The Morphological Basis of vicuña wool: Skin and gland structure in Vicugna vicugna (Molina 1782)

• We did a histological study of vicuna skin and glands.
• Complex hair follicles in fleece had a ratio of 42:1 secondary to primary fibers.
• The ratio was 12:1 in belly and legs.
• Metatarsal glands showed a unique structure not described previously.
• Other glands were found in caudal and interdigital areas.

The vicuña (Vicugna vicugna) is the smallest member of the Camelidae with one of the most valuable fibers in the world. However, little is known of the structural basis for this fiber or of the skin glands used in chemical communication in this species. The objective of this study was to examine the histological structure of the skin and hair follicles and the cutaneous glands. Skin samples from the fleece, belly and legs and glandular areas – metatarsal, caudal, anal and interdigital areas – were obtained from animals accidentally killed in captive captures at a government camelid ranch in Jujuy, Argentina. These samples were studied with histological techniques for light and electron microscopy to examine follicular structure and density in fleece compared to belly and leg areas. Glandular areas were similarly studied to determine type and density of skin glands. Compound hair follicles were found with an extremely high density of secondary hairs in relation to primary hairs (S:P ratio) in fleece (42 ± 2, mean ± standard error) and a significantly lesser density (p < 0.001) in belly and legs (12.0 ± 0.7). Follicle and hair diameters from the two areas were also significantly different with the fleece areas having smaller diameters. Secondary hair diameters in fleece were similar to previously published values (13.2 ± 0.3 μm). With respect to the glandular areas, the metatarsal glands had a striking appearance with an epithelium resembling a hollow honeycomb and a dermis showing a great deal of glandular tissue (simple tubular glands) with excretory ducts. Large sebaceous glands were found in the ventral region of the tail and eccrine sudoriferous glands in the interdigital region. The possible importance of these glands in chemical communication is discussed.