The southern dwarf siren, (''Pseudobranchus axanthus'') is a perennibranch

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...

lacking hind legs. Found exclusively in

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

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

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

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. They have long bodies with bushy

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s and small, three-toed fore legs. Coloration is generally brown, black, or gray, with yellow or tan stripes on their backs and sides. Adults reach a length of to . Southern dwarf sirens can easily be distinguished from

amphiuma ''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 ...

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 ''P. axanthus'' and ''P. 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 semiaquatic habitats.Petranka, 1998 ''P. axanthus'' is 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. In captivity, eggs were attached singly at night to floating vegetation in groups of two to five a day. Larvae hatch out at about 5 mm after around three weeks.

Diet

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

Daphnia magna ''Daphnia magna'' is a small planktonic crustacean (adult length 1.5–5.0 mm) that belongs to the subclass Phyllopoda. Description ''D. magna'' is a typical water flea of the genus ''Daphnia''. The females reach up to 5 mm in size, ...

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

Ecology

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

References

* Netting, M.G. & C.J. Goin. 1942. Descriptions of two new salamanders from peninsular Florida. Annals of the Carnegie Museum 29: 175-196. * Petranka, James W.; 1998, Salamanders of the United States and Canada, Smithsonian Institution Press, Washington. {{Taxonbar, from=Q2170383 Sirenoidea Amphibians described in 1942 Taxa named by M. Graham Netting Endemic fauna of Florida