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Species Description

Crayfish

Cambarus (Depressicambarus) englishi


Classification

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

Description

Cambarus englishi is a freshwater crayfish that usually has a carapace length measuring between 20.0 and 40.0 mm (0.75-1.6 in). The carapace is typically brownish-olive on the dorsal (backside) portion, with a straw-brown areola. The 1 st abdominal segment is mostly pinkish cream with blackish bands. The tail is blackish dorsally and is pale blue green on the ventral (belly, bottom) side. The olive green chelae (claws) are nearly triangle-shaped, with 5-8 orange tubercles (bumps). The eyes are moderately large and pigmented. The rostrum is often adorned with spines or tubercles. The straw brown areola is 4-5 times as long as it is broad and is marked with 4-6 pits or spots.

Life Cycle

There have been relatively few life history studies conducted on crayfish. The available life history data for Cambarus englishi 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 September and October. Egg-bearing females have not been collected. The life cycle of this species is likely similar to the generalized crayfish life history described below. Copulation usually occurs between autumn and spring, but there is speculation that the breeding season for C. englishi may extend through the summer. 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 summer and many usually die within 3 years of hatching.

Natural History

Adult Cambarus englishi crayfish often hide under rocks in shallow riffle areas of rivers during the day. 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 particularly aggressive with one another and their claw-to-claw combat can be quite intense.

Range

This species is native to the Tallapoosa River Basin . It has only been found in Harralson County , Georgia and Clay, Cleburne and Tallapoosa Counties in Alabama . This species appears to be restricted to shallow riffle areas within its narrow range.

Conservation Status

Cambarus englishi is listed as Rare and Imperiled in Georgia . It has an extremely limited range within the state, making it especially susceptible to water quality degradation, pollution and habitat destruction. Dramatic alterations or destruction of portions of its limited habitat in Georgia could possibly eliminate this species from the state.

Similar Species

The most similar species of crayfish that is found in association with Cambarus englishi in Georgia is C. halli. C. halli usually has a dark brown carapace, small eyes and is usually found along river banks near plant roots. C. englishi has a brownish olive carapace, larger eyes and is found in riffle areas.