Description
Elachistocleis erythrogaster is a small sized frog with an egg-shaped body and a snout-vent length ranging from 29 – 32 mm in males and 34 – 37 mm in females. It has a lengthy, curved snout that protrudes from its small, triangular head. It has prodigious choanae that is separated by a considerable distance and a big, ovular tongue. The nostrils, which are pointed anterolaterally, do not protrude and are separated by a relatively narrow internarial distance (~1.6 mm). Elachistocleis erythrogaster has a curved canthus rostralis and a level loreal region that has a sharp incline just above the lip. It has relatively small eyes that protrude a minimal amount and an interorbital region that is almost 2.5 times the diameter of each eye. Its tympanum are obscured. Elachistocleis erythrogaster has a discrete skinfold that goes laterally from the posterior portion of the head behind the eyes to the groin and another that goes across the chest between the two forelimb insertions. It has a large gland located posterior to the mouth corners and the skin located both dorsally and ventrally to the gland is smooth. Its cloacal vent points posterodorsally. It has short, plump forelimbs. Elachistocleis erythrogaster has small, ovular inner metacarpal tubercles that protrude slightly, large, longitudinally divided outer metacarpal tubercles, and small, circular subarticular tubercles. Elachistocleis erythrogaster has no supernumerary tubercles. The fingers do not terminate with grooves and have relative lengths of 1 < 2 < 4 < 3, with the third finger being about 1.5 times the length of the fourth. The hindlegs are short and plump. It doesn’t have any tubercles on the heels or knees, outer metatarsal tubercles, or supernumerary tubercles. However, the inner metatarsal tubercles are large and ovular and the subarticular tubercles are large and circular. The hindlegs end in unwebbed toes without lateral fringes. The toe terminals are not expanded and they have relative lengths of 1 < 2 < 5 < 3 < 4 (Kwet and Di-Bernardo 1998).

Elachistocleis erythrogaster is differentiated from other species of its genus by its deep black throat in both females and males, its sky-blue and deep black streaks on its lateral surface, and its flame-orange ventral surface with irregularly shaped sky-blue and deep black splotches on the posterior portion of the venter. It is easily differentiated from Elachistocleis ovalis, which occurs in the same region, by their differing adult morphology, coloration, advertisement call, and reproductive behaviors. Elachistocleis erythrogaster is larger than E. ovalis as an adult and also has a larger clutch size, larger eggs, and larger tadpoles. Elachistocleis erythrogaster has a louder and longer call than E. ovalis composed of fewer pulses and with a dominant frequency 1000 Hz lower than E. ovalis. Elachistocleis erythrogaster does not have the femoral stripe on the posterior surface of the thigh that is present in E. ovalis. Finally, whereas E. ovalis has tadpoles with chocolate-brown dorsal surfaces and slightly pigmented fins, E. erythrogaster has tadpoles with chocolate-brown dorsal and lateral surfaces and transparent fins with a curved tip. Elachistocleis ovalis tadpole tail ends in a sharp point. (Kwet and Di-Bernardo 1998).

In life, male Elachistocleis erythrogaster have deep black dorsal surfaces with streaks and splotches of sky-blue and flame-orange. Females of this species have flame-orange dorsal surfaces with streaks and splotches of sky-blue and deep black. The coloration of the dorsal surfaces of the limbs resembles that of the dorsum. The ventral surfaces of the limbs are flame-orange but on the hindlimbs that region is smaller due to the overlap of the deep black and sky-blue from the dorsal surfaces. There is no femoral stripe on the thighs and the lateral surfaces are sky-blue marbled with deep black. Elachistocleis erythrogaster has a flame-orange venter with irregularly shaped deep black splotches and sky-blue spots on the posterior half of the venter. The throat is deep black and has sky-blue marbling laterally. At the corner of the mouth is an irregularly shaped flame-orange splotch. In preservative, all dorsal surfaces are beige to chocolate-brown and are darker in males than in females. The marbled colors are not as clear as in life and the blue color does not show. The flame-orange ventral surfaces grow to a dull yellow but still display the irregular black spolotches. The throat remains black. Preserved, juvenile Elachistocleis erythrogaster have chocolate-brown ventral and dorsal surfaces except for several transparent spots on the chest, forelimb, and mouth (Kwet and Di-Bernardo 1998).

The dark splotches on the venter are usually found toward the posterior end, although they may extend anteriorly in some specimens. The flame-orange background of the venter has varying degrees of brightness (Kwet and Di-Bernardo 1998).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

Elachistocleis erythrogaster are found in the grasslands of the Araucaria plateau (Planalto das Araucarias) in Rio Grand do Sul, Sao Francisco de Paula and Sao Francisco de Cambara, Serra Geral, Brazil. They appear to be restricted to the southeastern border of the plateau (Kwet and Di-Bernardo 1998).

Life History, Abundance, Activity, and Special Behaviors
Elachistocleis erythrogaster individuals were found during heavy rains on warm (18^oC) nights. At the time males were heard calling from the early evening, gradually decreasing until after midnight. Their loud, long call was first mistaken for E. ovalis. The call consists of high-pitched, loud whistles lasting 3.9 – 4.2 seconds at a dominate frequency ranging from 3100 – 4500 Hz and a pulse rate of 110 – 125 pulses per second. Call characterization included an increase in frequency at the beginning of the call and repeated 1 – 3 times intermittently per minute. Males were found calling in vertical positions between blades of tall grass with their posterior ends in 10 – 20 cm deep water (Kwet and Di-Bernardo 1998).

During mating, males bind themselves to females using axillary amplexus and with a strong glue-like secretion. Two mating pairs brought into captivity laid 991 and 476 eggs, respectively. The black eggs were approximately 2.5 mm in diameter and formed a thin egg film on the surface of the after (Kwet and Di-Bernardo 1998).

In January 2001, anti-predator behavior of E. erythrogaster, triggered by light touching, was observed in five of six individuals. It consisted of the frogs inflating their lungs and straightening their hindlimbs, which the frogs held for approximately one minute. Elachistocleis erythrogaster also produced a white, sticky skin secretion, of which the toxicity is unknown but assumed to be noxious to predators. The frogs, however, did not expose their ventrums during the anti-predator response, making the function of their bright coloration currently unknown (Kwet and Sole 2002).

It is assumed that E. erythrogaster feed on termites and ants because of the well formed dermal fold behind the eyes that is known to protect E. ovalis from ants. It is also assumed that E. erythrogaster is fossorial and remains hidden most of the year, making it difficult to find and study (Kwet and Di-Bernardo 1998).

Trends and Threats
While the population trend of E. erythrogaster is stable, because of its limited range it is vulnerable to decline, thus justifying a near threatened IUCN Red List status. The only known threat is habitat loss to cattle ranching (Silvano et al. 2004).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing

Comments
The species authority is: Kwet, A., and Di-Bernardo M. 1998. Elachistocleis erythrogaster, a New Microhylid Species from Rio Grande do Sul, Brazil. Studies on Neotropical Fauna and Environment 33(1): 7-18.

Elachistocleis erythrogaster is part of the Ovalis-Bicolor species complex (Kwet and Di-Bernardo 1998).

The species was named for its red vent, where “erythros” means red and “gaster” means venter in Greek (Kwet and Di-Bernardo 1998).

Elachistocleis erythrogaster is only the second microhylid know from the Rio Grande do Sol (Kwet and Di-Bernardo 1998).

References

Kwet, A. and Sole, M. (2002). ''Elachistocleis erythrogaster (red-bellied oval frog). Defensive behavior.'' Herpetological Review, 33(1), 46.

Kwet, A., and Di-Bernardo M. (1998). ''Elachistocleis erythrogaster, a New Microhylid Species from Rio Grande do Sul, Brazil.'' Studies on Neotropical Fauna and Environment, 33(1), 7-18.

Silvano, D., Kwet, A., Garcia, P. (2004). Elachistocleis erythrogaster. The IUCN Red List of Threatened Species. Version 2014.3. www.iucnredlist.org. Downloaded on 17 February 2015.

Species Account Citation: AmphibiaWeb 2015 Elachistocleis erythrogaster <https://amphibiaweb.org/species/5427> University of California, Berkeley, CA, USA. Accessed Nov 22, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Nov 2024.

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