Salinity and temperature tolerance by Nymphon gracile (Leach) and Achelia echinata (Hodge) (Pycnogonida)

The tolerance of two species of pycnogonid, Achelia echinata (Hodge) and Nymphon gracile (Leach) to a range of salinities, temperatures and relative humidities has been examined. In most instances N. gracile is more resistant than A. echinata and indeed is found higher in the littoral zone during the warmer months and thus likely to be subjected to greater environmental fluctuation.