Kingdom – Animalia
Phylum – Arthropoda
Subphylum – Crustacea
Crustaceans include the barnacle, crab, crayfish, lobster, shrimp, water flea, and pill bug. Although largely aquatic, a few crustaceans are found in terrestrial habitats. Of the nearly 67,000 aquatic species of crustaceans, only about 10% occur in freshwater habitats. The smallest arthropod in the world is a 0.1 millimeter crustacean Stygotantulus stocki. The Japanese spider crab is the largest arthropod with a leg span of 3.8m!
Crustaceans have:
- hard exoskeleton.
- segmented bodies.
- jointed limbs.
- biramous (branching) appendages.
- larval stage.
- five-segmented head (cephalon).
- two pairs of antennae.
Malacostraca
In Illinois there are 71 known species:
Amphipoda – scuds – 19 species
Isopoda – pillbugs – 28 species
Decapoda – crayfish and shrimp – 23 species
Mysidacea – opossum shrimp – 1 species
- 40,000 species on earth
- abdominal appendages
- three tagmata
1. five-segmented head
2. eight-segmented thorax
3. six-segmented abdomen with telson
Ostracoda – seed shrimp
In Illinois there are 53 species:
Halocyprida
Myodocopida
Podocopida
- 70,000 species on earth
- body is not clearly segmented
- no gills
- no circulatory system
- body is flattened from side to side
- hinged “shell” made of chitin
Maxillopoda – barnacles, copepods
In Illinois there are 31 known species:
Branchiura – fish lice – 10 species
Copepoda – copepods – 21 species
- five-segmented head
- six-segmented thorax
- four abdominal segments with a telson
- feed with maxillae (mouthparts) rather than filter feed
Branchiopoda
In Illinois there are 52 known species:
Anostraca – fairy shrimp – 4 species
Conchostraca – clam shrimps – 5 species
Diplostraca – water fleas – 43 species
- 800 species on earth
- freshwater
- have gills on their appendages
Remipedia
- 30 extant species
- marine crustacea
- no known members in Illinois
- closest Crustacea relatives of the insects
Cephalocarida – horseshoe shrimps
- 12 extant species
- benthic marine crustacea
- no known members in Illinois