Southern Dwarf Siren

The Southern Dwarf Siren (Pseudobranchus axanthus) is a perennibranch salamander lacking hind legs. Found exclusively in Florida, it is one of two currently recognized species of dwarf sirens. Two subspecies are currently recognized; P. a. axanthus, the narrow-striped dwarf siren, and P. a. belli, the Everglades dwarf siren.

Contents 1 Physical description 2 Distribution 3 Reproduction 4 Diet 5 Ecology 6 References

Physical description

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

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.