Amphiuma is a genus of aquatic salamanders from the United States, the only extant genus within the family Amphiumidae . They are colloquially known as amphiumas. They are also known to fishermen as "conger eels" or "Congo snakes", which are zoologically incorrect designations or misnomers, since amphiumas are actually salamanders (and thus amphibians), and not fish, nor reptiles and are not from Congo. Amphiuma exhibits one of the largest complements of DNA in the living world, around 25 times more than a human.
Taxonomy
Numerous phylogenetic studies have indicated that amphiumas form a clade with the families Rhyacotritonidae (torrent salamanders) and Plethodontidae (lungless salamanders), with an especially close relationship to Plethodontidae. Despite this possible relationship, the two families must have still diverged very early on. The genus Proamphiuma from the Cretaceous is the earliest known member of the family, and closely resembles the modern species aside from less elaborate vertebral structures.
Description
Amphiumas have an elongated body, generally grey-black in color. They do have legs, but they are merely vestigial and very small. While amphiumas can be up to long, their legs measure only up to about . It is because of this that they are often mistaken for eels or snakes. They also lack eyelids and a tongue. Amphiumas also have a lateral line visible on the sides of their bodies, which is capable of detecting movement and is used in aid of hunting.
Female amphiumas lay their eggs in wet mud, and then remain coiled around them for about five months, until they hatch. The larvae have external gills, but after about four months these external gills disappear and the lungs begin to work. One pair of gill slits, with fully functioning internal gills, is retained and never disappears, so the metamorphosis remains incomplete.
Species
There are three extant amphiuma species, distinguished by the number of toes:
Extant
Extinct
†Amphiuma jepseni (Paleocene of Wyoming) †Amphiuma antica (Miocene of Texas)
Distribution
Amphiumas inhabit the southeastern part of the United States. They share much of the same distribution with the sirens, although they are not closely related.
In the past, amphiumas had a wider geographic range throughout North America, ranging all the way north to Wyoming.
Behavior
During the day, amphiumas hide in vegetation, and at night they become active hunters. Their prey includes frogs, snakes, fish, crustaceans, insects and even other amphiumas. Hunting and eating habits have been observed to be very similar to that of the axolotl, including the sucking in of food by their stomachs with vacuum force. If provoked, they can become aggressive. They can be found in most wetlands in the coastal plain of the southeastern U.S., even ones which periodically dry out, as they are able to estivate in the moist mud below drained marshland and other ephemeral wetlands. Amphiumas are rarely encountered on land.
It is the female that court the male before mating. When a pair is formed they wrap their bodies around each other, and the male will transfer a spermatophore directly into the female cloaca (cloacal apposition).
Food habits
The amphiuma's predatory behaviors and food selection are very calculated and variable depending on abundance of food. In addition to eating frogs, snakes, fish, crustaceans, insects, and other amphiuma, amphiuma have been found to eat annelids, vegetables, arachnids, mollusca, and larvae. Amphiuma seem to have a preference for eating crawfish. It has been documented that amphiuma will pass on smaller crawfish in order to consume larger ones. It is suggested that this limits wasting energy in pursuing prey with less caloric density. In captivity, the predatory behavior amphiuma display depends on the presence or lack of food. Amphiuma will remain inactive when food is absent, and will become more active once food has been introduced into their habitat. This shows that the amphiuma, although ancestral to many amphibia, has developed a deductive approach to its predation.