Histological and ultrastructural observations of the lophophore and larvae of the brachiopod, Notosaria nigricans (Sowerby 1846)

Abstract

The lophophore and the larva of the rhynchonellid brachiopod Notosaria nigricans are described in detail using techniques of light microscopy, scanning electron microscopy and transmission electron microscopy. The lophophore comprises two helical spirals, each capable of uncoiling and extending beyond the shell margin; the muscular system responsible is described. Occasionally sudden shell retraction amputates part of the uncoiled lophophore and regeneration occurs. The entire lophophore is covered with peculiar, and apparently unique, knobbed cilia. Their function remains obscure, but may be concerned with food capture since the lophophore of N. nigricans is unusual in being incapable of secreting mucus. The lophophore acts as a brood chamber for at least two larval stages, which generally occur in a definite orientation along the base of the filaments.