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Species Description

Crayfish

Cambarus (Jugicambarus) unestami


Classification

Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Family: Cambaridae

Description

Cambarus unestami is brownish-black in color and the abdominal segments are marked with a series of dark brown to black bars. The chelae (claws) are brown and marked with brownish-black splotches and at least 2 rows of tubercles (small bumps). The eyes are moderately large and the rostrum lacks marginal spines and tubercles. The areola is 3-6 times as long as it is broad. The carapace usually measures between 26 and 41 mm (1.0-1.6 in).

Life Cycle

There have been relatively few life history studies conducted on crayfish. The available life history data for Cambarus unestami is limited to the form or condition of specimens collected during certain times of the year. First-form (sexually mature) males have been collected during April, May, October and November. Egg-bearing females have been collected during April and May. The life cycle of this species is presumed to be fairly similar to the generalized crayfish life history described below. Copulation has not been observed, but probably occurs from autumn to spring. Copulation involves a sexually mature male crayfish grabbing a female and depositing sperm packages (spermatophores) into the seminal receptacle on the abdomen of a receptive female crayfish. Usually during the spring, females secrete a sticky substance on the underside of their abdomen and pleopods in order to attach their eggs. The eggs and sperm (from the seminal receptacle) are then released upon the sticky surface and fertilization occurs. A female carrying eggs on her abdomen and legs is said to be "in berry." Embryos develop and hatch on the underside of females in 2-20 weeks, likely depending upon species and temperature. The immature hatchlings molt (shed their exoskeleton to allow growth) and remain attached to their mother. These first-stage immature crayfish look fairly similar to typical crayfish, but have disproportionately large heads and eyes. Another molting takes place in about 1-2 weeks. These second-stage immature crayfish look even more like adult crayfish. Second-stage or third-stage immature crayfish leave their mother's surface and become independent. These young crayfish continue molting and growing and are usually sexually mature by their second or third autumn. Sexually mature males and females are believed to mate between autumn and spring. Many adult crayfish die within 3 years of hatching.

Natural History

Adult Cambarus unestami crayfish often hide among rocks or leaf litter in moderate to swiftly flowing streams during the day. This species is usually found in mountain streams at altitudes between 330 and 500 m (1083-1640 ft). From dusk until dawn, or on very cloudy days, crayfish come out of hiding and search for food in streams. Crayfish are usually omnivorous scavengers, feeding upon whatever is available. Crayfish eat aquatic vegetation, small fish, aquatic insects and snails. They use their chelae (claws) on their first 3 legs to grab, crush and tear their food. This food is further cut by a number of specialized mouthparts. The main predators of crayfish are fish, frogs, turtles, wading birds, raccoons, otters and humans. Crayfish usually walk slowly across the bottom of their stream habitat using their last 4 walking legs (periopods). When frightened or in danger, however, they quickly escape by "darting" backwards. Crayfish sometimes have extensive scaring on their chelae or are missing appendages. This occurs while escaping predators or fighting with other crayfish. Male crayfish are especially aggressive with one another and their claw-to-claw combat can be quite intense.

Range

This species is limited to streams on Lookout Mountain and Sand Mountain in northeastern Alabama and northwestern Georgia . It is found within Walker, Dade and Chattooga counties in Georgia . It prefers rock-bottomed, mountain streams with moderate to swift currents.

Conservation Status

This crayfish species is uncommon in Georgia . It has a very limited range in the northwestern portion of the state that is threatened by the ever-expanding Chattanooga , Tennessee metropolitan area. Habitat destruction, pollution and habitat degradation are presumably the most immediate threats.

Similar Species

Accurate crayfish identification can be difficult and should usually be verified by a trained individual. This species is only found in mountain streams and is sometimes the only crayfish within smaller streams. This species is usually fairly distinct from other mountain stream-dwelling crayfish within its limited range.