Relationship between cannibalism and increase of metabolic activity during transitional stage from larvae to juveniles in teleosts

动物每单位体重的静息代谢率M/W通常随着体重的增加而降低，用异速生长方程M/W=Aw^&lt；b-1&gt；表示，其中M是动物的耗氧量，W体重，b-1&lt；0。这一现象在物种间(物种间)和物种间(物种内)都是众所周知的。然而，硬骨鱼代谢个体发育的确切性质和生物学意义尚未在硬骨鱼中建立，因为幼体和幼体非常小和脆弱。结果表明，河豚的早期生活有两个阶段，即M/W随W的增加而增加。通过测定M/W和自相残食的频率，从湿W中的0.00068 g(刚孵化后)到3.0g(57日龄)，发现仔鱼达到0.01g时，M/W增加，并开始攻击和捕杀其他比它们小的鱼，直到0.01g以下的鱼消失。当幼体体重达到0.1g时，同样的情况再次发生。在自然条件下，这些现象意味着生长能力更快的个体确保更高的存活率，以减少捕食风险。鳃和假枝的发育也解释了河豚M/W的增加。

The resting metabolic rate per unit body mass, M/W, of animals usually decreases with increasing body mass, being expressed by an allometric equation M/W=aW^<b-1>, where M is oxygen consumption of an animal, W body weight, and b-1<0. This phenomenon is well known interspecifically (among species) as well as interspecifically (within a species). However, the precise nature and the biological meaning of the ontogeny of metabolism have not been established in teleost fishes, because of very small and fragile nature of larvae and juveniles. Here we show that a puffer fish Takifugu rublipes has two phases during early life in which M/W increases with increasing W. By determining M/W and the frequency of cannibalism from 0.00068 g in wet W (just after hatch) to 3.0g (57 days old), we found that larvae reached to 0.01g increased M/W, and they began to attack and kill other fishes smaller than them, until fish smaller than 0.01g disappeared. The same events again occurred when juveniles reached to 0.1g. In the natural condition, these phenomena imply that individuals with growing ability more rapidly are assured of higher survival to reduce predatory risk. Gill and pseudobranch developments also explained the increase of M/W in the puffer fish.