サルボオ Anadara subcrenata (Lischke) の浮游仔貝並に底棲初期の稚貝に就いて

抄録

The veliger larvae of Anadara subcrenata (pl.1, fig.1, 2. text-fig.3) were identified by tracing back the prodissoconch on the umbonal portion of the young shell (text-fig.2). The smallest veliger the author traced back was 0.11×0.09mm (pl.1, fig.1). The full grown veliger measures 0.08×0.20-0.32×0.22mm in size, its colour is yellow and provided with a few bristles as well as about 10 nearly concentric lines on its surface (pl.1, fig.2, text-fig.3). The veliger larva of this species has much resemblance to that of the allied and concurrent species Anadara inflata, but can be distinguished from it by a sharper umbo, smaller number of concentric lines and larger size of the full grown veliger stage. The new dissoconch, which is formed after the larva has entered into the benthic life, is gray in colour and distinct from the prodissoconch (pl.1, fig.3, text-fig.2, 4, 5). When the young shell attains a length of about 1mm, the radiating striae numbers about 30, thus the shell acquires the characteristic of the species (text-fig.5). The young shells are found attaching to seaweeds, Bryozoans, dead shells, etc. by byssus-threads in their early stage (pl.1, fig.4), and later they enter into the life in the mud of the bottom.