Description
Caecilia nigricans is a caecilian that ranges from 442 - 1,030 mm in length (Savage and Wake 2001). The body is cylindrical and elongated with its total length about sixty times its diameter. The head is an oval shape (Arroba 2017). The snout is rounded and very prominent. The eyes are visible, but small. The tentacles are below and slightly behind the nostril opening, visible on the lower surface of the snout (Boulenger 1902). Caecilia nigricans individuals have anywhere from 150 to 188 primary annuli and 42 to 62 secondary annuli (Savage and Wake 2001). The ventral opening is non-longitudinal (Lynch 2000). The tail is rounded at the tip. Caecilia nigricans have moderately large teeth, with about eight on each side of the upper jaw and six observed on each side of the lower jaw (Boulenger 1902).

While many characteristics among Caecilia are shared, C. nigricans has a distinct bluish coloration (Savage and Wake 2001). As opposed to some other Caecilia species, C. nigricans has non-contrasting primary folds (Lynch 2000). It differs from C. leucocephala (found in the same region) as it has more primary annuli [157 - 189 compared to 118 - 131], and is of a larger size [455 mm compared to 1,030 mm] (Savage and Wake 2001). Caecilia nigricans has fewer primary annuli than C. tenussima and C. thompsoni (Lynch 2000).

Caecilia nigricans color is relatively uniform all over. In life, C. nigricans has a slate gray coloration, with some hints of lavender around its sides. The areas around the mouth and vent are lighter and a whitish shade (Boulenger 1902, Smithsonian 2021).

The number of primary and secondary annuli vary from 150 to 188 primary annuli and 42 to 62 secondary annuli (Savage and Wake 2001).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Colombia, Ecuador, Panama

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

Caecilia nigricans occurs in the eastern lowlands of the southeastern Darien Province, Panama. They are also found throughout Pacific lowlands in Colombia and northern Ecuador, as well as the Caribbean drainage of Venezuela, Panama, and Colombia (Lynch 2000). Caecilia nigricans inhabits subterranean habitats, both aquatic and semi-aquatic. They can be found in a variety of different environments, including tropical rainforests, woodlands, and open areas (Lopez 2017). Caecilia nigricans has an upper elevation limit of 923 meters (Lynch 2000).

Trends and Threats
Caecilia nigricans is not a migrant species. Declines in areas may be due to the quality of habitat. There is currently no information on whether or not C. nigricans can survive in decaying open areas (IUCN 2019).

While protected in areas such as the Darien National Park in Colombia, the records of C. nigricans from Ecuador indicate that the species habitat is under the threat of deforestation (Lynch 2000). The increasing expansion of agriculture in Ecuador’s Chocoan forests has resulted in deforestation, habitat loss, and fragmentation (IUCN 2019).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Subtle changes to necessary specialized habitat
Habitat fragmentation

Comments
By sequencing the 12S, 16S, and ND1 mitochondrial genes and analyzing their phylogenetic relationships through Maximum Likelihood estimation and Bayesian Inference, it was determined that C. nigricans is a sister taxa to the group containing C. guntheri and C. buckleyi (Arroba 2017). However, other recent studies believe that this species is poorly taxonomized and is in need of review and potentially reclassification (IUCN 2019).

The name “caecilian” is from the Latin root “caecus” meaning blind. Its common name, the Rio Lita caecilian, was given after a river in Ecuador (the Rio Lita).

References

Arroba, L.T. (2017). "Sistemática del género Caecilia (Gymonphiona: Caeciliidae) de la vertiente del Pacífico de Ecuador." Escuela de Biología, 1-68.

Boulenger, G.A. (1902). ''Descriptions of new batrachians and reptiles from north-western Ecuador.'' Annals and Magazine of Natural History, Series , 7(49), 51-57. [link]

IUCN SSC Amphibian Specialist Group. 2019. Caecilia nigricans. The IUCN Red List of Threatened Species 2019: e.T59521A54355789. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T59521A54355789.en. Downloaded on 06 May 2020.

Lynch, JD (2000). "Una aproximacion a las culebras ciegas de Colombia (Amphibia: Gymnophiona)." Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales, 23, 317-338.

Savage, J. M., and Wake, M. H. (2001). ''Reevaluation of the status of taxa of Central American caecilians (Amphibia: Gymnophiona) with comments on their origin and evolution.'' Copeia, 2001(1), 52-64.

Smithsonian Tropical Research Institute. (2021). “Caecilia nigricans.” Smithsonian Tropical Research Institute. Downloaded on 15 September 2021 from https://stricollections.org/portal/taxa/index.php?taxauthid=1&taxon=10806&clid=3.

Species Account Citation: AmphibiaWeb 2024 Caecilia nigricans: Rio Lita Caecilian <https://amphibiaweb.org/species/1863> University of California, Berkeley, CA, USA. Accessed Nov 23, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 23 Nov 2024.

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