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 Major Groups | Crustacea (crustaceans)
 

Crustacea (crustaceans)

Crustacea is a diverse group with representatives in terrestrial, marine and freshwater habitats. Crustaceans are an important part of fish diets, particularly the microcrustaceans.

Descriptive Features:

  • typically with a hard, rigid exoskeleton composed of chitin, calcified in larger species (Decapoda)
  • body divided into 3 regions: head, thorax, and abdomen
  • carapace absent ( Copepoda, Anostraca, some Malacostraca) OR present  and covering some body segments (Notostraca, some Malacostraca) OR all body segments (Cladocera, Ostracoda, Conchostraca, Branchiura)
  • head appendages include 1st antennae (antennules), 2nd antennae, mandibles, 1st maxillae (maxillulae) and 2nd maxillae
  • body may bear paired appendages that are modified for feeding (mandibles, maxillae), locomotion (legs, pereiopods), grasping (claws, chelipeds), swimming (pleopods)
  • biramous limbs
  • gills may be present or absent
  • Total length:  250 m - 40 cm
  • Taxonomic Checklist: This guide provides a key to commonly recognised crustacean groups without assigning taxonomic level. 
         Anostraca (fairy shrimps)
         Branchiura (fish lice)
         Malacostraca (yabbies, crabs, shrimp, scuds)
         Notostraca (shield shrimps) 
         Cladocera (water fleas)
         Conchostraca (clam shrimps)
         Copepoda (copepods)
         Ostracoda (seed shrimps)

    Distribution: Australia wide

    Sensitivity Rating: 1 to 6 

    AUSRIVAS Taxacode: OZ999999

    Functional Feeding Group: shredders, gathering collectors, scrapers, filtering collectors, parasites, predators

    Ecology: Crustaceans are found in permanent waters, temporary ponds, caves, and aquifers. The water types range from extremely low salinity to salt lakes. Cladocera, Conchostraca, Copepoda and Ostracoda are planktonic. Anostraca, Branchiura, Malacostraca and Notostraca are benthic, littoral and pelagic. Many malacostracan crustaceans burrow into the substratum.
    Fish lice and some copepods are parasitic. Crustaceans are filter feeders, detritivores, omnivores, predators or scavengers. They have a varied diet across the group, largely dependent upon their own size and adaptations.
    Reproduction in crustaceans is varied, whilst some groups reproduce sexually, others are hermaphrodites and others employ parthenogenesis (reproduction without a male). Eggs may be stored in a variety of ways also. Cladocerans have a brood chamber, yabbies attach the eggs to body appendages, copepods retain the eggs in an external ovisac that is formed when the eggs are expelled. Nauplius is the 1st larval stage. It is planktonic and for decapods and cladocerans it occurs in the egg before hatching. There are several more stages before the adult form is reached. Body segments and appendages are added in each developmental stage. Growth equals moulting and ecdysis. A new soft skeleton is formed underneath the old, which is then shed and the body rapidly expanded for future growth by taking in water. Hardening of the new exoskeleton may take a few minutes or several hours. Some species consume the old skeleton to regain the calcium in it. The rate of moulting depends upon suitable environmental factors and population density.
     

    Cladocera (water fleas)

     

    Ostracoda (seed shrimps)

     

    Conchostraca (clam shrimps)

     

    Copepoda (copepods)

     

    Notostraca (shield shrimps)

     

    Anostraca (fairy shrimps)

     

    Branchiura (fish lice)

     

    Malacostraca (yabbies plus)

     
    Information Sources: Davie 2002, Williams 1980, Ingram et al 1997, Davis & Christidis 1997
     More ›››  key to minor groups