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At least 19 recordsLinked to original sources
PubMed1976

Functional anatomy of the hands of fur seals and sea lions.

Dissections and manipulations of the hands of 14 specimens of four genera of fur seals and sea lions and of generalized fissiped carnivores were used to identify the structural modifications involved in formation of the expanded forelimb paddles characteristic of these pinnipeds. The morphological peculiarities were then correlated with differences in locomotor function, both on land and in the water, on the basis of previously published data, for the purpose of identifying modifications of structure and function which have adaptive vale. Structural differences found in the manus of fur seals and sea lions include: (1) reduction in size of the ulnar side of the carpus and a radial shift in the length-order of the digits, (2) development of musculature in the antebrachial fascia which attaches to the caudal margin of the flipper, (3) orientation of the radial side of the manus dorsal and radial to the rest of the hand, (4) increased range of possible midcarpal movement and in deviational mobility at the first and fifth digits, (5) attachment of forearm musculature onto radial digits and (6) well-developed hypothenar muscles and absence of thenar muscles. Modifications in hand structure are viewed as providing a morphological basis for employment of the hand to advantage during aquatic locomotion while maintaining thrust-producing and potentially energy-conserving capacities during movement on land. As such these differences in structure and function are viewed as adaptations to locomotion in the water and on land which are extensions of locomotor adaptations attributed to modifications of forelimb structure and function associated with the generation of massive aquatic locomotor thrust. The adaptive value of such modifications is interpreted as allowing fur seals and sea lions to swim with speed and thereby capture elusive fast-swimming prey while maintaining a level of terrestrial locomotor ability compatible with their amphibious mode of life.

Animals↗
PubMed1986

Adenohypophysis of the elephant seal (Mirounga leonina): morphology and seasonal histological changes.

Changes in adenohypophyseal cell populations over a 12-month period were studied in the seasonally breeding elephant seal (24 adult males, 3 adult females, and 5 neonates) at Macquarie Island. The glands were weighed and fixed in formol sublimate. Selected sections were stained with the oxidation-alcian blue-periodic acid Schiff-orange G technique. Gonadotropic, thyrotropic, lactotropic, and somatotropic cells were readily identifiable; whilst corticotropes, inactive secretory cells of all types, and stellate cells were not stained and were counted collectively as chromophobic cells. Hypophyseal weight was low throughout autumn and winter, but increased significantly during the spring breeding season and the summer. Thyrotropes were distributed evenly throughout the pars distalis, but the other secretory cells showed areas of concentration. Acidophils were common peripherally, particularly lactotropes, while gonadotropes were largely confined to the 'basophilic wedge,' a narrow, central superior zone. In males, lactotropic and gonadotropic cells showed significant seasonal changes in number. Gonadotropes were more common in sexually active males than sexually quiescent ones, while lactotrope numbers were much greater at midsummer than midwinter. This lactotrope cycle appeared to be related to photoperiod but unrelated to breeding.

Animals↗
PubMed1987

Histological, histochemical, and fine structural observations on the spleen of seals.

Spleens of three species of Antarctic seals with different diving habits (Weddell seal, crabeater seal, and fur seal) have been studied with histological, histochemical, and electron microscopic methods. The spleens can be classified as nonsinusoidal, with capsule and trabeculae rich in innervated smooth muscle cells. The trabecular system is particularly well developed in the deep- and long-diving Weddell seal. As in other mammals the pulp can be divided into white and red pulp. In the white pulp, periarteriolar lymphatic sheaths and secondary lymphatic nodules occur; both are surrounded by a marginal zone rich in macrophages and eosinophils. The nodules can be observed frequently, which is in accordance with abundance of plasma cells in the red pulp. Well-developed white pulp and numerous plasma cells and eosinophils obviously reflect a high load of nematodes, which have mainly been found in lung and stomach. Additionally, in the red pulp morphological evidence for the following functions has been found: destruction of erythrocytes, erythropoiesis, and thrombopoiesis. In respect to blood flow through the red pulp, we interpret our observations in the following way: terminal branches of arterioles open into the space between the fibroblastic reticulum cells; blood draining from here is collected into pulp veins, which are mainly found near the trabeculae. Thus, the seals have an open vascular compartment in their spleens, as also occurs in the cat. The red pulp is innervated by numerous nerve fibers that seem to include both cholinergic and adrenergic ones. The target cells of these fibers seem to be the fibroblastic reticulum cells, whose state of contraction may influence the direction of blood flow through the red pulp.

Animals↗
PubMed1986

Stable nitrogen and carbon isotope ratios in bone collagen as indices of prehistoric dietary dependence on marine and terrestrial resources in southern California.

The ratios of 15N to 14N and 13C to 12C tend to be higher in marine than in terrestrial organisms. The concentrations of these isotopes in human bone collagen consequently can be used to make inferences about the contribution of marine and terrestrial resources to prehistoric diets. The utility of studying 15N/14N and 13C/12C ratios in conjunction with each other is illustrated by our analysis of 40 human burials from archaeological sites in the Santa Barbara Channel area of southern California. The mean delta 13C and delta 15N values (in per mil) of collagen from these skeletons decrease progressively from the Channel Islands (delta 13C = -14.0, delta 15N = +16.3) to the mainland coast (delta 13C = -14.5, delta 15N = +14.9) to the interior (delta 13C = -17.2, delta 15N = +10.9). These data suggest that Indians living on the Channel Islands during the late prehistoric period were heavily dependent on marine resources. The inhabitants of the mainland interior, in contrast, had a diet composed largely of terrestrial foods. From their isotope ratios, it appears that the Indians who lived on the mainland coast consumed a mixed diet containing substantial quantities of both marine and terrestrial resources. Differences in 15N/14N and 13C/12C ratios of individuals from mainland sites dating from the early and late prehistoric periods show that the marine component of the diet increased substantially through time. These isotopic data are consistent with pathological, faunal, and artifactual evidence of increased marine resource exploitation during the late prehistoric period.

Animals↗
PubMed1978

Arteriovenous anastomoses in the skin of seals. I. The Weddell seal Leptonychotes weddelli and the elephant seal Mirounga leonina (Pinnipedia: Phocidae).

The structure, distribution, density and innervation of arteriovenous anastomoses (AVAs) have been compared in the skin of Weddell and elephant seals, as part of a study of the structure and function of arteriovenous anastomoses in mammals. In both genera AVAs were coiled vessels with the segmental structure typical of "epithelioid" anastomoses and possessed a dense peripheral adrenergic innervation. In both Weddell and elephant seals there was no statistically significant difference between the mean density of AVAs in body skin and flipper skin. The majority, approximately 71% of AVAs occurred superficially in the dermis, fewer (23%) occurred in the deeper dermis, and 6% were present in the thick hypodermis (bubber). The density of AVAs in Weddell and elephant seals is approximately eight times greater than that reported in other animals and the superficial position of anastomoses over the whole of the body surface is characteristic of phocid seals. When open, AVAs in Weddell and elephant seals allow maximal heat loss from the skin surface by passing large volumes of blood into the superficial veins. AVAs in seals are important in dissipation of body heat, particularly when the animals are out of the water, and the entire surface area is thermoregulatory rather than specific regions such as the flippers.

Animals↗
PubMed1978

Arteriovenous anastomoses in the skin of seals. II. The California sea lion Zalophus californianus and the northern fur seal Callorhinus ursinus (Pinnipedia: Otariidae).

The structure, distribution and density of arteriovenous anastomoses (AVAs) were studied in body and flipper skin of a California sea lion and a nothern fur seal. In both animals AVAs consisted of arterial, intermediate and venous segments, and were generally larger and more tortuous in the sea lion than in the fur seal. In the sea lion the majority of AVAs (72%) occurred in the deeper region of the dermis, and the density was significantly greater in the flippers than in the body. In the northern fur seal most AVAs (76%) occurred in the superficial region of the dermis; the density of AVAs in flipper skin was significantly higher than in body skin, and the density in the hind flipper was significantly greater than in the foreflipper. Arteriovenous anastomoses are important in the regulation of body temperature in seals; when these animals are on land, AVAs function to dissipate body heat, and vascular thermoregulation occurs in the flippers but notover the general body surface. Due to differences in distribution and density, AVAs play a more significant role in thermoregulation in the northern fur seal than in the California sea lion.

Animals↗
PubMed1976

Visual evoked response (VER) changes during maturation in the Weddell seal.

Visual evoked responses (VER'S) were recorded from the cortex of immature Weddel seals, 3-365 days of age. Results indicated a high degree of maturity at birth evident from the multiphasic array of waveforms and the comparatively short onset latency of the VER. At low intensities, single flashes evoked an immature secondary response. Topographical distribution of VER's were confined largely to the gyrus immediately adjacent to midline, from the posterior aspect near lambda to the vertex. Recordings from CI-744 dosed seals displayed a well-demarcated developmental sequence of VER's, contrary to VER's recorded in flaxedilized seals. Onset latency and waveform configuration changed concomitantly as a function of age. During the postnatal period from birth to weaning, VER changes were related to major behavioral events such as the seal's first encounter with swimming and diving at 2 weeks of age and weaning at 6 weeks of age.

Age Factors↗
PubMed1975

Some anatomical aspects of the cardiovascular system of Antarctic seals and their possible functional significance in diving.

The hearts and ascending aortae of 11 Weddell seals, Leptonychotes weddelli, three adult Crabeater seals, Lobodon carcinophagus, two adult Ross seals, Ommatophoca rossi, and one adult Leopard seal, Hydrurga leptonyx, were examined for comparison with terrestrial forms. The Weddell seal specimens were from animals ranging in age from midterm in fetal development to mature adults. All specimens were collected in 1971, 1972, and 1973, from McMurdo Sound and the Ross Sea, Antarctica. The phocid hearts were characteristically broader and flatter than those of other carnivore families and they tended toward bifid apices. The heart form indices (height/circumference) averaged 31.5 compared to 39.0 for felids. The right ventricular chambers of the Antarctic seals were found to average longer in Weddells and narrower in all, than those reported for four other carnivore families. An elastic enlargement was present in the ascending aortae of all seals. The largest diameter of the aortic bulb averaged 25.5 mm more than the base of the aorta in the adult Weddell seals which represented an increase of 72.5% over the base. It is suggested that the general heart form, and especially the ascending aortae, are anatomical adaptations to diving. The compressed heart makes possible unimpaired function when the chest is compressed during deep dives. The aortic bulb maintains mean arterial blood pressure and perfusion of the brain and cardiac tissue during diving bradycardia.

Adaptation, Physiological↗
PubMed1975

A gross and microscopic study of the respiratory anatomy of the Antarctic Weddell seal, Leptonychotes weddelli.

Four species of Phocidae, or true seals, inhabit the waters surrounding the Antarctic continent. These animals are thought to have different diving capabilities. The Weddell seal, Leptonychotes weddelli, is known to be capable of attaining depths up to 600 meters. The respiratiory system of the Weddell seal shows the usual adaptations to an aquatic environment characteristic of other marine. These include lungs that undergo compression acollapse at depths greater than 70 meters; hyaline cartilage in the tracheo-bronchial tree as far as the terminal bronchioles; and large amounts of smooth muscle surrounding the distal-most bronchioles. The collapsible lungs provide a mechanism by which air is forced from the alveoli adjacent to the pulmonary capillary beds thereby preventing the absorption of nitrogen gas into the bloodsteam. The presence of hyaline cartilage throughout most of the tracheo-bronchial tree increases the effective dead air space that accommodates most of the air forced from the collapsed lungs. The smooth muscle surrounding the respiratory bronchioles prevents their collapse while under the pressures of a deep dive. Collapse of the respiratory bronchioles not supported by cartilage would trap air in the lung alveoli during a dive. In addition, large- sac-like "diverticulae" are found in the submucosa throughout the tracheo-bronchial tree. These diverticulae, which open directly into the lumen of the tree, appear to be modified glands whose cells, in most cases, do not appear to be specialized for secretory function. They are most numerous in the more distal bronchi and terminal bronchioles where they are situated on both the luminal and adventitial sides of the hyaline cartilage supporting the walls of the air passages. Diverticulae are not found in the respiratory bronchioles or in the respiratory portion of the lungs.

Acclimatization↗
PubMed1977

Structural correlates of forelimb function in fur seals and sea lions.

Dissections, manipulation of ligamentary preparations, analysis of limb proportions, and quantitative aspects of forelimb myology are used to correlate forelimb morphology in fur seals and sea lions (sub-family Otariinae) with previously published data as to their locomotor function (English, '76a). Comparisons to structure and function in generalized fissiped carnivores are then used to elucidate locomotor adaptations in fur seals and sea lions. Unique features of forelimb function during swimming in these pinnipeds include the amounts of abduction-adduction and rotary movements used. Modifications of the size, attachments and fasicle architecture of the muscles and the structure and range of possible movement of the joints suggest that in fur seals and sea lions these movements (1) take place about the glenohumeral (shoulder) joints, (2) that the movements are probably finely controlled, and (3) that they contribute to the generation of massive forward thrust via the cooperative activity of muscles capable of generating large amounts of force throughout the range of movement. Recovery movements occur through a similarly large range, and modifications of forelimb anatomy either to minimize or overcome water resistance are noted. The adaptive significance of these modifications is interpreted as allowing fur seals and sea lions to swim at speeds necessary to feed on the fast swimming prey presumably abundant in their adaptive zone.

Animals↗
PubMed1985

The intrarenal and pericapsular venous systems of kidneys of the ringed seal, Phoca hispida.

The kidneys of Phoca hispida are comprised of many closely adherent renculi, each of which is a small kidney, functionally independent of its neighbours except with respect to venous drainage. Venous blood from the rencular parenchyma drains to the periphery through interlobular veins. These interlobular veins empty into a perirencular plexus comprised of subcapsular veins on the free surface of the renculus, interrencular veins on adjoined surfaces, and marginal subcapsular veins lying in the furrows between adjoined renculi. A pericapsular plexus of large veins overlies the marginal subcapsular veins and has frequent connections with them. Blood drains from the pericapsular plexus into large superficial collecting veins that converge over the surface of the kidney toward the divided hilum and connect directly to the paired trunks of the posterior vena cava. There are also connections to other major venous systems of the region. There is no arcuate venous system, no major vein at the rencular hilum, and no vein of consequence emerging from the renal hilum. Venous outflow is virtually entirely directed to the peripheral plexuses. The venous pattern differs from that of most mammals in which blood drains from the renal parenchyma to arcuate veins and leaves the kidney through a renal vein, or veins, emerging from the hilum. The walls of veins in the kidney are remarkably thin in comparison to their size. Subcapsular veins up to 0.5 mm wide have walls on the parenchymal side that in places consist only of a thin, fenestrated endothelium and a basal lamina.

Animals↗