刀鲚仔稚鱼脊柱和附肢骨骼发育

Development of the vertebral column and the appendicular skeleton in the larvae and juveniles of Coilia nasus

使用硬骨-软骨双染色技术,描述了刀鲚(Coilia nasus)仔稚鱼(体长范围为7.0～33.9 mm)脊柱及附肢骨骼的形态发育特征。骨骼形成的顺序依次为肩带,背鳍支鳍骨、臀鳍支鳍骨,脉弓,髓弓,尾下骨,椎体,腹鳍支鳍骨、尾上骨,背鳍前支鳍骨,肋骨。胸鳍支鳍骨无后匙骨,左右乌喙软骨在腹面联合。侧尾下骨和第1尾下骨基部产生短暂的软骨质连接(20.1 mm SL)。第1、2尾上骨联合形成棒状尾上骨1+2。第1髓弓与脑颅之间区域具1游离髓弓。脊柱以体前中部位置为起点向前后发育。髓弓、脉弓的发育方式与鲱形目其他鱼类不同。脉弓首先以体中部为中心向前后发育;髓弓随后亦以从体中部向前后发育,12.4 mm SL个体开始同时从最前端向后发育。这一发育方式与鲱形目其他鱼类相比更接近高等鱼类。因此,刀鲚可能是进化过程中的过渡物种。

The development of the vertebral column and the appendicular skeleton of C.nasus was described.A series of wild specimens 7.0-33.9mm were cleared and stained for both cartilage and bone.All the skeletons developed in following sequence： pectoral girdle,dorsal and anal fin supports,haemal arches,neural arches and hypurals,vertebra,pelvic fin supports,epurals,predorsal bones,pleural ribs.According to the observation,the postcleithra was absent in C.nasus.Coracoid-scapula cartilages were joined at ventral part.Parhypural connected to hypural 1 by temporary cartilage connection in specimen 20.1mm SL.The anterior epurals 1 and 2 fused together,resulting in a rod-like epural 1＋2.An isolated neural arch was observed between neurocranium and first neural arch.The vertebral column developed both anteriad and posteriad center on the area ahead the middle section.All these characteristics were typical within engraulidid fish,except for the sequence of neural and haemal arches occurrence.The haemal arches started to develop both anteriad and posteriad from the middle part of notochord,and the neural arches also started to develop from the middle section and later also posteriad from just behind the head in specimen 12.4mm SL.This showed more similarity with higher fishes than fishes in Clupeiformes,thus C.nasus may be a transitional specie in evolution.