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Seed shrimps (Ostracoda)

Taxonomic group

Class: Ostracoda

Diagnostic features

Ostracods are small (less than 3mm long) swimming crustaceans that resemble small seeds. The entire body is contained within a bivalved carapace, much like a tiny mussel shell. The carapace is often pale or green. Sometimes the legs and antennae are seen protruding out beyond the valves of the carapace.

Typical habitats

Ostracods are generally found in slow flowing or stagnant waters, where they typically hover over or amongst the bottom sediments.


Ostracods are scavengers, feeding on any fine animal or plant matter they can stir up from soft sediments.

Indicator value

  • Hard bottom: 3
  • Soft bottom: 1.9

The tolerance values (ranging from 0 to 10) give an indication of which are the sensitive taxa (values of 8 or more) and which are the tolerant taxa (values of 3 or less). For more information see: Indicator species

Ostracods are associated with pond-like or slow-flowing habitats. Their occurrence in sewage treatment ponds suggests some species can tolerate poor water quality conditions. They have been assigned tolerance values of 3 (hard bottom sites) and 1.9 (soft bottom sites).