Description

Adult morphology

The hand is approximately 1.0 - 1.1 times the length of the forearm, totaling about 24% of the snout-vent length. The palmar tubercle is either oval or triangle-shaped, but is not well pronounced in many individuals. They lack an outer metacarpal fold and there are no supernumerary tubercles present. There are no fringes on the fingers, and their relative lengths are as follows: III > I > II > IV. Each finger has at least one relatively weak subarticular tubercle, but fingers III and IV have two of them. The fingers also have dorsal scutes and small discs (Grant and Myers 2013).

The tibia is approximately 43 - 46% of the snout-vent length and the foot is 38 - 44% of the snout-vent length. There is a pronounced tarsal keel about ⅓ of a tarsal length from the inner metatarsal tubercle. The outer metatarsal tubercle is very round, but the inner metatarsal tubercle is bigger and more of an elongate, oval shape. There is a weakened outer metatarsal fold at the outermost edge of the outer metatarsal tubercle that lined the foot edge. Appressed relative toe length are as follows: IV > III > V > II > I, with toes III and IV being webbed, but no toe fringes present. Toes I and II had one subarticular tubercle, while toes III and V had two and toe IV had two or three (Grant and Myers 2013).

DIAGNOSIS:

Both male and female individuals of S. punctiventris showed dark brown or black spotted markings down the center of their throats; these spots differentiate them from most other Silverstoneia species, which have solid colored throats, with the exception of S. gutturalis. Differences between S. punctiventris and S. gutturalis include shape, size, and arrangement of the throat’s markings: S. punctiventris’ spots are smaller, more circular, and seemingly randomly arranged while S. gutturalis’ spots are typically a bit larger in size, more oval-like in shape, and arranged in pairs throughout the neck. Silverstoneia gutturalis also featured a large splotch down the center of the throat beginning directly under the rictus whereas S. punctiventris only had the small, round markings. Silverstoneia punctiventris also has shanks with largely marked bands on the inner surface — composed of dark colored stripes or spots — while S. gutturalis has either no shank markings or very lightly colored ones. Lastly, the dorsal surface of the S. punctiventris’ feet had dark colored markings, usually circular or in thicker stripes, while S. gutturalis’ feet are lighter in color with few or no markings (Grant and Myers 2013).

COLORATION:

In life, S. punctiventris’ dorsum is a solid brown color with a white oblique, lateral stripe and a darker brown or black coloring between the ribs and hips. A bronze-colored stripe can also be found along the lips. The posterior thighs are a graded yellow that gradually becomes brighter toward the posteriorly. Their stomach and throat are a solid white with dark black markings, but became a solid yellow-green color under their back legs. Their eye color, both iris and the ring around the pupil, is a golden color (Grant and Myers 2013).

For coloration in preservative, see Grant and Myers 2013.

VARIATION:

Males and females slightly differed in color on the underside of the neck and stomach. Females had more circular and dark black markings on their entirely white undersides, while the males had a more grayish throat and lighter colored spots. Males also featured a swollen third finger and pale coloring on the lateral and dorsal surfaces of the thighs (Grant and Myers 2013).

Tadpole Description:

For comparisons of S. dalyi, S. erasmios, S. flotator, S. minima, S. nubicola, and S. punctiventris see Dias et al. 2021.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Colombia

View distribution map in BerkeleyMapper.

Silverstoneia punctiventris is found in Western Colombia and in some extreme parts of Eastern Panama. These frogs are regularly found in low and moderate elevations of 80 - 200 m along the mountain slopes of central Serranía del Baudó Colombia, facing the Pacific ocean. Although this species was collected near rocky clear-water rivers, S. punctiventris is not found strictly in riparian habitats and are considered forest-dwelling frogs as they are also found among the leaf litter in the flat areas of the lowland forest ground (Grant and Myers 2013).

Life History, Abundance, Activity, and Special Behaviors
Silverstoneia punctiventris has been found up to 5 m from streams along clear, rocky water and in the moist vegetation of forested areas away from the stream (Grant and Myers 2013). They are considered a non-migrant species (IUCN 2020).

Similarly to the many other species within the genus Silverstoneia, S. punctiventris is diurnal (Dias et al. 2021).

Male S. punctiventris seem to be strongly territorial, as they consistently returned to the same perches they were on after making calls and escaping into the leaf litter. Territorial calls consisted of two peeps, with the second peep being higher pitched than the other. The frequency of these calls were not recorded (Grant and Myers 2013).

There is not a lot of information on the reproductive mode of S. punctiventris; however, within the genus Silverstoneia, the parental care is done primarily by the males. This type of parental care involves the transport of their offspring, where the early-stage tadpoles ride on the backs of the males as they are carried from their terrestrial nests to aquatic sites (Dias et al. 2021).

Despite being a cryptically colored species, S. punctiventris contains alkaloids and volatile organic compounds (VOCs), making it a chemically defended species. From previous research, it is known that alkaloids can be toxic or unpalatable in taste. The alkaloids and some VOCs present in S. punctiventris may have olfactory avoidance functions, such as deterring predators with their smell (i.e. communicating to predators from a distance that the amphibian is toxic or unpalatable) or using odors as a form of camouflage (Gonzalez et al. 2021).

Trends and Threats
As of 2022, there is little to no information about the population size of S. punctiventris, but it is suspected that the population is decreasing due to the increasing decline in the range and quality of their habitat, thus earning it an IUCN Red List threat status of “Endangered”. Habitat is lost to the harvesting of wood, mining activities, and agriculture and aquaculture. However, the species’ distribution is near a ​​Parque Nacional Natural Utría in Chocó, Columbia, making it likely that members of this species are within and protected by the national park (IUCN 2020).

The increasing popularity of the pet trade could also pose a risk for S. punctiventris (IUCN 2020).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Mining
Intentional mortality (over-harvesting, pet trade or collecting)

Comments

PHYLOGENETIC RELATIONSHIPS:

Direct optimization parsimony analysis was performed on 12S ribosomal, 16S ribosomal, tRNAval, cytb and COI mtDNA, and the following nuclear loci: nuclear protein coding genes histone H3, rhodopsin, tyrosinase, RAG1, SIA, nuclear 28S ribosomal gene to create a Dendrobatidae phylogenetic tree. It found that S. punctiventris is sister to S. flotator. And the clade consisting of S. punctiventris and S. flotator is sister to S. nubicola (Grant et al. 2006).

Silverstoneia punctiventris was initially assumed to be a member of S. nubicola (Grant et al. 2006).

ETYMOLOGY:

This species' epithet, “punctiventris”, is derived from the Latin words “punctum,” meaning “dot or hole,” and “venter,” meaning “underside or abdomen”. Combined, these words refer to the dark spots that occur on the animals’ throat, chest, and upper belly (Grant and Myers 2013).

References

Dias, P.H.d.S., Anganoy-Criollo, M., Rada, M., Grant, T. (2021). “The tadpoles of the funnel-mouthed dendrobatids (Anura: Dendrobatidae: Colostethinae: Silverstoneia): External morphology, musculoskeletal anatomy, buccopharyngeal cavity, and new synapomorphies.” Journal of Zoological Systematics and Evolutionary Research, 59(3):691-717. [link]

Gonzalez, M., Palacios-Rodriguez, P., Hernandez-Restrepo, J., Gonzáalez-Santoro, M., Amézquita, A., Brunetti, A.E., Carazzone, C. (2021). “First characterization of toxic alkaloids and volatile organic compounds (VOCs) in the cryptic dendrobatid Silverstoneia punctiventris.” Frontiers in Zoolology, 18(39): 2021 [link]

Grant, T., Frost, D. R., Caldwell, J. P., Gagliardo, R., Haddad, C. F. B., Kok, P. J. R., Means, D. B., Noonan, B. P., Schargel, W. E., and Wheeler, W. C. (2006). ''Phylogenetic systematics of dart-poison frogs and their relatives (Amphibia: Athesphatanura: Dendrobatidae).'' Bulletin of the American Museum of Natural History, (299), 1-262.

Grant, T., Myers, C. W. (2013). ''Review of the frog genus Silverstoneia, with descriptions of five new species from the Colombian Chocó (Dendrobatidae: Colostethinae).'' American Museum Noviates, 3784, 1-58.

IUCN SSC Amphibian Specialist Group. (2020). “Silverstoneia punctiventris (amended version of 2017 assessment).” The IUCN Red List of Threatened Species 2020: e.T78586360A177155699. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T78586360A177155699.en. Accessed 22 Feb. 2022

Species Account Citation: AmphibiaWeb 2022 Silverstoneia punctiventris <https://amphibiaweb.org/species/8083> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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