The Southern Dwarf Siren (Pseudobranchus axanthus) is a perennibranch salamander

Salamander

Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...

 lacking hind legs. Found exclusively in Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

, it is one of two currently recognized species of dwarf sirens. Two subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 are currently recognized; P. a. axanthus, the narrow-striped dwarf siren, and P. a. belli, the Everglades dwarf siren.

Physical description

Southern dwarf sirens are thin, slimy salamanders that are frequently mistaken for eels. Dwarf sirens have long bodies with bushy gill

Gill

A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...

s and small, three-toed forelegs. Coloration is generally brown, black, or gray, with yellow or tan stripes on the back and sides. Adults reach a maximum length of 10–25 cm.

Southern dwarf sirens can easily be distinguished from amphiuma

Amphiuma

Amphiuma is a genus of aquatic salamanders, the only extant genus within the family Amphiumidae . They are also known to fishermen as "conger eels" or "congo snakes", which are zoologically incorrect designations...

s by size and the presence of hind legs, and from Siren spp. salamanders by the presence of three toes on each foot. Distinguishing between Pseudobranchus axanthus and Pseudobranchus striatus is more difficult, requiring comparison of patterns with a field guide, known distribution, or a karyotype test. P. axanthus has 32 chromosomes while P. striatus has 24. A costal groove count may assist in differentiating P. a. axanthus and P. a. belli, as the former has 34–37 costal grooves while the latter has 29–33 (Petranka, 1998).

Distribution

P. axanthus is found throughout eastern Florida, with P. a. axanthus located in the northern two thirds of the range and P. a. belli located in the southern third. P. axanthus prefers cypress ponds, ditches, swamps and marshes, and other aquatic and semi-aquatic habitats (Petranka, 1998). P. axanthus are frequently associated with water hyacinth.

Reproduction

Little is known about the reproduction of wild sirenid salamanders. Eggs of P. axanthus have been found from November through March and are usually attached singly to aquatic plants. Eggs average 3 mm in diameter and have three jelly envelopes (Petranka, 1998).

In captivity, eggs were attached singly at night to floating vegetation in groups of two to five a day. Larvae hatch out at approximately 5 mm after ~3 weeks.

Diet

Southern dwarf sirens eat a variety of food items, including small worms, chironomids, amphipods, and ostracods (Petranka, 1998). Dwarf sirens have surprisingly small mouths, but will likely eat any invertebrate that they can swallow. In captivity, adult Daphnia magna

Daphnia magna

Daphnia magna is a species of Daphnia which is native to northern and western North America. It is also widely distributed in Eurasia and in some regions of Africa.- Laboratory animal :...

, whiteworms, blackworms, and tubifex worms are readily taken.

Ecology

During dry spells, P. axanthus is known to aestivate in muddy burrows during dry spells, and adults have been kept for periods longer than two months in dry soil with no ill effects in laboratory (Petranka, 1998).