Theoretical study of evolution of egg size and early life history of aquatic organisms

金枪鱼和马林鱼等几种海洋中上层鱼类的幼体都有大颚，但这种独特的形态特征的生态学意义在进化生态学中几乎没有得到分析。中上层产卵鱼产生的卵子小且营养不良，公海洄游鱼类的产卵场和育苗场是贫营养的。我们推测，食人将是一种可能的生活方式，在幼虫期和大嘴将是一个适应性的形态特征，在贫营养的浮游环境中的食人。我们发现，开口张开的远洋远洋产卵器的大小是显着大于近海/沿海远洋产卵器。一个数学模型表明，在公海环境中，同类相食会趋于进化。我们的研究结果表明，在中上层鱼类的幼体阶段的同类相食性状的进化模式。

Larvae of several ocean pelagic fish species, such as tunas and marlins, have been known to have large jaws, but the ecological significance of this unique morphological character has been hardly analyzed in evolutionary ecology. Pelagic spawners produce small and nutrition-poor ova, and spawning and nursery grounds of the open ocean migratory fishes are oligotrophic. We hypothesize that cannibalism would be a possible life style in the larval period and the large mouth gape would be an adaptive morphological characteristic for a cannibal in the oligotrophic pelagic environment. We showed that mouth gape size of the open ocean pelagic spawners is significantly larger than that of offshore/coastal pelagic spawners. A mathematical model demonstrated that cannibalism would tend to evolve in high sea environment. Our findings suggest an evolutionary pattern of cannibalism trait in the larval stage of pelagic fishes.