マダコのふ化稚仔サイズに影響をおよぼす要因ならびに雌の体重と卵巣卵数の関係

抄録

Factors influencing the body size of Octopus vulgaris hatchlings were investigated using mature females individually reared in 1,000l tanks under natural seawater conditions at the Ehime Prefectural Chuyo Fisheries Experimental Station. We also investigated the relationship between the weight of mature females and the fecundity (number of eggs in the ovary), using octopus captured in northeastern Iyo-Nada of the Seto Inland Sea, Japan. A multiple linear regression between the mantle area index (MAI) of the hatchlings calculated as mantle length (distance from the mantle end to the midpoint between eyes, mm)×mantle width (maximum width of the mantle, mm), female body weight (BW,g) and water temperature (T,°C), was estimated as: MAI=0.000254BW-0.041T+3.210 (N=12, r=0.932, P＜0.001). The relationship between the body weight of the female (X, g) and the fecundity (Y) was estimated based on the current and previously published data of Hyogo Prefecture as: Y=1098X^0.655 (N=21, r=0.934, P＜0.001). Our conclusions include that the female body weight and the water temperature influence egg size and that the early settlement of the paralarvae reduces the high mortality rate observed during the planktonic phase.