending in an obtuse point. The tail musculature is cream and heavily pigmented with brown. Venters are pale brown. The tail fins do not extend onto the body, are translucent, and heavily marked with brown, especially on the dorsal fin. Mulaik (1937) described and figured the larval mouthparts. Heyer et al. (2006) described the larva in detail. Eggs. Eggs are light yellow and lack gelatinous envelopes. The vitellus is about 1.5 mm in diameter (Mulaik, 1937). DISTRIBUTION This species occurs from extreme southern Texas in the Rio Grande Valley (Cameron, Hidalgo, and Starr counties) to central Colombia and northern Venezuela. Important distributional references include Dixon (2000) and Heyer et al. (2006). Distribution of Leptodactylus fragilis LEPTODACTYLUS FRAGILIS 437 call from these cavities. Mulaik (1937) described the call as resembling the “plunk-plunk” from a drop of water falling into a cave pool, although Heyer et al. (2006) described it as “a rising harsh whistle.” Calls are given at the rate of 120–150 calls/min with a call duration of 0.16–0.2 sec. The call begins about 600–750 Hz and has a fast rise in intensity during the first third of the call, a weak increase in the next third, and another weak increase followed by a sharp drop in intensity at the end. The call rises to 1,000–1,200 Hz. The dominant fundamental frequency is 740–780 Hz in Texas (Fouquette, 1960; Heyer et al., 2006). Males call in the late afternoon and night during the rainy season. Males will also call away from the nest depression . The female responds to the male’s call and moves toward him. As she moves next to him, he leads her to the shallow depression. During this movement, the female makes what appears to be a reciprocal call, consisting of a rapid series of short notes or trill that is barely audible (Bernal and Ron, 2004). BREEDING SITES Mulaik (1937) found a clutch in a shallow depression 4 cm in diameter and 3 cm deep at the base of a grass hummock 30 cm from the nearest water. Male frogs of the genus Leptodactylus typically excavate similar shallow cavities located near ponds or pools for egg deposition. FOSSIL RECORD Fossil Mexican White-lipped Frogs are reported from Pleistocene deposits in Tamaulipas, Mexico (Holman, 2003; Heyer et al., 2006). SYSTEMATICS AND GEOGRAPHIC VARIATION Leptodactylus fragilis is a member of the fuscus group of the genus Leptodactylus, a diverse assemblage of >23 species that inhabit the Neotropics (Heyer, 1978). ADULT HABITAT The habitat of this species in Texas was described as “moist meadows, irrigated cane fields, drains and gutters in towns, beneath stones, logs, in sandy banks and fields; near streams and marshy places” (Wright and Wright, 1938). TERRESTRIAL ECOLOGY Nothing is known concerning the life history of L. fragilis at the northern end of its range. Mexican White-lipped frogs are unclassifiable...