乌龟Chinemys reevesii胚胎发育的初步观察

A PRELIMINARY OBSERVATION ON THE DEVELOPMENT OF THE EMBRYO OF TORTOISE,CHINEMYS REEVESII

乌龟产下来的受精卵是在母体内经历了卵裂、囊胚等发育阶段的。在其以后的胚胎发育过程中形成中胚层囊、卵黄囊血管区、羊膜和浆膜。较晚阶段的胚胎更有尿囊伸到浆、羊膜腔中,几乎包围了整个胚胎和卵黄囊、受精卵在人工设置的温床中,相对湿度80—84%,温度33±1℃—35±1℃,均可孵出稚龟。适宜孵化温度33±1℃,历时45—48天,比自然界提早出壳时间20—25天,这对提高孵化率、延长当龄稚龟的生长期和提高稚龟的成活率均有重要意义。

Immediately after its fertilization the ovum of tortoise underwent stages of both segmentation and blastula in the uterine tube of the female.Following the phases of its greatest conspicuousness in young embryos the mesoblastic sac rapidly becomes both relatively and actually smaller.The extra-embryonic membranes of the tortoise are four in number,the yolk-sac,the amnion,the serosa,and the allantois.The yolk-sac is the first of these to make its appearance.During the later stage of development,the allantois pushes out of the body of the embryo into the extra embryonic coelem and extends into the sero-amniotic cavity and finally encompasses the embryo and the yolk-sac.When an egg has been laid,development ceases unless the temperature of the egg is kept nearly up to the normal incubative temperature.Moderate cooling of the egg does not,however,result in the death of the embryo.In incubating eggs artificially,the incubators or artificial hotbed are usually regulated for a heat of 33 ?1 ± 35 + 1℃ and kept up to the relative humidity of 80-84%.Under these conditions the tortoise is ready for hatching on the forty-five to forty-eight days.It is twenty to twenty-five days Less than the period needed for natural incubation.lt is of great importance in raising survival rate of fertilized eggs and of equal significance for extending growth period of young tortoise to yearling.