Contaminants in Atlantic walruses in Svalbard Part 2: Relationships with endocrine and immune systems.

Marine mammals in the Barents Sea region have among the highest levels of contaminants recorded in the Arctic and the Atlantic walrus (Odobenus rosmarus rosmarus) is one of the most contaminated species within this region. We therefore investigated the relationships bewteen blubber concentrations of lipophilic persistent organic pollutants (POPs) and plasma concentrations of perfluoroalkyl substances (PFASs) and markers of endocrine and immune functions in adult male Atlantic walruses (n = 38) from Svalbard, Norway. To do so, we assessed plasma concentrations of five forms of thyroid hormones and transcript levels of genes related to the endocrine and immune systems as endpoints; transcript levels of seven genes in blubber and 23 genes in blood cells were studied. Results indicated that plasma total thyroxine (TT4) concentrations and ratio of TT4 and reverse triiodothyronine decreased with increasing blubber concentrations of lipophilic POPs. Blood cell transcript levels of genes involved in the function of T and B cells (FC like receptors 2 and 5, cytotoxic T-lymphocyte associated protein 4 and protein tyrosine phosphatase non-receptor type 22) were increased with plasma PFAS concentrations. These results suggest that changes in thyroid and immune systems in adult male walruses are linked to current levels of contaminant exposure.

A comparison of blood nitric oxide metabolites and hemoglobin functional properties among diving mammals.

The ability of marine mammals to hunt prey at depth is known to rely on enhanced oxygen stores and on selective distribution of blood flow, but the molecular mechanisms regulating blood flow and oxygen transport remain unresolved. To investigate the molecular mechanisms that may be important in regulating blood flow, we measured concentration of nitrite and S-nitrosothiols (SNO), two metabolites of the vasodilator nitric oxide (NO), in the blood of 5 species of marine mammals differing in their dive duration: bottlenose dolphin, South American sea lion, harbor seal, walrus and beluga whale. We also examined oxygen affinity, sensitivity to 2,3-diphosphoglycerate (DPG) and nitrite reductase activity of the hemoglobin (Hb) to search for possible adaptive variations in these functional properties. We found levels of plasma and red blood cells nitrite similar to those reported for terrestrial mammals, but unusually high concentrations of red blood cell SNO in bottlenose dolphin, walrus and beluga whale, suggesting enhanced SNO-dependent signaling in these species. Purified Hbs showed similar functional properties in terms of oxygen affinity and sensitivity to DPG, indicating that reported large variations in blood oxygen affinity among diving mammals likely derive from phenotypic variations in red blood cell DPG levels. The nitrite reductase activities of the Hbs were overall slightly higher than that of human Hb, with the Hb of beluga whale, capable of longest dives, having the highest activity. Taken together, these results underscore adaptive variations in circulatory NO metabolism in diving mammals but not in the oxygenation properties of the Hb.

Use of human chorionic gonadotropin in a male Pacific walrus (Odobenus rosmarus divergens) to induce rut and achieve a pregnancy in a nulliparous female.

Walrus in US zoos have a very low reproductive rate of 11 births in 80 years, and little is known about Pacific walrus (Odobenus rosmarus divergens) reproductive biology. To address this, we initiated a program in which detailed biological data were recorded on captive walrus. As part of a 7-year study, 1 male and 1 female 16-year-old captive Pacific walrus were carefully monitored with weekly serum hormone analysis, daily glans penis smears for spermatozoa, and abdominal ultrasound for pregnancy. The female ovulated once annually from late December through mid-January and then exhibited 9 months of sustained elevated progesterone. This nonconceptive estrous cycle profile is consistent with reports from wild walrus females. In contrast, the male's seasonal rut routinely occurred in late February through May with a serum testosterone peak in March. This profile differed from the reported adult male cycle in wild walrus of November through March. During the period of the female's ovulation, the male had nadir testosterone levels and was consistently azoospermic. Likewise, during the male's spermatogenic rut in the spring, the female was anovulatory with elevated progesterone. On this basis, the male was treated for 14 weeks with human chorionic gonadotropin (hCG) in an attempt to increase testosterone levels in synchrony with the female's annual ovulation. The treatment successfully induced rut characterized by sustained elevated serum testosterone levels and production of spermatozoa. The male and female successfully bred, and the female became pregnant. Upon discontinuation of hCG treatment, the male resumed baseline testosterone levels. We theorize that the lack of synchronization of rut and ovulatory cycles is a primary reason for reproductive failure in these captive walrus.

Temporal association of serum progesterone concentrations and vaginal cytology in walruses (Odobenus rosmarus).

Concentrations of serum estradiol-17ß and progesterone were monitored in six female walruses using an enzyme immunoassay. Progesterone concentrations increased from March to May in females aged 6 y or older, and subsequently declined (October). No significant elevation of estradiol-17ß concentration was detected before an elevation of progesterone concentration. Vaginal smears from four females were examined with Papanicolaou staining. In all females, most epithelial cells were basophilic intermediate-superficial cells; no color change from basophilic to eosinophilic of the cells was detected. Meanwhile, the percentage of anucleate cells in vaginal smears reached its highest value before the elevation of progesterone concentration, followed by an increase in the percentage of leukocytes. We inferred that the change in populations of anucleate cells and leukocytes in vaginal smears reflected ovarian status and CL formation in female walruses.

Serum chemistry reference values in free-ranging north Atlantic male walruses (Odobenus rosmarus rosmarus) from the Svalbard archipelago.

BACKGROUND: Information regarding health and disease is limited for walruses, a keystone species in arctic marine ecosystems. Serum chemistry analysis is a useful clinical tool for the health assessment of walruses, but only a few captive Pacific walruses have been evaluated. OBJECTIVES: The aim of this study was to determine serum chemistry reference values for free-ranging male Atlantic walruses (Odobenus rosmarus rosmarus) on Svalbard and to assess potential differences in animals with low and high tissue levels of organic pollutants. METHODS: Blood samples were collected from 17 wild, adult, male Atlantic walruses chemically immobilized with etorphine at eastern Svalbard (Norway). Serum was obtained for routine biochemical analysis as well as nonesterified free fatty acids (NEFA) and cortisol tests. Serum protein concentration was also measured by agarose gel electrophoresis. RESULTS: Reference values (ranges) included alanine aminotransferase (12-51 U/L), aspartate aminotransferase (54-137 U/L), alkaline phosphatase (42-243 U/L), creatine kinase (32-506 U/L), lactate dehydrogenase (480-1322 U/L), amylase (0-23 U/L), lipase (68-298 U/L), total protein (68-91 g/L), albumin (25.3-34.8 g/L), creatinine (84-137 mumol/L), urea (8.2-19.9 mmol/L), bilirubin (0-4 mumol/L), cholesterol (4.4-7.3 mmol/L), NEFA (0.1-0.4 mmol/L), triglycerides (0.6-2.2 mmol/L), calcium (2.0-2.7 mmol/L), phosphorus (1.7-2.8 mmol/L), sodium (147-162 mmol/L), potassium (4.7-7.4 mmol/L), chloride (102-115 mmol/L), and cortisol (<28-214 nmol/L). Walruses exposed to high levels of organic pollutants (n=6) had significantly lower (P=.022) phosphorus concentration than those with low levels of pollutants (n=6). CONCLUSIONS: The clinical chemistry reference values determined in this study can serve as baseline data for future health-related studies of walruses in a changing Arctic and may also be helpful for health evaluations of walruses in captivity. Impacts of the exposure of marine mammals to organic pollutants should be further investigated.

Viral and bacterial serology of free-ranging Pacific walrus.

Serum or heparinized plasma samples were obtained between 1994 and 1996 from 20 male and 20 female adult free-ranging Pacific walrus (Odobenus rosmarus divergens) from St. Lawrence Island and Round Island, Alaska. Samples were screened for antibodies to some potentially pathogenic bacteria and viruses. No sample had detectable antibody to Brucella spp. Three of 40 (8%) had low antibody titers to Leptospira interrogans serovars. Phocine distemper virus antibodies were not detected. Serologic responses to one or more caliciviruses (San Miguel sea lion virus 12 or vesicular exanthema of swine serotypes E54, F55, G55, 1934B) were detected in 18% (seven of 40) walrus. Antibodies to one or more subtypes of influenza A virus (H10, N2, N3, N5, N6, N7) were detected in 21% (eight of 38). Periodic screening of free-ranging populations for exposure to infectious diseases has become an important component of bio-monitoring programs to facilitate understanding and detecting trends in marine mammal populations.

Carnivora: the primary structure of the Pacific Walrus (Odobenus rosmarus divergens, Pinnipedia) hemoglobin.

The primary structure of the alpha- and beta-chains of the hemoglobin from the Pacific Walrus (Odobenus rosmarus divergens, Pinnipedia) is presented. Sequence analysis revealed only one hemoglobin component whereas two bands were found in polyacrylamide gel electrophoresis. The globin chains were separated by high-performance liquid chromatography and the sequences determined by automatic liquid- and gas-phase sequencing of the chains and their tryptic peptides. The alpha-chains show 20 and the beta-chains 12 exchanges compared to the corresponding human chains. In the alpha-chains one heme- and two alpha 1/beta 1-contacts were exchanged whereas in the beta-chains one alpha 1/beta 1-, one alpha 1/beta 2-and one heme-contact are substituted. Compared to Harbour Seal (Phoca vitulina) the Walrus hemoglobin shows 9 amino-acid replacements in the alpha-chains and 5 in the beta-chains. The relation between Pinnipedia and Arctoidea is discussed.