Description
Elachistocleis pearsei is a medium size microhylid frog with adult snout-vent length of 30 to 39 mm in males and 32.1 to 47 mm in females (Acosta-Galvis et al. 2022; Atencia Gándara et al. 2017). As with most members of this family, E. pearsei has a small triangular head with a pointed snout, small dorsolaterally positioned eyes with a skin fold behind, and concealed tympanum. The forelimbs are very short with slender fingers that lack membranes and no flattened or expanded fingertips (Carvalho 1954; Medina-Rangel et al. 2011; Vargas and Barrio-Amoros 2023). The body is oval shaped with smooth skin dorsally and ventrally (Vargas and Barrio-Amoros 2023; Ruthven 1914). The hind limbs are short and robust (Vargas and Barrio-Amoros 2023), consistent with their fossorial habits. The toes have no or only rudimentary webbing (Carvalho 1954; Medina-Rangel et al. 2011; Ruthven 1914). Elachistocleis pearsei possesses barely noticeable post-commissural glands (Acosta-Galvis et al. 2022).

Diagnosis

Elachistocleis pearsei differs from E. skuani because the former has a densely pigmented belly with irregular bright orange blotches (pale orange spots scattered towards the ventrolateral margins in E. sikuani), a larger body size with male adults ranging between 30 to 39 mm and females adults between 32.1 to 47 mm in snout-vent length (vs. 27.3 - 28.8 mm snout-vent length in adult males and 28.7 - 33.2 mm snout-vent length for adult females in the smaller E. sikuani) and barely noticeable post-commissural glands (well-defined in E. sikuani) (Acosta-Galvis et al. 2022).

Similarly, E. pearsei can be distinguished from E. tinigua because of the former’s bright orange irregular blotches on the belly (diffuse light orange blotches in E. tinigua), barely noticeable post-commissural glands (well-defined in E. tinigua) and an evident vertebral stripe (absent in E. tinigua) (Acosta-Galvis et al. 2022).

Coloration

In life, the dorsal coloration of E. pearsei is a dark bluish-gray or grayish brown with minute white or pinkish speckles (Ruthven 1914). Stebbins and Hendrickson (1959) describe the dorsal coloration of two animals from Huila, Colombia (reported as E. ovalis) as black with small ash-white spots formed by concentrations of guanophores. The ventral patterning has large, intense carrot-orange irregular spots that cover most of the belly and chest (Acosta-Galvis et al. 2022). The underparts of limbs, axillary and inguinal region, and area at the insertion of all four limbs are also covered with carrot-orange colored, irregular spots. The iris appears beige but under magnification looks dark brown with beige guanophores that are especially concentrated on the left and right sides of the pupil (Stebbins and Hendrickson 1959).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Colombia, Panama, Venezuela

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (1 records).

Elachistocleis pearsei can be found on the Pacific coast of Panama (de Sá et al. 2012), northern (Sucre, Cesar, La Guajira and Magdalena departments) and central (Caldas and Tolima departments) Colombia, and in the Maracaibo Lake Basin of Venezuela (Barrio Amoros et al. 2019). This species was also recently reported in Puntarenas, Costa Rica (Vargas and Barrio-Amoros 2023). Elachistocleis pearsei is found exclusively in lowlands from 0 to 1015 m elevation (Bernal et al. 2005) in wetlands or near ponds and seasonally flooded savannahs. This species tends to avoid deeper parts of swamps or very dry habitats (Acosta-Galvis et al. 2006; Atencia Gándara et al. 2017; Ruthven, 1914). They also inhabit plantations and distributed areas of former tropical dry forest habitat (Blanco-Torres et al. 2015; Vargas and Barrio-Amoros 2023).

Life History, Abundance, Activity, and Special Behaviors
Elachistocleis pearsei is a nocturnal species with marked seasonality, being more active during the rainy season, especially after heavy rain, with a dramatic drop in activity during the dry season (Atencia Gándara et al. 2017).

Elachistocleis pearsei’s diet is mainly made up of ants and termites (order Hymenoptera: Formicidae). However, it may consume other arthropods of different orders (Coleoptera: Scarabaeidae, Orthoptera, Diptera, Acari and Isoptera). Elachistocleis pearsei is an active forager (Atencia Gándara et al. 2017; Blanco-Torres et al. 2015; Ruthven 1914) and a fossorial species (Angarita-M. et al. 2015).

The call of E. pearsei has a metallic buzzer-like quality, long, hard and nasal, described as ‘beeee weeee’ with a pronounced "ventriloquial quality" in that herpetologists have difficulty in locating calling males by triangulation (Stebbins and Hendrickson 1959). Recordings of E. pearsei vocalization are available in Macaulay Library at the Cornell Lab; ML194653 from Bolívar, Venezuela and ML193940 from Panama Province, Republic of Panama.

Amplexus is presumed to be axillary, as with most microhylids (Carvajal-Castro et al. 2020). Acosta-Galvis et al. (2006) report finding a male and female in amplexus with the male still vocalizing.

Larva
The free-swimming larvae lack jaw sheaths, tooth rows, and papillae and have labial flaps that cover the mouth. Tadpoles have lateral eyes and terminal mouths. Snout lacks nostrils until very late in development (Lynch 2006).

Relation to Humans
As of 2023, there is no relation with humans. Elachistocleis pearsei is not exploited by humans.

Comments
Elachistocleis pearsei was placed in the E. surinamensis species group containing nine species (E. cesarii, E. magna, E. muiraquitan, E. pearsei, E. piauiensis, E. sikuani, E. skotogaster, E. surinamensis, and E. tinigua). Maximum likelihood phylogenetic analyses using 16S + COI inferred E. pearsei as the sister clade to E. tinigua and E. sikuani (Novaes-e-Fagundes et al. 2023). However, Acosta-Galvis et al. (2022), in a previous maximum likelihood analysis using 16S, suggested E. pearsei is the sister to E. panamensis and an undescribed Elachistocleis with E. tinigua as the sister species to E. sikuani.

Populations of this species were assigned to Relictimover pearsei (Carvalho 1954), but were moved to Elachistocleis by de Sá et al. (2012) based on molecular and osteological evidence. More recently, this species was moved to the genus Engystoma (Dubois et al. 2021), a change that has not been widely accepted (Vargas and Barrio-Amoros 2023).

The specimen registered in Costa Rica was not identified using the definitive morphological characteristics given by Acosta-Galvis et al. (2022), i.e., light bright orange blotches and no noticeable post-commissural glands.

References
Acosta-Galvis, A. R., Huertas-Salgado, C., and Rada, M. (2006). Aproximación al conocimiento de los anfibios en una localidad del Magdalena medio (Departamento de Caldas, Colombia). Revista Académica Colombiana de Ciencias, 30(115), 291–303. [link]

Acosta-Galvis, A., Sá, R., and Tonini, J. (2022). Two new species of Elachistocleis Parker, 1927 (Anura: Microhylidae: Gastrophryninae) from Colombia. Zootaxa, 5099, 527–548. [link]

Angarita-M, O., Montes-Correa, A., and Renjifo, J. M. (2015). Amphibians and reptiles of an agroforestry system in the Colombian Caribbean. Amphibian and reptile conservation, 8, 33–52. [link]

Atencia-Gándara, P., Conde, Ó., and Solano, L. (2017). Use of biological resources by Elachistocleis pearsei (Ruthven, 1914) (Anura: Microhylidae) in a lentic ecosystem from the Department of Sucre, Colombia. Acta Zoológica Mexicana, 33(1), 130–132. [link]

Barrio-Amoros, C., Rojas Runjaic, F., and Celsa Señaris, J. (2019). Catalogue of the amphibians of Venezuela: Illustrated and annotated species list, distribution, and conservation. Amphibian and Reptile Conservation, 13(1). [link]

Blanco-Torres, A., Duré, M., and Bonilla, M. A. (2021). Anurans trophic dynamic and guild structure in tropical dry forests of the Caribbean region of Colombia. Anais Da Academia Brasileira de Ciências, 93(4), 1-17. [link]

Carvajal-Castro, J. D., López-Aguirre, Y., Ospina-L, A. M., Santos, J. C., Rojas, B., and Vargas-Salinas, F. (2020). Much more than a clasp: Evolutionary patterns of amplexus diversity in anurans. Biological Journal of the Linnean Society, 129(3), 652–663. [link]

Carvalho, D. (1954). A preliminary synopsis of the genera of American mycrohylid frogs. Occasional Papers of University of Michigan Museum of Zoology, 555, 1-19. [link]

de Sá, R. O., Streicher, J. W., Sekonyela, R., Forlani, M. C., Loader, S. P., Greenbaum, E., Richards, S., and Haddad, C. F. B. (2012). Molecular phylogeny of microhylid frogs (Anura: Microhylidae) with emphasis on relationships among New World genera. BMC Evolutionary Biology, 12(1), 241. [link]

Dubois, A., Ohler, A., and Pyron, R. A. (2021). New concepts and methods for phylogenetic taxonomy and nomenclature in zoology, exemplified by a new ranked cladonomy of recent amphibians (Lissamphibia). Megataxa, 5(1), 1–738. [link]

Lynch, J. D. (2006). The tadpoles of frogs and toads found in the lowlands of Colombia. Revista Académica Colombiana de Ciencias, 30(116), 443–457. [link]

IUCN SSC Amphibian Specialist Group. 2021. Elachistocleis pearsei. The IUCN Red List of Threatened Species 2021: e.T57993A54352618. https://dx.doi.org/10.2305/IUCN.UK.2021-1.RLTS.T57993A54352618.en. Accessed in Dec 2023.

Novaes-e-Fagundes, G., Lyra, M. L., Loredam, V. S. A., Carvalho, T. R., Haddad, C. F. B., Rodrigues, M. T., Baldo, D., Barrasso, D. A., Loebmann, D., Ávila, R. W., Brusquetti, F., Prudente, A. L. C., Wheeler, W. C., Goyannes Dill Orrico, V., and Peloso, P. (2023). A tale of two bellies: Systematics of the oval frogs (Anura: Microhylidae: Elachistocleis). Zoological Journal of the Linnean Society, 197(3), 545–568. [link]

Ruthven, A. G. 1914. Description of a new engystomatid frog of the genus Hypopachus. Proceedings of the Biological Society of Washington 27, 77–80. [link]

Stebbins, R. C., and Hendrickson J. R. (1959) Field studies of amphibians in Colombia, South America. University of California Publications in Zoology 56(5), 497-8540.

Vargas, J., and Barrio-Amoros, C. (2023). Presence of the Plump Frog, Elachistocleis pearsei (Ruthven 1914), in Costa Rica. Reptiles and Amphibians, 30, 1-2. [link]

Species Account Citation: AmphibiaWeb 2024 Elachistocleis pearsei: Colombian plump frog <https://amphibiaweb.org/species/2211> University of California, Berkeley, CA, USA. Accessed Jan 4, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 4 Jan 2025.

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