The development of Japanese geoduck, Panopea japonica, grown under culture conditions, has been examined through the morphological characteristics in fertilized egg, larvae and juvenile. Gametes were stripped from ripe broodstock and placed into two separate containers. Eggs were washed through a 40 μm sieve and fertilized with dilute sperm solution. Developing larvae were maintained at 19 ± 1℃. Fertilized eggs with 81.6 μm diameter developed to trochophores within 14 h and to D-stage larvae (116 μm shell length) within 27 h. Larvae were spontaneously settled at shell length of 311 μm after 20 days. The hatching from fertilized eggs and larval rearing were normally available in 18.5-21.5℃, and the growth was good in a cashmilon substrate, as well as sand. After rearing of day 108 from metamorphosis, the shell length of juvenile P. japonica reached 13 mm, and growth rate of shell length of the juvenile was 117.5 μm/d.
