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Estuarine isopods (Austridotea)

Taxonomic group

Idoteidae: Austridotea

Diagnostic features

Austridotea isopods are found in South Island coastal streams near or within estuaries. They are somewhat elongated isopods, up to 1cm in length, capable of swimming, and the tail segment may have a pointed tip (A. annectens) or a rounded tip (A. lacustris).

Typical habitats

Our specimens came from Otago streams and rivers, in upper estuarine reaches where there was evidence of sea water intrusion. These were slow-flowing, muddy bottom sites.


Austridotea species feed primarily on plant detritus, but they will also eat algae and invertebrates.

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

Austridotea are common in the estuarine reaches of South Island rivers, including some draining largely farmland catchments. 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).