Roellig Kathleen, Goeritz Frank, Hildebrandt Thomas B
Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke Str. 17, 10315 Berlin, Germany.
Reprod Fertil Dev. 2010;22(2):448-58. doi: 10.1071/RD09098.
The European brown hare is one species in which reproduction appears to be particularly complex. Therefore, we studied the reproductive tract and prenatal development using high-resolution ultrasound of 159 pregnancies in 45 captive female hares. Consecutive examination of live hares was particularly useful in evaluating the very early stages of gestation. As such, it was possible to detect corpora lutea by Day 3 and embryonic vesicles, representing the earliest uterine embryonic stages, by Day 6. On Day 11, the heart beat of the embryo was detectable for the first time. We defined ultrasonographic milestones that were characteristic of the different stages of pregnancy. We also calculated growth models using eight different morphological parameters, including development of the corpus luteum. On the basis of these results, it is now possible to estimate the gestational age of a pregnant doe without knowing the date of conception. In contrast with the European rabbit, a distant relative, European hares give birth to precocial young. A comparison of the prenatal growth rate of both species suggests that the precocial state of the hare neonate is a more recently derived evolutionary characteristic, whereas the altricial condition of rabbits represents the ancestral mode.
欧洲褐兔是一种繁殖过程似乎特别复杂的物种。因此，我们利用高分辨率超声对45只圈养雌兔的159次妊娠进行研究，观察其生殖道和产前发育情况。对活体野兔进行连续检查在评估妊娠早期阶段特别有用。这样一来，在第3天就能检测到黄体，在第6天能检测到代表子宫胚胎最早期阶段的胚泡。在第11天首次检测到胚胎心跳。我们定义了超声检查的里程碑，这些里程碑是不同妊娠阶段的特征。我们还使用包括黄体发育在内的八个不同形态学参数计算了生长模型。基于这些结果，现在有可能在不知道受孕日期的情况下估算怀孕母兔的妊娠年龄。与远亲欧洲兔不同，欧洲野兔产下的幼崽是早成雏。对这两个物种产前生长率的比较表明，野兔幼崽的早成状态是一个较新演化而来的特征，而兔子的晚成状态则代表了祖先模式。
