Histology of selected tissues of the leopard seal and implications for functional adaptations to an aquatic lifestyle

Abstract

The microscopic anatomy of the cardio-respiratory system, digestive system, kidney, lymphatic system and integument was investigated in the leopard seal, Hydrurga leptonyx , by examining histological sections of tissues collected from leopard seals in Antarctica and New South Wales, Australia. The majority of the tissues had similar histological features to those described in terrestrial mammals and other pinniped species, particularly phocid seals. Differences noted included readily identifiable Purkinje cells within the endocardium, muscular rather than cartilaginous reinforcement of the smaller airways, a single capillary layer within the alveolar septa, limited and variable keratinization of the oesophageal epithelium, few lymphoid follicles within the lamina propria of the gastrointestinal tract, and an absence of a sporta perimedullaris musculosa described in the kidney of cetaceans and some pinniped species. Adaptations of the lung, spleen and integument, similar to those described in other pinnipeds, including reinforcement of the pulmonary terminal airways, prominent pulmonary interlobular septa, ample smooth muscle in the capsule and trabeculae of the spleen, increased thickness of the epidermis, welldeveloped dermal sebaceous glands, and a thick blubber layer, appear to confer upon the leopard seal advantages related to its aquatic lifestyle.

Integument in Antarctic seals: A comparative study and its relation to extreme environments

“…In contrast, the only contribution regarding the integument of Leptonychotes weddellii was done by Molyneux and Bryden (1978), on the dermal arteriovenous anastomoses. A similar situation occurs with Hydrurga leptonyx, as most of the studies on the integument of this species are broad and general descriptions (Gray et al, 2006). In the present contribution, we studied the integumentary system of specimens of three species of Antarctic phocids: southern elephant seal (M. leonina), leopard seal (H. leptonyx) and Weddell seal (L. weddellii; Figure 1).…”

“…Regarding leopard seal, Gray et al. () observed a discontinuous stratum granulosum, but they did not mention the presence of pyknotic nuclei in the stratum corneum. However, our observations revealed the absence of the stratum granulosum and the presence of pyknotic nuclei within the stratum corneum.…”

“…The pinnipeds, amphibious mammals that includes seals (Phocidae), fur seals and sea lions (Otariidae), and walruses (Odobenidae), spend most of their lives in open seas, reaching the coast (or pack ice) only to mate, give birth, moult, rest or even occasionally to escape from predators. Due to their semi-aquatic lifestyle and the extreme climates they live (mostly close to poles), the structure of their integumentary system (mainly associated with thermal insulation) has attracted considerable scientific interest for more than a century (see references, de Meijere, 1894;Erdsack et al, 2015;Gray, Canfield, & Rogers, 2006;Khamas, Smodlaka, Leach-Robinson, & Palmer, 2012;Ling, 1965Ling, , 1968Ling, , 1970Ling, , 2013Sokolov, 1960).…”

Posterior Respiratory Apparatus of Inia geoffrensis and Sotalia fluviatilis: Structure and Ultrastructure

“…In our findings, both in the cranial, middle and caudal regions, the cartilages were dorsally open. These cartilages have the function of coating the flat C-shaped rings present on the tracheal wall of some aquatic mammals (Gray et al, 2006).…”

Creation Nerves of the Lumbar and Sacral Plexus in California Sea Lions (Zalophus Californianus) and Northern Elephant Seals (Mirounga Angustirostris)/Formiranje Nerava Iz Lumbalnog I Sakralnog Pleksusa Kod Kalifornijskog Morskog Lava (Zalophus Californianus) I Severnomorskog Slona (Mirounga Angustirostris)

“…In separate investigations Fraser [7], Green [8], Freea [9], St Pierre [10], King [11], Dierout and Gullard [12] described the morphological characteristics of other marine mammals. A second group of investigators [6,[13][14][15][16] assessed their adaptations from the standpoint of functional morphology. Numerous investigations [17][18][19][20][21] of pinnipedia in that respect were associated with depth and duration of diving, as well as with the changes occurring in different organ systems during diving.…”