Meeting Abstract
The external acoustic meatus (EAM) of most baleen whales has no functional connection to the external environment. As a result, as whales age debris accumulates annually in the lumen, in the form of a lamellated ear plug, which have been used to age whales. Most analyses of the ear plug have either been anatomical (counting the layers) or biochemical (determining fat content). Recently it was shown in bowhead whales that the ear plug is formed by an annual molting of the EAM lining. The molting process proceeds with the entire epithelium being torn, at the level of the stratum basale, from the underlying dermis during the spring migration (May). Epithelial regeneration is mostly completed by the fall migration (October). Thus the epithelium remains intact for 6-7 months before it is torn off the following spring. Desmosomes are commonly found in skin, and are a diagnostic feature for maintaining strong cell adhesions. Desmosomes are held together intercellulary by desmoglein and desmocollin proteins, both of which are necessary for desmosomal adhesion. Several paraffin sections of EAM lining of both spring and fall bowhead whale were immunohistochemically examined for the presence of desmoglein and desmocollin. The results revealed near ubiquitous presence of desmoglein (both seasons) and desmocollin (fall), but absence of desmocollin in the stratum basal of the spring specimens. A similar absence of desmocollin has been described in several pathological conditions (e.g. dermatitis, hereditary tissue-fragility disorders), but its role in epithelial injury is not well understood.
