Calico Crayfish (Papershell Crayfish)

Faxonius immunis (formerly Orconectes immunis)

calico_crayfish.jpg

Photo of a papershell crayfish, also called calico crayfish.
The papershell crayfish is usually only found in the northern half of the state.
Chris Lukhaup
Family

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

Description

The calico crayfish is a rather plain, gray-green species; it is characterized by a pale central zone along the middle of the carapace and abdomen. The pincers are orange-tipped, and in mature males are uniquely tinged with purple. The rostrum is without lateral notches or spines near its tip.

The calico crayfish superficially resembles the virile crayfish (northern crayfish) and sometimes occurs in the same habitats. The latter species does not have a pale zone along the middle of the carapace and abdomen, and the rostrum has lateral notches or spines near its tip.

Size

Adult length: about 1¾ to 3½ inches.

Habitat and conservation

The calico crayfish (also called the papershell crayfish) occurs widely in the Prairie Region and along the floodplains of the Mississippi and Missouri Rivers. It is almost always found over a mud bottom in turbid waters that fluctuate drastically in area and depth. Typical habitats are shallow sloughs and the isolated pools of prairie creeks. This crayfish retreats to burrows in late summer as the habitats in which it occurs dry up.

Foods

Crayfish are generally omnivores, eating a wide variety of plant and animal materials. An important food for this species is algae scraped from the stems of aquatic plants and other submerged objects. Dead plant and animal remains, and small invertebrates, are also eaten.

image of Papershell Crayfish Calico Crayfish Distribution Map
Distribution in Missouri

Mostly found in northern Missouri north of the Missouri River.

Status

In Missouri, this is one of the most abundant and generally distributed species in the Prairie Faunal Region (roughly the northern half of the state) and on the floodplains of the Missouri and upper Mississippi rivers.

Life cycle

This species excavates burrows as deep as the water table as the habitat dries or winter approaches. Mating can occur at almost any time of year but apparently peaks in late summer or early fall. Eggs hatch in spring. The young remain with the female for a week or more, until they complete two molts, usually dispersing by June. The young molt frequently, and some mate their first year. Most males die after the mating season, and most females die after producing their first brood.

Human connections

These very prolific crayfish are sometimes raised and sold as bait. Because they are an important item in the diet of bass, bullheads, and trout, they contribute to healthy fisheries in our state.

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.