St. Francis River Crayfish

Orconectes quadruncus
Cambaridae (freshwater crayfish), in the order Decapoda (shrimp, crabs and lobsters)

This medium-small crayfish is brown, with blackish blotches and specks on the dorsal surface of the pincers and body (specks most numerous on abdomen). The pincers are often trimmed with red, and thickly set hairs (setae) are present in the gap at the base of the fingers. The only other small brown native crayfish within the general range of this species is the Big Creek crayfish. The two species cannot be separated with confidence without comparing the male reproductive structures (short and blunt in the St. Francis River crayfish; long and slender in the Big Creek crayfish). The two species are rarely found in the same stream.

Adult length: about 1 1/4 to 2 1/2 inches.
Habitat and conservation: 
Lives in clear, rocky streams, ranging from small headwater creeks to moderately large rivers. Prefers silt-free bottoms near or beneath dense beds of water willow or boulders. Its burrows are dug in gravelly substrate beneath rocks. Its distribution largely complements that of Big Creek crayfish; the two species might compete because of similarities in habits and habitat.
Crayfish are generally omnivores, eating a wide variety of plant and animal materials.
Distribution in Missouri: 
The St. Francis River crayfish occurs only in Missouri, in the St. Francis River and its tributaries (exclusive of Big Creek and other streams supporting populations of the Big Creek crayfish), in St. Francis, Iron, Madison and Wayne counties.
Imperiled. The St. Francis River crayfish occurs only in Missouri, with a localized distribution that has shrunk in past decades.
Life cycle: 
Like other Ozark stream crayfish, this species has both a fall and a spring reproductive season. In their first year, young will reach 1 to 1.5 inches in length, but few of these become sexually mature in their first year. Both males and females grow at different rates, but eventually reach the same maximum size. Most St. Francis River crayfish don't live more than two years.
Human connections: 
Crayfish feed many types of wildlife, including many species that humans hunt and fish. Crayfish commonly serve as bait, plus many people eat crayfish, too. Crayfish are fascinating, colorful creatures in their own right and are part of our rich natural heritage.
Ecosystem connections: 
Their opportunistic, omnivorous feeding makes them an important link in the food chain between plants and vertebrates, breaking down plant and other materials that are resistant to decomposition. Crayfish in turn are an important food for many other animals.
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