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PubMed2000

Selective heating of vibrissal follicles in seals (Phoca vitulina) and dolphins (Sotalia fluviatilis guianensis).

The thermal characteristics of the mystacial vibrissae of harbour seals (Phoca vitulina) and of the follicle crypts on the rostrum of the dolphin Sotalia fluviatilis guianensis were measured using an infrared imaging system. Thermograms demonstrate that, in both species, single vibrissal follicles are clearly defined units of high thermal radiation, indicating a separate blood supply to these cutaneous structures. It is suggested that the high surface temperatures measured in the area of the mouth of the follicles is a function of the sinus system. In seals and dolphins, surface temperature gradually decreased with increasing distance from the centre of a follicle, indicating heat conduction from the sinus system via the follicle capsule to adjacent tissues. It is suggested that the follicular sinus system is a thermoregulatory structure responsible for the maintenance of high tactile sensitivity at the extremely low ambient temperatures demonstrated for the vibrissal system of seals. The vibrissal follicles of odontocetes have been described as vestigial structures, but the thermograms obtained in the present study provide the first evidence that, in Sotalia fluviatilis, the follicles possess a well-developed sinus system, suggesting that they are part of a functional mechanosensory system.

Animals↗

PubMed2000

Respiration and heart rate at the surface between dives in northern elephant seals.

All underwater activities of diving mammals are constrained by the need for surface gas exchange. Our aim was to measure respiratory rate (fb) and heart rate (fh) at the surface between dives in free-ranging northern elephant seals Mirounga angustirostris. We recorded fb and fh acoustically in six translocated juveniles, 1.8-2. 4 years old, and three migrating adult males from the rookery at Año Nuevo, California, USA. To each seal, we attached a diving instrument to record the diving pattern, a satellite tag to track movements and location, a digital audio tape recorder or acoustic datalogger with an external hydrophone to record the sounds of respiration and fh at the surface, and a VHF transmitter to facilitate recovery. During surface intervals averaging 2.2+/-0.4 min, adult males breathed a mean of 32.7+/-5.4 times at a rate of 15. 3+/-1.8 breaths min(-)(1) (means +/- s.d., N=57). Mean fh at the surface was 84+/-3 beats min(-)(1). The fb of juveniles was 26 % faster than that of adult males, averaging 19.2+/-2.2 breaths min(-)(1) for a mean total of 41.2+/-5.0 breaths during surface intervals lasting 2.6+/-0.31 min. Mean fh at the surface was 106+/-3 beats min(-)(1). fb and fh did not change significantly over the course of surface intervals. Surface fb and fh were not clearly associated with levels of exertion, such as rapid horizontal transit or apparent foraging, or with measures of immediately previous or subsequent diving performance, such as diving duration, diving depth or swimming speed. Together, surface respiration rate and the duration of the preceding dive were significant predictors of surface interval duration. This implies that elephant seals minimize surface time spent loading oxygen depending on rates of oxygen uptake and previous depletion of stores.

Animals↗

PubMed2000

The ontogeny of metabolic rate and thermoregulatory capabilities of northern fur seal, Callorhinus ursinus, pups in air and water.

Young pinnipeds, born on land, must eventually enter the water to feed independently. The aim of this study was to examine developmental factors that might influence this transition. The ontogeny of metabolic rate and thermoregulation in northern fur seal, Callorhinus ursinus, pups was investigated at two developmental stages in air and water using open-circuit respirometry. Mean in-air resting metabolic rate (RMR) increased significantly from 113+/-5 ml O(2 )min(-)(1) (N=18) pre-molt to 160+/-4 ml O(2 )min(-)(1) (N=16; means +/- s.e.m.) post-molt. In-water, whole-body metabolic rates did not differ pre- and post-molt and were 2.6 and 1.6 times in-air RMRs respectively. Mass-specific metabolic rates of pre-molt pups in water were 2.8 times in-air rates. Mean mass-specific metabolic rates of post-molt pups at 20 degrees C in water and air did not differ (16.1+/-1.7 ml O(2 )min(-)(1 )kg(-)(1); N=10). In-air mass-specific metabolic rates of post-molt pups were significantly lower than in-water rates at 5 degrees C (18.2+/-1.1 ml O(2 )min(-)(1 )kg(-)(1); N=10) and 10 degrees C (19.4+/-1.7 ml O(2 )min(-)(1 )kg(-)(1); N=10; means +/- s.e.m.). Northern fur seal pups have metabolic rates comparable with those of terrestrial mammalian young of similar body size. Thermal conductance was independent of air temperature, but increased with water temperature. In-water thermal conductance of pre-molt pups was approximately twice that of post-molt pups. In-water pre-molt pups matched the energy expenditure of larger post-molt pups while still failing to maintain body temperature. Pre-molt pups experience greater relative costs when entering the water regardless of temperature than do larger post-molt pups. This study demonstrates that the development of thermoregulatory capabilities plays a significant role in determining when northern fur seal pups enter the water.

Air↗

PubMed2002

Aerobic capacities in the skeletal muscles of Weddell seals: key to longer dive durations?

In contrast to terrestrial animals that function under hypoxic conditions but display the typical exercise response of increasing ventilation and cardiac output, marine mammals exercise under a different form of hypoxic stress. They function for the duration of a dive under progressive asphyxia, which is the combination of increasing hypoxia, hypercapnia and acidosis. Our previous studies on short-duration, shallow divers found marked adaptations in their skeletal muscles, which culminated in enhanced aerobic capacities that are similar to those of athletic terrestrial mammals. The purpose of the present study was to assess the aerobic capacity of skeletal muscles from long-duration divers. Swimming and non-swimming muscles were collected from adult Weddell seals, Leptonychotes weddelli, and processed for morphometric analysis, enzymology, myoglobin concentrations and fiber-type distribution. The results showed that the skeletal muscles of Weddell seals do not have enhanced aerobic capacities compared with those of terrestrial mammals but are adapted to maintain low levels of an aerobic lipid-based metabolism, especially under the hypoxic conditions associated with diving. The lower aerobic capacity of Weddell seal muscle as compared with that of shorter-duration divers appears to reflect their energy-conserving modes of locomotion, which enable longer and deeper dives.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed2026

ERGA-BGE reference genome of the Mediterranean monk seal ( Monachus monachus), an IUCN Vulnerable species.

The Mediterranean monk seal, Monachus monachus, is the only pinniped that lives in the Mediterranean Sea and one of the rarest marine mammals in the world. The species was recently classified as "vulnerable" by the IUCN, considering an improvement in its overall status. However, the species' populations have undergone severe bottlenecks due to systematic persecution by humans over the past centuries. Today, the global population of M. monachus is estimated to be no more than 1,000 individuals. The Mediterranean monk seal is mainly using marine caves as resting and pupping sites. It is an opportunistic apex predator and as a result its role is considered important for maintaining the structure and function of marine ecosystems. Nowadays, the species is threatened mainly by the destruction of its habitat (due to coastal development, mass tourism, and pollution) and by the depletion of its prey due to overfishing. The Mediterranean monk seal is an emblematic species; its ecological importance and its vulnerable status render its protection and effective management necessary. The entirety of the genome sequence of a female specimen was assembled into 16 contiguous chromosomal pseudomolecules, one sex chromosome (X), and one mitochondrial genome. This chromosome-level assembly encompasses 2.4 Gb, composed of 316 contigs and 275 scaffolds, with contig and scaffold N50 values of 90.9 Mb and 157 Mb, respectively.

Biodiversity Genomics Europe↗

PubMed2001

Morbilliviral dermatitis in seals.

A juvenile female hooded seal (Cystophora cristata) and a juvenile male harp seal (Phoca groenlandica) stranded separately on the New Jersey (USA) coast and were taken to a marine mammal rehabilitation center. Both were lethargic and emaciated, had dermatitis, and died. Histologic skin lesions in the seals were similar and consisted of epidermal and follicular epithelial hyperplasia, hyperkeratosis, degeneration, and necrosis. The most distinctive finding was extensive syncytial zones bounded superficially by hyperkeratosis and deeply by hyperplastic basal cells. Eosinophilic intracytoplasmic inclusion bodies were present in epithelial cells. Morbilliviral antigen was demonstrated in the skin lesions by immunohistochemistry. Phocine distemper virus was detected in the skin by reverse transcription polymerase chain reaction and a phocine distemper virus-specific probe using the Southern blot technique. This is the first report of morbilliviral dermatitis in marine mammals.

Animals↗

PubMed1983

Luteal regression, follicle growth and the concentration of some plasma steroids during lactation in grey seals (Halichoerus grypus).

Ovaries of lactating grey seals, which had been shot, were measured to obtain the size of each follicle and corpus luteum. Plasma samples were collected by temporarily immobilizing lactating females. The single corpus luteum regressed rapidly after pupping and circulating progesterone levels declined at parturition and remained low throughout most of lactation. A single wave of follicular growth began about the time of parturition and gave rise to a single mature follicle towards the end of lactation. This coincided with high plasma oestradiol-17 beta concentrations and behavioural oestrus. A corpus luteum inhibited follicular growth in the ipsilateral ovary. The concentration of plasma progesterone increased in some seals late in lactation, indicating that ovulation sometimes occurred before the end of lactation. This was confirmed by observation of ovaries from shot seals.

Animals↗

PubMed1984

Gonadotrophin and progesterone concentrations in placentae of grey seals (Halichoerus grypus).

Chorionic gonadotrophin (CG) measured by bioassay and progesterone by immunoassay were present in the placentae of grey seals (Halichoerus grypus) from about 20 days after implantation until parturition. During this period a small and significant decrease in the concentration and a large increase in the total amount of placental CG occurred. The biological activity of seal placental CG was neutralized with an anti-hCG serum. There was a correlation between fetal length and the total amount of progesterone in the placenta. The corpus luteum persisted throughout pregnancy and there was a significant correlation (P less than 0.001) between CL diameter and the weight of the ipsilateral ovary. Hypertrophy of fetal testes and ovaries was observed and adult gonad size was reached at about the time of parturition. We suggest that placental CG is the hormone responsible for the precocious enlargement of fetal gonads in grey seals.

Animals↗

PubMed1985

Photoperiod and delayed implantation in the northern fur seal (Callorhinus ursinus).

An equation for determination of the photoperiod at any given latitude for any given date is presented and used in an analysis of reproductive timing in the northern fur seal in which there is an obligatory delay of implantation. Fur seals breeding on San Miguel Island, California (33 degrees N) displayed a mean date of parturition that was 14 days earlier (P less than 0.001) than that of the parent stock on the Pribilof Islands, Alaska (57 degrees N). Previous studies have shown that changes occur in the corpus luteum, in follicles in the ovary containing the corpus luteum, in concentrations of plasma progesterone and oestradiol-17 beta, and in the uterine lining when there is a mean photoperiod of 12.5 h/day. This photoperiod occurs at both locations at 62 days after the mean dates of parturition, and may act as a cue for the initiation of implantation in these seals.

Animals↗

PubMed1993

Testosterone response to a gonadotrophin-releasing hormone agonist in Hawaiian monk seals (Monachus schauinslandi).

Adult male Hawaiian monk seals were administered a gonadotrophin-releasing hormone (GnRH) agonist to determine its effectiveness in reducing the testicular production of testosterone. Blood samples were collected from four treated seals and two control seals at weekly intervals for 10 weeks and again at the beginning of the following breeding season. The GnRH-agonist had an initial, brief, stimulating effect on circulating testosterone, but this was followed by an inhibitory effect that lasted for 7 to 8 weeks. The plasma concentrations of testosterone were within normal ranges by the following spring. These results demonstrate a reversible form of long-term androgen suppression, which may have applicability in a variety of wildlife management programmes.

Animals↗

PubMed2001

Seroprevalence of Toxoplasma gondii in harbor seals (Phoca vitulina) in southern Puget Sound, Washington.

As part of the Puget Sound Ambient Monitoring Program of the Washington Department of Fish and Wildlife, serum samples from 380 harbor seals (Phoca vitulina) were tested for antibodies to Toxoplasma gondii in the modified agglutination test (MAT) incorporating formalin-fixed tachyzoites and mercaptoethanol. Antibodies to T. gondii were found in 29 of 380 (7.6%) seals with titers of 1:25 in 13, 1:50 in 14, and > or = 1:500 in 2 seals. Results indicate natural exposure of these wild marine mammals to T. gondii oocysts.

Agglutination Tests↗

PubMed2005

Salmonella and Campylobacter spp. in northern elephant seals, California.

Campylobacter and Salmonella spp. prevalence and antimicrobial drug sensitivity were determined in northern elephant seals that had not entered the water and seals that were stranded on the California coast. Stranded seals had a higher prevalence of pathogenic bacteria, possibly from terrestrial sources, which were more likely to be resistant.

Animals↗

PubMed1999

Streptococcus phocae infections associated with starvation in Cape fur seals.

Mortalities and abortions associated with starvation occurred at Cape Cross, Namibia, in Cape fur seals (Arctocephalus pusillus pusillus). Affected seals showed lethargy and emaciation, and the most common pathological signs were those of a respiratory infection, both in adults and offspring. Streptococcus phocae was isolated from adult seals, a cub and aborted foetuses.

Animals↗

PubMed1976

Clinical blood values of the northern fur seal, Callorhinus ursinus.

Clinical blood values are reported for 14 blood components in the northern fur seal (Callorhinus ursinus) and compared with human clinical ranges. Certain values such as cholesterol, globulins and blood urea nitrogen deviate markedly from published human values. The distribution of serum proteins in fur seals, man and northern elephant seals also are given and compared.

Animals↗

PubMed1979

Effects of handling stress on plasma enzymes in harp seals, Phoca groenlandica.

Three harp seal pups, Phoca groenlandica, were captured on the ice of the Gulf of St. Lawrence, and subjected to 3 h of transportation and handling stress. The activities of creatine kinase (CK), aspartate aminotransferase (AspAT), aldolase, alanine aminotransferase, gamma glutamyl transpeptidase, and leucine aminopeptidase were determined in serial blood samples collected for 4 d following the stress episode. Marked elevation of plasma CK activity was observed 3 h after capture. Values returned to normal in 12 h in two seals, and by 24 h in the third. Slight elevations in AspAT were also noted; the remaining enzymes were unaffected. Plasma CK is recommended as a sensitive indicator of handling stress in seals.

Alanine Transaminase↗

PubMed1993

Phocine distemper in harbor seals (Phoca vitulina) from Long Island, New York.

The first occurrence of phocine distemper (PD) disease in harbor seals (Phoca vitulina) from the United States is reported. Two seals stranded on Long Island, New York (USA) in February 1992 with clinical signs of respiratory distress, fever, and depression. Pneumonia and diffuse pulmonary congestion were the most significant post mortem findings. On histologic examination one seal had a diffuse broncho-interstitial pneumonia with formation of syncytia. The principal lesion in the second animal was nonsuppurative meningoencephalitis. Using immunoperoxidase staining, PD viral antigen was found in the cytoplasm of bronchiolar epithelium and cerebral cortex neurons. With a differential virus neutralization test, there were higher titers against phocine distemper virus (PDV) than against canine distemper virus. Thus, PDV is the most likely agent responsible for the observed lesions.

Animals↗

PubMed1996

Baseline coagulation assay values for northern elephant seals (Mirounga angustirostris), and disseminated intravascular coagulation in this species.

Coagulation assays, including platelet counts, antithrombin III, fibrinogen, fibrinogen degradation product levels, prothrombin (PT), activated partial thromboplastin (APTT) and activated clotting times (ACT), were performed on 20 healthy juvenile northern elephant seals (Mirounga angustirostris) stranded along the central California coastline from 15 March to 15 April 1994, to establish baseline parameters for this species. Elephant seals appear to have relatively short ACT, PT, and APTT times, while fibrinogen, platelet and antithrombin III levels are similar to domestic species. Based on these mean values in healthy animals, disseminated intravascular coagulation (DIC) was diagnosed in an elephant seal with low plasma fibrinogen and extended ACT, PT and APTT times; this animal had hemorrhages, mixed bacterial suppurative interstitial pneumonia with verminous arteritis, epicarditis, hepatitis and enterocolitis.

Animals↗

PubMed1997

Giardiasis in ringed seals from the western arctic.

Sixteen beluga whales (Delphinapterus leucas) and fifteen ringed seals (Phoca hispida) from the western arctic region of Canada were examined for giardiasis and cryptosporidiosis. Intestinal contents from the rectum and colon were collected from animals slaughtered by Inuit hunters. A fluorescent monoclonal antibody identified Giardia sp. cysts in three of 15 (20%) seals. Thus, ringed seals are implicated as a potential reservoir for this zoonosis in the arctic.

Animals↗