The biology of Schistomysis spiritus [Crustacea, Mysidacea]

Abstract

Schistomysis spiritus (Norman) breeds throughout the year in the Clyde and in Loch Ewe, Wester Ross, but breeding is more intense at some seasons than others. The over-wintering population in the Clyde breeds in March/April, the progeny growing and becoming sexually mature in July/August to produce a further generation which matures and breeds in October/November. In Loch Ewe the over-wintering population breeds in February, March and April and members of this spring generation begin breeding in May and continue to breed until September; the number of S. spiritus breeding in Loch Ewe decreases sharply after September and no autumnal peak of breeding, such as that in the Clyde, was found during the period investigated. The number of young carried in the marsupium varies seasonally, being 20–30 in May/June and 2–6 in midwinter. The food and the horizontal and vertical diurnal and seasonal movements of this species are discussed.