曼氏无针乌贼胚胎发育形态及发育时序的研究

The Embryonic Development of Sepiella maindroni

观察了室内培育的曼氏无针乌贼自然生产的受精卵形态和胚胎发育过程.结果表明,曼氏无针乌贼受精卵成乳头状,平均卵长10mm,平均卵宽5.5mm,受精卵外被黑色坚韧而富有弹性的三级卵膜,成串聚集一起成葡萄状.胚胎发育分为12个阶段：受精卵期、卵裂期、囊胚期、原肠胚期、初具形态期、腕分化期、心跳出现期、色素出现期、内骨骼形成期、尾腺出现期、缘膜形成期、孵化期.其胚胎大小从卵裂期开始增长,卵裂期胚胎长（3.40±0.12）mm,胚胎宽（3.29±0.14）mm,到孵化出膜前胚胎长达（8.17±0.33）mm,胚胎宽达（7.17±0.33）mm,增大了2倍左右.初具形态期各器官开始形成,胴部、头部、腕部开始分化.在19~21℃水温下,从受精卵到孵化出膜历时28~30d,初孵小乌贼仍挂着梨状卵黄囊,卵黄囊均长3.70mm,均宽2.75mm,在水中游动1~10min后就自动脱落,乌贼幼体一出膜就能喷墨,同时能开口摄食动物性饵料.

In this study,the process of the oosperm forming and embryonic development of Sepiella maindroni is observed using microscope.The result shows that the shape of oosperm of Sepiella maindroni resembles a papilla.The average length of oosperm is found to be 10 mm,and its average width is identified as being 5.5 mm.The embryo is wrapped by resilient membrane,which is in black,conglomerating with grape-like spheres.The process of the embryonic development is divided into 12 stages,each of which is listed as oosperm,cleavage,blastula,gastrula,rudimentary shape forming,wrist differentiation,heartbeat appearance,pigment appearance,endoskeleton forming,caudal gland appearance,velum forming and hatching.It is found that the embryonic size begins to grow in cleavage phase,in which the length of embryonic reaches（3.40±0.12） mm,and its width measures（3.29±0.14） mm.The size becomes（8.17±0.33） mm and（7.17±0.33） mm at hatching stage,which increases in an almost two-fold manner.In the phase of rudimentary shape forming,some organs are formed,and the head,mantle and carpal become obvious.It takes the oosperm 28~30 d to become a newborn Sepiella