Morphological analysis of the bumpy profile of phocid vibrissae

摘要

Organisms rely on sensory systems to obtain information about their surroundings. The secondarily aquatic lifestyle required marine mammals to develop novel sensory modalities to operate in water. Phocid seals have three groups of vibrissae, mystacial, supraorbital, and rhinal, all of which occur only on the face of the animal (Ling 1977). All species of phocid seals except bearded (Erignathus barbatus) and monk (Monachus spp.) seals have bumps along hair shafts of their mystacial vibrissae (Ognev 1935, King 1983, Hyvrinen and Katajisto 1984, Dehnhardt and Kaminski 1995, Marshall et al. 2006). The vibrissae have an ellipsoidal cross-section with a regularly repeating sequence of crests and troughs to give a sinusoidal profile along their length. This morphology is not known to be present in the hairs of any other mammalian group. The presence of the bumps along the length of the vibrissae allude to three possible functions, including drag reduction, increased sensitivity, and reduced signal interference. These functions are not mutually exclusive.