말백합, Meretrix petechialis (Lamarck)의 난 발생에 미치는 수온, 염분, 수용밀도의 영향

Effect of Water Temperature, Salinity and Rearing Density on the Egg Development of the Hard Clam, Meretrix petechialis (Lamarck)

말백합의 채란 채정 후 경과시간에 따른 수정률과 D형 유생의 발생률은 채란 채정 직후 수정한 것이 가장 높았으며, 1시간 이후부터는 수정률과 발생률이 급격히 감소하였다. 수정란의 적정 발생수온은 $25-27^{\circ}C$였으며, $33^{\circ}C$에서는 정상적으로 발생되지 않았다. 수정란에서 D형 유생까지 발생소요시간은 $20^{\circ}C$에서 37시간 15분, $25^{\circ}C$에서 20시간 50분, $30^{\circ}C$에서 15시간 20분이었다. 초기 발생에 있어 난 발생이 정지하는 생물학적영도는 평균 $12.4^{\circ}C$로 나타났다. 수정란이 D형 유생으로 발생 가능한 염분은 20.0-37.5 psu, 적정염분은 27.5-32.5 psu였다. 발생률이 높은 수정란의 수용밀도는 사육수 1 mL당 40개 이하였다.

This study was performed to describe the effect of water temperature, salinity and density on the eggs development of the hard clam, Meretrix petechialis. Eggs of Meretrix petechialis were turned out to be demersal isolated eggs of $82.3-86.1{\mu}m$ in an average diameter after spawning. The hatching rate of D-shaped larvae by elapsed time after spawning was the highest in fertilization immediately after spawning and distinguished decrease from 1 hour of spawning. The optimum water temperature for development of D-shaped larvae from fertilization was ranged between $25^{\circ}C$ to $27^{\circ}C$. However, D-shaped larvae was not developed at $33^{\circ}C$ of water temperature. The required time from fertilization to D-shaped larvae were 37.3 hours in $20^{\circ}C$, 20.8 hours in $25^{\circ}C$, and 15.3 hours in $30^{\circ}C$. Biological minimum temperature for the egg development was estimated to be $12.4^{\circ}C$ in average. The range of salinity for the development of eggs were 20.0-37.5 psu, optimum range was estimated to be 27.5-32.5 psu.