Reynolds S A, French K A, Baader A, Kristan W B
Department of Biology, University of California-San Diego, La Jolla 92093-0357, USA.
J Comp Neurol. 1998 Dec 14;402(2):155-67.
We present a description of the last half of embryonic development in the European medicinal leech, Hirudo medicinalis, based entirely on externally visible morphological features, and establish reliably observable stages during that development. Embryogenesis, from the time fertilized eggs are deposited in an eggcase (called a cocoon) to the emergence of juveniles from the cocoon, takes approximately 4 weeks at room temperature. The stages described in this paper extend from the completion of segmentation to the appearance of the final bands of pigmentation. Developmental stages are expressed as percentages of total embryonic developmental time. This staging table was constructed for embryos kept at 20 degrees C. In addition, the development of animals kept at 17 degrees C or at 24 degrees C was compared with those held at 20 degrees C. Development proceeds more quickly at higher temperatures. Because development in embryos held at higher or lower temperatures was linearly related to the stages determined for embryos held at 20 degrees C, the rate of development at any intermediate temperature can be predicted from the staging table at 20 degrees C by simple multiplication.
我们完全基于外部可见的形态特征，对欧洲医用水蛭（医蛭）胚胎发育的后半段进行了描述，并确定了该发育过程中可靠的可观察阶段。从受精卵被产在卵囊中（称为茧）到幼体从茧中孵出的胚胎发生过程，在室温下大约需要4周。本文所描述的阶段从分节完成延伸至最终色素带的出现。发育阶段以胚胎发育总时间的百分比表示。这个分期表是针对饲养在20摄氏度的胚胎构建的。此外，还将饲养在17摄氏度或24摄氏度的动物的发育情况与饲养在20摄氏度的动物进行了比较。在较高温度下发育进行得更快。由于饲养在较高或较低温度下的胚胎发育与饲养在20摄氏度的胚胎所确定的阶段呈线性关系，所以可以通过简单的乘法从20摄氏度的分期表预测任何中间温度下的发育速率。
