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 folliclesinus complex extended into the reticular layer of the dermis. In the proximal part of the sinus, trabeculae 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 dermal sheaths were laden with mechanoreceptors. 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.

Functional morphology of the trunk and paw pad skin of the African palm squirrel (Epixerus ebii)

“…Ibe et al (5) observed the presence of plantar digital pads and absence of palmar digital pads in the African giant pouched rat, unlike in the present study. The African giant pouched rat is a subterranean rodent which digs with the claws and uses the plantar pad to push excavated soil away (5). The broader plantar than palmar surface observed in this study may be compensatory for the lack of plantar digital pads.…”

“…Paw width was obtained as the greatest radial to ulnar extent of the paw, measured with centimeter rule. The experimental procedures of Ibe et al (5) were adopted for obtaining skin samples from the trunk and limbs for light microscopic examination and for histological preparation of the samples. The slides were stained with hematoxylin and eosin stains.…”

“…The integument connects the animal with the external environment and protects underlying organs from mechanical trauma and infection. Several studies have shown that the rodent integumentary properties are habitatspecific, and vary even for rodents of the same genus but diverse habitats (4)(5)(6). In the light of this, the present study aims to describe the gross and histologic structures of the trunk and paw pad skin of the African palm squirrel in relation to its habitat.…”

Processing rodent brain tissues: review of basic anatomical techniques for scientists with minimal knowledge of neuroanatomy

“…For electron microscopy, Karnovsky's fixative (Glutaraldehyde + Paraformaldehyde + Sodium hydroxide in buffer solution) will be more appropriate. On the shrinkage factor of the rodent brain, Ibe et al, (2010), showed that the AGR had negligible shrinkage following 3 days post fixation in 10% formalin. This assumption is adopted by the authors also.…”

“…e. Weighing the brain: Brain weight offers great insight into changes that may have occurred in the brain. These changes may vary from sexual dimorphisms (Ibe et al, 2010), to pathological changes (Skullerud, 1985;Mustapha et al, 2014). These weight parameters may be correlated against body parameters such as body (head, trunk and tail) lengths or body weights.…”