EPIDERMAL ULTRASTRUCTURE OF THE SOUTHERN RIGHT WHALE CALF (EUBALAENA-AUSTRALIS)

An ultrastructural analysis by transmission and scanning electron micr oscopy was carried out on normal epidermis of six southern right whale (Eubalaena australis) calves which stranded over a period of several months at Peninsula Valdes, Argentina. This was undertaken to 1) provi de the first normal skin ultrastructural data on this highly endangere d species which is known to display skin pathology in some instances, and 2) to elucidate further the integumentary specializations which ha ve developed in diving marine mammals. Southern right whale lipokerati nocytes demonstrated parakeratosis and numerous intracellular lipid bo dies, keratin and melanosomes, as reported for other cetacean species, but showed several unique ultrastructural features as well. These inc luded a high prevalence of intranuclear inclusion bodies resembling sm all fragments of cytoplasmic keratin, and close structural relationshi p between cytoplasmic lipid droplets and the nucleus. The subcellular morphology supported the concept of possible nuclear import of cytopla smic keratin and lipid metabolites through enlargements of the nuclear pore complex or other disruptions of the nuclear envelope. The light microscopy and scanning electron microscopy also revealed an irregular contour of the lipokeratinocytes which comprised the thick stratum ex ternum, and surface flaking of the outermost cells which were covered by stubby microvillous-like remnants of intercellular junctions. These results thus suggest that the long-term aquatic evolution of this cet acean species has resulted in a number of integumentary specialization s and that investigation of their submicroscopic cytology may help elu cidate the general cell biology of nuclear-cytoplasmic interactions.