Amphiuma means

 

(Photograph © Amphibians (Hofrichter 2000: Weltbild Verlag GmbH, Ausburg)

    Commonly called the Congo eel, or the lamper eel, amphiuma is not an eel at all, but an amphibian; more specifically, a salamader. The misnomer of eel is well-deserved however; long and slimy, amphiumas possess four minute, all but useless limbs. Despite this, these are the only amphibians that pose a physical (as opposed to chemical) threat to humans - they have strong jaws with a double row of razor sharp teeth which can deliver a savage bite (Smith, 1877, p. 20). Further adding to this frightening arsenal, amphiumas can grow quite large (just over 1 meter), making them the largest amphibians in their range. The three species of Amphiuma can be distinguished by the number of digits on their tiny limbs: pholeter has one toe, means has two, and tridactylum has three (Conant and Collins, 1998, p. 425).

TWO-TOED AMPHIUMA, Amphiuma means

Photo © John White. (http://www.npwrc.usgs.gov/narcam/idguide/ampmeans.htm)

    The two-toed Amphiuma is a large, slick-bodied salamander with a dark brown or black dorsum and a dark grey venter (Salthe, 1973). As the name suggests, it has two toes on each limb. Adult length is between 36.8 and 76 cm. Amphiuma is a pædomorphic salamander (a condition in which sexual maturity is reached before physical transformation is complete); adult skin is smooth and fully metamorphosed, however adults lack eyelids (as all larave do), and possess four branchial arches, with a gill slit between the third and fourth branchial arch, yet they lack external gills. Oddly enough, amphiuma is a fully aquatic salamander with fully developed lungs (Hofrichter, 2000, p. 45).

    Adults consume vertebrate and invertebrate prey, including salamanders, small frogs, crayfish, as well as a range of smaller invertebrates. Prey is not restricted to this, as amphiuma is an opportunist: it has been reported that they even tackle snakes from time to time, including Regina rigida, a snake not preyed upon by many other creatures (Enge, 1998). Although amphiumas have a powerful bite, they may in some cases use constriction to subdue prey (Zug, Caldwell, and Vitt, 2001, p. 261). Foraging activities occur at night; 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.



Habitat

Map © Laura Blackburn, Priya Nanjappa, and Michael J. Lannoo (2001) US Amphibian Dist. Maps (http://home.bsu.edu/home/00mjlannoo/) Photo by Beth M. Young (http://www.cahabariverpublishing.com/Tensaw_Delta/td.html)
   Amphiumas are primarily aquatic, although A. means has been seen moving overland on rainy nights (Zug, Vitt, Caldwell, 2001, p. 381).Preferring sluggish or static water, they inhabit ditches, sloughs, swamps, ponds, etc. throughout the coastal plain of Florida, Mississipi, Louisiana, Alabama, Georgia, and up the east coast to Virginia. During the day, Amphiuma retreats in abandoned crawfish holes and mammal burrows or in jumbles of bottom debris with head protruding in expectation of prey (Bishop, 1943, p.50).

Reproduction

Photo © Al Kinlaw. 
(http://www.flmnh.ufl.edu/natsci/herpetology/uf-herp/fldtrip5.htm)

    Because of amphiuma's secretive habits and generally disagreeable disposition, relatively little research has been done on its ecology, specifically its reproductive ecology. A year long study of A. tridactylum was carried out in Lousiana, and since tridactylum and means overlap in geographic range, and because they are genetically very similar (even to the point of being the same species - see Taxonomy) it may be assumed that the reproductive habits are similar. Some researchers have argued that there are differences in reproductive activities between A. means and A. tridactylum.

    Breeding occurs in the spring, males possessing enlarged testes and swollen cloaca between January and April. Copulation among amphiuma has been observed only once by Baker et al. (1947) during July in Tennessee, and was described as an eight-day event where the male chose between two females and sperm transfer occured via cloacal apposition. Between 150-200 are laid in midsummer. Even though amphiuma is aquatic, eggs are always laid on land, albeit close to water (Hofrichter, 2000, p. 45). The nest is tended by an adult, presumably the female; incubation is thought to last approximately five months (Fontenot, 1999). Hatching probably occurs sometime in the fall (Salthe, 1973). Larvae begin life between 45-64 mm. They have external gills. Based on percentages of gravid females found in the field (35-60%), it has been suggested that amphiuma follows a biennial, or even a triennial reproductive cycle (Fontenot, 1999).


Conservation

    Though not considered a "common" species, the amphiuma is not endangered, nor does it maintain any other special conservation status. The only immediate danger to these creatures is habitat loss.

Taxonomy

Photographer unknown. (http://www.parcplace.org/education/sparc/trip9.htm)

Amphiuma means Garden, 1821, p. 599. In Smith, Correspond. of Linn. Type locality not stated, but from context either Charleston, South Carolina or eastern Florida; restricted to Charleston, Charleston County, South Carolina by Schmidt, 1953;27. Holotype possibly rediscovered by Lonnberg, 1896:36, #15 labelled Siren lacertina in the Zoological Museum of the University of Upsala.

Sireni simile Linnaeus, 1821, p. 599. In Smith, Correspond. of Linn. Refers to an apparently lost letter from Linnaeus to Garden.

Chrysodonta larvaeformis Mitchill, 1822:503. Type locality Savannah, Chatham County, Georgia.

Amphiuma didactylum Cuvier, 1827:4. Substitute name.

Amphiuma tridactylum: Tshundi, 1838:97 (in part).

Sirenoidis didactyla: Fitzinger, 1843:34. New combination.

Amphiuma means: Gray, 1850:55. New combination.

Amphiuma means means: Goin, 1938:128.

Photo © Margaret Gunzburger

    Through the years A. means has been shuffled back and forth by taxonomist between species and subspecies status. Because the differences between tridactylum and means are so slight, some biologist have recommended using trinomials (Salthe, 1973). The group is currently split into three species. Recent evidence from genetics substantiates a close relation between the three. Protein analysis (by horizontal starch-gel electrophoresis) resulted in discovering that genetic distance between the one-toed amphiuma, A. ploleter, and the other two species, A. tridactylum and A. means is marked, while A. tridactylum and A. means are very similar genetically (Karlin and Means, 1994). Currently, scientist are unsure how amphiuma fits into the larger phylogentic tree: some believe the group to be very primitive as relating to other salamanders, while others consider them specialized, and therefore more advanced (Hofrichter, 2000, p. 45).

Suggested Cladograms for Urodela





(http://www.snakesandfrogs.com/scra/salamanders/images/amfum1.jpg)


Specimens

Preserved Specimens in Collections

Zoos Currently Housing Amphiuma

Links

Georgia Wildlife Web

Northern Prairie Wildlife Research Center

Biology of Nature

U.C. Berkeley

Tree of Life

Virginia Fish and Wildlife Information


References

Baker, L. C., and M. C. Caldwell (1947). Observation of copulation in Amphiuma tridactylum. J. Tennessee Acad. Sci. 12:206-218.

Bishop, Sherman C. (1943). Handbook of Salamanders: The Salamanders of the United States, of Canada, and of Lower California. Comstock Publishing, Ithaca.

Conant, R. and J. T. Collins (1991). A Field Guide to Reptiles and Amphibians: Eastern/Central North America. Houghton Mifflin: Boston.

Cuvier, G. J. L. F. (1827). Sur le genre de reptiles batraciens, nommé Amphiuma, et sur une nouvelle espece de ce genre (Amphiuma tridactylum). Mem. Mus. Hist. Nat. Paris. 14:1-14.

Enge, Kevin M. (1998). "Amphiuma means Diet." Natural History Notes, 29:3.

Fitzinger, L. (1843). Systema reptilium. I Ambyglossae. Vienna, 106 p.

Fotenot, Clifford L. (1999). "Reproductive Biology of the Aquatic Salamander Amphiuma tridactylum in Lousiana." Journal of Herpetology, 33:100-105.

Goin, C. J. (1938). The status of Amphiuma tridactylum Cuvier. Herpetologica 1:127-130.

Gray, J. E. (1850). Catalogue of the specimens of Amphibia in the collection of the British Museum. Pt. II. Batrachia Gradientia, etc. London, 72 p.

Hofrichter, Robert (2000). Amphibians: The World of Frogs, Toads, Salamanders, and Newts . Firefly Books: Buffalo.

Karlin, A. A., and D. B. Means (1994). "Genetic variation in the aquatic salamander genus Amphiuma." American Midland Naturalist, 132:1-9.

Salthe, S. N. (1973). "Amphiuma means Garden. Two-toed congo eel." Catalogue of American Amphibians and Reptiles, 148:1-2.

Smith, J. E. (1821). A selection of the correspondence of Linnaeus and other naturalists. Longman, Hurst, Rees, Orme and Brown, London. Vol. I, 630 p.

Smith, W. H. (1877). The Tailed Amphibians, Including the Cælcilians. Herald Publishing, Detroit.

Tschudi, J. J. (1838). Classification der Batrachier, mit Berucksichtigung der fossilen Thiere dieser Abteilung der Reptilien. Petitpierre, Neuchatel, 102 p.

Zugg, George R., Laurie J. Vitt, and Janalee P. Caldwell (2001). Herpetology: An Introductory Biology of Amphibians and Reptiles. Academic Press: San Diego.

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