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Semi-aquatic isopod (Styloniscus)

Taxonomic group

Styloniscidae: Styloniscus

Diagnostic features

Styloniscus is a small, slater-like isopod with a mottled grey-brown colouring and longer antennae than most aquatic isopods. This isopod normally lives above the water amongst damp vegetation, but it appears to deliberately enter the water on occasion.

Typical habitats

While they are not normally aquatic, many Styloniscus were observed moving around under water on the walls of an Auckland swimming pool, and we often find them in samples collected from bush-covered streams.


They probably feed on dead plant matter and the associated decomposer organisms.

Indicator value

  • Hard bottom: unassigned; Order Isopoda value 5
  • Soft bottom: unassigned; Order Isopoda value 4.5

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

Being only an occasional visitor to aquatic habitats, Styloniscus may indicate little about stream water quality. There are no tolerance values assigned to this genus but the Order Isopoda has been assigned tolerance values of 5 (hard bottom sites) and 4.5 (soft bottom sites).