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
Bannan caecilianCeylon caecilian
Koh Tao Island caecilian
Pattipola caecilian
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.
[Article by: Ronald A. Nussbaum, PhD]
