Abstract
Develoment precess and characteristics of eggs of the geoduck clam, Panope japonica are reporting in this study. Eggs and sperm were excised from gonad, artificially fertilized in an aquarium, reared under various temperature regimes, and record and record the larval period and the time need to reach a certain larval stage from ferilization. Unfertilized eggs of P. japonica appeared to be oval with a mean diameter of $70\mu$m and they became spherical after fertilization. The eggs of P. japonica can be classified as demersal. At a constant water temperature of $ 11^{citc}C$, it took 4 hours form fertilization to become four-cell stage, two days to become trochophore larvae, three days to become D-shape larvae, twenty-three days to become umbo stage, and thirty-six days to become fully grown veliger ready form settlement. A negative correlation was observed between the water temperature and the larval period of P. japonica. From fertilization to D-shape larvae, it took five days at 8$^{\circ}C$, while it was only two days to become D-shape larvae at $ 17^{citc}C$. Time required to D-shape larvae from fertilization was proportional to temperature, and the relationships were expressed as follows : To 8-cell stage, 1/t=0.0209 w-0.1167 (r=0.9967) To blastula stage, 1/t=0, 0055 w-0.0192 (r=0.9825) To trochophore stage, 1/t=0.0034 w-0.0155 (r=0.9907) To D-shape larvae stage, 1/t=0.0014 w-0.0023 (r=0.9843) (t, time in hours ; w, water temperature) Bioligical minimum temperature for egg development was calculated as 3.82$^{\circ}C$ in average.
코끼리조개의 인공종묘생산 기술개발의 일환으로 성숙된 모패를 절개법에 의하여 인공수정시켜 난 발생 및 유생의 발달과정을 관찰한 결과를 요약하면 다음과 같다. 코끼리조개의 난은 분리침성란으로 나타났으며, 방란직후 알의 모양은 타원형이나 수정이 되면 직경 $70\mu$m의 구형으로 된다. 수정난의 발생은$ 11^{citc}C$에서 4시간 후 4세포기로 되고, 2일이 지나면 담륜자 유생(trochophore larvae), 수정 후 3일째에는 D상 유생, 23일째에는 각정기, 36일째에는 성숙유생으로 되었다. 수온(w)에 따른 각 단계별 소요시간(t)의 관계를 보면, 8세포 : 1/t=0.0209 w-0.1167 (r=0.9967) 포배기 : 1/t=0.0055 w-0.0192 (r=0.9825) 담륜자기 : 1/t=0.0034 w-0.0155 (r=0.9907) D상 유생기 : 1/t=0.0014 w-0.0023 (r=0.9843) 상기 식에서 산출된 코끼리조개의 생물학적 기초수온은 3.82$^{\circ}C$였다.
