Cajun Dwarf Crayfish and Shufeldt’s Dwarf Crayfish

Shufeldt’s Dwarf Crayfish (Swamp Dwarf Crayfish)

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Cajun Dwarf Crayfish

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Cambarellus puer and C. shufeldtii
Cambaridae (freshwater crayfish) in the order Decapoda (shrimp, crabs, and lobsters)

The two species of dwarf crayfish are appropriately named for their size. Both are reddish brown to gray, with a paired series of dark, wavy stripes or dashed lines along the dorsal surface. The tail fan usually has a dark central blotch. The pincers are narrow and long. The two species can be distinguished by examining the male reproductive structures, which are straight in Shufeldt’s dwarf crayfish (C. shufeldtii; sometimes called swamp dwarf crayfish) and curved in the Cajun dwarf crayfish (C. puer).

These two dwarf crayfish can be distinguished from the young of other lowland crayfish by the conspicuous dark pigment in the tail fan, and the lengthwise dark stripes or lines on the carapace. Also, the rostrum is flat, without a central troughlike depression.

Adult length: 1 to 1½ inches. Most do not get much larger than an inch.
Habitat and conservation: 
They are found in shallow, temporary pools during wet seasons, including swamps, sloughs, and roadside ditches. During periods of drought, swamp dwarf crayfish, though not burrowers, retreat to cells they dig in mud or moist soil.
Crayfish are generally omnivores, eating a wide variety of plant and animal materials.
Distribution in Missouri: 
These small crayfish occur sporadically throughout the Bootheel lowlands. Shufeldt’s dwarf crayfish also occurs on the floodplain of the upper Mississippi River.
While apparently secure over their entire range, in Missouri both species are vulnerable to being extirpated from the state and are listed as Species of Conservation Concern.
Life cycle: 
Breeding can occur at almost any time of year the crayfish are active, often with two seasonal peaks: in late winter to early spring, and in midsummer. Although some young hatch, grow, and mate during their first year, most mate for the first time the next spring, when they are nearly one year old. As with other crayfish, as they grow they shed their shell-like exoskeletons. Unlike many other species, dwarf crayfish breed while still less than 1½ inches long.
Human connections: 
Because of their small size, dwarf crayfish are not generally used by humans as food or bait. At least one researcher has suggested that the swamp dwarf crayfish might be useful as a forage species for pond fish such as fingerling bass and sunfish.
Ecosystem connections: 
Dwarf crayfish are probably eaten by fish, turtles, wading birds, and other vertebrates that share their habitat.
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