Adaptive Morphology of the Mystacial Vibrissae in the African Giant Pouched Rat (Cricetomys gambianus, Waterhouse-1840)

Abstract

Anatomy of the mystacial vibrissae in the African giant pouched rat was investigated to establish the role played by these structures in the adaptation of the rodent to its subterranean environment. Gross morphology was based on direct observation of the mystacial vibrissae with the naked eyes, while histology was based on light microscopic examination of the same structure stained with haematoxylin and eosin (H/E), Masson's trichrome (MT) and Masson-Fontana reducing method for melanin. The mystacial vibrissae were aligned in 5-6 rows on each side of the face. The length increased rostrocaudally in each row. The mean number of vibrissae was 55.29 (± 3.42). The vibrissal follicle-sinus complex extended into the reticular layer of the dermis. In the proximal part of the sinus, trabecu-lae of connective tissues connected the internal and external dermal sheaths. The most distal part of the sinus contained blood vessels. The external dermal sheaths were thick and held in position by muscle fibres. Mean thickness of the cortex and medulla in the complex were 1.626 µm (± 0.110) and 0.775 µm (± 0.057), respectively. The thick external der-mal sheaths were laden with mech-anoreceptors. The thick cortex provided the needed elasticity necessary for touch and sensation. In conclusion, the well developed mystacial vibrissa in the African giant pouched rat is an important compensation for poor vision, necessary for an effective adaptation.