Description

Diagnosis: Ranitomeya sirensis is a very small Peruvian dendrobatid, reaching about 15-17 mm SVL (three adult males 14.7-15.4 mm, 1 adult female 16.8 mm SVL). It can be distinguished from all other dendrobatids by its uniform red dorsum and turquoise-green limbs. The venter is turquoise-green with a rectangular red patch on the belly, and the chin is red. Skin texture is slightly granular on the dorsum, while the venter is moderately granular, and limbs are smooth. The first finger is much shorter than second; all fingers have conspicuously enlarged finger discs at least twice finger width. The tympanum is visibly concealed posterodorsally. Neither teeth nor an omosternum are present.

Description: Male SVL measures 14.7-15.4 mm, and the single female specimen measured 16.8 mm in SVL. The head is narrower than the body. The snout is subtruncate when viewed dorsally, and sloping in lateral view. The canthus rostralis is rounded, while the loreal region is flat. The tympanum is vertically elliptical, but is hidden posterodorsally. Hands are relatively large, with all fingers except the first possessing considerably expanded discs (at least 2x finger width). The third finger is the longest, followed by the fourth, second, and first. A circular metacarpal tubercle lies at the base of the palm, and a smaller inner metacarpal tubercle is present at the base of the first finger. On the first, second and fourth fingers, there is one subarticular tubercle; in contrast, there are two on the third finger. All subarticular tubercles are inconspicuous with the exception of the distal subarticular tubercle on the third finger, which is distinctly raised. Hindlimbs are moderate in length, with the heel of the adpressed limb reaching the tympanum. The fourth toe is the longest, followed by the fifth, third, second and first. All toes except the first have expanded discs. The medium-sized inner and small outer metatarsal tubercle have rounded surfaces and are protuberant. Hands and feet lack webbing, supernumerary tubercles, and lateral fringe. The dorsal skin is slightly granular, while the venter is moderately granular and the limbs are smooth (Aichinger 1991).

The head and dorsum are red and lack spots or stripes. The arms and legs are turquoise. However the coloration is lighter on the anterodorsal side of the proximal half of the upper arm and on the proximal part of the thigh extending to the body. The venter is turquoise-green with a five by three mm red patch on the belly. The area below the rectangular patch and on the ventral surface of the legs are turquoise. The surface of the palms and soles are black. Iris is black (Aichinger 1991).

Similar species: Other small poison-dart frogs having a bright red dorsal coloration may be confused with this species. Ranitomeya sirensis differs from Oophaga speciosa, Andinobates opisthomelas, and Minyobates steyermarki by having turquoise-green limbs, from Oophaga granulifera in having only slightly granular skin, and from Oophaga pumilio by having a rectangular red patch on the turquoise-green venter (Aichinger 1991).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Peru

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

Ranitomeya sirensis is endemic to the Cordillera El Sira, a single mountain in the Serranía de Sira mountain range in east-central Peru (departments of Huanuco, Pasco, and Ucayali) at elevations of 750-1000 m asl. It is found in (Stuart et al. 2008).

Life History, Abundance, Activity, and Special Behaviors
Like other dendrobatids, R. sirensis is diurnal (Aichinger 1991). R. sirensis may be arboreal due to its long hands and well-developed discs; it is presumed to use phytotelms for breeding (Aichinger 1991). It is oviparous; a female specimen was found to contain two mature eggs and three immature oocytes (Aichinger 1991). Individuals are quite agile and were observed to jump around "continuously" (Aichinger 1991). This species is sympatric over part of its elevational range with Adelphobates quinquevittatus, which occurs from 260 to 1080 m asl (Aichinger 1991).

Trends and Threats
It is thought to be rare, but population surveys have not been done for this species (Stuart et al. 2008). It was first collected in 1976 and again in 1987-1988 (Aichinger 1991), and most recently reported in 2007 (Von May et al. 2008). D. sirensis is found in one protected area, the Reserva Comunal El Sira (Stuart et al. 2008). However, this area is inhabited (it is an indigenous people's reserve) and habitat disturbance may be occurring due to farming and human settlement (Stuart et al. 2008). In the lower part of the range, selective logging is also taking place (Stuart et al. 2008). R. sirensis is an inhabitant of primary cloudforest and it is not known whether it has significant tolerance for disturbed habitat (Stuart et al. 2008).

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 is named after the type locality, Serranía de Sira (Aichinger 1991). In 2011, the genus Dendrobates was subdivided into seven genera, including the new genus Ranitomeya by Brown et al (2011).

This species was featured as News of the Week on 19 October 2020:

Many members of the Peruvian poison frog genus Ranitomeya show a wide variety of color patterns, and two or more color morphs can exist within a single species. Ranitomeya sirensis has yellow stripes over most of its range, but has a deep red color in the Sira mountains near the Brazilian border. Twomey et al. (2020) investigate this divergent coloration to determine the nature of the pigments in the skin of these frogs and the patterns of gene expression underlying pigment processing. First, with chromatography, they identified the carotenoid pigments in the skin and liver. As in previous studies, they found carotenoids associated with yellow coloration in both morphs (with a substantially higher amount in the red morph), as well as a number of ketocarotenoids in the red morph. These are modified carotenoids associated with red coloration. They then found in genetic tests that the red morph expresses a dysfunctional form of beta-carotene oxygenase 2 (BCO2: a carotenoid cleavage enzyme), which normally degrades carotenoids. This allows carotenoids to build to higher concentrations in the red morph, consistent with the results of their chromatographic analyses. They also found significantly higher expression of a carotenoid ketolase (CYP3A80: a cytochrome P450 enzyme) in the livers of red morph frogs. This appears to be the key enzyme converting carotenoids to ketocarotenoids, hence giving the red morph its distinctive appearance. By combining chemical analyses of pigmentation with genomic analyses of gene expression, this study bridges the gap between genotype and phenotype, a key goal of evolutionary analysis (Written by Kyle Summers).

References

Aichinger, M. (1991). ''A new species of poison-dart frog (Anura:Dendrobatidae) from the Serrania de Sira, Peru.'' Herpetologica, 47, 1-5.

Brown J.L., Twomey E., Amézquita A., De Souza M.B., Caldwell J.P., Lötters S., Von May R., Melo-Sampaio P.R., Mejía-Vargas D., Perez-Peña P., Pepper M., Poelman E.H., Sanchez-Rodriguez M., and Summers K. (2011). "A taxonomic revision of the Neotropical poison frog genus Ranitomeya (Amphibia: Dendrobatidae)." Zootaxa, 3083, 1-120. [link]

Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.

Von May, R., Catenazzi, A., Angulo, A., Brown, J. L., Carrillo, J., Chávez, G., Córdova, J. H., Curo, A., Delgado, A., Enciso, M. A., Gutiérrez, R., Lehr, E., Martinez, J. L., Medina-Müller, M., Miranda, A., Neira, D. R., Ochoa, J. A., Quiroz, A. J., Rodríguez, D. A., Rodríguez, L. O., Salas, A. W., and Seimon, T. (2008). ''Current state of conservation knowledge on threatened amphibian species in Peru.'' Tropical Conservation Science, 1(4), 376-396.

Species Account Citation: AmphibiaWeb 2020 Ranitomeya sirensis: Sira Poison Frog <https://amphibiaweb.org/species/6580> University of California, Berkeley, CA, USA. Accessed Nov 24, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 24 Nov 2024.

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