Antarctic Seal Species Research Articles

Records of three vagrant Antarctic seal species (Family Phocidae) from New Zealand: crabeater seal (Lobodon carcinophaga), Weddell seal (Leptonychotes weddellii) and Ross seal (Ommatophoca rossii)

Records of three vagrant Antarctic seal species from New Zealand are summarised. Crabeater seals (Lobodon carcinophaga) occurred on eight occasions between 1885 and 2015, and Weddell seals (Leptonychotes weddellii) on five occasions between 1926 and 2007. There was a single record of a Ross seal (Ommatophoca rossii), from Paekakariki in 2002. The majority of occurrences for all three species were from the southern North Island, particularly Wellington, where five of the crabeater seals either swam up the Hutt River or were on the adjacent Petone Beach. There are no known verifiable records from any of New Zealand's subantarctic islands. Specimens of nine animals (six crabeater seals and three Weddell seals) are held by New Zealand museums.

Limited use of sea ice by the Ross seal (Ommatophoca rossii), in Amundsen Sea, Antarctica, using telemetry and remote sensing data

To understand the use and importance of the Antarctic sea ice to the Ross seal (Ommatophoca rossii), four adult females were tagged with Argos satellite transmitters in the Amundsen Sea, Antarctica. The Ross seal is the least studied of the Antarctic seal species and nothing was previously known about their behaviour in the Amundsen Sea. During almost 1 year, their movements, haul out behaviour and time spent at different temperatures were logged. By comparing their movements with daily ice maps, distances to the ice edge were calculated, and seals dependence on sea ice for resting, breeding and moulting was analysed. The tagged seals spent on average 70.8 % (range 66.8–77.8 %) of their time in the water and hauled out mainly during the moult in December–January, and in late October–mid-November during breeding. During the pelagic period, they were on average 837.5 km (range 587–1,282 km) from the ice edge indicating a fully pelagic life during several months. Their pelagic behaviour suggests that Ross seals, although being an ice obligate species, may adapt comparatively easy to climate change involving ice melting and recession and thereby potentially being less sensitive to the reduction of sea ice than other Antarctic seal species. Although nothing is known about their mating behaviour, they appear to be relatively stationary during moulting and breeding, hence requiring a small ice surface. Although previous studies in other parts of Antarctica have found similar results, still many questions remain about this peculiar species.

SERUM CHEMISTRY AND ANTIBODIES AGAINST PATHOGENS IN ANTARCTIC FUR SEALS, WEDDELL SEALS, CRABEATER SEALS, AND ROSS SEALS

Information on health parameters, such as antibody prevalences and serum chemistry that can reveal exposure to pathogens, disease, and abnormal physiologic conditions, is scarce for Antarctic seal species. Serum samples from Antarctic fur seals (Arctocephalus gazella, n=88) from Bouvetøya (2000-2001 and 2001-2002), and from Weddell seals (Leptonychotes weddellii, n=20), Ross seals (Ommatophoca rossii, n=20), and crabeater seals (Lobodon carcinophagus, n=9) from the pack-ice off Queen Maud Land, Antarctica (2001) were analyzed for enzyme activity, and concentrations of protein, metabolites, minerals, and cortisol. Adult Antarctic fur seal males had elevated levels of total protein (range 64-99 g/l) compared to adult females and pups (range 52-79 g/l). Antarctic fur seals had higher enzyme activities of creatine kinase, lactate dehydrogenase, and amylase, compared to Weddell, Ross, and crabeater seals. Antibodies against Brucella spp. were detected in Weddell seals (37%), Ross seals (5%), and crabeater seals (11%), but not in Antarctic fur seals. Antibodies against phocine herpesvirus 1 were detected in all species examined (Antarctic fur seals, 58%; Weddell seals, 100%; Ross seals, 15%; and crabeater seals, 44%). No antibodies against Trichinella spp., Toxoplasma, or phocine distemper virus (PDV) were detected (Antarctic fur seals were not tested for PDV antibodies). Antarctic seals are challenged by reduced sea ice and increasing temperatures due to climate change, and increased anthropogenic activity can introduce new pathogens to these vulnerable ecosystems and represent a threat for these animals. Our data provide a baseline for future monitoring of health parameters of these Antarctic seal species, for tracking the impact of environmental, climatic, and anthropogenic changes in Antarctica over time.

Genetically effective population sizes of Antarctic seals estimated from nuclear genes

We analyzed eight nuclear microsatellite loci in three species of Antarctic seals; Weddell seal (Leptonychotes weddellii; mean N = 163), crabeater seal (Lobodon carcinophaga; 138) and Ross seal (Ommatophoca rossii; 35). We estimated genetic diversity (Θ) and effective population size (N E) for each species. Autosomal microsatellite based N E estimates were 151,200 for Weddell seals, 880,200 for crabeater seals, and 254,500 for Ross seals. We screened one X-linked microsatellite (Lw18), which yielded similar N E estimates to the autosomal loci for all species except the Ross seals, where it was considerably larger (~103 times). Microsatellite N E estimates were comparable with previously published N E estimates from mitochondrial DNA, but both are substantially lower than direct estimates of population size in all species except the Ross seals. The ratio of maternally versus biparentally derived estimates of N E for Ross seals was not consistent with the hypothesis that they are a polygynous species. We found no sign of a recent, sustained genetic bottleneck in any of the species.

Major histocompatibility complex class II DOA sequences from three Antarctic seal species verify stabilizing selection on the DO locus.

To provide additional support for the sequence conservation and hence the regulatory role of the MHC class II DOA locus, we obtained the nucleotide sequences of exon 2 and exon 3, along with the intervening intron, of the Ross seal, and sequences from the exon 2 region from the Weddell and leopard seals. These are the first reports of the sequences of this locus from a carnivore species. The results demonstrate strong conservation among mammals for the exon sequence and produce a gene genealogy that is consistent in topology with a species tree.

Dinucleotide microsatellite markers from the Antarctic seals and their use in other Pinnipeds

AbstractTwenty‐four microsatellite loci were isolated from three species of Antarctic seals (Subfamily Monachinae, Tribe Lobodontini). Eleven loci were cloned from Weddell seal, Leptonychotes weddellii, seven from leopard seal, Hydrurga leptonyx, and six from crabeater seal, Lobodon carcinophagus. Variability was assessed in Weddell seals collected in McMurdo Sound, leopard seals from Bird Island, South Georgia, and crabeater seals sampled in the eastern Ross Sea. All loci were variable in the three species used for cloning and 22 of these loci amplified variable products in the Ross seal, Ommatophoca rossii. Cross‐species amplification was largely successful, with an average of 19 loci amplifying products in other phocids.

Congener specific determination of compounds of technical toxaphene (CTTs) in different antarctic seal species

Gas chromatography and electron-capture, negative-ionization, mass spectrometry (GC-ECNI-MS) in combination with a non-polar stationary phase (CP-Sil 2) was applied to study the composition of residues of the multicomponent toxaphene mixture in seal blubber from the Antarctic. In samples of the five Antarctic seal species eleven compounds of technical toxaphene (CTTs) were detected and six of them quantified by application of single standard compounds. Five abundant CTTs in seal blubber were included in the “Parlar 22 components standard” (commercially available) and one further was isolated and quantified for the first time. Finally, high levels of toxaphene were determined in Weddell seals and crabeaters confirming that toxaphene is a major organochlorine pollutant in the Antarctic.

Antibodies against european phocine herpesvirus isolates detected in sera of Antarctic seals

Neutralizing antibodies against European phocine herpesvirus were detected in sera of to two Antarctic seal species, Weddell seals (Leptonychotes weddellii) and crabeater seals (Lobodon carcinophagus), collected in the eastern Weddell Sea. A large number of positive sera crossneutralized canine herpesvirus, but only few sera also contained antibodies to feline herpesvirus. The Weddell seals suffered from a respiratory disease when the sera were collected (January–February, 1990). The significance and possible origin of herpesvirus infections in Antarctic seals documented for the first time in this communication is discussed. All sera were negative for antibodies against phocine and canine distemper viruses.

Histological, histochemical, and fine structural observations on the spleen of seals.

Spleens of three species of Antarctic seals with different diving habits (Weddell seal, crabeater seal, and fur seal) have been studied with histological, histochemical, and electron microscopic methods. The spleens can be classified as nonsinusoidal, with capsule and trabeculae rich in innervated smooth muscle cells. The trabecular system is particularly well developed in the deep- and long-diving Weddell seal. As in other mammals the pulp can be divided into white and red pulp. In the white pulp, periarteriolar lymphatic sheaths and secondary lymphatic nodules occur; both are surrounded by a marginal zone rich in macrophages and eosinophils. The nodules can be observed frequently, which is in accordance with abundance of plasma cells in the red pulp. Well-developed white pulp and numerous plasma cells and eosinophils obviously reflect a high load of nematodes, which have mainly been found in lung and stomach. Additionally, in the red pulp morphological evidence for the following functions has been found: destruction of erythrocytes, erythropoiesis, and thrombopoiesis. In respect to blood flow through the red pulp, we interpret our observations in the following way: terminal branches of arterioles open into the space between the fibroblastic reticulum cells; blood draining from here is collected into pulp veins, which are mainly found near the trabeculae. Thus, the seals have an open vascular compartment in their spleens, as also occurs in the cat. The red pulp is innervated by numerous nerve fibers that seem to include both cholinergic and adrenergic ones. The target cells of these fibers seem to be the fibroblastic reticulum cells, whose state of contraction may influence the direction of blood flow through the red pulp.

Seal population dynamics and ecology

Abstract This paper examines the effect of ecological factors on life history events and population dynamics of the Antarctic seal species. Data for the crabeater (Lobodon carcinophagus) and Weddell (Leptonychotes weddelli) seals allow considerable insight into the most significant influences on population growth patterns. For the Weddell, it is suggested that random environmental events seem to play a significant role and influence different demographic parameters. When these are correlated with influences by man, caution is desirable, as the overall influence on the population may be considerable. For the crabeater, while the data are rather meagre, the role ofleopard seal (Hydrurga leptonyx) predation on young of the year appears significant. Additional data on leopard seal contact are needed. In general, the structural differences between the pack ice and the fast ice environments and the influence of predators seem to be the most important factors influencing both the life history patterns and the seasonal events which play a significant role in the population dynamics of the Antarctic seal species.

Subsurface Crypts, Oogenesis, and the Corpus Luteum in the Ovaries of Seals

EXAMINATION of a series of the reproductive organs from three species of antarctic seals, collected by the members of the Falkland Islands Dependencies Survey, has brought to light several interesting phenomena in the ovaries of the Weddell seal (Leptonychotes weddelli), the crab-eater seal (Lobodon carcinophagus) and the leopard seal (Hydrurga leptonyx).