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Description

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A large, eel-like aquatic salamander. All four limbs are present, but extremely tiny, and there are only two toes on each. As in other species of Amphiuma (Family Amphiumidae), there is a single gill slit, no external gills, and the eyes are lidless (Petranka 1998). Adult two-toed amphiumas range in size from 46 - 116 cm total length. There are 57 - 60 costal grooves (average 58). The laterally compressed tail is 20-25% of the total body length. The dorsum is black to dark brown or grey and the venter is only slightly lighter (Salthe 1973; Petranka 1998). A dark patch on the chin is difficult to see against the ground coloration (Salthe 1973). Hatchlings are about 55 mm total length and all four limb are functional at the time of hatching. Gills are resorbed almost immediately after hatching. Juveniles are similar in color to adults. See Petranka (1998) and references therein.

The three species of Amphiuma are similar but can be differentiated based on the number of toes (one, two, or three), coloration, and body size.

Amphiuma means and A. tridactylum are genetically similar, while A. pholeter is quite distinct and represents an ancient evolutionary offshoot (Karlin and Means 1994). Some authors have argued that A. means and A. tridactylum should be treated as conspecifics. These species, which are sympatric over much of their ranges, differ in coloration, number of toes, and some body proportions. See Salthe (1973) for discussion of this issue.

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Distribution and Habitat

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Two-toed amphiumas are found in Coastal Plain habitats from southeastern Virgina to eastern Louisiana, near New Orleans. Juveniles and adults live in or near swamps, cypress bays, ditches, sloughs, temporary pools, and sluggish streams (Salthe 1973; Petranka 1998).This species is almost completely aquatic, but individuals occasionally move overland on rainy nights (Conant and Collins 1991).

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Life History, Abundance, Activity, and Special Behaviors

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Courtship has not been documented. Breeding apparently occurs during winter months. Fertilization is internal. Females deposit eggs under large cover objects like rocks and logs or in underground burrows. The female coils around the egg mass and attends the eggs until hatching, usually 5 to 6 months after oviposition. Average clutch size is about 200, range 106 - 354 (Salthe 1973; Petranka 1998).

Adults consume vertebrate and invertebrate prey, including salamanders, small frogs, crayfish, as well as a range of smaller invertebrates. Amphiumas have a powerful bite. Foraging activities occur at night and during the day animals retreat to underground burrows, sometimes over a meter deep. Important predators of amphiumas are aquatic snakes like mud and rainbow snakes (Farancia), water snakes (Nerodia), cottonmouths (Agkistrodon), and large wading birds. Defensive behavior of amphiumas is primarily bites from their strong jaws. People should take care when handling these animals. See Petranka (1998) and references therein.

Two-toed amphiumas often function as top predators in their freshwater systems. Their importance in influencing species diversity and community structure is not known. This would be a productive area of investigation, particularly because the wetland habitats where they occur are threatened with continuing loss (Petranka 1998).

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Life History, Abundance, Activity, and Special Behaviors

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The continuing loss of wetland habitats is a threat to populations of amphiumas, and undoubtedly many populations have already been eliminated. Long term studies on amphiuma population trends have not been conducted (Petranka 1998).

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Lifespan, longevity, and ageing

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Maximum longevity: 27 years (captivity)
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Two-toed amphiuma

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The two-toed amphiuma (Amphiuma means) is a snake-like salamander found chiefly in the southeastern United States. It is commonly, but incorrectly, called "congo snake", "conger eel" or the "blind eel". Two-toed amphiumas are some of the largest extant amphibians in the world.

Description

Two-toed amphiumas can grow from 39 to 1,042 g (1.4 to 36.8 oz) in mass and from 34.8 to 116 cm (13.7 to 45.7 in) in length.[3][4][5] They have four vestigial legs that end in two toes; the number of toes is one of the primary differences between Amphiuma means and its relatives, the one-toed and three-toed amphiumas. The head is pointed and wedge-shaped, and the eyes are small. Adults retain a single gill slit on each side of the head. They are black, dark grey or dark brown in color.[4]

Behavior

Two-toed amphiumas are nocturnal, and are often difficult to handle because of their slippery skins. They may leave water temporarily if weather is wet enough. They dig burrows in muddy stream bottoms, or may invade the burrows of other aquatic creatures.

They are harmless to humans when left alone, but, when disturbed, they can deliver a tough bite, which may lead to a severe infection. Unlike other salamanders, which are mute, A. means gives a clear whistle when disturbed.

Reproduction

Amphiumas breed from June to July in North Carolina and northern Florida. Females lay about 200 eggs in a damp cavity beneath debris, close to standing water, and they remain coiled around them during incubation (which lasts around five months). Hatchlings are about 2 in (51 mm) long with three pairs of light-colored external gills soon lost after hatching.[6]

Feeding

Two-toed amphiumas feed on small fish, tadpoles, crawfish, insects and insect larvae. They are also recorded to prey on reptiles and amphibians such as southern cricket frogs, southern leopard frogs, greater sirens, peninsula newts, water snakes of the genus Nerodia and small mud turtles. Their hunting behavior is not thoroughly understood, but they are believed to forage actively for food and to wait under debris and in burrows for prey to approach them. They likely detect prey through olfaction.[6]

Habitat and range

Amphiumas live in areas of shallow, heavily vegetated water in swamps, bayous, lakes, and ponds, as well as wet prairies.[6] Their range includes southeastern Virginia, eastern North Carolina, South Carolina, southern Georgia and Alabama, Florida, south Mississippi and southeastern Louisiana.[7]

References

  1. ^ Fossilworks
  2. ^ Hammerson, G. (2004). "Amphiuma means". IUCN Red List of Threatened Species. IUCN. 2004: e.T59074A11879454. Retrieved 11 February 2020.
  3. ^ Heisler, N.; Forcht, G.; Ultsch, G.R.; Anderson, J.F. (1982). "Acid-base regulation in response to environmental hypercapnia in two aquatic salamanders, Siren lacertina and Amphiuma means". Respiration Physiology. 49 (2): 141–58. doi:10.1016/0034-5687(82)90070-6. PMID 6815749.
  4. ^ a b Caudata Culture Species Entry – Amphiuma. Caudata.org. Retrieved on 2013-01-03.
  5. ^ Deyle, Anna C. (2011) Population Genetics of Amphiuma means and Siren lacertina in Central Florida. M.S. Thesis, University of South Florida
  6. ^ a b c "Amphiuma means". amphibiaweb.org. AmphibiaWeb. Retrieved 26 December 2018.
  7. ^ "Amphiuma means". amphibiaweb.org. AmphibiaWeb. Retrieved 26 December 2018.
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Two-toed amphiuma: Brief Summary

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The two-toed amphiuma (Amphiuma means) is a snake-like salamander found chiefly in the southeastern United States. It is commonly, but incorrectly, called "congo snake", "conger eel" or the "blind eel". Two-toed amphiumas are some of the largest extant amphibians in the world.

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