(CLADOCERA, CONCHOSTRACA or OSTRACODA)

Water fleas, clam shrimps, mussel shrimps or seed shrimps

Code: None allocated

Members of the three crustacean classes Cladocera, Ostracoda and Conchostraca have a bivalved carapace covering the whole body. This makes them look superficially like bivalved molluscs. Identification to Crustacea can be based on the form of the body inside the shell or carapace: bivalved molluscs have a soft, unsegmented body; crustaceans have a segmented body bearing several pairs of legs, gills, swimming organs or feathery filter-feeding structures.

The Cladocera (water fleas) are generally very small but some species reach 5-6 mm. The bivalved carapace covers the body but the head is free. Distribution is Australia-wide. Of the three crustacean classes with bivalved carapaces these are the least likely to be mistaken for bivalved molluscs.

The Conchostraca (clam shrimps) are small to medium size (up to 25mm), generally green, green-blue or brown,and often translucent. They have several to many trunk appendages and the second antennae protrude from the carapace. They are found in lakes, dams, ponds and temporary pools and are widespread across Australia and can more readily be confused.

The Ostracoda (mussel shrimps, seed shrimps) resemble Conchostraca but are usually somewhat smaller. The carapace is generally translucent and may be notched in outline and/or carry complex patterns of knobs, pores or hairs. Both the first and second antennae are long , setose and may protrude from the carapace.