The species name, “langonei,” is a reference to Dr. José Antonio Langone, a prominent Uruguayan herpetologist (Maneyro et al. 2008).

Description
Melanophryniscus langonei is a stout-bodied frog described from three females and one juvenile. Females have a snout-vent length range of 20.49 - 21.52 mm, which is three times the length of the head. The head is slightly wider than long. Melanophryniscus langonei have short snouts that appear mucronated dorsally, and rounded when viewed laterally. The nostrils are oval and positioned anterolaterally. The species has large eyes with the eyelid having many warts. The pupils are oval and horizontal. The interorbital space is larger than eye diameter, while the latter is smaller than the distance from eye to nostril. The species does not present snout swelling, parotid glands, nor tympanic membranes. The dorsal skin has glandular warts tipped with keratin spines, save for the vertebral line, which has no warts and is smooth. Individuals have two paravertebreal glandular ridges that extend from snout to urosyile, along with two irregular glandular ridges on each side of the body that go from the upper eyelid to the posterior region of the body. The forearms, hands, and feet have coni. The hands also have oval inner metacarpal tubercles and rounded outer metacarpal tubercles, both equal in size. Palmar supernumerary tubercles are conicled and dispersed. Melanophryniscus langonei have blunt fingers that are slightly webbed, and the relative finger lengths are IV < II < I < III. The fingers have conical subarticular tubercles that are divided on finger I and III. The feet also have oval inner metatarsal tubercles and rounded outer metatarsal tubercles, though these are smaller than the inner tubercles. The toes are webbed and relative lengths are I < II < V < III < IV. The webbing formula is I 1 - 1 II 1½ - 1 III 2 - 1½ IV 1½ - 2 V. The toe’s subarticular tubercles are also conical and divided on fingers I and IV. There are some small supernumerary tubercles (Maneyro et al. 2008).

Melanophryniscus langonei in general can be differentiated by its dorsal coloration and glandular wart placement from the M. moreirae and M. stelzneri group species, which include: M. stelzneri, M. montevidensis, M. atroluteus, M. dorsalis, M. fulvoguttatus, M. rubriventris, M. cupreuscapularis, M. klappenbachi and M. krauczuki. Another group species that M. langongei can be discriminated from is the M. tumifrons group, which contains M. tumifrons, M. pachyrhynus, M. devincenzii, M. macrogranulosus, M. cambaraensis, M. orejasmirandai, M. simplex and M. spectabilis. In comparison with this group, M. langonei is generally smaller and lacks snout swelling (Maneyro et al. 2008).

Melanophryniscus langonei is morphologically similar to M. sanmartini, but certain features are unique to M. langonei. Melanophryniscus langonei is characterized by having a lighter brown dorsum that has six darker glandular ridges. This species also has a uniformly black gular region. Melanophryniscus sanmartini lacks ridges and has rounded glandular warts throughout the dorsum that are concentrated more on the cephalic region; this species also has a black gular region, but near the tip, there is saffron coloration (Maneyro et al. 2008).

In life, the dorsal coloration of M.langonei, along with the vertebral line and loreal region, upper limb and flank regions are all light brown. The glandular warts along the dorsum have white keratin spines. The glandular ridges, running longitudinally across the dorsum are darker brown. There are also light brown stripes on the upper arm closer to the body. The ventrum is uniformly black, with the exception of the belly and ventral side of the upper arms, which feature spotted orange-red coloration. The palmar surface of the hands are red, while the plantar surfaces of the feet are black, with the exception of red tubercles. In preservative, red coloration becomes a white color (Maneyro et al. 2008).

The juvenile specimen had similar external characteristics as the adult females (Maneyro et al. 2008).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Uruguay

View distribution map in BerkeleyMapper.

This is a species endemic to the north-eastern region of Uruguay, bordering Brazil. At the time of the species description, M. langonei has only been found within a 15 km region within the Department of Rivera, and has yet to be found in Brazil. The species is suspected to be dispersed in an area less than 100 km² of the type localities. Melanophryniscus langonei has been noted to prefer shallow soils and is dispersed in non-specific ways relating to elevation. The area of Rivera is a softly hilly grassland, and mean elevation where both the holoytpe and paratypes have been found ranges from 190 - 230 m (Maneyro et al. 2008).

Life History, Abundance, Activity, and Special Behaviors
Melanophryniscus langonei can be found year round but are thought to reproduce in the winter. This is hypothesized from collected specimens: a juvenile caught in September and the presence of mature ovules in another specimen caught in May. As with other species in the genera, M. langonei may exhibit explosive breeding following rain (Maneyro et al. 2008).

The species is presumed to be insectivorous (Carreira and Maneyro 2019).

Melanophryniscus langonei and M. sanmartini can be found in sympatry in some localities (Maneyro et al. 2008).

Larva
Between Gosner Stages 29 - 37, tadpoles have a total length range of 20.0 - 22.7 mm and an oval body with a length range of 7.0 - 8.0 mm. Their maximum body width ranges from 5.3 - 5.8 mm and the body's maximal height is 4.5 - 5.0 mm. The head is narrower at the nostrils than at the eyes. The nostrils are located approximately equidistance between the snout tip and the eyes. The internarial distance is slightly smaller than the interorbital distance. The eye itself is 0.6 - 0.8 mm in diameter, and there is a pineal organ between the eyes. Tadpoles have medium-sized, anteroventral, emarginate oral discs that are about 24% of the body length. The oral disc has thick marginal papillae, which are not present on the mental and rostral regions, with the dorsal gap being larger than the ventral gap. There are also either no submarginal papillae at the corners of the mouth or the papillae are scarce. They have a labial tooth row formula of 2/3(1), however, it is not unusual for individual labial teeth to be missing. The jaw sheaths are thin and serrated, with the upper sheath being curved and the lower being V-shaped. The short spiracle is sinistral and located in the posterior half of the body, with about 4.0 - 5.0 mm from the snout tip to the spiracle tube opening, and is directed posterodorsally. The inner spiracle tube wall is fused to the body. The oval spiracle tube opening is narrower than the tube and visible from the dorsal and lateral views. The conical vent tube can be found running along the margin of the ventral fin and has a dextral opening. The straight tail has a length of 12.8 - 14.7 mm long and a maximal height of 4.3 - 4.8 mm of which 1.5 - 1.7 mm is tail musculature. The tail musculature tapers but does not reach the tip of the tail (Baldo et al. 2014).

The oral discs and body length of M. langonei is most similar to the lentic tadpoles of the M. stelzneri group, but their labial tooth row formula, and general body structure, is more in line with phytotelm species. For comparisons with tadpoles from 22 other species, please see Baldo et al. (2014)

In preservative, the dorsum is dark brown and the ventrum is dark and opaque. The tail musculature is light brown while the fins are transparent with scattered melanophores (Baldo et al. 2014).

Tadpoles live in small ponds (Baldo et al. 2014).

Trends and Threats

This species is particularly threatened by habitat modification, specifically forestation and the introduction of non-native tree species Eucaliptus and Pinus species. Additionally, M. langonei is expected to be affected by climate change. Their small distribution range magnifies the effect of threats (Maneyro et al. 2008).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
Melanophryniscus langonei described based on morphology (Maneyro et al. 2008) and was formerly assigned to the M. moreirae group (Baldo et al. 2014).

References
Baldo, D., Candioti, F. V., Haad, B., Kolenc, F., Borteiro, C., Pereyra, M. O., Zank, C., Colombo, P., Bornschein, M. R., Sisa, F. N., Brusquetti, F., Conte, C. E., Nogueira-Costa, P., Almeida-Santos, P., and Pie, M. R. (2014). Comparative morphology of pond, stream and Phytotelm-dwelling tadpoles of the South American Redbelly Toads (Anura: Bufonidae:Melanophryniscus). Biological Journal of the Linnean Society, 112(3), 417–441. [link]

Maneyro, R., Naya, D. E., and Baldo, D. (2008). A new species of Melanophryniscus (Anura, Bufonidae) from Uruguay. Iheringia. Série Zoologia, 98(2), 189–192. [link]

Carreira, S., and Maneyro, R. (Eds.). (n.d.). Libro Rojo de los Anfibios y reptiles del uruguay - la diaria. La Diaria. [link]

Species Account Citation: AmphibiaWeb 2024 Melanophryniscus langonei: Redbelly toad <https://amphibiaweb.org/species/7155> University of California, Berkeley, CA, USA. Accessed Feb 2, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 2 Feb 2025.

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