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

Abstract

Chemical signals play a decisive role in communication in many mammal species. In red deer (Cervus elaphus), the dark ventral patch has recently been described as a male chemical signal involved in intrasexual competition. Morphological specializations of the hair of this area might contribute to retaining the volatile compounds found here. In this study, we examined differences in the ultrastructure between hair associated with the dark ventral patch and hairs from the dorsolateral region of the body as a control. We obtained a gallery of images from a scanning electron microscope to study the possible variation in the detailed anatomy as well as 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 that the hairs of the dark ventral patch were narrower than those from the dorsolateral region. We also found a different cuticular scale pattern of the dark ventral patch hairs, suggesting a possible specialization for the retention of compounds associated with this chemical signal. Moreover, some intersexual 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 our better understanding of this chemical communication in red deer.