Reproductive cycle of the brachiopodTerebratulina retusa on the west coast of Scotland

Abstract

The reproductive cycles of two populations of the Recent articulate brachiopodTerebratulina retusa (Linnaeus) are described, based on samples taken between October 1985 and October 1986. Stereological analysis of the gonads revealed a single synchronised spawning event between late November and the end of January in the Firth of Lorn. In a second population, in Loch Fyne, spawning took place repeatedly throughout the spring and summer, with greatest spawning activity occurring in the late autumn.T. retusa from Loch Fyne were approximately three times more fecund than those from the Firth of Lorn. Productivity in the Clyde Sea area is approximately five times higher than in Firth of Lorn and higher fecundities and spawning frequencies of the Loch Fyne population are attributed, in part, to greater food availability. The initiation of gametogenesis appears to be mediated by the mobilisation of reserves stored in the outer mantle epithelium during the winter. Primary productivity increases dramatically in the spring and gametogenesis shows a corresponding increase.