Odontophrynus americanus is a robust-bodied leptodactylid frog with an average snout-vent length of 42.2 mm for males and 44.6 mm for females. The head, when viewed from above, is rounded and is wider than it is long. The snout is blunt and truncate. The eye is circular and the pupil is horizontal. The upper eyelids have warts that are approximately the same size. The tympanum is not visible. The dorsum is covered in warts and ridges. The belly is granular. It has a short glandular inner tarsal fold and a single glandular ridge on the posterior forearm. The limbs are short at about half the length of the hind limbs. Their slender fingers are smooth on top and the second and fourth fingers are almost equal in length with the third finger being the longest. The fingers have claw shaped terminal phalanges. Webbing is present on hind limbs. Their lengths of their toes are as follows: 4 > 3 > 5 > 2 > 1. No disks are present. They have an enlarged inner metatarsal tubercle used for burrowing. They have one median vocal pouch and paired lateral vocal slits. No nuptial pads, enlarged temporal glands, enlarged parotoid glands, or tibial glands were present (Savage and Cei 1965).
The tadpole’s body shape is globose. The fins meet with the body about 1/3 length from the head. The eyes and nostrils are located dorsally. The tadpoles have sinistral spiracles with median vents. They have complex mouthparts with weakly serrated beaks. Labial papillae are present laterally and along the lower labium, while papillae are absent on the median upper labium (Savage and Cei 1965). The tadpoles have 2/3 denticle rows with the first lower row and second upper row in two parts (Starrett 1960).
Odontophrynus americanus can be differentiated from similar species because the adults have similarly-sized warts on the upper eyelids and back. They have an absence of enlarged paratoid, postorbital, temporal, and tibial glands as well as an absence of the tensor fasciae latae muscle. Their labial papillae are not pigmented heavily with black coloration (Savage and Cei 1965). Additionally, unlike most frogs, Odontophrynus americanus is tetraploidy with a total of 44 chromosomes (Bogart 1967). The tetraploid O. americanus, is morphologically cryptic with the diploid O. cordobae. The two can be differentiated, statistically, by their similar release call with O. americanus having a single pulsed release call similar to their advertisement call (Grenat and Martino 2013). They can also be differentiated based on range (Martino and Sinsch 2002). Odontophrynus americanus can also be differentiated from the diploid O. juquinha by O. americanus being tetraploid, having chromosomal differences, having a lower pulse rate in their advertisement call, and having larger tadpoles (Rocha et al. 2017).
Adults have dark blotches on lighter coloration. The upper surfaces of their head, body, and limbs are brown with dark brown blotches outlined in black, sometimes with reddish coloration. On the side of their heads and upper lips, they have large rectangular light and dark blotches. Their undersides are an off-white color with slight brown mottling. Adult males have throats that are dark gray (Savage and Cei 1965). Sexual dimorphism is absent (Quiroga et al. 2015).
Tadpoles are dorsally and laterally brown, while they are ventrally transparent. Their tail fins and musculature are pigmented along with the presence of light spots. There is a light line that runs along the underside of the fin (Savage and Cei 1965).
Savage and Cei (1965) noted differences between populations from Bolivia and Choya, Provincia de Santiago del Estero, Argentina, with the former having smaller males and the latter having atypical coloration.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Argentina, Brazil, Paraguay, Uruguay
Odontophrynus americanus is found in the semi-arid regions in subtropical Argentina, the humid forests of Bolivia, coastal central and southeastern Brazil, southern Paraguay, and Uruguay. It is common to the Campo, Chaco, and Pampa dry forest formations (Savage and Cei 1965). It occurs in terrestrial and freshwater systems in open grasslands and savannahs. In addition to natural areas, O. americanus can also reside near agricultural lands and urbanized areas (Cabagna et al. 2006). During or shortly after heavy rainfalls, it can be found at flooded areas or temporary ponds (Aquino et al. 2010). It occurs in elevations ranging from sea level to 900 meters (Savage and Cei 1965).
Life History, Abundance, Activity, and Special Behaviors
Odontophrynus americanus is nocturnal. This species is abundant in the wild. They are semi-aquatic and found in semi-arid regions and humid forests (Savage and Cei 1965). Odontophrynus americanus is a generalist feeder.
The species is an explosive breeder that mate in freshwater permanent, semi permanent, and temporary ponds after heavy rains. Matured females occur in every month except in June. During breeding, males call at night in or at the edge of the water to attract females (Valdez and Maneyro 2016).
Male O. americanus call frequency is 1025 – 1075 Hz and the pulse rate is 524 – 558ms (Rosset and Baldo 2014). The duration of the call is 170 – 381 ms (Grenat and Martino 2013).
Male frogs are territorial and the males undergo physical combat to fight each other for a mate (Valdez and Maneyro 2016). The males use the axillary amplexus position when mating. This species does not have aposematic body coloration, but instead have cryptic coloration (Grenat 2012).
After mating, females release their eggs on the muddy bottom of their mating sites (Grenat 2012). There have not been enough studies done to determine the number of eggs in their clutch, however, clutch size is correlated to the size of the mature females (Valdez and Maneyro 2016). A closely related species, Odontophrynus cordobae, lays eggs in a range between 1180 to 7080 eggs (Grenat 2012). It takes seven to nine months for O. americanus tadpoles to develop (Gallardo 1963). A clutch completes its development in 12 to 15 days. Development and metamorphosis are influenced by temperature (Martino 1999). There is no parental care after mature females deposit their eggs. Their larvae thrive in the habitat they were hatched in (Echeverria et al. 2007).
The tadpoles are benthic feeders and eat plant debris and algae (Echeverria et al. 2007). They are preyed on by various animals including invasive species such as Rana catesbeiana (Leivas 2013). Their defenses mechanisms are to burrow into the ground with their hind legs and to change their posture to a flat body with stretched legs (Maffei and Ubaid 2016).
Trends and Threats
Odontophrynus americanus has stable populations and there are no major threats against the species. Despite their stable populations, there may be some arising threats due to anthropogenic activity. Since this species occur in agricultural areas, insecticides such as Fenitrothion, could be a threat to this species. The species seem to recover quickly, but the insecticide, even in low doses, still has effects in aquatic environments (Lajmanovich et al. 2009). If their food sources are poisoned, Odontophrynus americanus could be threatened by secondary poisoning. Cypermethrin, a pyrethroid insecticide, could also pose a threat to this species because it is lethal to tadpoles even in low concentrations and it affects adults by disrupting their genetic makeup through breaking, deleting, or rearranging their chromosomes (Cabagna et al. 2006).
Fortunately, this species is abundant throughout its regions; therefore, they are of least concern, and no conservation work has been done (Aquino et al. 2010).
Possible reasons for amphibian decline
Intensified agriculture or grazing
Local pesticides, fertilizers, and pollutants
The species authority is: Duméril, A. M. C., Bibron, G. (1841). Erpétologie Genérale ou Histoire Naturelle Complète des Reptiles. Volume 8. Paris: Librarie Enclyclopedique de Roret.
Odontophrynus americanus is derived from the prefix “odonto-” meaning “teeth” and “americanus” meaning “American.”
This species was originally known as Pyxicephalus americanus (Savage and Cei 1965). In the context of its previous name, “pyxis” means “round or box,” “cephalus” means “head." The species has also been known as Tomopterna americanus by Fitzinger in 1843 and as Ceratophrys americana by Boulenger in 1882 (Savage and Cei 1965).
In 2022, Rosset et al. synonymized O. occidentalis with O. americanus on the basis of surprising similarities of the position, number, size, and shape of the glandular warts and geographic range. (The range of O. americanus overlapped with O. occidentalis in the Sierra de Cordoba of Argentina and is adjacent to the range of O. cultripes in Estado do Sao Paulo, Brazil (Savage and Cei 1965).) They further provide taxonomic details and basis for Odontophrynus americanus and O. asper (Rosset et al 2022).
Unlike most frogs, Odontophrynus americanus are tetraploids with a total of 44 chromosomes (Bogart 1967).
Aquino, L., Kwet, A., Reichle, S., Silvano, D., Scott, N., Lavilla, E. & di Tada, I. (2010). Odontophrynus americanus. (errata version published in 2016) The IUCN Red List of Threatened Species 2010: e.T57186A86441009. Downloaded on 15 February 2017.
Bogart, J.P. (1967). ''Chromosomes of the South American amphibian family Ceratophryidae with a reconsideration of the taxonomic status of Odontophrynus americanus.'' Canadian Journal of Genetics and Cytology, 9(3), 531-542.
Cabagna, M.C., Lajmanovich, R.C., Peltzer, P.M, Attademi, A.M., Ale, E. (2006). ''Induction of micronuclei in tadpoles of Odontophrynus americanus (Amphibia: Leptodactylidae) by the pyrethroid insecticide cypermethrin.'' Toxicological and Environmental Chemistry, 88(4), 729-737.
Duméril, A. M. C., and Bibron, G. (1841). Erpétologie Générale ou Histoire Naturelle Complète des Reptiles. Volume 8. Librairie Roret, Paris.
Echeverria, D. D., Volpedo, A.V., Mascitti, V.I. (2007). ''Diet Of Tadpoles From A Pond In Iguazu National Park, Argentina.'' Gayana, 71(1), 8-14.
Gallardo, J.M. (1963). ''Observaciones biológicas sobre Odontophrynus americanus (D. et B.) 1841.'' Ciencia e Investigación, 19(6), 177–186.
Grenat, P,R., Gallo, L.M.Z, Nancy Edith Salas, N.E., Martino, A.L. (2012). ''Reproductive Behaviour and Development Dynamics Of Odontophrynus Cordobae (Anura, Cycloramphidae).'' Journal of Natural History , 46(17-18), 1141-1151.
Grenat, P. R., Martino, L. (2013). ''The Release Call as a Diagnostic Character between Cryptic Related Species Odontophrynus Cordobae and O. Americanus (Anura: Cycloramphidae).'' Zootaxa, 3635(5), 583–586.
Lajmanovich, R.C., Attademi, A.M., Peltzer, P.M., Junges, C.M. (2009). ''Inhibition and recovery of cholinesterases in Odontophrynus americanus tadpoles exposed to fenitrothion.'' Journal of Environmental Biology, 30(5), 923-926.
Leivas, P. T., Savarias, M., Lampert, S., Lucas, E.M. (2013). ''Predation of Odontophrynus americanus (Anura: Odontophrynidae) by the invasive species Lithobates catesbeianus (Anura: Ranidae) in an Araucaria Forest remnant in Southern Brazil.'' Herpetological Notes, 6, 603-606.
Maffei, F. Ubaid, F. K. (2016). ''Defensive behavior of Odontophrynus americanus (Dumeril & Bibron, 1841) (Amphibia, Anura, Odontophrynidae).'' Neotropical Biology and Conservation, 11(3), 196-197.
Martino AL. (1999). ''Análisis estructural de una comunidad de anfibios anuros (Barreto, Córdoba, Argentina).'' PhD. Thesis. 152 pp. Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional
Quiroga, L. B., Sanabria, E. A., Marangoni, F. (2015). ''Sexual Size Dimorphism and Age in Odontophrynus cf. barrioi (Anura: Odontophrynidae) from the Monte Desert, Argentina.'' Journal of Herpetology, 49(4), 627-632.
Rocha, P.C., de Sena, L.M.F, Pezzuti, T.L., Leite, F.S.F., Svartman, M., Rosset, S.D., Baldo, D., de Anhietta Garcia, P.C. (2017). ''A new diploid species belonging to the Odontophrynus americanus species group (Anura: Odontophrynidae) from the Espinhaço range, Brazil.'' Zootaxa, 4329(4), 327-350.
Rosset SD, Baldo D, Borteiro C, Kolenc F, Cazzinga NJ, Basso NG. (2022). "Calling frogs by their name: long-lasting misidentification of tetraploid frogs of the genus Odontophrynus (Anura: Odontophrynidae)." Herpetological Monographs, 36, 80–98.
Rosset, S., Baldo, D. (2014). ''The Advertisement Call and Geographic Distribution of Odontophrynus lavillai Cei, 1985 (Anura: Odontophrynidae).'' Zootaxa, 3784(1), 079–083 .
Savage, J. M. and Cei, J. M. (1965). ''A review of the leptodactylid frog genus Odontophrynus.'' Herpetologica, 21(3), 178-195.
Starrett, P. (1960). ''Descriptions of tadpoles of Middle American frogs.'' Miscellaneous Publications Museum of Zoology, University of Michigan, 110, 5-37.
Originally submitted by: Wilson Xieu, Eric Truong, and Rachel Alexis de Jesus Parungao (first posted 2017-12-06)
Edited by: Ann T. Chang, Michelle S. Koo (2022-12-29)
Species Account Citation: AmphibiaWeb 2022 Odontophrynus americanus: American Ground Frog <https://amphibiaweb.org/species/5606> University of California, Berkeley, CA, USA. Accessed Feb 5, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Feb 2023.
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