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

Abstract

Abstract. The reproductive cycles of two populations of the Recent articulate brachiopod Terebratulina 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.

Oogenesis in the articulate brachiopodTerebratulina retusa

“…The follicular envelope degrades and the contents appear to be phagocytosed (James et al 1991 b). Whilst still within the follicular capsule, the mature ovum is irregular in shape.…”

Functional morphology of the gonads of the articulate brachiopodTerebratulina retusa

“…The present investigation was conducted as part of an integrated study of the reproductive biology of the articulate brachiopod Terebratulina retusa which included stereological analysis of the reproductive cycle (James et al 1991 a) and an ultrastructural study of gametogenesis (James et al 1991 b and in preparation).…”