Prairie Research Institute

Illinois Natural History Survey

The world is home to more than 42,000 species of crustaceans, ranging in size from giant spider crabs to microscopic zooplankton. Although most of them are marine, several thousand occur in almost every type of freshwater habitat found on the planet. They represent important food sources for thousands of other organisms, including humans, and dramatically affect the physical and biological structure of ecosystems. Understanding their role in the natural world is of critical importance.

INHS crustacean biologists investigate the distribution, status, phylogenetic relationships, ecology, behavior, and physiology of crustaceans, particularly crayfishes and crustacean zooplankton species.


Crayfishes are a critically important link in energy flow in aquatic ecosystems, as they eat algae and other plant matter and convert it into animal tissue. More than half of the United States’ 410+ species and subspecies need conservation attention, however, and very few of these are protected by law.

INHS scientists use traditional survey methods (kick-seining) and newer techniques like environmental DNA (eDNA) to assess the distribution and status of North American crayfishes, including threatened, endangered, and invasive species. They also use molecular and morphological techniques to explore crayfish systematics and ecology and to discover and describe new crayfish species.

INHS data informs conservation and management strategies for these vital organisms and the specialized habitats they depend on.


Zooplankton are an essential part of any aquatic system as all fish species depend on them to sustain at least one stage in their development. Researchers with INHS field stations monitor zooplankton in the Midwest and study zooplankton abundance and community structures in reservoirs, rivers, and lakes.

Scientists also investigate how exotic and invasive species affect native zooplankton populations. Invasive carp specifically have the potential to disrupt food chains by feeding primarily on zooplankton.

Crustacean collection

The INHS Crustacean Collection is one of the largest state collections of crustaceans in North America, containing over 130,000 specimens and 16,000 lots of approximately 400 species in 30 families. It contains primary types of 13 species and secondary types of 20 species. Almost all are from North America. About 50 percent of the collection is from Illinois; the remainder is mostly from the southeastern United States. The best represented groups are crayfishes, shrimps, scuds, slaters, and pill bugs. A few lots of marine crustaceans found along the North American coastline are also present in the collection. INHS also maintains a tissue collection that contains high-quality tissues from a portion of our vouchered specimens, mostly those collected after 1998. Data from the crustacean collection can be searched online.

Read more about all INHS biological collections.


American Crayfish Atlas

INHS scientists developed the American Crayfish Atlas, the first website to provide nationwide coverage of crayfish distributions, showing where crayfish species have been found and the extent of their ranges.

The atlas contains more than 43,000 records, gleaned from the INHS crustacean collection and from over 50 sources, including museums and the research literature and various institutions and state agencies, whose information had not been cataloged or made visible online.

The atlas is particularly valuable for researchers and state and federal management agencies involved in making crayfish conservation assessments. One of the primary criteria to evaluate the species of greatest conservation need is the total extent of their range. With the atlas, groups and agencies can quickly and accurately determine the ranges for various crayfish species.

INHS Field Guide to Crayfishes of the Midwest

The Field Guide to Crayfishes of the Midwest is the most up-to-date reference available for the identification of crayfishes found in aquatic habitats across Minnesota, Wisconsin, Iowa, northern Missouri, Illinois, Indiana, Michigan, and Ohio. It includes distribution maps; a dichotomous and identification key; general information on crayfish biology, conservation, and collecting techniques; and species-specific information on habitat, key identification features, and conservation notes for all species found in this region. The guide and a companion spiral-bound key are available for purchase through the INHS online shop.

The Crayfishes of Kentucky

The Crayfishes of Kentucky provides an up-to-date list of crayfish species found in Kentucky, along with distribution maps, illustrations, photos, an identification key, information on the habitat and biology of each species, and a summary of the historical efforts of crayfish biologists in Kentucky. The guide is available for purchase through the INHS online shop.