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 pholeter Neill, 1964(b)
One-Toed Amphiuma

D. Bruce Means¹

1. Historical Versus Current Distribution. One-toed amphiumas (Amphiuma pholeter) are found in a narrow distribution of only about 80–120 km (50–75 mi) inland from the seashore in the eastern Gulf Coast Plain of the southeastern United States, from Jackson County, Mississippi (Floyd et al., 1998), to Levy and Hernando counties, Florida (Stevenson, 1967; Means, 1996a). They are known from two localities in the Ochlockonee River drainage of Georgia (Means, 1996a) and only two localities in Alabama (Carey, 1984, 1985). In Florida, one-toed amphiumas are known from about 40 localities (Means, 2001a; Florida Natural Areas Inventory, personal communication). Knowledge of the species' current distribution has accumulated recently; because the species was first recognized by Neill (1964b), there are no historical data with which to make a comparison.

2. Historical Versus Current Abundance. Current abundance of one-toed amphiumas is difficult to assess because their microhabitats are difficult to sample. Usually, at most localities, only one or two specimens are found during several person-hours of vigorous searching. At only three or four localities in Florida is it possible to find one-toed amphiumas on a regular basis (personal observations). However, no declines in current abundance at these sites have been noted over the past three decades of monitoring (personal observations).

3. Life History Features. Life history is poorly known, but see Means (1977, 1992b, 1996a, 2001a).

A. Breeding.

i. Breeding migrations. None reported.

ii. Breeding habitat. Presumably the same as that of juveniles and adults; gravid females have been found co-occurring with juveniles and adults.

B. Eggs.

i. Egg deposition sites. Eggs and hatchlings have not been found (Means, 1996a). As with two-toed amphiumas (A. means), brooding females may coil around their eggs during development.

ii. Clutch size. Unknown.

C. Larvae/Metamorphosis.

i. Length of larval stage. Poorly known; larval life is thought to be short (personal observations).

ii. Larval requirements.

a. Food. Food requirements of larvae are unknown.

b. Cover. Presumably the same as transformed juveniles and adults.

iii. Larval polymorphisms. None reported.

iv. Features of metamorphosis. Hatchlings may have thin, feathery gills and a short larval life before metamorphosing into air-breathing juveniles.

v. Post-metamorphic migrations. None reported.

vi. Neoteny. One-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. Not known to differ from that of adults because small, thin individuals (that upon dissection are obviously juveniles and probably recent hatchlings) have been collected in several localities with adults (personal communication).

E. Adult Habitat. Means (1977) analyzed the habitat qualities of 13 localities of one-toed amphiumas and found that individuals are primarily found in deep, liquid, amorphous mucks derived from hardwood and cypress litter. The most important habitat variables associated with one-toed amphiumas are (1) streams of low–moderate gradient; (2) swampy and periodically inundated floodplains; (3) mixed bottomland hardwoods and cypress; (4) seepage; and (5) vulnerability to drought. Muck, as compared with peat, is usually liquid, and decomposition of the organic material in it has progressed so far that it is relatively amorphous, not having large pieces of wood and leaf litter. Amphiumas cannot locomote through fibrous peat and are rarely found in shallow muck deposits of < 15 cm (6 in) deep (personal observations), presumably because it increases their vulnerability to predators such as raccoons.

F. Home Range Size. Unknown.

G. Territories. Have not been reported.

H. Aestivation/Avoiding Dessication. Means (1992b, 2001a) reported excavating individuals from the bottom of moist muck, where they had obviously sought refuge from drought. Animals were coiled in small chambers made by their bodies and were stimulated during excavation to move into small tunnels they appeared to have excavated.

I. Seasonal Migrations. Means (2001a) noted that in winter, one-toed amphiumas were occasionally found under large logs buried along stream courses in first-order stream valleys where the species is not found in the spring, summer, or fall. Means (2001a) speculated that some individuals migrated upstream into seepage heads of first-order valleys to find protection from cold weather in warm seeps.

J. Torpor (Hibernation). Individuals found in November–March are cold to the touch and sluggish (personal observations). In winter, one-toed amphiumas are less abundant in muck beds, indicating that they may migrate into either different microhabitats (i.e., the peaty soil held together by dense root mats of wetland shrubs) or upstream into the warmer headwater seepages.

K. Interspecific Associations/Exclusions. On several occasions, Means (2001a) has taken a few juvenile two-toed amphiumas in the same muck beds with one-toed amphiumas, but adult two-toed amphiumas have not been found at these sites.

L. Age/Size at Sexual Maturity. Means (2001a) determined that total length of a large sample of mixed sexes and juveniles was 218.3 mm (s.d. ± 41.8 mm, range 89.3–314.2 mm, n = 204), and there was no sexual dimorphism in body size. The smallest of eight gravid females was 247.3 mm in total length, but it is not known how long is required for individuals to achieve sexual maturity.

M. Longevity. Juveniles (probably recent hatchlings) were raised in the laboratory on a diet of earthworms. They reached average size in about 1 yr and lived in captivity for 5 yr before dying accidentally (Means, 2001a).

N. Feeding Behavior. Natural food contents of the guts of 100 one-toed amphiumas included sphaeriid clams, physellid snails, aquatic earthworms (Sparganophilus spp.), asellid isopods, the larvae of mayflies, tipulid flies, chironomid midges, culicid mosquitoes, stoneflies, megalopterans, tabanid flies, adults and larvae of small aquatic beetles, planarians, and occasional terrestrial beetles and lepidopteran larvae that drop onto the surface of the muck (Means, 2001a). Notably lacking from the diet are dragonfly naiads, salamander larvae, frog tadpoles, and small fish that co-habit the same mucky sites (Means, 2001a).

O. Predators. Potential predators found in the same muck beds with one-toed amphiumas are common snapping turtles (Chelydra serpentina), mud turtles (Kinosternon subrubrum), mud snakes (Farancia abacura), red-bellied water snakes (Nerodia erythrogaster), brown water snakes (N. taxispilota), queen snakes (Regina septemvittata), ring-necked snakes (Diadophis punctatus), cottonmouths (Agkistrodon piscivorus), two-toed amphiumas, southern leopard frogs (Rana sphenocephala), and bronze frogs (R. clamitans; Means, 2001a).

P. Anti-Predator Mechanisms. One-toed amphiumas have a noxious skin secretion that produces foam when animals are collected. This secretion is bitter tasting and slightly numbing (personal observations).

Q. Diseases. None observed.

R. Parasites. Parasites or gut symbionts taken from the alimentary canal include unidentified trematodes, cestodes, nematodes, and acanthocephalans (Means, 2001a).

4. Conservation. One-toed amphiumas are considered Rare in Florida (Means, 1992b), Rare in Georgia (J. Jensen, Georgia Department of Natural Resources, personal communication), under consideration for Endangered status in Mississippi (T. Mann, personal communication), and poorly known in Alabama (Means, 1986c). This Rare status may be a matter of their secretive nature and proclivity for mucky and swampy environments, which makes effective sampling difficult.

¹D. Bruce Means
Coastal Plains Institute and Land Conservancy
1313 Milton Street
Tallahassee, Florida 32303
means@bio.fsu.edu

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Dec 2024.

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