Description
Nectocaecilia petersii is an aquatic caecilian described from adult specimens ranging from 240 - 720 mm (Boulenger 1882; Gorzula and Señaris 1999; de Fraga et al. 2018). The head itself is slightly narrower than the body, with a head length of around 13.3 - 16.0 mm and head width of around 10.8 - 12.0 mm (Taylor 1968; Wilkinson 1989; Maciel and Hoogmoed 2011). A rounded snout protruding beyond the snout is prominent, and relatively large, sub-triangular nostrils are visible from a dorsal view as slight notches. Small tentacular apertures are proximal to and behind the nostrils, closer to the nostrils than to the corner of the mouth; the tentacles are positioned anteriorly and not visible from a dorsal view (Boulenger 1882; Taylor 1968; Maciel and Hoogmoed 2011). The eyes are indistinct through the skin, described as distinct in an open orbit by Maciel and Hoogmoed (2011), but in socket and covered by a vague, milky-white spot by Taylor (1968). The iInterorbital distance is a little greater than the distance from snout tip to eye and greater than distance between eye and tentacle (Taylor 1968; Maciel and Hoogmoed 2011).

Within the mouth, the anterior of the thick tongue is not fully attached to the floor of the mouth. Nectocaecilia petersii also has two large narial plugs and open choanae, within which are large valves, and when the mouth is closed, the narial plugs fit into the choanae (Taylor 1968; Maciel and Hoogmoed 2011). Regarding dentition, four series of small, subequal, and monocuspid teeth can be seen (Boulenger 1882; Maciel and Hoogmoed 2011). There are a maximum of 38 premaxillary-maxillary teeth, with the posterior ones being slightly smaller than the anterior teeth. The prevomerine-palatine teeth extend posteriorly beyond the choanae, with a maximum of 34. The posterior teeth are smaller than the anterior. No diastema are between the premaxillary-maxillary teeth and prevomerine-palatine teeth. The palatal teeth and dentary teeth are around the same size as the premaxillary-maxillary teeth, for a maximum of 30 dentary teeth. A maximum of six splenial teeth, which smaller than the dentary teeth, are also present (Maciel and Hoogmoed 2011).

The body of N. petersii is elongate, roughly 27 - 37 times longer than wide, slightly wider than deep, and sub-cylindrical. The greatest diameter of the body is 16 mm, and no dorsal keel, dorsal fin, or ventral fin is present. Nuchal grooves, which feature dorsal transverse grooves on either collar, are distinct laterally, but may be indistinct dorsally and ventrally. Primary annuli range from 131 - 145 and N. petersii lacks secondary annuli, dermal scales, and subdermal scales. The primary annuli are complete posteriorly, but narrowly interrupted dorsally and ventrally along roughly 28 anterior annuli (Boulenger 1882; Taylor 1968; Maciel and Hoogmoed 2011).

An unsegmented terminal shield and sub-circular vent disk can be observed on N. petersii. Anterior to the vent, the most posterior annulus has four anal denticulations. Paired anal papillae may or may not be present. Posterior to the vent, there are five anal denticulations and the region may be compressed laterally (Maciel and Hoogmoed 2011). From the back edge of the vent to the body’s terminus, the distance is about 3 mm (Taylor 1968). Lastly, the tail itself is rounded and indistinct (Boulenger 1882).

DIAGNOSIS:

As of 2023, Nectocaecilia is a monotypic, with N. petersii being the only species. Numerous morphological characteristics separate N. petersii from other genera in Typhlonectidae, the family it is a member of. A lack of a dorsal fin, cylindrically compressed bodies, and closer proximity of tentacle foramen to the nare than eye separate N. petersii from Typhlonectes, Potomotyphlus, and whose dorsal fins are present, bodies are laterally compressed, and tentacles are in the middle between the eye and nare (Taylor 1968; Wilkinson 1989; Maciel and Hoogmoed 2011; Vitt and Caldwell 2014; de Fraga et al. 2018). Their lack of a dorsal keel and sub-triangular nostrils further differentiates N. petersii from Pseudotyphlonectes natans and Typhlonectes cunhai (Wilkinson 1989).

COLORATION:

Presumably in preservation, Boulenger (1882) describes the Upper Amazon Caecilian to be a uniform dark olive-gray with a whitish spot around the eyes. Taylor (1968) later describes the same specimen as a uniform olive-slate, the ventral surface slightly lighter than the dorsal, and the head a definite slate-color. A milky-white spot around the eyes can be seen, in addition to a lighter area around the vent.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Peru, Venezuela

View distribution map in BerkeleyMapper.

At an elevational range of 0 - 100 m, N. petersii can be found in the southern Amazonas State of Venezuela, the tropical lowlands of northwestern Amazonian Brazil, and presumably the tropical lowlands of Amazonian Columbia (Gorzula and Señaris 1999; IUCN 2004; Maciel and Hoogmoed 2011; de Fraga et al. 2018; Barrio-Amorós et al. 2019). More specifically, Gorzula and Señaris (1999) observed N. petersii in the locality of Cerro Yapacana in Venezuela. Nectocaecilia petersii has also been observed in the Brazilian localities of Reserva de Desenvolvimento Sustentável Mamirauá, Rio Tea, Alter do Chão, the Tapajós sub-basin, which cover four watersheds (Orinoco, Negro, Solimões, and Tapajós) that connect to the Amazon River (Maciel and Hoogmoed 2011; de Fraga et al. 2018; Maciel et al. 2021). Alter do Chão features patches of secondary forests and is interspersed by savannas and anthropic areas; this locality has an annual precipitation of 1,985 mm, while the Mamirauá Reserve and Rio Tea have an annual precipitation of 2,739 - 3,279 mm (de Fraga et al. 2018).

The discovery of N. petersii in Alter do Chão and the Tapajós sub-basin of the state of Acre by de Fraga et al. (2018) and Maciel et al. (2021) respectively suggest the Upper Amazon Caecilian is widely distributed throughout the Amazon. Therefore, IUCN (2004) and Barrio-Amorós et al. (2019) state that the species can presumably be found in Columbia.

Life History, Abundance, Activity, and Special Behaviors
de Fraga et al. (2018) theorize N. petersii may have more generalized habitat requirements because they found the species in a large altitudinal gradient with habitat heterogeneity and a wide range of precipitation. The distribution of aquatic caecilians are usually affected by precipitation and subsequent food availability and growth rates. Additionally, the Amazon River is theorized to affect dispersal and gene flow of the species, but more research is needed.

Nectocaecilia petersii reside within eel, Synbranchus, burrows near the banks of creeks/streams or within the roots of floating vegetation (Gorzula and Señaris 1999; Maciel and Hoogmoed 2011). Gorzula and Señaris (1999) describe the Synbranchus burrows utilized by N. petersii to be surrounded by a substrate of packed decomposed leaves, clay, and sand. Although smaller than N. petersii, the eels were not small enough to suggest they are prey items to caecilians (Gorzula and Señaris 1999). At night, the Upper Amazon Caecilian can be seen crawling on creek banks, potentially foraging (Gorzula and Señaris 1999; de Fraga et al. 2018). Additionally, if approached, the caecilian may burrow its head into the mud to hide, and if held, it may release mucus (Maciel et al. 2021).

Regarding reproductive behavior, the Upper Amazon Caecilian is viviparous, with the embryo developing within the oviducts of the mother caecilian (Taylor 1968; Wake 1977). First, the yolk provides nutrition, until its depletion, to the embryo. Then, the developing embryos engage in a form of matrotrophy called histotrophy, where the embryo absorb maternal secretions from walls of the uterus, in addition to feeding on the eggs or embryos of siblings. Lastly, the fetuses develop large sac-like gills, which surround the embryo and contact the uterine wall, functioning as a pseudo-placenta and allowing nutrient and gas exchange between fetus and parent (Vitt and Caldwell 2014).

Taylor (1968) described small fetuses of N. petersii with larval dentition, removed from the right oviduct of a pigmented area of the holotype. Roughly 75 - 100 teeth can be seen on each side of the lower jaw of a fetus. Near the tongue, the teeth lack terminal cusps and are slightly concave, while more rounded or adversely, slightly pointed teeth terminally form a “splenial” row with a lingually unattached row. On the upper jaw, the teeth are recurved and needle-like. At least 12 rows arranged in a quincuncial fashion could be seen, some of the inner rows being immature and not attached, forming a ribbon-like strip along the crests and inner faces of the premaxillary and maxillary teeth. The vomers and palatines lack teeth (Taylor 1968). The fetuses of N. petersii have gills attached dorsolaterally in the nuchal region (Wilkinson 1989).

Larva
This species displays viviparity (Taylor 1968, Vitt and Caldwell 2014). However a fetal description is provided in the "Life History" section above.

Trends and Threats
In the western portion of its range, N. petersii occurs in several protected areas, such as the Neblina National Park of Venezuela (IUCN 2004; Maciel and Hoogmoed 2011; de Fraga et al. 2018). However, the caecilian may be threatened by mining activities in Yapacana and Venezuelan Guayana, in addition to climate change and general habitat degradation (IUCN 2004; de Fraga et al. 2018; Señaris and Rojas-Runjaic 2020). de Fraga et al. (2018) believed the conservation assessment for N. petersii is out-of-date, and that more data is needed to update it.

Relation to Humans
It is possible that N. petersii is what local Ye’kuana people, who reside in the Alto Orinoco of southern Venezuela, described as “lombrices gigantes” and are eaten as delicacy (Gorzula and Señaris 1999, Paoletti et al. 2003). The Ye’kuana people traditionally consume several different earthworm species, partially used as a principal source of protein for mothers following parturition (Paoletti et al. 2003).

Possible reasons for amphibian decline

General habitat alteration and loss
Mining
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
Boulenger (1882) originally described the Upper Amazon Caecilian as Chthonerpeton petersii. Presumably due to a difference in larval dentition and numerous morphological differences, Taylor (1968) moved the caecilian to the genus Nectocaecilia. Wilkinson (1989) further supported this move due to morphological and osteological characteristics, in particular the position of the tentacular aperture and the number of nuchal and post-cloacal vertebrae. As of 2023, Nectocaecilia is monotypic (de Fraga et al. 2018), however its exact placement is still unclear.

OTHER INTERESTING INFORMATION:

The Curripaco and Baniva ethnic groups refer to N. petersii as anguilas (“eels”) and culebritas (“little snakes”), and the Ye’kuana people may refer to them as lombrices gigantes (“giant earthworms”) (Gorzula and Señaris 1999)

To find information about the holotype of N. petersii, refer to the Natural History Museum Data Portal.

References
Abraham Mijares, Enrique La Marca, Mark Wilkinson. 2004. Nectocaecilia petersii. The IUCN Red List of Threatened Species 2004: e.T59577A11952241. https://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T59577A11952241.en. Accessed on 20 April 2023.

Barrio-Amorós, C. L., Rojas-Runjaic, F. J. M., and Señaris, J. C. (2019). Catalogue of the amphibians of Venezuela: illustrated and annotated species list, distribution, and conservation. Amphibian & Reptile Conservation, 13(1), 1-198. [link]

Boulenger, G. A. (1882). Catalogue of the Batrachia Gradientia s. caudata and Batrachia apoda in the collection of the British Museum. 2d ed., London: Printed by order of the Trustees [link]

de Fraga, R., Santos-Jr, A. P., Souza, E., Kawashita-Ribeiro, R. A., Ribeiro, S., and Maciel, A. O. (2018). Notes on the poorly known caecilian Nectocaecilia petersii (Gymnophiona: Typhlonectidae) of the Brazilian Amazon. Phyllomedusa: Journal of Herpetology, 17(2), 289-293. [link]

Frank, N., and Ramus, E. (1995). A complete guide to scientific and common names of reptiles and amphibians of the world. NG Publishing, Inc.

Gorzula, S., and Senaris, J. C. (1998). Contributions to the herpetofauna of the Venezuelan Guayana. I. A data base. Scientia Guianae, 8, xvii - 269. [link]

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

Maciel, A. O., de Almeida, M. R. N., da Silva Sales, A. B., de Souza Oliveira, A., de Queiroz Andrade, L. G., da Fonseca, W. L., & Bernarde, P. S. First record of Nectocaecilia petersii (Boulenger, 1882)(Gymnophiona: Typhlonectidae) for the state of Acre, Brazil. Zootaxa, 2984, 1-53. [link]

Paoletti, M. G., Buscardo, E., VanderJagt, D. J., Pastuszyn, A., Pizzoferrato, L., Huang, Y. S., Chuang, L.-T., Millson, M., Cerda, H., Torres, F., & Glew, R. H. (2003). Nutrient content of earthworms consumed by Ye'Kuana Amerindians of the Alto Orinoco of Venezuela. Proceedings of the Royal Society of London. Series B: Biological Sciences, 270(1512), 249-257. [link]

Peters, W. (1879). Über die Eintheilung der Caecilien und insbesondere über die Gattungen Rhinatrema und Gymnopis. Monatsberichte der Königlichen Preussische Akademie des Wissenschaften zu Berlin, 1879, 924-945 [link]

Señaris, C., and Rojas-Runjaic, F. J. (2020). Amphibians and reptiles of Venezuelan Guayana: Diversity, biogeography and conservation. In: Rull, V., Carnaval, A. (eds) Neotropical Diversification: Patterns and Processes. Fascinating Life Sciences. Springer, Cham., pp. 571-633. [link]

Taylor, E. H. (1968). Caecilians of the world. University of Kansas Press.

Vitt, L. J., and Caldwell, J. P. (2013). Herpetology: an introductory biology of amphibians and reptiles. Academic press. [link]

Wake, M. H. (1977). Fetal maintenance and its evolutionary significance in the Amphibia: Gymnophiona. Journal of Herpetology, 11(4), 379-386. [link]

Wilkinson, M. (1989). On the status of Nectocaecilia fasciata Taylor, with a discussion of the phylogeny of the Typhlonectidae (Amphibia: Gymnophiona). Herpetologica, 45(1), 23-36. [link]

Species Account Citation: AmphibiaWeb 2024 Nectocaecilia petersii: Upper Amazon Caecilian; Cecilia de Peters <https://amphibiaweb.org/species/1958> University of California, Berkeley, CA, USA. Accessed Dec 26, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Dec 2024.

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