Orbach Dara N, Marshall Christopher D, Mesnick Sarah L, Würsig Bernd
Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas, United States of America.
PLoS One. 2017 Mar 31;12(3):e0175037. doi: 10.1371/journal.pone.0175037. eCollection 2017.
Complex foldings of the vaginal wall are unique to some cetaceans and artiodactyls and are of unknown function(s). The patterns of vaginal length and cumulative vaginal fold length were assessed in relation to body length and to each other in a phylogenetic context to derive insights into functionality. The reproductive tracts of 59 female cetaceans (20 species, 6 families) were dissected. Phylogenetically-controlled reduced major axis regressions were used to establish a scaling trend for the female genitalia of cetaceans. An unparalleled level of vaginal diversity within a mammalian order was found. Vaginal folds varied in number and size across species, and vaginal fold length was positively allometric with body length. Vaginal length was not a significant predictor of vaginal fold length. Functional hypotheses regarding the role of vaginal folds and the potential selection pressures that could lead to evolution of these structures are discussed. Vaginal folds may present physical barriers, which obscure the pathway of seawater and/or sperm travelling through the vagina. This study contributes broad insights to the evolution of reproductive morphology and aquatic adaptations and lays the foundation for future functional morphology analyses.
阴道壁的复杂褶皱是一些鲸类和偶蹄类动物所特有的，其功能尚不清楚。在系统发育背景下，评估了阴道长度和累积阴道褶皱长度与体长之间以及它们相互之间的关系，以深入了解其功能。解剖了59只雌性鲸类动物（20种，6个科）的生殖道。采用系统发育控制的主轴回归法来确定鲸类雌性生殖器的比例趋势。发现了一个哺乳动物目中无与伦比的阴道多样性水平。不同物种的阴道褶皱数量和大小各不相同，且阴道褶皱长度与体长呈正异速生长关系。阴道长度并不是阴道褶皱长度的显著预测指标。讨论了关于阴道褶皱作用的功能假说以及可能导致这些结构进化的潜在选择压力。阴道褶皱可能构成物理屏障，阻碍海水和/或精子通过阴道的路径。本研究为生殖形态的进化和水生适应性提供了广泛的见解，并为未来的功能形态分析奠定了基础。
