大鳗螈

A large, eel-like, aquatic salamander. Greater sirens, like other members of the family Sirenidae, lack hindlimbs and eyelids, have horny beaks on the upper and lower jaws, and are gilled throughout life (Martof 1974). Greater sirens have four toes on the front limbs and three gill slits (Martof 1973; 1974; Petranka 1998). Adults range from 50 - 98 cm total length but most are less than 70 cm (Petranka 1998). The tail is 26 - 40% of the total length (Martof 74). There are ventral and dorsal fins on the tail (Martof 1973). Modal number of costal grooves is 37-38 (Martof 1973; Petranka 1998). Adult males have enlarged jaw (masseter) muscles which make the head appear larger than in females (Petranka 1998). Hatchlings are 16 cm total length (13 cm snout to vent length), and possess a relatively shorter tail than adults and a tail fin which extends from the base of the head to the tip of the tail (Martof 1973).Adult coloration varies from olive green to light gray above and sometimes there are dark spots on the head, back and sides. The sides are lighter colored than the dorsum and usually have flecks of pale green. The venter is bluish grey and often has pale green flecks. Description from Petranka (1998). Juveniles have light, often yellow, body stripes that fade with age (Martof 1973; Petranka 1998).No subspecies are currently recognized, but geographic variation is poorly understood (Petranka 1998). The recent report (Flores-Villela and Brandon 1992) that greater sirens occur in Texas and Mexico (previously specimens were thought to be S. intermedia) is a large extension to the known range and suggests that detailed surveys across the distribution of greater sirens may uncover interesting patterns.

Occurs in coastal plain habitats from the vicinity of Washington, D. C., to southern Florida and westward to southwestern Alabama (Petranka1998). Greater sirens have also been documented from localities in southern Texas and northeastern Mexico (Tamaulipas) (Flores-Villela and Brandon 1992).Greater sirens inhabit a variety of permanent and semi-permanent aquatic habitats, including ditches canals, marshes, rice fields, lakes, and slow-moving streams and rivers (Petranka 1998). Sites are often muddy or heavily vegetated. Young are often found among water hyacinth roots (Martof 1973)

Courship and mating have not been observed. Fertilization is presumed to be external (Martof 1974; Sever et al. 1996). Few nests have been found in nature. Females apparently lay eggs in late winter to early spring (February to March) (Petranka 1998). Eggs are laid in small groups of less than 10 eggs, although a single female may lay more than 100 eggs total (Petranka 1998 and references therein).Greater sirens eat a range of prey items, including a high proportion of molluscs (snails and freshwater clams). Animals are active primarily at night and retreat to burrows during the day. When temporary pools of water dry up, sirens will aestivate underground and can easily survive for months. Greater sirens vocalize using clicks and yelps, as do lesser sirens. These sounds are produced when animals are disturbed and also may serve for intraspecific communication. Greater sirens are locally abundant in Florida, Georgia, and eastern South Carolina. See Petranka (1998) and references therein.Despite their large size and abundance in some regions, relatively little is known about the biology and ecology of greater sirens.

In northern and western portions of the range, greater sirens are patchily distributed. More understanding of these peripheral populations is needed (Petranka 1998). Diminshing availability of wetland habitats is a threat to greater siren populations.