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Species Description

Crayfish

Cambarus (Jugicambarus) parvoculus


Classification

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

Description

The carapace of this small-eyed crayfish lacks distinguishing markings, making identification difficult. The carapace is a dark olive to purplish brown color. The abdomen is dark olive brown and darkest in the front half of each segment. The reddish or olive brown chelae (claws) are fairly short with a well-defined row of 5-8 creamy tubercles (small bumps). The areola of this crayfish is of moderate width and has 2-4 spots or pits in the narrowest portion. The carapace usually measures less than 33 mm (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 parvoculus 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, October and November. Females carrying eggs 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. The exact breeding season of this species is currently unknown, but copulation is believed to occur sometime between fall and 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 C. parvoculus crayfish often hide under rocks or leaf litter in clear, swift streams. 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

Cambarus parvoculus is found within the Cumberland River Basin in Tennessee to the Kentucky River and Tennessee River Basin in portions of Georgia , Tennessee and Virginia . Within Georgia , this species is only found in Dade County in the extreme northwestern corner of the state.

Conservation Status

This crayfish is listed as rare in Georgia and is threatened by habitat destruction and pollution within its limited range.

Similar Species

Identification of this rare species is difficult because it lacks distinct markings or patterns. Identification is usually best performed by individuals that have been trained to distinguish subtle anatomical features.