Herdina Anna Nele, Kelly Diane A, Jahelková Helena, Lina Peter H C, Horáček Ivan, Metscher Brian D
Department of Theoretical Biology, University of Vienna, Vienna, Austria.
J Anat. 2015 Mar;226(3):229-35. doi: 10.1111/joa.12274. Epub 2015 Feb 6.
The baculum (os penis) has been extensively studied as a taxon-specific character in bats and other mammals but its mechanical function is still unclear. There is a wide consensus in the literature that the baculum is probably a sexually selected character. Using a novel approach combining postmortem manipulation and three-dimensional (3D) imaging, we tested two functional hypotheses in the common noctule bat Nyctalus noctula, the common pipistrelle Pipistrellus pipistrellus, and Nathusius' pipistrelle Pipistrellus nathusii: (i) whether the baculum can protect the distal urethra and urethral opening from compression during erection and copulation; and (ii) whether the baculum and corpora cavernosa form a functional unit to support both the penile shaft and the more distal glans tip. In freshly dead or frozen and thawed bats, we compared flaccid penises with artificially 'erect' penises that were inflated with 10% formalin. Penises were stained with alcoholic iodine and imaged with a lab-based high-resolution x-ray microtomography system. Analysis of the 3D images enabled us to compare the changes in relative positions of the baculum, corpora cavernosa, urethra, and corpus spongiosum with one another between flaccid and 'erect' penises. Our results support both functional hypotheses, indicating that the baculum probably performs two different roles during erection. Our approach should prove valuable for comparing and testing the functions of different baculum morphologies in bats and other mammals. Moreover, we have validated an essential component of the groundwork necessary to extend this approach with finite element analysis for quantitative 3D biomechanical modeling of penis function.
阴茎骨（os penis）作为蝙蝠和其他哺乳动物的分类群特异性特征已得到广泛研究，但其机械功能仍不清楚。文献中广泛认为阴茎骨可能是一个性选择特征。我们采用一种结合尸检操作和三维（3D）成像的新方法，在普通夜蝠Nyctalus noctula、普通伏翼Pipistrellus pipistrellus和纳氏伏翼Pipistrellus nathusii中测试了两个功能假设：（i）阴茎骨在勃起和交配过程中是否能保护尿道远端和尿道口免受压迫；（ii）阴茎骨和海绵体是否形成一个功能单元来支撑阴茎体和更远端的龟头尖端。在刚死亡或冷冻解冻的蝙蝠中，我们将松弛的阴茎与用10%福尔马林充气的人工“勃起”阴茎进行了比较。阴茎用酒精碘染色，并用实验室的高分辨率x射线显微断层扫描系统成像。对3D图像的分析使我们能够比较松弛阴茎和“勃起”阴茎之间阴茎骨、海绵体、尿道和尿道海绵体相对位置的变化。我们的结果支持了这两个功能假设，表明阴茎骨在勃起过程中可能发挥两种不同的作用。我们的方法对于比较和测试蝙蝠和其他哺乳动物中不同阴茎骨形态的功能应该是有价值的。此外，我们已经验证了用有限元分析扩展该方法以对阴茎功能进行定量3D生物力学建模所需基础工作的一个重要组成部分。
