Crawling and clustering behaviour of 3 species of intertidal mussels in New Zealand

Abstract

Three species of mytilid bivalves (Mytilus edulis aoteanus, Perna canaliculus, Aula-comya maoriana) co-exist in the eulittoral zone of some rocky shores in New Zealand. However, their distributions within this zone show micro-geographic differences. To determine the possible role of behaviour on these diiferences, separate experiments on the species’ abilities to crawl out from under gravel and to distribute themselves in mixed-species clusters were performed. When small mussels (1–2 cm long) were covered with 3 cm of pea gravel (0.3–0.8 cm grain size), P. canaliculus crawled to the surface much more rapidly than did the other 2 species, which were generally similar in crawl-out ability. When numbers of small mussels (1–4 cm long) of the 3 species were mixed together in various combinations and held in sea water, A. maoriana predominated inside the resultant clusters, whereas P. canaliculus was judged to be slightly more abundant than M. e. aoteanus on the outside of such clusters. © 1984 Taylor & Francis Group, LLC.