Amphiuma tridactylum
Three-toed Amphiuma, Conger Eel, Congo Eel, Congo Snake, Lamprey Eel, Ditch Eel, Fish Eel
family: Amphiumidae

© 2009 Gonçalo M. Rosa (1 of 8)

View distribution map using BerkeleyMapper.

Conservation Status (definitions)
IUCN (Red List) Status Least Concern (LC)
See IUCN account.
NatureServe Status Use NatureServe Explorer to see status.
Other International Status None
National Status None
Regional Status None


bookcover The following account is modified from Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo (©2005 by the Regents of the University of California), used with permission of University of California Press. The book is available from UC Press.

Amphiuma tridactylum Cuvier, 1827
Three-Toed Amphiuma

Jeff Boundy1

1. Historical versus Current Distribution. The distribution of three-toed amphiumas (Amphiuma tridactylum) is within the Gulf Coast Plain centered around the lower Mississippi River from the Brazos River Valley in Texas to central Alabama, and north to southern Illinois and extreme southwestern Kentucky.

2. Historical versus Current Abundance. According to Petranka (1998), three-toed amphiumas are locally common and currently do not appear to need protection. The loss of swamps and other forms of wetland habitat have been offset by the creation of canals, ditches, and permanent ponds (Petranka, 1998).

3. Life History Features.

A. Breeding. Reproduction is aquatic.

i. Breeding migrations. Unknown and unlikely.

ii. Breeding habitat. All records of amphiuma nests have been out of water (Salthe, 1973b). However, Baker (1945, in Salthe, 1973b) felt that these observations were artifactual, that nests generally occur underwater and that observed nests were those stranded by drought conditions. Cagle (1948) suggested that females prefer to lay eggs underwater in submerged debris (in Salthe, 1973b).

B. Eggs.

i. Egg deposition sites. Three-toed amphiumas mate using internal fertilization. Baker (1937, in Salthe, 1973b) outlined courtship behaviors, and copulation has been observed by Baker and colleagues (1947). In Tennessee, Sturdivant (1949) reported mating from December–June (see also Salthe, 1973b; Behler and King, 1998), and nesting from August to mid winter (Parker, 1937, in Salthe, 1973b). In Louisiana, mating was reported from April–September, depending on weather conditions (Wilson, 1940; Cagle, 1948; Rose, 1966a; Salthe, 1973b; and Dundee and Rossman, 1989). In Louisiana, males are in reproductive condition from January–April (Fontenot, 1999). Ovum diameter varies between 5–7 mm (Cagle, 1948; Salthe, 1973b; Petranka, 1998; Fontenot, 1999).

ii. Clutch size. About 200 eggs are laid in a strand 5–12 cm long that becomes tangled in the nesting cavity (Behler and King, 1998; Petranka, 1998). Cagle (1948) counted follicles and found an average of 98 eggs (range 42–131). However, Rose (1966a) examined larger females and found an average of 201 eggs with a maximum of 354 (see also Dundee and Rossman, 1989; Bartlett and Bartlett, 1999a). Similarly, working in Louisiana, Fontenot (1999) found a mean of 201.4 eggs (range 44–282, n = 14). Cagle (1948) and Fontenot (1999) suggest that the incubation period may be about 5 mo. Eggs ready to hatch have been found in August in Arkansas (Hay, 1888; Salthe, 1973b) and November in Louisiana (Baker, 1945, Salthe, 1973b). In Louisiana, oviposition begins in early July (Fontenot, 1999). Many reports suggest that females may have biennial (Wilson, 1942; Cagle, 1948; Salthe, 1973b; Dundee and Rossman, 1989) or triennial (35% gravid females; Fontenot, 1999) reproductive cycles. Dundee and Rossman (1989) repeat Viosca’s findings that three-toed amphiumas may be ovoviviparous.

C. Larvae/Metamorphosis.

i. Length of larval stage. Apparently short; gills are lost about 3 wk after hatching (Ultsch and Arceneaux, 1988; Petranka, 1998). Cagle (1948) and Liner (1954) found young with vestiges of external gills in November in Louisiana and Alabama. Hatchlings average 64 mm in length (Dundee and Rossman, 1989).

ii. Larval requirements. Found in the same habitats as adults.

a. Food. Unknown.

b. Cover. Young animals have been found schooling (Parker, 1939; Baker, 1945, in Salthe, 1973b).

iii. Larval polymorphisms. Have not been reported.

iv. Features of metamorphosis. Gills are lost about 3 wk after hatching (Ultsch and Arceneaux, 1988; Petranka, 1998). Metamorphosing animals are about the same size as hatchlings, approximately 60–75 mm TL (Barbour, 1971; Dundee and Rossman, 1989).

v. Post-metamorphic migrations. Unknown and unlikely.

vi. Neoteny. Three-toed amphiumas, as well as the other two species in the family Amphiumidae, are considered to be obligate neotenes (Duellman and Trueb, 1986).

D. Juvenile Habitat. Juveniles use smaller retreats (e.g., tiny holes in mud, discarded cans, etc.) and floating mats of vegetation (C. Fontenot, personal communication) more often than adults.

E. Adult Habitat. Adults are nocturnal; according to Petranka (1998) peak activity occurs 3–4 hr after sunset. Adult three-toed amphiumas occupy bottomland swamps, bayous, cypress swamps, and streams (Behler and King, 1998; Conant and Collins, 1998). They are especially abundant in drainage ditches in suburban and agricultural areas of the lower Mississippi River (Behler and King, 1998). Three-toed amphiumas will frequently inhabit crayfish burrows and can co-exist with fishes (Petranka, 1998). Three-toed amphiumas will move overland during and following heavy rains, and Petranka (1998) reports they have been observed ≤ 12 m away from the water’s edge.

F. Home Range Size. Usually remain within a restricted area, but Cagle (1948) reports dispersal ≤ 396 m (see also Petranka, 1998).

G. Territories. Adult males will fight, suggesting that either territories are defended or there is competition for females (Dundee and Rossman, 1989).

H. Aestivation/Avoiding Dessication. According to Petranka (1998), adult three-toed amphiumas are capable of burrowing through soft mud and utilizing crayfish burrows. They can remain in these refugia for many months without feeding.

I. Seasonal Migrations. Barbour (1971) reports that on rainy nights, amphiumas may be seen wandering on land in swampy areas. They are also known to cross roads, especially during rains (J.B., personal observations).

J. Torpor (Hibernation). Unknown.

K. Interspecific Associations/Exclusions. Three-toed amphiumas occur sympatrically with two-toed amphiumas (Amphiuma means) in parts of their range.

L. Age/Size at Reproductive Maturity. From 45.7–106 cm (18–41 3/4 inches; Behler and King, 1998), although Fontenot (1999) found the minimum size of gravid females to be 33 cm body length.

M. Longevity. Not reported.

N. Feeding Behavior. Crawfish constitute a large proportion of the diet, followed by annelids, insects, mollusks, fishes, and even skinks. Fontenot and Fontenot (1989) found the remains of a snapping turtle (Chelydra serpentina; see also Petranka, 1998). Vegetation is probably ingested incidentally. Seasonal differences reflect prey availability (Chaney, 1951; Dundee and Rossman, 1989). After capturing prey, amphiumas often twist violently, which may assist in incapacitating the prey or reduce the risk of the prey attacking them (see Petranka, 1998). The biomechanics of feeding have been detailed by Erdman and Cundall (1984).

O. Predators. Preyed upon by mudsnakes (Faracina abacura) and cottonmouths (Agkistrodon piscivorous; Behler and King, 1998).

P. Anti-Predator Mechanisms. Amphiumas are known to inflict a painful bite and are also known to flee when capture is attempted (Barbour, 1971; Dundee and Rossman, 1989; Petranka, 1998). Amphiumas may whistle when agitated (Baker, 1937; see also Petranka, 1998). Amphiumas are covered with a mucus slime and have thick skin, which makes them extremely difficult to grasp.

Q. Diseases. None reported.

R. Parasites. The trematodes Telorchis stunkardi, Cephalogonimus amphiumae, and Megalodiscus americanus; as well as the nematode, presumably Filaria amphiumae, were documented in amphiumids from Louisiana (Chandler, 1923). Turtle leeches (Placobdella sp.) were found on an amphiuma in Louisiana (Saumure and Doody, 1998).

4. Conservation. Because these animals breathe through their skin, certain chemicals can adversely affect their respiration, forcing them from the water. For example, rotenone, a widely used poison that causes fish gills to constrict, is thought to similarly constrict the integumentary vessels of amphiumids (Dundee and Rossman, 1989). The use of such chemicals as a management technique in amphiumid habitat could contribute to the decline of the species. Large-scale amphiuma kills were noted in Louisiana following flushing of chlorine into a drainage ditch and after a gasoline spill in a bayou and swamp (J.B., personal observations). Three-toed amphiumas are considered widespread and abundant in Louisiana. Several dozen per year are sold from Louisiana as pets, while from several hundred to about 1,000 are sold annually to biological suppliers for laboratory experiments. Most are taken as off-catch during crayfish trapping. Commercial take dropped drastically during a 3-yr drought, but this was due to a reduction in crayfish trapping (J.B., personal observations).

1Jeff Boundy
Louisiana Department of Wildlife and Fisheries
P.O. Box 98,000
Baton Rouge, Louisiana 70898-9000

Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.

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