Typhlonectes compressicauda
TAXONOMY
Caecilia compressicauda Duméril and Bibron, 1841, French Guiana. Typhlonectes compressicauda is a member of a group of five genera thought to be closely related because of certain shared, derived characters, mostly associated with semi-aquatic to aquatic habits. The group is recognized as a family by most biologists expert on caecilians, but some phylogenetic analyses place them within the paraphyletic family Caeciliidae. It is difficult to distinguish compressicauda from T. natans; much of the information in the literature purportedly describing T. compressicauda and its biology really pertains to T. natans.
OTHER COMMON NAMES
None known.
PHYSICAL CHARACTERISTICS
Typhlonectes compressicauda, like most "typhlonectids," lacks secondary body annuli, and its annuli are distinct. Animals are gray to dark blue–black, and nearly uniform in color. Adults are 11.8–21.7 in (300–550 mm) total length. They have moderately long, flattened heads. They also have a slight dorsal "fin" or ridge that extends from the anterior third of the body to its end. The vent (cloacal) region is flattened, forming a disk that is paler in color. Features associated with its aquatic habit include the body fin, lateral body compression, large choanae, and development of both lungs.
DISTRIBUTION
Typhlonectes compressicauda is found throughout the Guianas and the Amazon region; the closely related and very similar T. natans is restricted to Colombia and northwestern Venezuela.
HABITAT
This caecilian is fully aquatic, inhabiting slow-moving, warm tropical rivers and streams.
BEHAVIOR
Individuals are known to share burrows and leave them at sunset to forage for food. They have many mucous glands all over their bodies, and the secretion is apparently toxic and distasteful to fishes. Predators include large fish, snakes, and birds. There are several reports in the literature of observation of courtship by nudging and coiling around each other, intromission, and of birth in captivity the ability to view the animals in aquaria has allowed more extensive observation of their feeding, swimming, and reproductive behavior than that of the more secretive terrestrial caecilians. Pheromones have been suggested to be involved in mate attraction.
FEEDING ECOLOGY AND DIET
The animals root around in the mud of the sides and bottoms of the waterways they inhabit. They eat arthropods of various sorts, including shrimp, insect pupae, and so on, and small fish. They have the strong-bite mechanism typical of caecilians. In captivity, they feed on pieces of earthworms and liver. They do not seem to use chemosensory cues extensively to find food items; they seem to perceive presence of prey by touch or motion.
REPRODUCTIVE BIOLOGY
Typhlonectes compressicauda is viviparous, as all typhlonectids are suspected to be. The species has a seven to nine month gestation period; a female can have six to 14 developing young, with a mean of 10. The gills of typhlonectid embryos fuse into large sacs. The gills may function in uptake of nutrients as well as gaseous exchange. The gills are shed shortly after birth. The fetal dentition, different in structure and arrangement from that of the adults, is used to ingest oviductal secretions. Fetuses are fully metamorphosed at birth; even their hemoglobin has changed from the embryonic to the adult.
CONSERVATION STATUS
This species has been collected extensively, apparently with no indication of diminution of its numbers. It has been taken by fishermen (and scientists) using nets to catch fish. No formal designation of its conservation status has been attempted, but the species apparently remains locally abundant, so far as is known.
SIGNIFICANCE TO HUMANS
The ecological significance of the species has not been determined; presumably its carnivorous habits and abundance make it an effective part of the riverine food web. Many animals have been imported and sold in aquarium stores as rubber eels or black eels; only rarely are they identified as amphibians, and then they are usually called T. compressicauda. In fact, the species that has been most imported is T. natans, so many of the reports in aquarium journals bear an incorrect species name.
