Kerala caecilians

(Uraeotyphylidae)

Class Amphibia

Order Gymnophiona

Family Uraeotyphylidae

Thumbnail description
Small to medium-sized caecilians with strongly subterminal mouths; short tails; small, distinct eyes; tentacular openings far forward, below the nostrils; primary annuli mostly or entirely subdivided by secondary annuli; and numerous dermal scales; either nearly uniformly dark lead-gray in coloration or bicolor, with undersurfaces that are whitish to yellowish cream

Size
Subadults and adults range in total length from 5.7 to 11.9 in (145 to 303 mm)

Number of genera, species
1 genus; 5 species

Habitat
Moist soil and litter in rainforests and deforested areas

Conservation status
Not threatened

Distribution
Western Ghats, peninsular India

Evolution and systematics

Until 1968 all caecilians were placed in a single family. In that year, E. H. Taylor established two new families, the Ichthyophiidae and Typhlonectidae, leaving the majority of genera and species in the original family, the Caeciliidae. Taylor retained the genus Uraeotyphlus and its four species in the Caeciliidae but thought that, based on morphologic similarities, it might belong to the Ichthyophiidae. He was reluctant to place Uraeotyphlus in the Ichthyophiidae, because the life histories of all species of the genus were unknown. In 1979R. A. Nussbaum transferred Uraeotyphlus to the Ichthyophiidae and placed it in its own subfamily, Uraeotyphlinae. W.E. Duellman and L. Trueb raised Uraeotyphlinae to family rank in 1986, and in 1996 M. Wilkinson and R. A. Nussbaum provided morphologic evidence that Uraeotyphlidae and Ichthyophiidae are sister groups. No subfamilies are recognized.

In morphologic features uraeotyphlids appear to be inter-mediate between the relatively more primitive rhinatrematid and ichthyophiid caecilians and the more advanced caeciliids. Relatively primitive characteristics of uraeotyphlids include numerous skull bones, weakly fused skull bones, eyes not covered by bone, the presence of a tail, and numerous scales. Advanced features include a strongly recessed mouth, far forward and subnarial (below the nostrils) position of the tentacular apertures, imperforate stapes (stapes bone not perforated), and lack of tertiary subdivision of the primary annuli. Based on molecular genetic data, uraeotyphlids are phylogenetically intermediate between the more ancestral ichthyophiids/rhinatrematids and the more derived caeciliids.

The skull of uraeotyphlids, with its projecting snout and strongly recessed mouth, suggests that they are better burrowers than rhinatrematids and ichthyophiids are, but they are not nearly so well adapted for burrowing as caeciliids. The latter have fewer and more solidly fused skull bones, which presumably increase burrowing efficiency compared with the uraeotyphlids.

Studies of the evolutionary relationships of uraeotyphlids and ichthyophiids based on molecular genetic data show that, most likely, they originated and diversified in isolation on the Indian continent as it drifted northward toward Asia during the Cenozoic. After contacting Asia, ichthyophiids spread out from India across Southeast Asia and the Indo-Malayan Archipelago.

The alternative scenario, that India was without ichthyophiids and uraeotyphlids when it was isolated in the Indian Ocean and received them from Asia after contact with Asia, is not supported by the genetic data.

Physical characteristics

These are small to medium-sized caecilians with short, true tails; weakly stegokrotaphic skulls (solid-skull roof), with the roofing bones nearly covering the underlying adductor mandibulae (jaw-closing) muscles; stapes not perforated by the stapedial artery; and a recessed (subterminal) mouth. The tentacular apertures are far forward of the eye, below the nostrils. Most primary annuli are subdivided by secondary annuli; the most anterior few primaries may not be subdivided. There are no tertiary annuli, and annular grooves normally do not completely encircle the body. Numerous scales are present in the annular grooves.

Distribution

These caecilians inhabit the Western Ghats in Kerala State, peninsular India.

Habitat

Their habitat is rainforest and disturbed, deforested areas within the rainforest belt. They usually are found in moist soil near streams, marshes, or other bodies of water.

Behavior

Other than their burrowing locomotion, nothing is known about their behavior.

Feeding ecology and diet

The guts of adults contain soil, earthworms, and fragments of insects. Larvae also have insect remains and mineral soil in their digestive tracts.

Reproductive biology

Almost nothing is known about the reproductive habits of uraeotyphlids. It had been assumed that they are egg layers with direct development (lacking a larval stage), because of the presence of large ovarian eggs full of yolk in some specimens, the lack of oviductal embryos in museum specimens, and the lack of reported larvae. At least one species, Uraeotyphlus oxyurus, however, has a larval stage, which suggests that the other species also might have one. The presence of larvae is considered to be an ancestral character state, which helps us understand the evolutionary position of uraeotyphlids.

Conservation status

Not threatened.

Significance to humans

None known.

Species accounts

List of Species

Kannan caecilian

Uraeotyphlus narayani

taxonomy

Uraeotyphlus narayani Seshachar, 1939, Kannan, Travancore, India.

other common names

None known.

physical characteristics

Adults range in size from 7.8 to 9.3 in (199 to 237 mm) in total length. These bicolor caecilians have a dark blue-gray dorsum and a pale, flesh-colored venter. There are 169–178 primary annuli and 77–83 secondary annuli; only the most anterior primaries are not subdivided by secondary annuli.

distribution

These caecilians are found in Kannan and Kottayam, Kerala State, India.

habitat

Details of the habitat are unknown, but the Kannan caecilian lives within the rainforest belt, presumably in moist soil and forest floor litter. Like many caecilians, this species probably occurs in agricultural areas carved out of rainforest.

behavior

Their behavior has not been described.

feeding ecology and diet

The diet is unknown, but presumably it consists of earthworms and small litter or soil invertebrates.

reproductive biology

The reproductive habits of these caecilians are not known.

conservation status

Not threatened.

significance to humans

None known.

Red caecilian

Uraeotyphlus oxyurus

taxonomy

Caecilia oxyura Duméril and Bibron, 1841, Côte du Malabar.

other common names

None known.

physical characteristics

This relatively stout-bodied species ranges in size from 7.3 to 11.9 in (185 to 303 mm) in total length. It is nearly uniformly dark bluish gray and slightly paler below. The common name is a misnomer, because there is no red coloration. There are 98–107 primary annuli and 89–104 secondary annuli. Nearly all of the primary annuli are subdivided by secondary annuli, except occasionally the most anterior one or two primaries. Numerous scales are present in the annular folds.

distribution

The species ranges across Taliparamba, Wynaad, Tinnivelly, Allur near Trichur, and Anamallai Hills in Kerala, India.

habitat

These caecilians inhabit the rainforest belt and are found in moist soil and forest floor litter in and adjacent to forest.

behavior

Their behavior is unknown, but presumably they are burrowers.

feeding ecology and diet

The diet is not known, but earthworm and insect remains have been found in the guts of museum specimens. Larvae also contain insect remains.

reproductive biology

The reproductive habits of these caecilians are largely un-known, but the species has functional (feeding) larvae that metamorphose at about 3.5 in (90 mm) in total length.

conservation status

Not threatened.

significance to humans

None known.

Resources

Books

Taylor, Edward Harrison. Caecilians of the World: A Taxonomic Review. Lawrence: University of Kansas Press, 1968.

Periodicals

Gower, D. J., A. Kupfer, O. V. Oommen, et al. "A Molecular Phylogeny of Ichthyophiid Caecilians (Amphibia: Gymnophiona: Ichthyophiidae): Out of India or Out of Southeast Asia?" Proceedings of the Royal Society of London B. (in press).

Nussbaum, R. A. "The Evolution of a Unique Jaw-closing Mechanism in Caecilians (Amphibia: Gymnophiona) and Its Bearing on Caecilian Ancestry." Journal of Zoology, London 199 (1983): 545–554.

——. "The Taxonomic Status of the Caecilian Genus Uraeotyphlus Peters." Occasional Papers of the Museum of Zoology, University of Michigan no. 687 (1979): 1–20.

Nussbaum, R. A., and M. Wilkinson. "On the Classification and Phylogeny of Caecilians (Amphibia: Gymnophiona): A Critical Review." Herpetological Monographs 3 (1989): 1–42.

Wilkinson, M. "On the Life History of the Caecilian Genus Uraeotyphlus (Amphibia: Gymnophiona)." Herpetological Journal 2 (1992): 121–124.

Wilkinson, M., and R. A. Nussbaum. "On the Phylogenetic Position of the Uraeotyphlidae (Amphibia: Gymnophiona)." Copeia (1996): 550–562.

Ronald A. Nussbaum, PhD