施氏鲟的性腺分化及养殖水温对其性腺分化的影响

Histological observation of gonadal differentiation and effect of rearing temperature on sex differentiation in Amur sturgeon Acipenser schrenckii

利用组织学方法观察了养殖施氏鲟（Acipenser schrenckii）原始生殖细胞（PGCs）的起源、迁移和原始生殖腺的形成及分化。结果表明,施氏鲟PGC最早出现于1.5 dph（days post-hatching）的仔鱼中肾管（又称吴尔夫氏管）原基一侧的中胚层中。3~7 dph,PGCs数目增多,并聚集成细胞索,17~31 dph,PGCs沿肠系膜向肾管区下方迁移,并与生殖嵴细胞一起形成原始性腺;40～60 dph时成群的小细胞团由肾区向原始性腺迁移,原始性腺上皮细胞柱状;90~120 dph,原始性腺中出现生殖上皮和性细胞,脂肪细胞和血管增多。180 dph以后,施氏鲟幼鱼性腺在组织学水平上出现光滑型（精巢）和褶皱型（卵巢）2种性腺组织结构,标志施氏鲟幼鱼性腺在解剖学水平上已经分化。本实验结果表明,孵化后31～180 d为其性腺分化的关键期。将孵化后56 d的仔鱼分别在不同的水温（27℃±0.5℃、24℃±0.5℃、21℃±0.5℃、18℃±0.5℃和15℃±0.5℃）中培育至210 d,组织学观察其性腺的发育和分化,结果发现,温度可影响施氏鲟幼鱼性腺分化的时间,但不影响其性腺分化的方向。高温（24℃和27℃）可使施氏鲟幼鱼提前性腺分化,其中27℃组较对照组（21℃）提前50 d,24℃组提前30 d;低温（15℃组）则延长幼鱼性腺分化的时间。施氏鲟幼鱼的性别分化不属于温度依赖型。

Temperature-dependent sex determination has been demonstrated in some species of fish and tempera-ture during the period of sex differentiation typically produces male or female-dominant population.This research investigated the gonadal sex differentiation and effect of rearing temperature on the sex ratio in larval Amur stur-geon Acipenser schrenckii.In 1.5 days post-hatch,a PGC is visible along the dorsal epithelium of the body cavity,between the mesentery and the kidney.Later,in 3-7 days post-hatch,the numbers of the primordial germ cells（PGC） increased,and gathered into cell cable.At 17-31 dph,PGCs along the mesenteric migrate to below the kidney area and cells together to form the gonadal ridges.When 40-60 dph,the original gonadal development,groups of small cells from kidney area migrate to original gonad,original gonadal columnar epithelial cells.At 90-120 dph,germinal epithelium and cells appears in the original gonad,fat cells and blood vessels increase.Pu-tative ovaries with notches in the germinal epithelium and presumed testes with smooth germinal epithelium ap-peared in 180 days post-hatch,signs of juvenile Acipenser schrenckii already on the level of differentiation of go-nads in anatomy.Ovaries with proliferating oogonia and early meiotic oocytes clusters were observed in 210-day-old juveniles.In a temperature controlled experiment,the proportions of females were 50% at 21℃,43.3% at 15℃,43.3% at 18℃,50% at 24℃,and 46.7%（the same as 1：1 sex ratio） at 27℃.These results suggest that morphological sex differentiation in Amur sturgeon occurs at approximately 180 days after hatch,and though the high temperatures can not change the 1：1 sex ratio in this species,but it can help to promote gonadal devel-opment of juvenile Amur sturgeon.