Steindachner's Dwarf Frog

The genus Physalaemus is diagnosed by the following character combination: (1) tubercles absent on dorsum; (2) vomerine teeth absent; (3) hypertrophied antebraquial tubercles absent; (4) parotoid glands absent; (5) flank glands absent; (6) tympanic membrane not visible; (7) skull-mandible articulation never occurring anterior to the transversal plane of the junction between the alae and the cultriform process of the parasphenoid; (8) anterior margin of exoccipitals overlapped by frontoparietals; (9) quadratojugals and developed maxillary process of quadratojugals present; (10) eggs laid within foam nests (Nascimento et al. 2005).P. ephippifer is a stockier member of the cuvieri species group. The cuvieri group can be described by the following character combination: size small to moderate (21.0- 39.6 mm SVL); head as long as wide; dorsum lacking tubercles; snout rounded or sub-elliptical when viewed from above, rounded and protruding when viewed in profile; canthus rostralis is rounded and the loreal region is concave; presence of tarsal fold, except in P. fischeri (though Lynch 1970 compared the group members and did not find a tarsal fold for any species other than P. pustulatus); presence of tarsal tubercle; external and internal metatarsal tubercles conical, lacking keratinized margins and having the same base length; fringe absent on fingers but may or may not be present on toes;; toes lacking webbing; vocal sac well developed; inguinal glands present or absent, but small if present and never associated with a dark ocellus; glandular ridge absent; broad glandular area on flanks absent; sacral gland present or absent, and variable within a species; skull slightly wider than long; skull-mandible articulation on same transversal plane of intersection between the alae and cultriform process of the parasphenoid; distance between nasals is narrow, except for P. cicada; nasals overlap the anterior margin of the sphenethmoid; parietal portion of the frontoparietal is enlarged; fontanelle on frontoparietal is not exposed; angle between ventral ramus of squamosal and maxilla varies between 42° to 66°; vomerine dentigerous process is broad and well-developed; well-developed neopalatines present; anterior ramus of pterygoid contacts neopalatine; parasphenoid cultriform process is medium-sized and spike-shaped; both premaxillary and maxillary teeth are present; anterior hyale processes are present; constriction at the base of alary processes of the hyoid plate; and hyoid has a slightly broad to broad alary process (Nascimento et al. 2005).Diagnosis - A small Physalaemus (males 26- 28 mm) of the cuvieri group; dorsum brown with darker spots; flanks dark brown from !oreal to inguinal regions; transversal dark brown bars on the upper surface of limbs; venter cream with brown reticulations in the pectoral and gular regions (Martins 1998).Lynch (1970) also noted the following characteristics for P. ephippifer: first finger not longer than second; body glands (parotoid, flank, inguinal) are absent, and males have large subgular vocal sacs and nuptial pads.P. ephippifer has a diploid chromosome number of 2n=22, with pairs 3. 4, and 7 being submetacentric, and the rest being metacentric. This species also has heteromorphic sex chromosomes (a female-specific W chromosome and a male-specific Z chromosome, pair 8) (Nascimento et al. 2010; Conte et al. 2011). First described by Steindachner (1864).

Physalaemus ephippifer is found in central and eastern Amazonian Brazil, eastern Venezuela (Gorzula and Señaris 1998), Suriname (Furness et al. 2010) and apparently occurs in Guyana as well (Ernst et al. 2005), although this has been questioned by Frost. It inhabits both anthropogenic habitats and forest clearings and edges, with an altitudinal range of 0-350 m asl (Reynolds et al. 2004). During the day it is found in leaf litter; at night it can be found in pond or lake shallows (Martins 1998).

This species is nocturnal. During the day, these frogs bury themselves in the loose soil. They can survive long dry periods underground. With the start of the rainy season in February, the three-month mating season begins. Males call after dark, usually in chorus, from shallow water in temporary ponds or open areas such as a cattle meadow (Hodl 1998, 1990), or from forest lakes (Martins 1998). The advertisement call has been described as "whine-like," ascending initially then decreasing in frequency, followed by a series of about 5 pulses (Kaefer et al. 2011). The whine functions in mate recognition, while the pulses may have a similar function in enhancing attractiveness to females as the chucks and squawks of the related and well-studied species P. pustulosus and P. petersi) (Kaefer et al. 2011). However, the chucks and squawks of P. pustulosus and P. petersi are facultative (not present in every call), while the pulses were found to be an integral component of P. ephippifer calls recorded at Maracá Island, Roraima State, Brazil and Monte Alegre, Pará State, Brazil. An earlier study of P. ephippifer from the Belém region of Brazil (Ryan and Rand 1999) discussed only the whine component and did not mention whether pulses were present. A representative call of P. ephippifer from Maracá Island was found to last for .41 sec, reaching its maximum amplitude at 0.1 sec and then steadily declining (Kaefer et al. 2011). The initial frequency averaged 818 Hz, with the maximum frequency at 840 Hz and the final frequency at 443 Hz (Kaefer et al. 2011). Females tend to deposit their clutches on the edge of banks in shallow ponds, orienting themselves and the amplexed male in a perpendicular position to the shoreline. Amplexus occurs in the water, but the amplexed pair usually leaves the water, then returns several minutes before oviposition. Eggs are released three hours after mating, and foam nest building immediately follows (Hödl 1988, 1990). Nest construction lasts about 40 minutes, with alternating bouts of activity and rest. At the start of nest building, a transparent liquid jelly is released by the female into a "foam-beating chamber", which is bordered by the female's legs and by plants protruding from the water just behind the mating pair. Eggs are only discharged once a foam mass has formed. During phase I of foam nest construction, the male clings to the female while the female assumes a bent-spine position (the "signal" position). During phase II, the male's legs are drawn to the female cloaca (making a "basket formation") as the eggs are extruded; he uses his feet briefly to hold the eggs. During phase III, the male then brings his legs to the water surface and kicks in percussive-rotary movements, responding to female genital secretions of foam which last three to four seconds. Up to 92 repetitions of the kick sequence are necessary to establish the nest. A few minutes after the last kick sequence, the male loses his grip before the female leaves the nest. The larvae hatch on the third day, after the foam begins to dissolve. After four to six days, the foam completely disappears. Tadpoles continue their development in the water (Hödl 1988, 1990).Because P. ephippifer tadpoles develop in small temporary ponds lacking fish and with few if any predatory insects, it has been suggested that foam nesting in this species may serve to reduce conspecific predation by other larvae. In support of this hypothesis, eggs removed from the foam mass are readily consumed by P. ephippifer tadpoles (Hödl 1990).Predators include the colubrid snake Liophis reginae semilineatus (Albarelli and Santos-Costa 2010).

This species is common and its numbers are increasing. It thrives in disturbed habitats. It can be found near human settlements as well as in forest clearings and on forest edges. Its range overlaps with several protected areas (Reynolds et al. 2004).

Physalaemus ephippifer is a species of frog in the family Leptodactylidae. It is found in central and eastern Brazilian Amazonia, the Guianas (Guyana, Suriname, French Guiana), and southern Venezuela (Bolívar state). It might not occur in French Guiana.