Crustaceans make up a large group of arthropods that includes animals such as crabs, lobsters, crayfish and shrimp. They breathe with gills and have two pairs of antennae.
DuPage County’s native crustaceans — crayfish and shrimp — belong to the order Decapoda, which is from the Latin for “10-footed,” referring to the five pairs of jointed legs all decapods possess.
Seven kinds of crayfish are native to the Chicago region: the devil, digger, calico, northern clearwater and northern crayfish and the white river and prairie crawfish. They're all omnivores that eat plants, fish and carrion, and they're all important sources of food for fish, marsh birds, snakes and turtles.
Prairie crayfish (Procambarus gracilis)
Crayfish begin life as clusters of fertilized eggs, which attach to the female’s abdomen from several days to several weeks, when the female is said to be “in berry.” Newly hatched young look like tiny adults and remain on the female for several days while they grow.
Like other arthropods, crayfish grow by continuously molting. They shed their exoskeletons, allowing their bodies to grow before forming new hard exteriors. They're vulnerable to hungry predators during this time because they're soft and slow. A crayfish can molt 14 times during its first year. After that, mature females generally molt once a year; males, twice.
Crayfish need moist gills to breath and will burrow to reach groundwater. "Primary" burrowers spend most of the year in burrows — some up to 9 feet deep — and emerge only to breed or look for food. Their excavations produce chimneylike mounds of mud, which appear in fields in the spring. “Tertiary” burrowers live in streams but will spend short periods of time in burrows during droughts. “Secondary” burrowers fall somewhere between the two, spending fair amounts of time in streams and burrows.
At least one type of native freshwater shrimp lives in DuPage: the Mississippi grass shrimp, which is also called the glass or ghost shrimp. Except for its eyes, it's completely transparent. At times, recently ingested plants in its intestines give its abdomen a greenish tinge. It has long antennae and a laterally flattened body and resembles a much smaller version of marine shrimp sold in grocery stores.
Mississippi grass shrimp live in aquatic plants in lakes, ponds and backwaters. They eat algae, plants, and live and dead animals and are an important source of food for fish, especially small fish that also hide in vegetated areas.