The ecology and life cycle of a population of Modiolarca tumida (Hanley, 1843) (Bivalvia: Mytilidae) of the coast off north-eastern England

Abstract

The life history of a population of Modiolarca tumida occurring off the Northumberland coast is described. Modiolarca tumida lives primarily in the tests of ascidians. On settlement the young spat seek an ascidian host, climb close to the inhalent and exhalent apertures of the host and there wrap the test around themselves using the byssus. Initially, there is a preference for Ascidiella scabra as the host species but, with increasing size, Modiolarca is more and more often found in Polycarpa pomaria. While numbers per ascidian vary, usually <5 occur in each host. However, immediately following settlement very occasionally 100+ have been recorded. Modiolarca tumida is relatively short-lived, with few living longer than two years. Spawning occurs at the end of July and August at the end of its first year of life and at the same time in subsequent years in the case of the minority that survive. © The Author 2008. Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved.