Minnesota Crustaceans

Subphylum Crustacea

Crustacea (crustaceans) is the subphylum of animals that is characterized by the following:

  • Crustaceans have a hard external skeleton (exoskeleton).
  • Most crustaceans are aquatic.
  • The head has five appendages: two pairs of antennae, a pair of mandibles (jaws for holding and tearing food), and two pairs of maxillae (for transferring food to the mandibles).
  • The head and thorax are fused together (cephalothorax), which is usually covered by a single continuous shield (carapace).
  • Early development of most crustaceans includes a stage in which only a few limbs are present (nauplius larval stage). In this stage there is a unique structure with which the larva chews its food (naupliar arthrite), and a single, simple, median eye (naupliar eye).
  • Most crustaceans have appendages or limbs on the thorax and abdomen that split into two branches (biramous).
  • Crustaceans carry their eggs until they hatch, then release larvae into the water.


The study of crustaceans is called carcinology. There are almost 68,000 described crustacean species worldwide. About 15% of these are inland water species, the remainder are marine species. In North America, about 1,500 freshwater species have been described.

In the United States, 22 crustacean species are protected under the Endangered Species Act. In Minnesota, two are considered invasive.



  virile crayfish  
  Photo by Kirk Nelson  
Recent Additions

Rathke’s woodlouse


Rathke’s woodlouse is a non-native isopod. It is native to central Europe, was introduced into North America, and now occurs from Newfoundland south to Tennessee and west to South Dakota. It is not uncommon in Minnesota. It is found in places with at least some dampness, including on rotting logs; under logs, stones, and boards; and in woodsheds and greenhouses. It is mostly a scavenger, eating plant and animal organic matter, but sometimes also feeds on living plants.

Unlike pill woodlice (Family Armadillidae), Rathke’s woodlouse cannot roll into a ball.

  rusty crayfish  
    Photo by Alfredo Colon  

Rusty crayfish


Rusty crayfish (Orconectes rusticus) is a medium- to large-sized freshwater crustacean. It is native to Michigan, Ohio, and Kentucky. It is used extensively by fishermen as bait, and is sold as an aquarium pet. Unused bait and release of aquarium pets have resulted in the introduction of this species across the United States. It is considered invasive outside of its native range.

Rusty crayfish are extremely aggressive. They out-compete and eventually eliminating native crayfish species when introduced into a new site. Juveniles have a higher metabolic rate, eat twice as much, and develop much faster than native crayfish species of similar size.

Rusty crayfish is identified by a rust-colored spot on each side of its upper shell; a rust-colored stripe on the uppers side of its abdomen; and very large claws with an S-shaped movable finger.

  rusty crayfish  
    Photo by LMG  

Virile crayfish


Virile crayfish (Orconectes virilis) is a medium- to large-sized freshwater crustacean. It is widespread and abundant across North America. It is native to central United States and Canada, from Quebec to Tennessee in the east, to Alberta and Colorado in the west. It is introduced and considered invasive outside of its native range from coast to coast.

Virile crayfish prefer streams with rocky bottoms, moderate flow and turbidity, abundant cover, and stable water levels. They often use rocks, logs, or other organic debris as cover. They occasionally dig burrows into muddy banks, especially when water levels are low. To survive the winter, they migrate to deeper water that does not completely freeze and they become inactive.

Virile crayfish are identified by the dappled, olive-brown body with pairs of dark brown splotches on the abdomen; the shape of the shield (carapace) covering the front part of the body; and the broadly flattened, usually bluish claws.

  virile crayfish  
    Photo by Kirk Nelson  
Other Recent Additions











This list includes only crustaceans that have been recorded in Minnesota, but not all of the crustaceans found in Minnesota.

Profile Photo Video    

brickwork woodlouse (Porcellio spinicornis)


burrowing amphipod (Diporeia sp.)


calico crayfish (Orconectes immunis)


common pill bug (Armadillidium vulgare)


Couse tadpole shrimp (Lepidurus couesii)


curly woodlouse (Cylisticus convexus)


devil crayfish (Cambarus diogenes)


eastern alkali fairy shrimp (Branchinecta readingi)


eastern fairy shrimp (Eubranchipus holmanii)


Ellis Bog crangonyctid (Crangonyx richmondensis)


freshwater shrimp (Gammarus fasciatus)


golden crayfish (Orconectes luteus)


holarctic clam shrimp (Lynceus brachyurus)


knobbedlip fairy shrimp (Eubranchipus bundyi)


northern clearwater crayfish (Orconectes propinquus)


northern river crangonyctid (Crangonyx pseudogracilis)


northern spring amphipod (Gammarus pseudolimnaeus)


ornate fairy shrimp (Eubranchipus ornatus)


powder blue isopod (Porcellionides pruinosus)

Profile Photo Video  

Rathke’s woodlouse (Trachelipus rathkii)


red swamp crayfish (Procambarus clarkii)

Profile Photo Video  

rusty crayfish (Orconectes rusticus)


scud (Hyalella azteca)


smoothlip fairy shrimp (Eubranchipus intricatus)


spinytail fairy shrimp (Streptocephalus sealii)

Profile Photo Video  

virile crayfish (Orconectes virilis)


White River crawfish (Procambarus acutus)


Armadillidium vulgare (common pill bug)

Branchinecta readingi (eastern alkali fairy shrimp)

Cambarus diogenes (devil crayfish)

Crangonyx pseudogracilis (northern river crangonyctid)

Crangonyx richmondensis (Ellis Bog crangonyctid)

Cylisticus convexus (curly woodlouse)

Diporeia sp. (burrowing amphipod)

Eubranchipus bundyi (knobbedlip fairy shrimp)

Eubranchipus holmanii (eastern fairy shrimp)

Eubranchipus intricatus (smoothlip fairy shrimp)

Eubranchipus ornatus (ornate fairy shrimp)

Gammarus fasciatus (freshwater shrimp)

Gammarus pseudolimnaeus (northern spring amphipod)

Hyalella azteca (scud)

Lepidurus couesii (Couse tadpole shrimp)

Lynceus brachyurus (holarctic clam shrimp)

Orconectes immunis (calico crayfish)

Orconectes luteus (golden crayfish)

Orconectes propinquus (northern clearwater crayfish)

Orconectes rusticus (rusty crayfish)

Orconectes virilis (virile crayfish)

Porcellio spinicornis (brickwork woodlouse)

Porcellionides pruinosus (powder blue isopod)

Procambarus acutus (White River crawfish)

Procambarus clarkii (red swamp crayfish)

Streptocephalus sealii (spinytail fairy shrimp)

Trachelipus rathkii (Rathke’s woodlouse)


























Rathke’s woodlouse

rusty crayfish

virile crayfish



No Species Page Yet?

If you do not see a linked page for an amphibian in the list at left you can still upload a photo or video as an email attachment or report a sighting for that amphibian. Click on one of the buttons below and type in the common name and/or scientific name of the amphibian in your photo, video, or sighting. A new page will be created for that amphibian featuring your contribution.

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