共查询到20条相似文献,搜索用时 15 毫秒
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Chromosome analyses were carried out on bone marrow cells from three elephant seal pups (Mirounga leonina), a species characterized by a 2n = 34 chromosome number. Arm ratios for the different chromosomes were calculated to facilitate the classification of chromosomes into groups. The karyotype of the southern elephant seal differs from other reported 34-chromosome phocids in the morphology of the Y chromosome and in that of one of the autosomal chromosome pairs. 相似文献
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The southern elephant seal population at Macquarie Island has undergone a serious decline since regular surveys were commenced in 1949. Approximately 2,900 cows and 250 bulls were counted in the isthmus study area during the 1985 breeding season. Comparisons with 20 other counts made in the same area between 1949 and 1984 showed that, although there was considerable fluctuation between the years, the number of seals ashore has dropped at an average rate of 2.1% per year, resulting in a net decrease of approximately 50% for both males and females. This is similar to the ratio of decline of elephant seal populations in the southern Indian Ocean. The census information from all major elephant seal populations was reviewed and it was concluded that there may be a common factor, or group of factors, acting to reduce the Macquarie Island and Indian Ocean populations, while the populations of the South Atlantic seem to be stable. Several potential explanations for these observations are advanced, but it is concluded that a greater knowledge of the ecology of the seals is needed if the declines are to be understood. 相似文献
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Body growth of 137 female southern elephant seals (Mirounga leonina) over 1 year of age was investigated at subantarctic Macquarie Island. An asymptotic straight line, snout–tail body length of 2.57±0.03 m was estimated to be attained at 9 years of age, using a three-parameter Gompertz equation. A significant increase of approximately 0.1 m (5%) in mean body length of females between 1 and 10 years of age was estimated to have occurred between the 1950–1960s and 1990s at Macquarie Island. This is consistent with a reduction in both the rate of population decline and the age of onset of sexual maturity. Age determination using dental cementum layers and the importance of standardised measurements in pinniped growth studies are discussed. 相似文献
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A. R. Carlini M. E. I. Márquez G. Soave D. F. Vergani P. A. Ronayne de Ferrer 《Polar Biology》1994,14(1):37-42
An analysis of milk constituents during various stages of lactation in the southern elephant seal Mirounga leonina was carried out. Forty-six milk samples were taken from 30 females throughout lactation during 1985, 1987, 1990 and 1991 on Stranger Point, King George Island, South Shetland Islands. Total nitrogen (TN), non-protein nitrogen (NPN), sugar, fat, ash and water were measured, and from some of these data true protein and energy content were calculated. The results showed a high degree of variation in water and fat concentrations among samples at different stages of lactation. During the first 20 days the fat content of milk increased from about 12 to approximately 52%, while water content fell from 70 to 33%. The composition of milk changes rapidly during the first days post-partum. Protein, minerals and sugar appear to remain stable after the fourth day of lactation. Milk samples contain significant levels of sugars; thin layer chromatography indicates the presence of lactose and glucose together with other unidentified components. There is evidence of a striking change in composition of the milk in the later part of lactation; the progressive increase in the fat:water ratio is abruptly reversed just prior to weaning. 相似文献
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A R Carlini M E Márquez S Ramdohr H Bornemann H O Panarello G A Daneri 《Physiological and biochemical zoology : PBZ》2001,74(4):531-540
Weaning mass in southern elephant seals is highly variable, the heaviest pups being three times as heavy as the lightest ones. After weaning, pups undergo an extensive postweaning period in which they draw on their reserves. To quantify the energy expenditure during the postweaning period, changes in mass, body composition, and postweaning duration were measured in southern elephant seals at King George Island, South Shetland Islands, Antarctica. Overall, mean pup weaning mass was 154 +/- 26 kg (n=117) and did not differ between sexes. Mean minimum postweaning duration was 42.5 +/- 7.5 d. Heavier animals at weaning had lower mass-specific mass loss rates than lighter ones, and a faster depletion of body reserves was associated with a shorter postweaning period. The proportion of body mass represented by fat at weaning was 37% +/- 4% (n=47) and did not differ between sexes. Of these pups, 36 were recaptured after a mean period of 36 d after weaning. On average, total mass loss measured in these animals (39 kg) was composed of 39% water, 47% fat, and 12% protein. The composition of mass loss was not significantly different between sexes and was not related to weaning mass or total body energy reserves. However, fatter animals at weaning lost more fat per kilogram lost than thinner ones. Late in the fast, males and females appeared to be in a similar body condition. Nevertheless, the overall proportion of body mass represented by fat at this time was lower than that presented by the same animals at weaning. We estimated that during the postweaning period pups lost, on average, 30% of their mass at weaning. This comprised approximately 35% of the energy and 32% of the fat in the pup's body. 相似文献
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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. 相似文献
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A. R. Carlini H. O. Panarello M. E. I. Marquez G. A. Daneri G. E. Soave 《Polar Biology》2000,23(6):437-440
Deuterium-labeled water was used to measure changes in the proximate body composition during the lactation period and after weaning in southern elephant seal pups at King George Island, South Shetland Islands, Antarctica. During the lactation period (23.0 ± 1.4 days) pups gained a mean of 4.9 ± 0.5 kg/day (n=7). Of the total mass gain (112 ± 8 kg), 38% was water, 48% was fat, and 11% was protein. This represented an increase in total body gross energy of 2437 ± 145 MJ. The proportion of body mass represented by fat was less than 2% at birth, increasing to 35 ± 2% at weaning. We followed the pups during a mean period of 36 ± 3 days after weaning. During this period, pups had a mean loss of 1.21 ± 0.10 kg/day (n=7) comprising 39% water, 48% fat, and 12% protein. The energy cost over this period was 952 ± 168 MJ, which represented, on average, 39% of the total energy gained during the suckling period. Accepted: 3 January 2000 相似文献
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B. S. James T. McIntyre C. A. Tosh H. Bornemann J. Pl?tz M. N. Bester 《Polar Biology》2012,35(11):1759-1766
Access to different environments may lead to inter-population behavioural changes within a species that allow populations to exploit their immediate environments. Elephant seals from Marion Island (MI) and King George Island (KGI) (Isla 25 de Mayo) forage in different oceanic environments and evidently employ different foraging strategies. This study elucidates some of the factors influencing the diving behaviour of male southern elephant seals from these populations tracked between 1999 and 2002. Mixed-effects models were used to determine the influence of bathymetry, population of origin, body length (as a proxy for size) and individual variation on the diving behaviour of adult male elephant seals from the two populations. Males from KGI and MI showed differences in all dive parameters. MI males dived deeper and longer (median: 652.0?m and 34.00?min) than KGI males (median: 359.1?m and 25.50?min). KGI males appeared to forage both benthically and pelagically while MI males in this study rarely reached depths close to the seafloor and appeared to forage pelagically. Model outputs indicate that males from the two populations showed substantial differences in their dive depths, even when foraging in areas of similar water depth. Whereas dive depths were not significantly influenced by the size of the animals, size played a significant role in dive durations, though this was also influenced by the population that elephant seals originated from. This study provides some support for inter-population differences in dive behaviour of male southern elephant seals. 相似文献
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D. J. Griffiths 《Journal of Zoology》1984,203(2):181-191
The tubules of the head and body of the elephant seal epididymis undergo large increases in diameter and principal cell height for the duration of the breeding season, and regress at the conclusion of breeding. The tubules of the tail show a lesser development, and only towards the end of breeding. Spermatozoa, first produced in the testis in August, reach the tail of the epididymis in September, and are present in large numbers throughout the epididymis in October and November. In December, the first month of sexual quiescence following the breeding season, sperm are almost totally absent from the epididymis. 相似文献
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Maternal and physical factors play a significant role in animal life-history variability, which means that large scale climate change has the potential to affect the size and dynamics of animal populations indirectly through maternal investment and directly through conditions that animals are exposed to. However, little is known about the effects of large-scale oceanographic events such as the El-Ni?o southern oscillation (ENSO) that influence productivity in the Southern Ocean and the abundance, quality and distribution of prey. The possible mechanisms by which physical factors and primary productivity could influence life-history traits, such as survival of apex predators, includes direct influences such as food availability and foraging success and indirect influences such as stored maternal investment and resource transfer during lactation. Here, we quantify the relative contribution of maternal investment and climate conditions at remote foraging sites to survival in the first year of life for southern elephant seals. We present evidence linking climate (ENSO) and variations in a key demographic parameter--first-year survival--and demonstrate that survival was highest during ENSO events and that the ability of mothers to store and acquire resources, which is typically related to ocean productivity, is the most important determinant of survival in the first year. This functional link provides valuable insights that can be used to model the responses of the seal populations to climate change scenarios. 相似文献
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Juvenile seals branded on the isthmus of Macquarie Island as pups displayed a high degree of philopatry. They returned more often and in greater densities to the northern third of the island within 10 km of their birth sites. Juvenile seals were observed to haul out more frequently and in greater numbers on the east coast as opposed to the west. Juvenile seals typically hauled out on two occasions, once during the winter, and once to moult. The probability of recapturing (resighting) branded and tagged seals was greater during the mid-year haulout. First-year survival estimates were obtained from searches of all Macquarie Island beaches for marked (branded and tagged) seals. From a branded population of 2000 seals, 897 were known to be alive at age 1 year, and minimum first-year survival was calculated at 44.85%. To this minimum estimate was added the number of seals overlooked during systematic and standardised searches of the island, and a revised estimate of 65.60% was calculated. Survival rates calculated using a custom model and a conventional mark-recapture model (MARK) were compared and no differences detected. Actual survival data and probability of sighting estimates were included in the revised estimate of first-year survival of southern elephant seals at Macquarie Island. There were no differences in the number of surviving males and females. Accepted: 25 October 1998 相似文献
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D. J. Griffiths 《Journal of Zoology》1984,203(2):193-204
The testis of the Southern elephant seal demonstrates seasonal changes in weight, with highest values early in the breeding season (September-November) and lowest values in mid-winter (May-June). Weight changes originate in the seminiferous tubules, there being little variation in the interstitial tissue.
Spermatogenesis begins in August, one month before the breeding season, and stops in November. Testicular testosterone concentration is significantly elevated in the months July-September. Plasma testosterone concentration is high only in September, the first month of breeding. 相似文献
Spermatogenesis begins in August, one month before the breeding season, and stops in November. Testicular testosterone concentration is significantly elevated in the months July-September. Plasma testosterone concentration is high only in September, the first month of breeding. 相似文献
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Thirteen female southern elephant seals moulting at Macquarie Island lost an average of 4.46±0.80 kg/day (10.01±1.20g/kg/day). There was no significant difference between this rate of body mass loss and that reported for moulting female southern elephant seals from South Georgia. Moulting female southern elephant seals however exhibited larger mass specific mass loss than either female northern elephant seals or male southern elephant seals, indicating a higher metabolic cost of moult in these animals. 相似文献