Biological Relationships of an Intertidal Bryozoan Population

Summary The biological relationships of intertidal bryozoans from northern New Zealand are recorded. Bryozoans were found to be food organisms for echinoids, starfish, brittle-stars, chitons and opisthobranchs. Space competition between bryozoans and sessile organisms is discussed. Among opposing bryozoan colonies there are five growth responses that may be exhibited. Of the sessile organisms studied on the shore, bryozoans and Spirorbis occupied the most space. The association between Hippopodinella adpressa and gastropod shells is discussed with reference to current opinions regarding bryozoan-mollusc associations. It is concluded that the attractive factor to H. adpressa larvae is a calcareous substrate but that pagurid tenancy of gastropod shells may have reinforced the evolutionary forces responsible for the association with shells.