Asian tailed caecilians

(Ichthyophiidae)

Class Amphibia

Order Gymnophiona

Family Ichthyophiidae

Thumbnail description
Relatively primitive, medium-size to large caecilians that have a true tail and a subterminal (recessed) mouth; are either unicolor (lavender gray) or unicolor with paler lateral stripes

Size
Adults range in size from 6.7 to 21.7 in (170 to 550 mm) in total length

Number of genera, species
2 genera; 39 species

Habitat
The primary habitat is the forest floor (leaf litter and soil) of tropical rainforests; many species do well, however, in deforested areas under cultivation

Conservation status
Endangered: 1 species; Vulnerable: 1 species

Distribution
India, Sri Lanka, and Southeast Asia

Evolution and systematics

E. H. Taylor established this family in 1968. He believed ichthyophiids to be the most primitive of caecilians based on the presence of a tail, numerous subdivided annuli, many dermal scales in the annular grooves, and small but distinct eyes. He also assumed that all species had the ancestral (primitive) life history pattern, which includes oviparity (egg laying) and aquatic larvae that metamorphose into terrestrial adults. The life history, however, was and still is known for very few species. Taylor's Ichthyophiidae contained both Southeast Asian (Ichthyophis and Caudacaecilia) and South American (Epicrionops and Rhinatrema) genera. In 1977 R. A. Nussbaum removed the South American genera to their own family (Rhinatrematidae) and argued that the South American taxa are relatively more primitive than the Southeast Asian ichthyophiids based on morphologic characteristics. Subsequent molecular studies have supported this argument. No subfamilies are recognized.

Physical characteristics

Ichthyophiids have true tails, stegokrotaphic skulls (without temporal openings), subterminal mouths, and a relatively advanced dual jaw-closing mechanism in which the retroarticular process curves upward and the interhyoideus muscle is well developed. Primary annuli are subdivided into complete secondary and tertiary annuli. The annuli (up to 420 in some species) are orthoplicate (straight) posteriorly but angled anteriorly on the ventral surface of the anterior portion of the body. Numerous dermal scales are found in all the annular grooves. The tentacular openings are positioned in front of the eyes, usually no more than halfway to the nostrils. Species are either nearly unicolor (lavender-gray) or unicolor with yellow-cream lateral stripes.

Distribution

These caecilians occur in India, Sri Lanka, the Philippines, southern China, Thailand, Myanmar, Laos, Vietnam, and the Indo-Malayan Archipelago west of Wallace's Line.

Habitat

Asian tailed caecilians are always associated with moist soil or leaf litter or both in tropical rainforests or disturbed areas near rainforest.

Behavior

The behavior of ichthyophiids is poorly studied. All species are burrowers. Maternal guarding of embryos is known for some species. Newly hatched larvae are attracted to light. In terraria adults leave their burrows at night and crawl on the surface. They also have been found on the surface at night during heavy rains in their natural habitats.

Feeding ecology and diet

The feeding habits of ichthyophiids are poorly known. Guts of museum specimens contain large amounts of soil, probably from ingesting earthworms. Partially digested earthworms often are seen, as are parts of insects. In captivity ichthyophiids can be maintained solely on earthworms. They also eat crickets and even strips of meat (beef), fish, and chicken.

Reproductive biology

As with all caecilians, fertilization is internal. Spermatozoa are placed inside the female's cloaca via the male's phallodeum (copulatory organ). Large white eggs strung together by gelatinous strands are deposited in hidden nests, where the female attends them until they hatch. Upon hatching, the larvae leave the nest and wriggle to a stream, where they spend an unknown amount of time feeding on small aquatic organisms until they metamorphose into subadults. After metamorphosis, they leave the streams and take up a terrestrial, burrowing lifestyle.

Conservation status

Ichthyophis glandulosus is Endangered and I. mindanaoensis is Vulnerable.

Significance to humans

None known.

Species accounts

List of Species

Bannan caecilian

Ichthyophis bannanicus

taxonomy

Ichthyophis bannanicus Yang, 1984, Mengla County, Xishuangbanna, Yunnan, China.

other common names

None known.

physical characteristics

This is a medium-size to large caecilian; adults grow to 7.5–15.2 in (190–386 mm) in length. This striped species has 322–388 annular folds along the body. The tentacle is positioned in front of the eye, about one-third to one-half the distance from the eye to the nostril. It is difficult to distinguish from several other striped Ichthyophis species from Southeast Asia.

distribution

This species is known only from the region of the type locality near Mengla, Yunnan, China.

habitat

Larvae have been collected in small streams and pools in deforested areas near rice paddies. Adults have been found under logs and in mud adjacent to pools and streams after rain.

behavior

The behavior of this species is largely unknown. Adults burrow in moist soil in terraria. Larvae can swim, but normally they burrow and crawl in litter and silt on the bottoms of pools and streams.

feeding ecology and diet

Museum specimens (adults) have earthworms in their stomachs. They readily eat earthworms and crickets in captivity.

reproductive biology

Courtship, mating, and nests are unreported. The life cycle includes a larval stage.

conservation status

Not threatened.

significance to humans

None known.

Ceylon caecilian

Ichthyophis glutinosus

taxonomy

Caecilia glutinosa Linnaeus, 1758, habitat in Indies.

other common names

None known.

physical characteristics

This is a medium-size to large caecilian that attains a length of 9.1–16.1 in (230–410 mm). It is a striped species; adults have 342–392 annuli along the body. The tentacular aperture is distinctly closer to the eye than to the nostril and close to the margin of the mouth. The species is similar to Ichthyophis bannanicus and a few other striped Ichthyophis species from Southeast Asia.

distribution

The species occurs in Sri Lanka.

habitat

Most specimens have been taken from deforested agricultural areas. They have been found in piles of rotting vegetation and

manure and in loose, wet soil. One individual was dug up from the soil of a moist meadow.

behavior

The behavior of this species is poorly known. When prey (earthworms) are grasped on the surface, the caecilian retreats backward into the burrow while vigorously twisting its head and neck to subdue the prey. Sometimes the caecilian spins on its longitudinal axis, which may break the prey into small, more manageable pieces.

feeding ecology and diet

Subadults and adults eat mainly earthworms but also other small litter and soil invertebrates. The food of larvae is unknown, but they eat small bloodworms and earthworms in captivity.

reproductive biology

Details of courtship and mating have not been reported, but the species is oviparous. Females deposit 25–38, large white eggs in jelly strings. The eggs are placed in hidden nests (cavities in soil), and the female coils around them until they hatch. Larvae range in size from about 2.8 to 4.5 in (70 to 115 mm) in total length. The larvae metamorphose (in captivity) after about 280 days.

conservation status

Not threatened.

significance to humans

None known.

Koh Tao Island caecilian

Ichthyophis kohtaoensis

taxonomy

Ichthyophis kohtaoensis Taylor, 1960, Koh Tao Island (west side), Gulf of Siam.

other common names

German: Koh-Tao-Blindwuehle.

physical characteristics

The Koh Tao Island caecilian is a medium-size to large caecilian; it attains a length of 7.6–13.8 in (192–350 mm). This striped Ichthyophis species has 362–366 annular folds along the body. This caecilian is similar to I. bannanicus and I. glutinosus, but it has a smaller head with a more rounded snout.

distribution

The species occurs on Koh Tao Island in the Gulf of Siam and mainland peninsular Thailand.

habitat

It inhabits the forest floor of tropical rainforest and deforested agricultural sites.

behavior

These caecilians are burrowers. Sometimes they are seen on the surface at night.

feeding ecology and diet

The diet is largely unstudied, but this species eats earthworms and other small invertebrates.

reproductive biology

Females deposit nine to 47 large white eggs in jelly strings in hidden nests, usually cavities in the soil. The female remains coiled around the eggs until they hatch after about 70–80 days. The hatchlings grow from about 2.8 to 5.9 in (70 to 150 mm) in length in 10–14 months, at which time they metamorphose.

conservation status

Not threatened.

significance to humans

None known.

Pattipola caecilian

Ichthyophis orthoplicatus

taxonomy

Ichthyophis orthoplicatus Taylor, 1965, Pattipola, Central Province, Ceylon.

other common names

None known.

physical characteristics

The Pattipola caecilian is a medium-size to large species that grows to 8.3–12.1 in (210–307 mm) in length. This unstriped caecilian is a uniform lavender-gray with 282–335 annular folds along the body. The tentacular opening is distinctly closer to the eye than to the nostril.

distribution

This species occurs in Sri Lanka.

habitat

Adults have been found in piles of rotting vegetation and manure and in soil along streams.

behavior

Their behavior is largely unknown, although they are burrowers.

feeding ecology and diet

The stomachs of these caecilians contain soil and remains of earthworms and insects.

reproductive biology

The details of their reproductive biology are unknown, but it is presumed that they are similar to the habits of other species of Ichthyophis.

conservation status

Not threatened.

significance to humans

None known.

Resources

Books

Himstedt, W. Die Blindwühlen. Magdeburg, Germany: Wolf Graf von Westarp, 1996.

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

Periodicals

Breckenridge, W. R., and S. Jayasinghe. "Observations on the Eggs and Larvae of Ichthyophis glutinosus." Ceylon Journal of Science (Biological Science) 13, nos. 1 and 2 (1979): 187–202.

——, S. Nathanael, and L. Pereira. "Some Aspects of the Biology and Development of Ichthyophis glutinosus (Amphibia: Gymnophiona)." Journal of Zoology (London) 211 (1987): 437–450.

Gans, C., and R. A. Nussbaum. "On the Ichthyophis (Amphibia: Gymnophiona) of Sri Lanka." Spolia Zeylanica 35, parts I and II (1980): 137–154.

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.

——. "Rhinatrematidae: A New Family of Caecilians (Amphibia: Gymnophiona)." Occasional Papers of the Museum of Zoology, University of Michigan no. 683 (1977): 1–30.

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

Ronald A. Nussbaum, PhD