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Species Description

Knotty Burrowing Crayfish

Cambarus (Jugicambarus) nodosus


Classification

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

Description

The carapace of the Knotty Burrowing Crayfish is olive-tan in color. The abdomen and tail are a noticeably darker olive-tan color. The margins of the short, rounded rostrum are orange in appearance and lack both spines and tubercles (small bumps). The areola is fairly broad and adorned with 2-4 spots or pits. The chelae (claws) are nearly rectangular in shape and are marked with reddish tubercles. The eyes of the Knotty Burrowing Crayfish are small and its carapace usually measures between 24 and 34 mm (1.0-1.3 in) in length.

Life Cycle

There have been relatively few life history studies conducted on crayfish. The available life history data for Cambarus nodosus 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, June, October, November and December. Females carrying eggs or young have been collected during June. The life cycle of this species is presumed to be fairly similar to the generalized crayfish life history described below. The exact breeding season of the Knotty Burrowing Crayfish is currently unknown, but copulation is believed to occur sometime between fall and late 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. 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." 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 Knotty Burrowing Crayfish are found in complex burrows in ditches and seepage areas. The constructed burrows often have multiple branches and passageways. The openings of the burrow are usually marked with poorly constructed chimneys (mounds of sand or mud placed around openings above ground). This species is also sometimes found under rocks in seepage areas and ditches. Occasionally, adults leave the general safety of their burrows to search for food or a mate at night. Crayfish are generally omnivorous scavengers, feeding upon any food source available within their habitat. Food for this species may include plant material, insects and perhaps other crayfish. 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. Crayfish usually walk slowly using their last 4 walking legs (periopods). When frightened or in danger, however, they quickly escape by "darting" backwards into their burrows.

Range

The Knotty Burrowing Crayfish is found in ditches and seepage areas within the Savannah , Hiwassee and Chattahoochee river drainages of Georgia , North Carolina and Tennessee . Within Georgia , this crayfish is only found within Lumpkin, Rabun, Towns and White counties in the northeastern portion of the state.

Conservation Status

This species is listed as uncommon within the state of Georgia . It is threatened by habitat destruction and pollution within its limited range.

Similar Species

The Knotty Burrowing Crayfish does not have easily distinguished features and identification of this crayfish species is often best verified by trained professionals