A study of hair morphology in the family Bovidae

Abstract

I. A brief review of the present knowledge of hair and its structure is given. 2. Classification schemes for the various fibre and medulla outlines as seen in cross-sections, pigment characteristics and medullary structure have been drawn up. Existing classifications of fibre and medullary structure as seen in whole mounts have been extended. 3. The hairs from kudu, impala, blue wildebeest and grey duiker are all described separately within the framework of these classifications. 4. Macroscopically, colour differences between fibres of the four species have been observed. Fibres from the grey duiker have a yellow band near the tip in most cases, differentiating them from those of the kudu, impala and blue wildebeest. Yet macroscopic determination of colour of a single fibre is highly unreliable. 5. The different types of fibres usually described do not occur in these species. Only body hairs and ornamental hairs can be distinguished, with certainty. 6. There are differences in scale pattern between the kudu and grey duiker: the base tends to have an irregular mosaic pattern alternating with an irregular wave pattern towards the tip. In the impala an irregular mosaic pattern is mostly found on the ectal and ental sides of the fibre with an irregular wave pattern occurring on the ridge, while in the blue wildebeest an irregular wave pattern is found ectally and entally on the fibre with an irregular mosaic pattern in the groove. The cuticle as seen in cross-section has no particular diagnostic value. In whole mounts its appearance is of some use. 7. On the shape of its fibre outline (papillo-convex) alone the impala can be identified. The blue wildebeest fibre is totally different in outline (fabiform) from those of the kudu, impala and grey duiker. A great similarity in fibre contour, elliptical and oval, is found between the kudu and grey duiker. 8. No conspicuous differences in fibre outline have been found between male and female. The young animals differ from the adults in this respect. 9. Differences in distribution and characteristics of the pigment are evident among the four species. Differentiation in dispersal of the pigment is found between base and shaft, and shaft and tip in whole mounts. Usually the base is of a lighter colour, the shaft darker in colour and the tip the darkest region of all. No noticeable differences in pigmentation occur between the two sexes. Fibres at the same sites in the young animal usually are not so intensely pigmented. Medullary pigment is generally similar to that of the cortex in the same fibre but only less in amount. 10. Medullary outlines of body hairs in the kudu and grey duiker follow a similar pattern to that of the fibre outline, although the shape is sometimes more irregular. In the impala and blue wildebeest the medullary outline usually differs from fibre outline. 11. In body hairs, medullary diameter parallels fibre diameter. The thicker the fibre the more irregular does the medullary outline become. Ornamental hairs have a relatively smaller medulla, or it may be entirely absent (frequently the case in the blue wildebeest). When a medulla is found in ornamental hairs, its outline does not conform to the fibre outline. 12. Striations on the medullary-cortical border are present in the kudu and impala only. 13. Fibre tips in whole mounts are flagelliform in the kudu and grey duiker. The blue wildebeest and impala body hairs have acicular tips while their ornamental hairs have flagelliform apices. 14. In all species the extreme apical region is usually of a lighter colour than the rest of the tip. Only the grey duiker has a yellowish band below the tip. 15. Shapes of base and root have no particular diagnostic value, due to the lack of interspecific variation in these regions. 16. Statistical analysis of the measurements of the greatest and least fibre and medullary diameters as well as whole fibre and medullary diameters reveals that: (a) The greatest fibre diameter is constantly higher than whole fibre diameter. (b) The greatest fibre diameter is considered to be the most accurate reflection of fibre thickness : the least fibre diameter is influenced too much by deviation from the more common fibre shapes (oval and elliptical). (c) For determining interspecific differences regardless of age and sex, the mean greatest fibre diameter and the mean whole fibre diameter appear to be equally reliable. (d) The males of the group have hair with the largest mean values for greatest and least fibre diameters as well as whole fibre diameter following by females and young in that order. (e) The shoulder appears to be the best region for assessing the importance of the three fibre diameter measurements where sex and age are unknown : highly significant differences are shown between species. (f) Sex differences in regional distribution of fibre thickness taking all four species together are relatively small. The female pattern does not deviate much from the male pattern but there is little parallelism in this respect between the young of each species and the adults. (g) The diagnostic value of medullary diameters is not high although a general correlation exists between significant differences of fibre and medullary measurements. 17. The value of the indices (fibre, fibre/medulla-, greatest, least and whole diameter) as numerical indicators of shape is limited by any deviation of fibre outline from the more common round, oval or elliptical shapes. In practice these indices are arduous to compile and unreliable in application. 18. Generally speaking it is impossible to identify a fibre on a single factor either morphologically or statistically (with the impala as an exception). For a conclusive identification of any fibre all relevant factors must be considered together. On this basis it is possible to distinguish between fibres from kudu, impala, blue wildebeest and grey duiker with certainty.