The Big Sandy crayfish (Cambarus callainus) is a freshwater, tertiary burrowing crustacean of the Cambaridae family. Tertiary burrowing crayfish do not exhibit complex burrowing behavior; instead, they shelter in shallow excavations under loose cobbles and boulders on the stream bottom. The Big Sandy crayfish is closely related to the Guyandotte River (C. veteranus) crayfish and both species share many basic physical characteristics. Adult body lengths range from 75.7 to 101.6 millimeters (mm) (3.0 to 4.0 inches (in)), and the cephalothorax (main body section) is streamlined and elongate, and has two well-defined cervical spines. The elongate convergent rostrum (the beak-like shell extension located between the crayfishs eyes) lacks spines or tubercles (bumps). The gonopods (modified legs used for reproductive purposes) of Form I males (those in the breeding stage) are bent 90 degrees to the gonopod shaft (Loughman 2014, p. 1). Diagnostic characteristics that distinguish the Big Sandy crayfish from the Guyandotte River crayfish include the formers narrower, more elongate rostrum; narrower, more elongate chelea (claw); and lack of a well-pronounced lateral impression at the base of the claws immovable finger (Thoma et al. 2014, p. 551). Carapace (shell) coloration ranges from olive brown to light green, and the cervical groove is outlined in light blue, aqua, or turquoise. The rostral margins and post orbital (behind the eye) ridges are crimson red. The abdominal terga (dorsal plates covering the crayfishs abdomen) range from olive brown to light brown to light green and are outlined in red. The walking legs of the Big Sandy crayfish range from light green to green blue to green, and the chelae are usually aqua but sometimes green blue to blue (Loughman 2014, p. 12; Thoma et al. 2014, p. 547).
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