Structure, development and composition of the integument of the southern right whale, Eubalaena australis

Abstract

The general architecture of the skin of the southern right whale, Eubalaena australis, is comparable to that described for other cetacean species. As found in bowhead whales, Balaena mysticetus, of the same family, southern right whales possess an acanthotic epidermis and a notably thick hypodermis. Epidermal rods and extensive papillomatosis support these unique characteristics. A "fat-free" reticular dermis makes the integument of southern right whales more like that of odontocetes than that described for balaenopterids. Skin samples taken in South African and Antarctic waters showed evidence of superficial moultin'g throughout the austral winter and in mid-summer. Unidentified "microfIora" and fungal microbes were detected on the skin of whales sampled in both South African and Antarctic waters. The predominance of "microfIoral" aggregations on cows and calves in OctoberlNovember suggests that these micro-organisms are acquired in coastal waters. A Candida-like invasive fungal infestation of the skin of a stranded neonate was recorded for the first time in this species and may be related to the demise of this animal. The film-forming diatom, Bennettella [Cocconeis] ceticola, was not detected on any skin samples. This may imply that southern right whales exhibit high cellular proliferation rates, which prevent diatomaceous films from forming. Neonatal southern right whales undergo a spectacular form of ecdysis approximately 6-7 days after birth. Histologically, "rough-skinned" neonates possess a distinct "fault line" above the distal tips of the dermal papillae, that becomes characterised by intercellular oedema, which causes all the cell layers above the plane to separate from those below it. The fatty acid composition of the dermal and hypodermal layers provides indications of prey species consumed as well as reflecting physiological processes within the digestive system of the southern right whale. Total lipid values in the blubber of late season cows and calves are reported for the first time. A new hand¬held biopsy system for collecting deep-core integument samples from free-swimming balaenids is described. It is a practical and cheaper alternative to projectile systems and the head design allows for the collection of samples that can be used for multidisciplinary research on right whales (e.g. histology, toxicology and blubber composition studies).