Ross Seals Research Articles

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.

Pleistocene Ross seal(ommatophoca Rossi)from New Zealand (note)

Abstract A fossil seal jaw from the Early Pleistocene (Wanganui Series; Hautawan Stage) of Napier, New Zealand, is identified as that of an Ommatophoca rossi juvenile of less than 1.8 m body length.

Distribution and abundance of the Weddell seal in the western Ross Sea, Antarctica

Summary The distribution and abundance of the Weddell seal (Leptonychotes weddelli Lesson) in the fast ice and pack ice of the western Ross Sea, Antarctica, were investigated during 1967 and 1968 from icebreakers and accompanying helicopters. It was estimated that there were about 50,000 Weddell seals in the western Ross Sea between Cape Adare and McMurdo Sound. Weddell seals appear to breed mainly in the fast ice along the Victoria Land coast and less frequently in some nearby areas of pack ice. Fast ice is preferred to pack ice. Most Weddell seals in the pack ice were adults. General observations on the distribution of crabeater, leopard, and Ross seals are included.

GIANT EPIPHYSES IN A ROSS SEAL.

THE Ross Seal (Ommatophoca rossi) is a relatively little-known animal and it was not until recently, when the British Museum (Natural History) received two frozen specimens from the British Antarctic Survey, that any detailed investigation of it could be attempted. Several curious characters have been noted in the first of these seals to be dissected, including a peculiarity of the flippers.

OBSERVATIONS ON TERRESTRIAL LOCOMOTION IN ANTARCTIC SEALS

Observations are reported on the modes of terrestrial locomotion among Antarctic members of the Phocidae. An account is given of the sinuous (or “swimming”) type of progression found most developed in the crabeater seal Lobodon carcinophagus (Hombron and Jacquinot), and of its occurrence in the leopard seal Hydrurga leptonyx (Blainville). This type of movement has not been seen in the Weddell seal Leptonychotes weddelli Lesson, where the undulatory (caterpillar‐like) method is the normal locomotory pattern on land. The fore‐flippers are not used by the adult Weddell seal in terrestrial locomotion, but the pup does make some use of the fore‐flippers during the first 10 to 15 days of postnatal life. The locomotory patterns used by the elephant seal Mirounga leonina Linn, and the probable methods used by the Ross seal Ommatophoca rossi Gray, are noted. The observation that the harp seal Pagophilus groenlandicus (Erxleben) shows the sinuous type of movement under stress is recorded.

Résultats du Voyage du SY Belgica en 1897, 1898, 1899, sous le Commandemant de A de Gerlache de Gomery

THE cruise of the steam-yacht Belgica, organised by the Belgian Government, may be regarded as the first of the series of expeditions fitted out during the last few years to explore the Antarctic and to collect systematically its zoological and botanical products. Consequently, it fell to the lot of this expedition to be the first to bring back specimens of certain animals previously known, more or less imperfectly, by examples obtained by the early expeditions to the South Polar regions, such as that of the Erebus and Terror. The most noticeable instance of this is afforded by the seal known as Ommatophoca rossi, which had been previously known only by two skulls and a skin brought home by the Erebus and Terror Expedition (1839–43). Fortunately, the fasciculus of the Rapports dealing with the seals (by Captain Barrett-Hamilton) was published in 1902, and ante-dates the British Museum report on the Southern Cross Expedition, thereby securing to the Belgica the full credit for having been the first to increase our knowledge of this interesting species.