IUCN threat status:

Least Concern (LC)

Comprehensive Description

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Description

An elongate, permanently-gilled, aquatic salamander. Like sirens (which are also in the Family Sirenidae), dwarf sirens lack hind limbs. Other features of sirens and dwarf sirens are lack of eyelids and presence of a horny beak on the upper and lower jaws (Martof 1974). Pseudobranchus have a single gill slit (Martof 1972 1974). There are only three toes on the front limbs and the bushy, external gills sometimes hide the relatively reduced front limbs. Adults reach 10-22 cm total length, and females are slightly larger than males (Martof 1972; Petranka 1998). The tail is about 40% of the total length (Martof 1972). Juveniles differ from the adults in the presence of a dorsal fin which extends from the base of the head to the tail tip (Martof 1972; Petranka 1998).

Adult P. striatus have a brownish to black dorsal ground color with parallel yellow or tan stripes running along the back and sides from head to tail tip. There is geographic color variation and two or three subspecies are recognized. Pseudobranchus s. striatus, the broad-striped dwarf siren, has a dark brown to blackish middorsal stripe with a narrow yellow line running down the middle and broader yellow lateral stripes. The venter has a lighter ground color than the back and is heavily mottled with yelow. This subspecies is also considered somewhat stocky in build. Pseudobranchus s. spheniscus, the slender dwarf siren, is smaller and more slim-bodied. This subspecies has a narrow, wedge-shaped head and two (rarely three) narrow tan or yellow lateral stripes. Pseudobranchus s. lustricolus, the Gulf Hammock dwarf siren, is not recognized by all authors; the distribution and affinities of this form merit futher investigation (Moler and Kezer 1993; Petranka 1998). A stocky subspecies, individuals have a dark, broad middorsal stripe containing three narrow yellow stripes. There are two light lateral stripes as well, the upper orangish brown and the lower silvery white. Descriptions from Petranka (1998).

Prior to 1993, a single species of dwarf siren was recognized (e.g. Conant and Collins 1991). Moler and Kezer (1993) studied the chromosomes of Pseudobranchus striatus and split that taxon into two separate species with different chromosome complements: P. striatus (n = 24) and P. axanthus (n = 32). The two species are found in sympatry in northern and mid-peninsular Florida, although they seem to prefer different micro-habitats. Pseudobranchus axanthus occur in open ponds and marshes, and P. striatus in cypress swamps. In addition, P. axanthus are commonly found in floating water hyacinth and P. striatus are never found in water hyacinth, preferring a similar floating plant called frog's bit (Limnobium spongia) (Moler and Kezer 1993).

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