The Gastropod Genus Bembicium Philippi

Abstract

A history of the nomenclature of the littorinid genus, Bembicium Phllippi, 1846, and its characters are given, and the anatomy of species of the genus is discussed. Three species are recognized and redescribed: a reef-living species, B. nanum (Lamarck); an estuarine species, B. auratum (Quoy & Gaimard); and the species B. melanostoma (Gmelin) which normally inhabits sheltered bays and inlets.

Although all are intertidal animals, and show some measure of adaptability, each appears to be best suited to a particular habitat. B. melanostoma and B. nanum are usually found where the chlorinity of the water is close to that of the sea. B. auratum can withstand considerable variation in the chlorinity of its environment for periods of time which are not likely to be exceeded in its normal habitat. B. melanostoma mostly lives at higher tidal levels than B. nanum. In the aquarium B. nanum proved the most susceptible to desiccation.

The egg masses of B. melanostoma contain fewer and larger eggs than those of B. auratum. In the laboratory spawning of B. auratum occurred during the spring and early summer. Under the same conditions specimens of B. melanostoma deposited eggs in October. The differences between the eggs and their development, and between the times of spawning of the two species collected from different littoral regions are also discussed.