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Species Description

Crayfish

Cambarus (Depressicambarus) halli


Classification

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

Description

The carapace of Cambarus halli is dark brown to olive and adorned with cream-colored tubercles (small bumps). The abdomen is dark olive and decorated with a narrow pinkish-yellow band on each segment. The chelae (claws) are olive with a row of 5-7 orange tubercles. The wide areola is dark olive brown and has 3-9 spots or pits in the narrowest portion. The rostrum has distinctive spines or tubercles near its red edges. The carapace of this species usually measures between 29 and 38 mm (1.1-1.5 in) in length.

Life Cycle

There have been relatively few life history studies conducted on crayfish. The available life history data for Cambarus halli 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, September and October. Egg-bearing females have been collected during April. The life cycle of this species is presumed to be fairly similar to the generalized crayfish life history described below. Based upon the condition of specimens during different times of the year, Cambarus halli copulation is believed to occur between September and April. 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. During the appropriate time(s) of year, 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." Each female usually carries between 94 and 182 eggs while "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. Many adult crayfish die within 3 years of hatching.

Natural History

Adult Cambarus halli crayfish often hide under leaf litter, debris and exposed plant roots in streams. This species is found in both choppy areas and slower portions of streams throughout its range. 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, detritus, 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 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 are sometimes found with extensive scaring on their chelae or 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 found within streams of the Tallapoosa River Basin in portions of Georgia and Alabama . It is found in Paulding, Harralson and Carrol counties in Georgia . It is found in choppy and slower portions of streams, often hidden under leaf litter, plant roots or debris.

Conservation Status

Cambarus halli is listed as Rare and Imperiled in Georgia . It is only found within the Tallapoosa River Basin and this limited range has been fragmented and altered by construction of several reservoirs. Pollution and further habitat destruction also threaten this rare crayfish.

Similar Species

This species is very similar in color to Cambarus englishi. The two species are often best distinguished by trained individuals that can identify and differentiate subtle anatomical features.