Ultrasonographic characterisation of prenatal development in European brown hares (Lepus europaeus PALLAS, 1778): an evolutionary approach
Kathleen Roellig A B , Frank Goeritz A and Thomas B. Hildebrandt AA Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke Str. 17, 10315 Berlin, Germany.
B Corresponding author. Email: kathleen_roellig@gmx.de
Reproduction, Fertility and Development 22(2) 448-458 https://doi.org/10.1071/RD09098
Submitted: 17 April 2009 Accepted: 8 August 2009 Published: 4 January 2010
Abstract
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.
Additional keywords: embryogenesis, growth curve, Lagomorpha, luteogenesis, organogenesis, precocial, reproduction, ultrasonography.
Acknowledgements
The authors acknowledge their former research assistant Andrea Krause and the animal keepers Bärbel Baumann and Mathias Otto from the experimental field station in Niederfinow. The authors also thank Jaroslav Slamečka and the staff of the Institute for Animal Production in Nitra (Slovakia) for their support in establishing the breeding colony. Special thanks go to Dr Robert Hermes, Dr Barbara Drews, Dr Barbara Vogler, Dr Catherine Reid, Dr Britta Behr and Sylvia Albrecht for their support during the practical animal examinations and Dr Brandon Menzies for the help with the preparation of the manuscript.
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