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

动物单位体重的静息代谢率M/W通常随体重的增加而降低，用异速生长方程M/W=aW^<b-1>表示，其中M为动物耗氧量，体重W， b-1<0。这种现象在种间（物种之间）和种间（物种内）都是众所周知的。然而，由于硬骨鱼的幼体和幼体非常小和脆弱，其代谢个体发生的确切性质和生物学意义尚未确定。本研究表明，河豚早期有两个阶段，随着W的增加，M/W增加。通过测定M/W和同类相食的频率，从湿W（刚孵化）的0.00068 g到3.0g（57日龄），我们发现，当幼鱼达到0.01g时，M/W增加，它们开始攻击和杀死比它们小的其他鱼类，直到小于0.01g的鱼类消失。当青少年达到0.1g时，同样的事件再次发生。在自然条件下，这些现象意味着生长能力越快的个体存活率越高，从而降低了捕食风险。鳃和假分支的发育也解释了河豚鱼的重比增加。

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.