MASKING AND INGESTION PREFERENCES OF THE SPIDER CRAB NOTOMITHRAX-URSUS (BRACHYURA, MAJIDAE)

In laboratory tests, the spider crabs Notomithrax ursus, collected nea r Kaikoura peninsula, South Island, New Zealand, were shown to mask wi th some species of algae more than others. The types of algae most pre ferred as masking material were branched algae such as Halopteris spic igera and Corallina officinalis. Thallose-like algae such as Ulva sp., and strap-like algae such as Cladhymenia oblongifolia, were less pref erred. It was also shown that algae with which N. ursus prefers maskin g are also the algae that N. ursus prefers to eat. The conflicting req uirements of masking and food storage, and possible reasons for algal choice are discussed.