远海梭子蟹胚胎发育观察

External morphological characteristics during the embryonic development of Portunus pelagicus

在水温25～26℃、盐度30和pH 7.8～8.4条件下,观察远海梭子蟹胚胎发育全过程,其结果发现,远海梭子蟹胚胎发育经历卵裂、囊胚、原肠胚、无节幼体、后无节幼体和原溞状幼体等六个阶段。远海梭子蟹卵排出约28 h开始表面卵裂,约40 h,形成囊胚,约60 h,预定内胚层细胞出现,并与集中在其周围的细胞一起内陷,形成原肠胚。约90 h,3对附肢的无节幼体出现,约110 h,5对附肢的后无节幼体出现,约140 h,7对附肢的原溞状幼体出现。复眼、心跳、色素形成均在原溞状幼体阶段完成。原溞状幼体孵出时(约300 h),颚足长出羽状刚毛,变为溞状幼体。整个胚胎发育过程约300 h。

The embryonic development of Portunus pelagicus was studied under laboratory conditions at a water temperature of 25-26 ℃, salinity of 30, and pH of 7.8-8.4. The embryogenesis of Portunus pelagicus was divided into six stages： cleavage, blastula, gastrula, nauplius, metanauplius, and protozoea. Embryogenesis lasted about 300 h post spawning. Eggs began superficial cleavage about 28 h after spawning when the nucleus appeared at the surface of the egg till the egg divided into 16 ceils. The blastula stage was observed about 40 h post spawning and gastrula stage appeared when the presumptive endoderm and other cells near them invaginated. The fourth-stage of embryogenesis, nanplius, was characterized by three pairs of appendages appearing about 90 h post spawning, while metanauplius, the fifth-stage of embryogenesis, was characterized by five pairs of appendages, which appeared about 110 h post spawning. The sixth stage of embryogenesis was protozoea, which was characterized by seven pairs of appendages appearing about 140 h post spawning. The compound eye, heart and pigment cells were also found in the protozoea stage. After the natatory seta formed on the top of maxilliped, the protozoea developed into the zoea at the time of hatching （about 300 h post spawning）.