Description
Potomotyphlus kaupii is a fully aquatic, typhlonectid caecilian (Maciel et al. 2017) that has total length between 36 - 695 mm. There may be regional differences in size. The total length is 28.8 - 68.1 times the mid-body width. The heads are relatively small, slightly depressed ventrally, longer than wide, and narrower in relation to the body. The snouts project beyond the mouth. The nostrils are subtriangular, may or may not be visible when viewed from above, and possess two large narial plugs. The eyes are not covered by skin and are visible in open orbits in most specimens, but can be indistinct in some specimens, independent of body size. The distance between the eyes is greater than the distance from the eye to the nostril and greater than the distance between the eye and the tentacular aperture. There are small anterior tentacles below the nostrils and near the margin of the mouth. These tentacles are closer to the nostrils than the corner of the mouth and cannot be seen from above. The tongue is completely attached, anteriorly, to the mandibular mucosa. There are four series of teeth, all being monocuspid. Premaxillary-maxillary tooth count has a maximum of 60 teeth with no distinct variation in size. Prevomerine-palatine teeth have a maximum count of 53 and are smaller than the premaxillary-maxillary teeth. The dentary teeth number up to 64 and are approximately the same size as the premaxillary-maxillary teeth, however, the posterior teeth are smaller in size. The splenial teeth have a maximum number of 12 and are approximately the same size as the prevomerine-palatine teeth (Maciel and Hoogmoed 2011).

The body as a whole is laterally compressed so that it is deeper than it is wide. Additionally, the body possesses a dorsal keel or fin that is especially prominent on the posterior portion of the body. Nuchal grooves are positioned laterally and ventrally, and vary in degrees of distinction. The primary annular grooves are interrupted dorsally. Along the body there are 83 - 102 primary annuli with no secondary grooves. The last 3 - 6 annuli are only laterally distinct and there are no annuli present from the approximate level of the cloaca to the terminal tip of the body. Dermal and subdermal scales are absent. The terminus shows marked sexual dimorphism with females having a narrower and more pointed terminus. The cloacal disk is elongate anteriorly and rounded posteriorly. The disk shows variation in whether it is depressed, but is surrounded by fleshy folds of skin in both sexes. Some specimens show anterior denticulations that are elongate along the cloacal disk. Anal denticulations range from 7 to 11 with a similar number for the posterior and anterior edge of the cloaca. Paired anal papillae are present in a minority of male specimens (Maciel and Hoogmoed 2011).

Potomotyphlus kaupii can be differentiated from most other Brazilian Amazonian caecilian species by having an anteriorly elongated cloacal disk and 83 – 102 primary annuli. More specifically, the absence of dermal scales differentiates P. kaupii from all Brazilian Amazon Brasilotyphlus, Caecilia, and Microcaecilia. The lack of a true tail and a snout that projects beyond the mount differentiates P. kaupii from Rhinatrema bivittatum and R. ron. The focal species can be differentiated from Siphonops annulatus by having tentacles that are closer to the nostrils than the eyes and lacking white rings around the body (Maciel and Hoogmoed 2011). From other member of the family Typhlonectidae, of which it is a member, it can be differentiated by lacking choanal valves with long medial apertures (Wilkinson and Nussbaum 1997). More specifically, P. kaupii can be differentiated from Nectocaecilia petersi by the focal species having a laterally compressed body with a dorsal fin (Maciel and Hoogmoed 2011), fewer primary annuli, and fewer vertebrate. Potomotyphlus kaupii has more primary annuli and vertebrate than Chthonerpeton indistinctum. From Atretochoana eiselti, Potomotyphlus kaupii is unique in having an elongated cloacal disk, a different pattern of cloacal disk denticulations, and relatively smaller head, nuchal collars, and anterior body in comparison with the rest of the body. Lastly, P. kaupii has more vertebrate than members of its sister genus, Typhlonectes (Wilkinson and Nussbaum 1997).

In life, Kaup’s caecilians are shades of gray or brown with the grooves along the body possibly being darker. A freshly dead female had a blue-grey color on its body and a paler head. The dead specimen had a white-blue underside and the grooves of the primary annuli were darker than the rest of the body. A live specimen had grey dorsal coloration that transitioned into a blue head and a whitish ventral surface (Maciel and Hoogmoed 2011). In preservative, the range of dorsal coloration is dark grey-brown to blue-grey (Wilkinson and Nussbaum 1997).

There is sexual dimorphism that is manifested in the cloacal region with the males having a more sunken disc than females and smaller females having no cloacal depression. Females also have a narrower and more pointed terminus. Lastly, anal papillae are not present in all individuals (Maciel and Hoodmoed 2011).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Venezuela

View distribution map in BerkeleyMapper.

Potomotyphlus kaupii has a distribution that includes the Amazon and Orinoco drainage systems. Specifically, the species can be found in the countries of Ecuador, Columbia, Venezuela, French Guiana, Peru, and Brazil in the Brazilian states of: Acre, Amapà, Amazonas, Goiàs, Parà, Rondônia, and Roraima (Oliveira et al. 2012). In French Guiana, the species was specifically found in the Oyapock River between French Guiana and Amapá, Brazil (Maciel and Hoogmoed 2011). The species may also extend into Bolivia (Wilkinson et al. 2010).

This aquatic species is found in inland wetlands, forests, and grasslands at elevations up to 500 m (Wilkinson et al. 2010).

Life History, Abundance, Activity, and Special Behaviors

Potomotyphlus kaupii is believed to be fully aquatic (Wilkson and Nussbaum 2006, Maciel et al. 2017). Specimens have been reportedly collected at night in a cataract area of shallow water at the edge of a river suggesting they can probably survive in running water (Maciel and Hoogmoed 2011).

They are known to eat small fish in the wild (Presswell et al. 2002) and are regularly caught in shrimp traps in Belém, Brazil (Maciel and Hoogmoed 2011).

Like most other aquatic members of the family Typhlonectidae, P. kaupii possesses lungs. However, the species also has many circulatory and respiratory adaptations similar to the lungless A. eiselti, indicating that P. kaupii utilizes some form of cutaneous respiration (Maciel et al. 2017).

Trends and Threats
Potomotyphlus kaupii is listed as “Least Concern” by the IUCN Red List because of its wide distribution, a presumably large population, and a presumably stable population trend. It is also found in protected areas through its range (Wilkinson et al. 2010). However, in Ecuador, the species has a “Near Threatened” status (Coloma et al. 2011).

Relation to Humans
In Belèm, Brazil, P. kaupii are often caught in shrimp traps (Maciel and Hoogmoed 2011).

Possible reasons for amphibian decline

General habitat alteration and loss

Comments
Initially, the species was thought to be the sister taxa to the lungless A. eiselti based on 141 morphological characters and life history (Wilkson and Nussbaum 1999). However, Maximum Likelihood analysis on 12S, 16S, and CO1 mitochondrial DNA along with CXCR4, H3, SIA, Slc8a3, and Rag1 nuclear genes indicates that P. kaupii is sister to the members of the genus Typhlonectes and that the shared morphological characters with A. eiselti are the result of convergent evolution. The results further indicate that A. eiselti is sister to the clade composed of P. kaupii and the members of the genus Typhlonectes; while, this relationship is poorly supported in the molecular analysis, it was a consistent result and is supported in a joint molecular and morphological analysis (Maciel et al. 2017).

The families Typhlonectidae and Caeciliidae have well supported molecular and morphological evidence of being sister taxa (Maciel et al. 2017). Potomotyphlus kaupii is within the family Typhlonectidae. As of 2019, P. kaupii was the only known species in the genus.

Potomotyphlus kaupii was first described and named Caecilia kaupii by Berthold 1859. Since it was first described, it has been given many different names including Caecilia dorsalis, Typhonectes dorsalis, Chthonerpeton microcephalum, Typhonectes kaupii, and Potomotyphlus melanochrus (Frost 2016).

This species was featured as News of the Week November 4, 2024:

Caecilians largely live fossorial and/or aquatic lifestyles, making them less easily studied and thus, less understood than other amphibian groups. Araujo et al. (2024) aimed to fill in some basic ecological data for the Amazonian aquatic caecilian Potomotyphlus kaupii, by continuously observing a number of individuals over a 14-month period as well as examining museum specimens. Females were consistently more abundant than males in the population studied. Female and male bodies could be differentiated in individuals that were 360 mm or larger, a larger circumference at midbody and body mass in females, but larger cloacae in males. Additionally, larger females contained a greater number of eggs than smaller females. Interestingly, the researchers observed cloacal discharge when handled, which had never been observed before in P. kaupii but has been observed in other vertebrates, including squamate reptiles and frogs, and may be a defense mechanism. (Written by Molly Womack)

References

Coloma, L. A., Guayassamin, J. M., Guerrero-Menèndez, P., (2011). ''Potomotyphlus kaupii''. In: NRL 2011. National Red List of Threatened Species. www.nationalredlist.org. Downloaded 3 December 2016. [link]

Frost, D. R. (2016). Amphibian Species of the World: an Online Reference. Version 6.0 Accessed 7 December 2016. Electronic Database accessible at http://research.amnh.org/herpetology/amphibia/index.html. American Museum of Natural History, New York, USA.

Maciel, A. O., Hoogmoed, M. S. (2011). ''Taxonomy and distribution of caecilian amphibians (Gymnophiona) of Brazilian Amazonia, with a key to their identification.'' Zootaxa, 2984, 1-53.

Maciel, A.O., Sampaio, M.I.C., Hoogmoed, M.S., Schneider, H. (2017). ''Phylogenetic relationships of the largest lungless tetrapod (Gymnophiona, Atretochoana) and the evolution of lunglessness in caecilians.'' Zoologica Scripta, 46(3), 255-263. [link]

Oliveira, U. S. C., Meneghelli, D., Messian, M. R., Gomes, I. B. S. R., Coragem, J. T. (2012). ''First record of Potomotyphlus kaupii (Berthold, 1859) (Gymnophiona: Typhlonectidae) for the state of Rondônia, Brazil.'' Herpetology Notes, 5, 155-156. [link]

Presswell, B., Gower, D. J., Oomen, O. V., Measey, J., Wilkinson, M. (2002). ''Scolecophidian snakes in the diets of south American caecilian amphibians.'' Herpetological Journal, 12, 123-126. [link]

Wilkinson, M. and Nussbaum, R.A. (1997). ''Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae).'' Biological Journal of the Linnean Society, 62, 39-109.

Wilkinson, M., Measley J., La Marca, E., Coloma, L. A., Ron, S., Castro, F., (2010). ''Potomotyphlus kaupii''. In: IUCN 2010. Red List of Threatened Species. www.iusnredlist.org. Downloaded 21 March 2019.

Wilkinson, M., and Nussbaum, R. A. (1999). ''Evolutionary relationships of the lungless caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae).'' Zoological Journal of the Linnean Society, 126, 191-223.

Species Account Citation: AmphibiaWeb 2024 Potomotyphlus kaupii: Kaup's Caecilian <https://amphibiaweb.org/species/1960> University of California, Berkeley, CA, USA. Accessed Dec 4, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 4 Dec 2024.

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