Cambarus

Cambarus is a large and diverse genus of crayfish from the United States and Canada. The adults range in size from about 5 centimeters (2 in) up to approximately 15 centimeters (6 in). 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. Cambarus bartonii is dark brown, while species like Cambarus pauleyi range from subtle to vibrant blues and reds. Other species are light green or grayish in color. Most species of Cambarus are restricted to the United States and Canada. They are distributed along the eastern coast, extending from New Brunswick to northern Florida. However, the genus extends as far westward as the Rocky Mountains of Wyoming and Colorado, inhabiting a variety of freshwater environments. Devil crayfish (Cambarus diogenes) are perhaps the most widespread species in the genus, having been found in thirty states spanning approximately 2 million kilometers. Though, most species of Cambarus are not so widely distributed. Cambarus occupy a range of freshwater environments including streams, rivers, lakes, and burrows. Burrowing species of the genus include Cambarus dubius. Cambarus also include many cave-dwelling species, both troglobites and troglophiles. While salinity and temperature changes minimally affect Cambarus, the genus has shown an intolerance to pollution. Like other crayfish, Cambarus are foragers. Diets are largely plant-based, though Cambarus also consume small marine organisms like molluscs, larvae, tadpoles and amphibian eggs. Cambarus consume small rodents or birds when available. In their first year, Cambarus typically consume 1-4% of their overall body-weight each day. The genus is central to many freshwater food webs as they help maintain water quality through consumption of algae. One of the largest crayfish genera, Cambarus includes a sizable number of vulnerable species. Cave-dwellers like Cambarus jonesi are at risk due to their lack of genetic diversity and low population count. Other species like Cambarus veteranus are at risk due to human practices like logging and mining, which increase sediment amounts in freshwater environments. Increased sediment causes these freshwater environments to be inhabitable, and Cambarus are forced to relocate as a result. Moulting occurs among Cambarus approximately 5-10 times during their first year, and 3-5 times during subsequent years. Cambarus remain relatively inactive during periods of moulting, as the shedding of chitin exoskeletons leaves them more vulnerable to predation and injury. Many species of Cambarus continue to grow well into adulthood.