Lobsters in Illinois? Maybe not, but we have plenty of their miniature crayfish relatives.


A burrowing crayfish. (Photo courtesy of Missouri Department of Conservation)

Sure, we don’t have lobsters here in landlocked Will County, but no one would be surprised to see what looks like a miniature version – a crayfish – in their local pond or stream. And, indeed, lobsters and crayfish are closely related.

Like lobsters and other common sea creatures such as crabs and shrimp, crayfish are crustaceans. Most of the crustaceans we know are aquatic, but a few, including woodlice, which you may know as roly-polies, live on land. Even some species of crayfish are more terrestrial than others and spend a lot of time on land. What all crustaceans have in common is that they have a tough exoskeleton, paired, jointed appendages, and three body regions: a head, thorax, and abdomen, according to the Illinois Natural History Survey.

Crayfish belong to the order Decapoda, a term that translates to ten feet, according to National Geographic. Their 10 feet include four pairs of walking legs as well as their most dominant physical feature, a large set of pincers or claws called a chelae, which they use to hunt for food and defend themselves against predators.

All those claws and legs also have a super power. If a crayfish is caught, it can amputate its own legs or claws to escape through a muscle reflex, according to the Iowa Department of Natural Resources. These appendages, however, are not lost forever. Self-amputated legs and claws will regenerate over time. That’s why it’s not uncommon to see crayfish in the wild with different sized legs and claws.

Like other crustaceans and arthropods, crayfish molt as they grow. Because their exoskeletons are tough and inflexible, they eventually outgrow them and replace them with a bigger one, reports the Iowa Department of Natural Resources. When young and growing rapidly, they molt frequently, sometimes even daily. As they get older and bigger, molting becomes less frequent.

In the days following a molt, while their skin is still soft, crayfish are more vulnerable to predators that might otherwise leave them alone. They are able to speed up the growth of their new, larger exoskeleton by eating the old shells, which contain calcium needed for the growth of the new shell, reports the Iowa Department.

Crayfish eat just about anything they come across, but they mostly eat dead plants and animals, reports the Iowa Department of Natural Resources. They will also use their claws, or pincers, to catch fish, insects, and other invertebrates. They play a central role in the food chain as they are an important food source for a variety of animals, from mammals like mink and raccoons; and reptiles like snakes and tortoises; amphibians like frogs and salamanders; and waders such as herons and egrets.

Crayfish are mostly solitary, usually only coming together to mate. They usually mate in the fall and the female will lay eggs the following spring, according to the Missouri Department of Conservation. The females then attach the eggs, sometimes numbering in the hundreds, to their abdomen using a glue-like substance. After several weeks, the eggs hatch, but the young crayfish remain attached to their mother’s abdomen until they molt twice. After that, they will begin to venture out on their own, returning if threatened.

Crayfish live in freshwater habitats almost everywhere except Antarctica and India, reports National Geographic. There are about 600 species in all, and some of the regions with the greatest diversity of crayfish are the southeastern United States and Australia. Illinois is home to several types of crayfish. According to the Illinois Department of Natural Resources, some of the most common include devil crayfish, digger crayfish, northern clearwater crayfish, prairie crayfish, rusty crayfish, male crayfish and the white river crayfish. Most local species are native, but the rusty crayfish is an invasive species native to the southern United States.

Rusty crayfish are aggressive and can take over habitat areas of native crayfish species. In some places, they have completely eliminated native species from their original habitats, reports the IDNR. They are mainly found in the northern part of the state, and they have been present here since at least 1973. They are thought to have been accidentally introduced by anglers who used them as bait and released unused crayfish when they have finished fishing.

What we call a crayfish here in Illinois goes by many other names in the United States and beyond. In the South, crayfish are the most common nickname, and in some parts of the United States they are more commonly called crayfish, reports National Geographic. In some places mudbug is the preferred term, and in Australia they are known as yabbies.

Whatever you call them, they’re considered a keystone species, which means their presence is vital to the overall health of the ecosystem, reports National Geographic. However, of more than 600 species of crayfish in the world, including about 400 in the United States, 32% are threatened with extinction. For another 20% of species, the available data are insufficient to determine whether their populations are stable or at risk.

The reasons for their population decline vary across the world. Here in the United States, major factors include dams, urban development, pollution and habitat loss, according to National Geographic. In Australia, climate change is a huge factor, putting 65% of species at major risk, along with competition from invasive species, agricultural development and overexploitation. In the United States, 5% of species are at increased risk due to climate change.



About Author

Comments are closed.