Description
Allobates ignotus is a slender-bodied frog with adult males that have a snout vent length range of 16.4 - 18.3 mm and adult females that have snout-vent length range of 16.9 - 20.9 mm. The head is longer than wide and is slightly narrower than the body. The snout is slightly rounded and protrudes beyond the upper lip, the nares protrude slightly and are angled to the sides, the canthal ridges are slightly rounded when viewed from the side, and the loreal region is flat. The eyes are about two-fifths the length of the head. The lower, anterior part of the tympanum is distinct, and the rest is obscured by a bulge. The skin is mostly smooth with granules around the sacrum and thigh regions. The forelimbs are moderately sized, and the hands are the same length as or slightly longer than the forearms. The first finger is the same length as or slightly longer than the second finger, the third finger is the longest, and the fourth finger is the second-longest. The fingers have very slight keels, and the finger discs are slightly enlarged. The hind limbs are also moderately sized, and the toes have basal webbing from toes two to four. The fourth toe is the longest, followed, in order of decreasing size, by the third, fifth, second, and first toe. The toe discs are moderately enlarged, and the toes have slight fringes, which are most prominent on the second, third, and fourth toes (Anganoy-Criollo 2012).

Free-swimming tadpoles have been described at Gosner stages 25 - 29. The average total length of the tadpoles is 12.2 mm at stages 25 - 26, 16.2 mm at stage 27, and 19.4 mm at stages 28 - 29. Tadpoles have an ovoid body, and the tail makes up more than half the total length. The snout is rounded, the nostrils are circular or ovoid, and the nostrils and eyes are positioned dorsally. The oral disc is positioned ventrally and is mostly surrounded by papillae, except on the anterior side. The jaw sheaths are keratinized, and the lower jaw sheath has serrations with rounded tips. The spiracle is cylindrical and positioned sinistrally, and the vent is short and positioned dextrally. The inner intestines can be seen through the translucent skin. In addition, the lateral line system is visible and symmetrical from the supraorbital to the ventral trunk lateral lines. The tail tip is rounded, and the dorsal fin starts where the tail meets the body (Granda-Rodríguez et al. 2018).

DIAGNOSIS:

Unlike all other Allobates species, A. ignotus has three continuous stripes down each side, basal webbing between toes two through four, and the preaxial side of the third finger enlarged in adult males. The back is smoother than in other Allobates species. Morphologically, of all Allobates, A. ignotus most closely resembles A. wayuu. However, A. ignotus has a cream-colored ventral region in both sexes and a dark brown chest region in males, whereas A. wayuu has a mottled ventral region and no sexual dimorphism in the chest coloration. Additionally, the dorsolateral stripes reach the thigh in A. wayuu but not in A. ignotus, and adult A. ignotus are larger than adult A. wayuu (Anganoy-Criollo 2012). With regards to vocalizations, A. ignotus’ mating calls have more notes, on average, than others of the Allobates genus (between six and 116 notes per call). Allobates myersi and A. paleovarsensis only give 5 - 10 and 3 - 21 notes per call, respectively (Granda-Rodríguez et al. 2018).

COLORATION:

Live adults are brown overall with dark brown markings on the back and head. A broad, dark brown lateral band above a thin, pale lateral stripe extends along the frog’s sides from snout to vent. The forelimbs are dull-yellow. Females have dull-yellow hind limbs, and males have brown hind limbs. All the limbs have dark brown rings. The coloration in preservative is similar, but the forelimbs are more cream-colored and the ventrums are cream-colored in preserved females and darker in males (Anganoy-Criollo 2012).

Tadpoles in preservative are translucent with brown dots that are uniformly distributed on the body, and the jaw sheaths are black or dark brown (Granda-Rodríguez et al. 2018).

VARIATION:

Adult males and females have slight sexual dimorphism in their coloration. Females have dull-yellow hind limbs, and males have brown hind limbs. The frogs’ undersides are cream-colored in preserved females, and darker in males: the chest and throat region are mostly brown in preserved males, and mostly black in live males (Anganoy-Criollo 2012).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Colombia

View distribution map in BerkeleyMapper.

Allobates ignotus is found in western Serranía del Perijá and the Department of La Guajira, Colombia. It occurs in both the wet and dry tropical forests of this region between elevations of 194 and 1236 meters, with a range of 605 km² (Granda-Rodríguez et al. 2018).

Life History, Abundance, Activity, and Special Behaviors
Allobates ignotus is diurnal (Anganoy-Criollo 2012) and active year-round in these riparian habitats. They dwell in and around leaf litter and among the rocky substrate, wooden logs, and the lowest branches of the trees adjacent to shallow and slow-moving streams (Granda-Rodríguez et al. 2018).

The male’s advertisement call consists of a series of pulsed notes with an average overall call duration of about 8 seconds, an average rate of 3.94 notes per second, and a frequency range of 4,600 - 14,000 Hz. Calls can have between six and 116 notes per call. Males show some degree of call site fidelity (Granda-Rodríguez et al. 2018).

Their reproductive mode is characterized by indirect development and free-swimming tadpoles. Tadpoles have been found in puddles near the edges of a stream (Granda-Rodríguez et al. 2018).

Trends and Threats
Potential threats to this species include habitat loss and degradation due to drought, mining and mining waste, and other chemical pollutants (Granda-Rodríguez et al. 2018). There is also livestock farming in the region, which is a possible threat (IUCN 2017).

The population has fluctuated and is suspected to be in decline according to surveys performed between 2010 and 2014 in the Canime Creek Basin of Columbia. However, Granda-Rodríguez et al. (2018) recorded the species in six new locations and recommended downgrading their conservation status from “Endangered” to “Vulnerable.”

Relation to Humans
Allobates ignotus occurs in disturbed habitat used for mining and cattle farming (Granda-Rodríguez et al. 2018).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Prolonged drought
Mining
Habitat fragmentation
Local pesticides, fertilizers, and pollutants

Comments
Allobates ignotus was assigned to the genus Allobates based on various morphological characters, including the pattern and coloration of stripes, the type of toe webbing, the size of the fingers and finger discs, the coloration of the throat and testes, and the tongue morphology (Anganoy-Criollo 2012). Additionally, A. ignotus tadpoles have a relatively wide gap in their second row of anterior labial teeth, and molecular and phenotypical evidence indicate that this could be a synapomorphy of Allobates (Granda-Rodríguez et al. 2018). As of 2012, the phylogenetic relationship of A. ignotus to other species within Allobates is unknown (Anganoy-Criollo 2012).

ETYMOLOGY:

The species epithet, “ignotus” means “unknown” in Latin, and refers to the lack of research on Columbian species in the genus Allobates (Anganoy-Criollo 2012).

References

Anganoy-Criollo, M. (2012). "A new species of Allobates (Anura, Dendrobatidae) from the western flank of the Serranía de Perijá, Colombia." Zootaxa, 3308(1), 49-62. [link]

Granda-Rodríguez, H.D., Montes-Correa, A.C., Jimenez, J.D., Criollo, M.A. (2018). “Natural history and conservation of the Nurse Frog of the Serranía del Perijá Allobates ignotus (Dendrobatoidea: Aromobatidae) in northeastern Colombia.” Acta Herpetologica, 13(1), 51-64. [link]

IUCN SSC Amphibian Specialist Group. (2017). "Allobates ignotus." The IUCN Red List of Threatened Species 2017: e.T77187242A85872707. https://dx.doi.org/10.2305/IUCN.UK.2017-2.RLTS.T77187242A85872707.en. Downloaded on 15 February 2021.

Species Account Citation: AmphibiaWeb 2021 Allobates ignotus: Nurse frog of the Serranía de Perijá <https://amphibiaweb.org/species/7824> University of California, Berkeley, CA, USA. Accessed Nov 15, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 15 Nov 2024.

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