从体内脂肪的转移过程探讨凤鲚和刀鲚溯河产卵洄游距离的差异性

为探讨凤鲚和刀鲚溯河产卵洄游距离差异的可能原因,本研究从雌性繁殖群体体内脂肪储备和转移的角度,对这两个近缘种进行了分析。对凤鲚的研究结果显示,到达产卵场的个体中,5月份个体的体长、体质量和肌肉脂肪含量均显著大于6、7、8月份的个体,表明个体大、肌肉脂肪积累多的个体较早地完成了生殖洄游过程。与同一发育时期的刀鲚相比,凤鲚的平均肝体指数相对较大,Ⅲ、Ⅳ期卵巢指数GSI高出约5倍。表明在繁殖季节,凤鲚体内更多的能量集中到卵巢及更容易被转移的器官。脂肪含量分析显示,凤鲚的肌肉和肝脏脂肪含量分别约是刀鲚相同发育阶段脂肪含量的1/3和1/2,但卵巢脂肪含量则相反。表明凤鲚将更多的脂肪积聚在繁殖器官中,而刀鲚则主要积聚在运动器官中。从躯干脂肪总量的变化分析,刀鲚躯干脂肪总量从Ⅱ期的97.73%下降至Ⅳ期的91.02%,凤鲚则从Ⅱ期的91.02%迅速下降至Ⅴ期的34.69%。二者的肝胰脏脂肪含量较稳定,但凤鲚的卵巢脂肪含量要明显地高于刀鲚。研究表明,这种将体内大部分脂肪用于性腺发育,躯干脂肪又很快耗尽的现象,可能是小型短距离溯河产卵洄游鱼类的共有特征。

Research on the differences of anadromous migratory distance between Coilia mystus and Coilia nasus based on the transfer process of body lipid

In order to figure out the possible reasons of the different migratory distances between Coilia mystus and C. nasus, we investigated the relationships between migration distance of the two sibling species and lipid reserves and transfer in this paper. Study of C. mystus showed that individuals arriving at spawning ground in May were significantly greater in body length than those in June, July and August. In particular, those larger-sized females with higher somatic lipid content arrived at spawning ground and spawned earlier than others. The average hepatosomatic index of C. mystus was relatively higher than that of C. nasus during the same development period, and the gonadosomatic index of C. mystus at stages III and IV was about five times higher than that of C. nasus, indicating more energy centralized in ovary and easy-transferred organs of C. mystus during the spawning season. Although lipid content in muscle and liver of C. mystus was about one-third and half of that in C. nasus respectively during the same development period, C. mystus accumulated more lipid in ovary, a reproductive organ. Total trunk lipid in C. nasus decreased from 97.73% at phase II to 91.02% at phase IV, compared to rapid decrease from 91.02% at phase II to 34.69% at phase V in C. mystus. The amount of lipid in hepatopancreas was relatively stable in both species, whereas the lipid proportion in ovary of C. mystus was obviously higher than that of C. nasus. The finding that C. mystus allocated most of the body lipid for gonadal development and rapidly consumed trunk lipid may represent the common characteristic of short-distance migratory fish.