鲂鱼的头骨发育及其适应意义

DEVELOPMENT OF THE SKULL OF Megalobrama skolkovii AND IT'S ADAPTIVE SIGNIFICATION(Teleostel,Cyprinidae)

本文对鲂鱼（Ｍｅｇａｌｏｂｒａｍａｓｋｏｌｋｏｖｉｉ）头骨的早期发育过程及其与鱼苗的存活功能需要之间的关系进行了研究。头骨发育的全过程可划分为５个阶段，即软颅阶段、咽颅膜骨附加阶段、脑颅开始骨化阶段、脑颅快速骨化阶段和骨化完成阶段。刚出膜仔鱼头部即有软骨存在，最先出现的硬骨是膜质上颌骨和主鳃盖骨，脑颅最先开始骨化的是基枕骨和侧枕骨，随后才是副蝶骨。头骨发育过程与鱼苗早期存活的功能需要之间有着密切的关系。

The development of skull of Megalobrama skolkovii was divided into five phases:1)Cartilage phase.2)The dermal bones in splanchnocranium phase.3) The beginning of ossification in neurocranium phase.4)The fast ossification in neurocranium phase.5)The perfect ossification phase.Before the larve hatched, there are no cartilages.When the larva has just hatched,trabuculae,parachordal cartilages,Meckel's cartilages,palatoquadrate cartilages,hyosymplectic cartilages,ceratohyal cartilages and the 1st-3nd ceratobranchial cartilages are all present.Then the cartilagious floor of the neurocranium develops.Maxillae and opercles are the first-two dermal bones of the skull, then are premaxillae and dentaries.The first-two bones of the neurocranium are basioccipital and exoccipitals,then is paraspnenoid, frontals and parietals appear after the ossification of prootics and vomer.At the same time,most of the splanchnocranium bones are existent,including ectopterygoid,mesopterygoid,metapterygoid, preopercles,infraopercles,interopercles and branchiostegal rays. Then, orbitosphenoids, alisphenoids,sphenotics,epiotics and pterotics all begin ossification.The splanchnocranium has developed well when the fry is 50-55 mm in total length,the neurocranium has developed well when the fry is 7O-77 mm in total length. The relationship between the early cartilages and bones with the mechanical demands of biological function such as breething and feeding has been discussed.