Cambarus callainus

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The genus Cambarus is the second largest freshwater crayfish genus inhabiting the Northern Hemisphere, with only sixty fewer species than the genus Procambarus. Though Cambarus are varied across species, the two terminal elements that make up the male form I gonopod form ninety degree angles with the central appendage, allowing for their identification. Unlike the genus Procambarus whose first pleopod tends to have three processes at the tip, Cambarus has only one or two. Cambarus reach 17–26 mm carapace lengths in their first year, while average adult carapace length ranges from 55–62 mm.

As a genus containing nearly 100 species, Cambarus’s coloration is variable.^[2] Cambarus bartonii is dark brown, while species like Cambarus pauleyi range from subtle to vibrant blues and reds.^[2] Other species are light green or grayish in color.