Burger D, Dolivo G, Marti E, Sieme H, Wedekind C
Swiss Institute of Equine Medicine, Agroscope and University of Berne, Avenches, Switzerland.
Department of Clinical Research, Vetsuisse Faculty, University of Berne, Berne, Switzerland.
Proc Biol Sci. 2015 May 22;282(1807):20150407. doi: 10.1098/rspb.2015.0407.
Odours of vertebrates often contain information about the major histocompatibility complex (MHC), and are used in kin recognition, mate choice or female investment in pregnancy. It is, however, still unclear whether MHC-linked signals can also affect male reproductive strategies. We used horses (Equus caballus) to study this question under experimental conditions. Twelve stallions were individually exposed either to an unfamiliar MHC-similar mare and then to an unfamiliar MHC-dissimilar mare, or vice versa. Each exposure lasted over a period of four weeks. Peripheral blood testosterone levels were determined weekly. Three ejaculates each were collected in the week after exposure to both mares (i.e. in the ninth week) to determine mean sperm number and sperm velocity. We found high testosterone levels when stallions were kept close to MHC-dissimilar mares and significantly lower ones when kept close to MHC-similar mares. Mean sperm number per ejaculate (but not sperm velocity) was positively correlated to mean testosterone levels and also affected by the order of presentation of mares: sperm numbers were higher if MHC-dissimilar mares were presented last than if MHC-similar mares were presented last. We conclude that MHC-linked signals influence testosterone secretion and semen characteristics, two indicators of male reproductive strategies.
脊椎动物的气味通常包含有关主要组织相容性复合体（MHC）的信息，并用于亲属识别、配偶选择或雌性在孕期的投入。然而，MHC相关信号是否也会影响雄性生殖策略仍不清楚。我们利用马（Equus caballus）在实验条件下研究了这个问题。12匹种马分别先后接触一匹陌生的MHC相似的母马和一匹陌生的MHC不相似的母马，或者反之亦然。每次接触持续四周时间。每周测定外周血睾酮水平。在接触两匹母马之后的那一周（即第九周），分别采集三份精液样本，以确定平均精子数量和精子速度。我们发现，当种马与MHC不相似的母马靠近时，睾酮水平较高；而当与MHC相似的母马靠近时，睾酮水平则显著较低。每份精液样本的平均精子数量（而非精子速度）与平均睾酮水平呈正相关，并且还受到母马呈现顺序的影响：如果最后呈现的是MHC不相似的母马，精子数量会高于最后呈现MHC相似母马的情况。我们得出结论，MHC相关信号会影响睾酮分泌和精液特征，而这两者都是雄性生殖策略的指标。
