Ultrastructural morphological features of the hair in a sexual signal: the dark ventral patch of male red deer

Chemical signals play a decisive role in communication in many mammal species. In male Iberian red deer, the dark ventral patch has been recently described as a sexual chemical signal involved in intrasexual competition. Morphological specializations of the hairs of this area might contribute to retaining the volatile compounds found here. In this study, we examined the differences in ultrastructure between hairs associated with the dark ventral patch and hairs from the dorsolateral region of the body as a reference. We obtained a gallery of images from a scanning electron microscope to study the possible variation in detail anatomy and the surface and pattern of cuticular scales of hairs of the two body regions examined. In addition, we used a 2D-3D microscope to measure hair diameter (thickness) and the shape and size of the cuticular scales. We found differences in the thickness of the hairs of the dark ventral patch, which were narrower than hairs from the dorsolateral region. We also evidenced a unique cuticular scale pattern of the dark ventral patch hairs, suggesting a possible specialization of the hairs for the retention of compounds associated with this chemical signal. Moreover, some inter-sexual differences in hair morphology also support this idea. This study shows, for the first time, the differentiation of hairs related to the dark ventral patch, which contributes to the understanding of this chemical communication of Iberian red deer.

化学信号在诸多哺乳动物的通讯交流中发挥决定性作用。近期研究表明，雄性伊比利亚红鹿的腹部深色斑块是一种参与种内竞争的性化学信号。该区域毛发的形态特化或有助于留存此处的挥发性化合物。本研究以躯干背外侧区域毛发作为对照，对比了腹部深色斑块区域毛发的超微结构差异。我们通过扫描电子显微镜（scanning electron microscope）获取图像集，以探究两个采样区域毛发的细微解剖结构、角质鳞片（cuticular scales）的表面形态与分布模式的潜在差异。此外，我们借助2D-3D显微镜测量了毛发直径（厚度）以及角质鳞片的形态与尺寸。结果发现，腹部深色斑块区域的毛发更细，显著窄于背外侧区域毛发。本研究还证实，腹部深色斑块区域的毛发拥有独特的角质鳞片分布模式，提示该区域毛发或特化为留存与该性化学信号相关的化合物。此外，毛发形态存在的部分两性差异也进一步佐证了这一推测。本研究首次揭示了伊比利亚红鹿腹部深色斑块相关毛发的形态分化，有助于加深对伊比利亚红鹿化学通讯机制的理解。