Larval and Postlarval Development of the New Zealand Pipi, Paphies Australis (Bivalvia: Mesodesmatidae)

Pipi (Paphies australis) were conditioned, spawned and the resultant larvae reared to settlement in the laboratory. Adult pipi were successfully conditioned after 23 d at 22° C. Spawning was induced using a combination of increased temperature and a dilute sperm solution. Settlement occurred 18-22 d after spawning at a mean shell length of 264 μm. After settlement and metamorphosis pipi gradually began to take on the adult shape. Cultured juveniles were grown to 37 mm shell length both in the laboratory and later in the wild. Once in the wild, cultured pipi grew from 13 to 37 mm in 17 mo with a strong seasonal component to their growth. Microscopic examination revealed slight differences in shell morphology between pipi larvae and the closely related tuatua (Paphies subtriangulata) and toheroa (Paphies ventricosa). Pipi were more rounded and smaller than both tuatua and toheroa at a similar stage of development. The results of scanning electron microscopic examination of larval shell hinge structure confirmed previous preliminary findings for pipi. The larval shell ligament is posterior to the center of the provinculum in pipi but central in both the tuatua and toheroa. These differences are sufficient to enable larval pipi to be distinguished from larval toheroa and tuatua.