Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Guide to New Zealand's freshwater invertebrates

Groundwater isopods ( Paranthuridae : Cruregens )

Diagnostic features

The freshwater paranthurid isopods have elongated bodies, making them look quite unlike the more familiar slater-shaped isopods. Cruregens is easily distinguished from the similar-shaped Paranthura by the absence of eyes (which are present in Paranthura). Cruregens also has little or no body pigmentation, unlike Paranthura.

Typical habitats

Cruregens is one of several pale, eyeless crustaceans known to live in groundwater, and they are infrequently recorded in streams.


Being groundwater invertebrates, they presumably feed on bacterial biofilms.

Indicator value

The occurrence of Cruregens in streams indicates a connection to interesting groundwater communities, but 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).