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PubMed2002

PBDEs in the San Francisco Bay Area: measurements in harbor seal blubber and human breast adipose tissue.

To explore the levels of polybrominated diphenyl ethers (PBDEs) in California, samples from 11 archived harbor seals (Phoca vitulina Richardsi) from the San Francisco Bay and breast adipose tissue samples from 23 women were analyzed. The levels of PBDEs in human tissue samples were in the low ng/g fat range, with PBDEs 47, 153, 154, 99, and 100 as the major congeners. Average sigma PBDEs (86 ng/g fat) in these California women are the highest human levels reported to date. An inverse relationship between concentration of PBDEs and age of these women was apparent. The levels of PBDEs measured in harbor seal blubber were in the low ng/g to low microg/g fat range, with the same major congeners as those measured in the human tissues. PBDE 47 was the highest among all congeners measured in both human tissue and seal blubber samples. The concentrations of PBDEs in harbor seals in the San Francisco Bay have increased dramatically over the past decade, with current levels among the highest reported for this species.

Adipose Tissue↗
PubMed1998

GC/MS analysis of PCB congeners in blood of the harbor seal Phoca vitulina from San Francisco Bay.

Here we report a validated technique for quantifying up to 20 specific PCB congeners in 1-2 g samples of whole blood with a detection limit below 1 ng/g (ppb) wet weight. Specimens were analyzed from 14 harbor seals sampled in south San Francisco Bay, California during 1991-1992. Ratios of specific congeners to PCB-153, and other aspects of congener pattern, agreed with published values for PCB's detected in seal blood. PCB-153 constituted 30 percent of our sigma PCB values. The mean sigma PCB concentration for the San Francisco Bay seals was 50 ppb, about three times the average level reported for blood of captive seals fed exclusively on fish from the Baltic's PCB-contaminated Dutch Wadden Sea. Such experimental populations have exhibited depressed reproductive success and impaired immune function. These findings support concerns about the ecological effects of PCB contamination in San Francisco Bay.

Animals↗
PubMed2003

Contrasting changes of sensitivity by lymphocytes and neutrophils to mercury in developing grey seals.

Mercury is the principal metal contaminant in the St Lawrence Estuary. It impairs humoral, cellular and non-specific immune responses in many species. Since the immune system of juvenile seals is immature, it should react differently to the effects of contamination compared to that of mature animals. Phagocytosis and lymphoblastic transformation responses have been evaluated in the peripheral blood leukocytes of eight juvenile grey seals at different intervals of time over 11 weeks. Dose-response curves of 10(-9)-10(-3)M of methylmercury chloride have also been performed in vitro for evaluation of these two immune functions. The immune response of grey seals differs during their development. The phagocytosis response increased from the 2nd to 5th week post-weaning and then reached a plateau. As for the lymphoblastic transformation response, it was stable from the 2nd to the 3rd week post-weaning, increased significantly at week 4 post-weaning and then reached a plateau. These data suggest that these animals should be particularly vulnerable to infections, diseases and parasites before the 5th week post-weaning. Furthermore, mercury decreased the immune response, and age of seals had an effect on cell sensitivity to mercury. Concentrations of 10(-5)M of methylmercury chloride decreased phagocytosis and lymphoblastic transformation responses. Phagocytosis is more affected by MeHgCl contamination before this immune function reaches complete development which occurs at week 5 post-weaning. On the other hand, lymphoblastic transformation is more affected by this contaminant after its complete development which occurs at week 4 post-weaning.

Age Factors↗
PubMed1999

Molecular cloning and phylogenetic analysis of beluga whale (Delphinapterus leucas) and grey seal (Halichoerus grypus) interleukin 2.

Interleukin 2 (IL-2) is a lymphokine produced by activated T helper lymphocytes which exerts immunoregulatory effects on a variety of immune cells, including T cells, activated B cells, natural killer cells, and lymphokine-activated killer cells. In this study, we cloned and determined the entire beluga whale (Delphinapterus leucas) and grey seal (Halichoerus grypus) IL-2-encoding cDNA sequences, and analysed their genetic relationships with those from several mammalian species obtained from the Genbank Database. The encoding nucleic acid sequences of beluga whale and grey seal IL-2 were 465 and 468 bp in length, respectively. The identity levels of IL-2 nucleic and deduced amino acid sequences from the beluga whale and grey seal with those from the other mammalian species, ranged from 59.9% to 89.5%, and 52.9% to 77.3%, and from 61.1% to 93.2%, and 58.7% to 88.4%, respectively. Phylogenetic analysis based on both nucleic and amino acid sequences showed that the beluga whale IL-2 was closely related to that of the ruminant species, which includes the bovine, while the grey seal IL-2 was closely related to that of the canine.

Amino Acid Sequence↗
PubMed1999

Antigenic characterization of mycobacteria from South American wild seals.

Tuberculosis-producing mycobacteria have been previously described in marine mammals (Cousins et al., 1990, 1993; Romano et al., 1995; Bernardelli et al., 1996). The strains belonged to the M. tuberculosis complex (M. tuberculosis, M. bovis, M. microti and M. africanum), but showed genetic and biochemical differences. The antigenic composition of mycobacteria isolated from wild seals was analyzed by Western blots, using antibodies against some selected antigens. The antigenic content was compared with that of M. bovis, M. tuberculosis and M. microti isolates. The lack of Hsp65 protein in supernatants suggested a low degree of cell lysis in the three-week cultures used. SOD, P27 lipoprotein, MPB64 and antigen 85 were observed in all the strains studied. The wild seal strains, as well as M. tuberculosis, did not produce MPB70 and MPB83. Only very weak bands of P36 antigen were observed in culture supernatants from wild seal mycobacteria. Summarizing, the antigenic composition of mycobacterial strains from wild seals is different from M. bovis strains.

Animals↗
PubMed1989

Investigation of seal mycoplasmas for their cytotoxic potential on tracheal organ cultures of SPF and gnotobiotic rats.

Eleven mycoplasma strains isolated from several organs of diseased seals during the seal epidemic in the Baltic and North Sea in 1988 and the seal epidemic along the New England coast in 1979-1980, were investigated for their cytotoxic potential by inoculation into tracheal organ cultures of SPF and gnotobiotic rats. The mycoplasma strains belonged to three different species. Administration of 2.0 x 10(2) to 4.5 x 10(7) colony forming units of all of the mycoplasma strains caused an inhibition of the ciliary activity and cytopathological changes within the epithelial cells appearing as bleb-like protuberances by observation with the inverted microscope. There was, however, a distinct difference in the strength of the cytopathological changes caused by the three mycoplasma species. Semi- and ultrathin sections of tracheal rings infected with the seal mycoplasma strain 852, observed by light and electron microscopy, revealed a heavy tissue injury of the tracheal epithelium and dumbbell-shaped mycoplasmas adhering to degenerated epithelial cells.

Animals↗
PubMed2000

An empirical genetic assessment of the severity of the northern elephant seal population bottleneck.

A bottleneck in population size of a species is often correlated with a sharp reduction in genetic variation. The northern elephant seal (Mirounga angustirostris) has undergone at least one extreme bottleneck, having rebounded from 20-100 individuals a century ago to over 175,000 individuals today. The relative lack of molecular-genetic variation in contemporary populations has been documented, but the extent of variation before the late 19th century remains unknown. We have determined the nucleotide sequence of a 179 base-pair segment of the mitochondrial DNA (mtDNA) control region from seals that lived before, during and after a bottleneck low in 1892. A 'primerless' PCR was used to improve the recovery of information from older samples. Only two mtDNA genotypes were present in all 150+ seals from the 1892 bottleneck on, but we discovered four genotypes in five pre-bottleneck seals. This suggests a much greater amount of mtDNA genotypic variation before this bottleneck, and that the persistence of two genotypes today is a consequence of random lineage sampling. We cannot correlate the loss of mtDNA genotypes with a lowered mean fitness of individuals in the species today. However, we show that the species historically possessed additional genotypes to those present now, and that sampling of ancient DNA could elucidate the genetic consequences of severe reductions in population size.

Animals↗
PubMed1998

Changes in fibrinolytic activity in diving grey seals.

In order to test the hypothesis that enhanced fibrinolytic activity is a factor which prevents the blood of diving seals from clotting, we instrumented two female grey seals (Halichoerus grypus) with subcutaneous electrodes for measurements of heart rate (HR) and an extradural intravertebral venous catheter for collection of blood samples before, during and after simulated dives of 10 min duration. Blood samples were used for in vitro determination of clot lysis time (CLT), which is a measure of the level of fibrinolytic activity, and for analyses of plasma levels of cortisol, noradrenaline and adrenaline (A). The seals displayed profound diving bradycardia indicative of a substantial reduction in blood flow rates (pre-dive HR: 78 (63-98) bpm; dive HR: 8 (7-10) bpm; (median (range); n = 2)) and elevated catecholamine levels (pre-dive A: 121 (98-184) pg.ml-1; peak dive/post-dive A: 3510 (447-6181) pg.ml-1), both of which are factors which promote blood coagulation. Nevertheless, we found that CLT always increased in connection with diving (pre-dive CLT: 436 (356-568) min; peak CLT during diving: 1380 (640-1800) min), which implies a reduced, rather than enhanced, fibrinolytic activity in this situation. These results show that enhanced fibrinolytic activity is not part of the defence system which prevents fatal clotting from occurring in diving grey seals.

Animals↗
PubMed2004

The impact of sexual selection on Corynosoma magdaleni (Acanthocephala) infrapopulations in Saimaa ringed seals (Phoca hispida saimensis).

In free-living animals sexual selection is a central force shaping the spatial distribution of individuals in a population as well as sexual size dimorphism. We studied the influence of sexual selection on spatial distribution, female-to-male body size ratio, and female mating success of acanthocephalans in a natural host population of Saimaa ringed seal (Phoca hispida saimensis) harbouring a single intestinal helminth species, Corynosoma magdaleni. The acanthocephalans were always found along the full length of the small intestine; however, the site selection varied among the individual seals according to the age of the infection. The distribution of male acanthocephalans was not random with respect to females, with larger males tending to aggregate around non-mated females. A higher proportion of C. magdaleni females had copulated in seals with relatively more male worms. Male-male competition for access to females can be intense in C. magdaleni infrapopulation and may select for large males. We found that the larger the infrapopulation size, the smaller the males compared to females. In addition, the greater the female bias in the infrapopulation, the smaller the testes of males. Our study shows that sexual selection may be an important determinant of spatial distribution, male body size and female mating success of C. magdaleni in Saimaa ringed seal.

Acanthocephala↗
PubMed2003

Indication of geographic variaritions of organochlorine concentrations in the blubber of Antarctic Weddell seals (Leptonychotes weddelli).

A sample cleanup procedure using microwave-assisted extraction (MAE) with focus open vessel (FOV-MAE) technique was validated for the determination of organohalogen compounds in the blubber of a Weddell seal (Leptonychotes Weddelli) from the Antarctic (King George Island, 62 degrees 14' S, 58 degrees 40' W). Good reproducibility in replicate analysis of samples confirms the suitability of the method for samples with very low persistent organic pollutant (POP) concentrations. The method was used to analyze three additional blubber samples of Weddell seals from King George Island. This community of Weddell seals showed the lowest DDT (11-19 microg/kg) and PCB (1-2.5 microg/kg) concentrations so far detected in comparable marine mammals from all over the world. The concentrations determined in the four Weddell seals were also typical for the population at King George Island. However, the DDT and PCB concentrations on King George Island were one order of magnitude lower than in samples of the same species from other sites in the Antarctic (located between 69 degrees S and 78 degrees S). This suggests a wide variability of organohalogen levels in the Antarctic, depending on the geographic site. King George Island (62 degrees S) is found at the outskirts of the Antarctic Peninsula, i.e., the region with the mildest climate in the Antarctic. Low organohalogen levels at this site were attributed to a lower degree of condensation in comparison with locations further south. Most of the reference samples were taken in the Weddell and Ross Seas, i.e., from coastlines as close as possible to the pole. Consequently, other sites on the same latitude as the Weddell and Ross Seas are found on the Antarctic continent This raises the question whether high proportions of organohalogens are being deposited on the Antarctic continent where they are not available to marine organisms. Although this hypothesis has to be proven in follow-up studies, our study clearly demonstrates that it is complicated, if not impossible, to derive time trends in concentrations of POPs in biota from different reference sites in the Antarctic.

Adipose Tissue↗
PubMed2004

Toxicokinetics of PCDD, PCDF, and coplanar PCB congeners in Baikal seals, Pusa sibirica: age-related accumulation, maternal transfer, and hepatic sequestration.

To assess the toxicokinetic behavior and potential toxicity of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) in Baikal seals, congener-specific levels and tissue distribution were evaluated in the liver and blubber, and the effects of biological factors including sex and growth were assessed. Total 2,3,7,8-TCDD toxic equivalents (TEQs) were in the range of 210-920 pgTEQ/g fat wt (180-800 pgTEQ/g wet wt) in the blubber and 290-7800 pgTEQ/g fat wt (10-570 pgTEQ/wet wt) in the liver. Non-ortho coplanar PCB126 was the most TEQ-contributed congener accounting for 37-59% of the total TEQs in the liver. From the unique congener profiles, weak metabolic properties of Baikal seals for 2,3,7,8-TCDF and 1,2,3,7,8-P5CDF are suggested. Concentrations of most congeners linearly increased with age in male seals, whereas in adult females the levels revealed an age-related decline. The increasing and declining rates were congener-specific. Maternal transfer rates of 5 representative congeners from adult female to pup through lactation, which was estimated from male-female differences in the body burden, was 1.1 ngTEQ/kg/day for the first pup and decreased with every lactational epoch. The liver-blubber distribution of 1,2,3,4,7,8-H6CDD, 1,2,3,6,7,8-H6CDD, PCB81, PCB126, and PCB169 was dependent on the hepatic total TEQ, indicating hepatic sequestration by induced cytochrome P450 (CYP). These results indicate that congener profile in Baikal seals is governed by complex factors including sex, tissue concentration, binding to CYP, and rates of absorption and metabolism/excretion.

Adipose Tissue↗
PubMed2004

Polybrominated diphenyl ethers and organochlorines in archived northern fur seal samples from the Pacific coast of Japan, 1972-1998.

The present study clearly indicated possible prolonged and chronic marine pollution by polybrominated diphenyl ethers (PBDEs) unless the international regulatory measures are reinforced substantially. Fat tissues of female northern fur seals (Callorhinus ursinus), collected at 10 time periods between 1972 and 1998 from the Pacific coast of northern Japan, were analyzed for PBDEs and organochlorine compounds (OCs). PCBs and DDTs were the predominant contaminants in the fur seal samples. PBDEs were detected in all the samples analyzed, the values ranging from 0.33 to 100 ng/g lipid wt. with predominance of BDE-47. The lowest PBDE levels were in the fur seals collected in 1972, with the peak concentration around 1991-1994 and then decreased to about 50% in 1997-1998. Compositions of higher brominated congeners increased since 1972, while some lower brominated congeners decreased, implying a change in the pattern of use, particularly the increased use of highly brominated diphenyl ethers during 1972-1998. In the meantime, PCB compositions in fur seals showed no temporal variation, suggesting a continuous input of PCBs into the marine environment in significant quantities. As peak concentrations of PBDEs occurred later than OCs, it is essential to follow up the patterns of PBDEs pollution that may be of great concern in the future. To our knowledge, this is the first report on the contamination by PBDEs in marine mammals from the Asia-Pacific waters.

Animals↗
PubMed2001

For whales and seals the ocean is not blue: a visual pigment loss in marine mammals.

Most terrestrial mammals have colour vision based on two spectrally different visual pigments located in two types of retinal cone photoreceptors, i.e. they are cone dichromats with long-to-middle-wave-sensitive (commonly green) L-cones and short-wave-sensitive (commonly blue) S-cones. With visual pigment-specific antibodies, we here demonstrate an absence of S-cones in the retinae of all whales and seals studied. The sample includes seven species of toothed whales (Odontoceti) and five species of marine carnivores (eared and earless seals). These marine mammals have only L-cones (cone monochromacy) and hence are essentially colour-blind. For comparison, the study also includes the wolf, ferret and European river otter (Carnivora) as well as the mouflon and pygmy hippopotamus (Artiodactyla), close terrestrial relatives of the seals and whales, respectively. These have a normal complement of S-cones and L-cones. The S-cone loss in marine species from two distant mammalian orders strongly argues for convergent evolution and an adaptive advantage of that trait in the marine visual environment. To us this suggests that the S-cones may have been lost in all whales and seals. However, as the spectral composition of light in clear ocean waters is increasingly blue-shifted with depth, an S-cone loss would seem particularly disadvantageous. We discuss some hypotheses to explain this paradox.

Animals↗
PubMed1999

Where have all the fathers gone? An extensive microsatellite analysis of paternity in the grey seal (Halichoerus grypus).

Microsatellites were used to conduct an extensive analysis of paternity of grey seals from two Scottish breeding colonies at North Rona (n = 1189) and the Isle of May (n = 694), spanning more than a decade. A maximum of 46% of pups at North Rona and 29% of pups at the Isle of May could be allocated a father, even though the majority of candidate males for specific study sites within each colony were believed to have been sampled. Based on the paternities which could be assigned, both colonies showed evidence of reproductive skew, apparently due to the presence of approximately five males who were exceptionally successful. Some males were assigned paternities at least 10 years before, and colleagues 10 years after, being sampled, implying a reproductive lifespan of at least 10 years, and there are indications that the real maximum lies in the range 15-20 years. Male grey seals appear to have at least two breeding strategies they can adopt. On land, some males benefit from a traditionally polygynous system. However, between 50 and 70% of grey seal pups born at a particular colony are not fathered by males who are likely to be sampled by us, implying that these males seldom venture ashore here. We conclude that aquatic mating may play a much larger role in the grey seal than has previously been thought.

Animals↗
PubMed2000

Postsealing genetic variation and population structure of two species of fur seal (Arctocephalus gazella and A. tropicalis).

Commercial sealing in the 18th and 19th centuries had a major impact on the Antarctic and subantarctic fur seal populations (Arctocephalus gazella and A. tropicalis) in the Southern Ocean. The intensive and unrestricted nature of the industry ensured substantial reductions in population sizes and resulted in both species becoming locally extinct at some sites. However, both species are continuing to recover, through the recolonization of islands across their former range and increasing population size. This study investigated the extent and pattern of genetic variation in each species to examine the hypothesis that higher levels of historic sealing in A. gazella have resulted in a greater loss of genetic variability and population structure compared with A. tropicalis. A 316-bp section of the mitochondrial control region was sequenced and revealed nucleotide diversities of 3.2% and 4.8% for A. gazella and A. tropicalis, respectively. There was no geographical distribution of lineages observed within either species, although the respective PhiST values of 0.074 and 0.19 were significantly greater than zero. These data indicate low levels of population structure in A. gazella and relatively high levels in A. tropicalis. Additional samples screened with restriction endonucleases were incorporated, and the distribution of restriction fragment length polymorphism (RFLP) and sequence haplotypes were examined to identify the main source populations of newly recolonized islands. For A. tropicalis, the data suggest that Macquarie Island and Iles Crozet were probably recolonized by females from Marion Island, and to a lesser extent Ile Amsterdam. Although there was less population structure within A. gazella, there were two geographical regions identified: a western region containing the populations of South Georgia and Bouvetoya, which were the probable sources for populations at Marion, the South Shetland and Heard Islands; and an eastern region containing the panmictic populations of Iles Kerguelen and Macquarie Island. The latter region may be a result of a pronounced founder effect, or represent a remnant population that survived sealing at Iles Kerguelen.

Animals↗
PubMed1994

Digestibility of krill (Euphausia superba and Thysanoessa sp.) in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus).

Apparent digestible efficiency (% DE) was studied by use of dietary Mn as an inert marker, in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus) which had been eating krill. Median % DE in minke whales (n5) eating krill of the genus Thysanoessa sp. (energy density (ED) 23.8 kJ/g) was 93 (range 87-93). Median % DE in crabeater seals (n6) eating krill of the species Euphausia superba (ED 20.8 kJ/g) was 84 (range 79-85), which is significantly lower than the % DE of krill in minke whales (P = 0.008). Since the chemical composition in E. superba and in Thysanoessa sp. is similar, it is suggested that the complex multi-stomached system of minke whales, which contains both chitinase (EC 3.2.1.14)-producing as well as several other types of bacteria, is superior to the single-stomached system of crabeater seals with regard to krill digestion. It is worth noting, however, that the % DE of krill in the crabeater seal is still very high.

Animals↗
PubMed2000

PCB-associated alteration of hepatic steroid metabolism in harbor seals (Phoca vitulina).

Hepatic cytochrome P-450 (CYP450) isozymes are involved in xenobiotic detoxification and steroid metabolism. Seals are highly exposed to polychlorinated biphenyls (PCBs) in the environment, resulting in CYP450 induction, which may have concomitant effects on CYP450 steroid metabolism. Experiments were conducted to determine rates of steroid metabolism in harbor seal (Phoca vitulina) liver. CYP450 was induced with increasing liver PCB concentrations between 0.2 and 5.73 microg/g (wet weight). Progesterone metabolism was significantly decreased with increasing liver PCB concentration. Testosterone metabolism was also increased with increasing liver PCB concentration. The results indicate a change in steroid metabolism associated with increasing PCB burden, suggesting that PCBs may have a modulating effect on hepatic steroid biotransformation in environmentally exposed seals. The possible implications of this for endocrine homeostasis in seals are discussed.

Animals↗
PubMed2006

Magnetic resonance imaging and radiographic findings of seal finger.

PURPOSE: To describe the magnetic resonance imaging (MRI) and radiographic findings of five patients with seal finger. MATERIAL AND METHODS: The MR images and radiographs of five patients with seal finger were retrospectively evaluated. MRI was performed on four patients in the subacute phase, and follow-up imaging was done on one of them at 5 months. One patient had MRI only at a later stage 5 years after onset. Radiographs were taken three times in the subacute phase and once at a later stage. One patient had had seal finger in another finger previously. RESULTS: Short-tau inversion-recovery (STIR) sequence showed extensive subcutaneous soft tissue edema in all four patients in the subacute phase and tenosynovitis of the flexion tendons in two cases. Three patients had edema in 2-3 phalanges, and effusion in the distal interphalangeal (DIP) joint was seen in one case. At the later stage, no signal pathology in soft tissues or bones was seen in STIR images. In the subacute phase, radiographs showed digital soft-tissue swelling in three patients, and one patient had a narrowed DIP joint, periarticular osteoporosis, and a periosteal reaction. At the later stage, flexion contracture of the finger was seen. CONCLUSION: In addition to soft-tissue infection, seal finger causes bone marrow edema, tenosynovitis, and effusion in the interphalangeal joints visible as increased signal intensity in STIR images. Radiographs reveal periarticular osteoporosis with loss of cartilage in the subacute phase and flexion contracture at the later stage. MRI (STIR) allows more precise delineation of the inflammatory process compared to radiography.

Adult↗