Wild Seal Research Articles

Comparative Microbial Community Analysis of Fur Seals and Aquaculture Salmon Gut Microbiomes in Tasmania

In Tasmania, Australian fur seals (Arctocephalus pusillus doriferus) regularly interact with Atlantic salmon (Salmo salmar L.) aquaculture lease operations and opportunistically consume fish. The microbial communities of seals and aquaculture salmon were analyzed for potential indicators of microbial sharing and to determine the potential effects of interactions on wild seal microbiome composition. The high-throughput sequencing of the V1–V3 region of the 16S rRNA genes from the gut microbial communities of 221 fur seals was performed: 41 males caught at farms, 50 adult scats from haul-outs near farms, 24 necropsied seals, and controls from Bass Strait breeding colonies, encompassing 56 adult scats and 50 pup swabs. QIIME2 and R Studio were used for analysis. Foraging at or near salmon farms significantly shifted seal microbiome biodiversity. Taxonomic analysis showed a greater divergence in Bacteroidota representatives in male seals captured at farms compared to all other groups. Pathogens were identified that could be monitoring targets. Potential indicator amplicon sequence variants were found across a variety of taxa and could be used as minimally invasive indicators for interactions at this interface. The diversity and taxonomic shifts in the microbial communities of seals indicate a need to further study this interface for broader ecological implications.

Comparative iTRAQ-based quantitative proteomic analysis of spotted seal (Phoca largha) pups inhabiting different environments

Captive breeding is among the most effective approaches for ensuring the conservation of numerous endangered species. However, only a few studies have examined the effects of captive maintenance of animals at the molecular level. In this study, we adopted the isobaric tags for relative and absolute quantification (iTRAQ) approach to compare protein expression in the blood of endangered spotted seal pups (Phoca largha) inhabiting different environments. We identified 519 proteins from 2,628 peptides, the expression of 158 of which differed significantly between short-term captive and wild seals. In addition, 140 proteins were identified as being differentially expressed between short-term and long-term captive seals, whereas 235 proteins were differentially expressed between the wild and long-term captive groups (p < 0.05). In wild seal pups, proteins associated with the maintenance of cardiomyocyte cell stability and integrity, protection of the heart, and prevention of anemia were upregulated, reflecting the high stress and energetic costs associated with movement and foraging. In addition, significant differences were detected among the three groups with respect to immune-related proteins. The results of this study advance our current understanding of protein expression in spotted seals and provide data that will contribute to the future conservation of this species.

Differences in the Activities of Serum Antioxidant and Immune Factors between Wild and Captive Spotted Seal (Phoca largha) Pups from the Liaodong Bay Colony

The innate immune system plays a vital role to resist the environmental stresses and infectious pathogens in marine mammal pups. To get a baseline level of innate immune capacity in spotted seals, the concentrations of several antioxidant and immune-related factors in the serum of wild and captive spotted seal (Phoca largha) pups from the Liaodong Bay colony were measured and compared. Cu/Zn superoxide dismutase and peroxidase were mainly responsible for the antioxidant system of spotted seal pups, and wild pups possessed stronger antioxidant capacity than captive ones. Against infectious pathogens, wild spotted seal pups also had an advantage over the captive counterparts. Specifically, the activities of acid phosphatase, phenoloxidase, and lysozyme in the serum of wild spotted seal pups were significantly higher than those in captive animals. The present study provides the normal activities of several serum immune enzymes for wild and captive spotted seal pups from the Liaodong Bay colony, which is benefit to the conservation of this species.

Interannual differences in postrelease movements of rehabilitated harbor seal pups (Phoca vitulina richardii) in the Salish Sea

AbstractDespite the large number of harbor seals (Phoca vitulina richardii) rehabilitated worldwide, few studies have been conducted on postrelease movement and behavior of rehabilitated harbor seal pups. We compared interannual differences in movements and survival of 24 rehabilitated seal pups released in the Salish Sea in 2010 (n = 10), 2012 (n = 5), 2013 (n = 5), and 2014 (n = 4). We also compared the postrelease movement of these seals to the movement of 10 wild seal pups tracked in the same ecosystem in 2010. Transmission duration, total cumulative distance, and average daily distance varied annually. Maximum linear distance traveled from the release site was similar for the rehabilitated seal groups. Compared to wild seals (n = 10), and consistent with prior studies, rehabilitated pups (n = 24) traveled significantly farther daily and cumulatively than wild weaned pups. Unlike in a prior study in this ecosystem, we found no significant difference between transmission duration in wild and rehabilitated pups.

Blood plasma chemistry in White Sea bearded seals across different age groups

Blood chemistry values are reported for the bearded seal species (Erignathus barbatus barbatus Erxleben, 1777) from the White Sea. 27 blood plasma indices are used to describe the state of the metabolism of proteins, carbohydrates, lipids, minerals (total protein, albumin, α-, β-, γ-globulins, urea, creatinine, uric acid, glucose, lactic acid, total lipids, triglycerides, cholesterol, calcium, phosphorus, sodium, potassium, magnesium, iron, copper, chlorides, aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transferase, creatine kinase, alkaline phosphatase, lactate dehydrogenase) in 3-, 5- and 10-year-old seals. The values of the studied parameters are similar to published data for bearded seal populations in other Arctic regions, as well as being in close agreement with indicators of other pinniped species of the same age. The plasma content of total protein, albumin, α-, β-, γ-globulins, urea, uric acid, total lipids, calcium, magnesium, sodium, and chlorides is invariable in animals of the studied ages. In common with other pinnipeds and land-based mammals, age-related changes in metabolic rates in the studied animal groups are most pronounced in the activity level of key metabolism enzymes. While aspartate aminotransferase, alanine aminotransferase and γ-glutamyl transferase activity is higher in adult seals than in immature animals, alkaline phosphatase, creatine kinase and lactate dehydrogenase activity is lower. Changes in biochemical parameters of bearded seal blood at the ages of 3, 5 and 10 years indicate a catabolic orientation in metabolism at all studied development stages. Although more research is needed to investigate the biological significance of a number of blood indices, the data presented in this study provide initial baseline blood chemistry parameters for use in assessing the condition of individual seals, as well as informing monitoring and management efforts for wild seal populations.

“Nose-metrics” of wild southern elephant seal (Mirounga leonina) males using image analysis and geometric morphometrics

“Nose-metrics” of wild southern elephant seal (<i>Mirounga leonina</i>) males using image analysis and geometric morphometrics

Positive social behaviours are induced and retained after oxytocin manipulations mimicking endogenous concentrations in a wild mammal.

The neuropeptide hormone oxytocin modulates numerous social and parental behaviours across a wide range of species, including humans. We conducted manipulation experiments on wild grey seals (Halichoerus grypus) to determine whether oxytocin increases proximity-seeking behaviour, which has previously been correlated with endogenous oxytocin concentrations in wild seal populations. Pairs of seals that had never met previously were given intravenous injections of 0.41 µg kg−1 oxytocin or saline and were observed for 1 h post-manipulation. The dose was designed to mimic endogenous oxytocin concentrations during the observation period, and is one of the lowest doses used to manipulate behaviour to date. Seals given oxytocin spent significantly more time in close proximity to each other, confirming that oxytocin causes conspecifics to seek others out and remain close to one another. Aggressive and investigative behaviours also significantly fell after oxytocin manipulations. Despite using a minimal oxytocin dose, pro-social behavioural changes unexpectedly persisted for 2 days despite rapid dose clearance from circulation post-injection. This study verifies that oxytocin promotes individuals staying together, demonstrating how the hormone can form positive feedback loops of oxytocin release following conspecific stimuli, increased motivation to remain in close proximity and additional oxytocin release from stimuli received while in close proximity.

English

The aims of this study were to identify bacteriocinogenic activity in 13 enterococci isolated from fecal samples of wild South American (Arctocephalus australis) and Subantarctic fur seals (Arctocephalus tropicalis); to determine the physicochemical characteristics and antimicrobial spectrum of antimicrobial compounds against Gram-positive and Gram-negative bacteria; and to evaluate the presence of bacteriocin structural genes by PCR. Out of 13 enterococci screened for antimicrobial activity, five enterococci showed activity against Listeria monocytogenes ATCC 35152, an important pathogen linked to food. Of these, only the E. mundtii strain J5 maintained the activity after the pH was adjusted (pH 6.5). The activity of antimicrobial compounds from the E. mundtii strain J5 (ACs-J5) was lost after proteolytic enzyme treatment; however, the activity was maintained after heat, pH (acidic and basic conditions) and chemical treatment. ACs-J5 showed narrow spectrum activity. Only the mundticin KS gene was detected in the J5 strain and no plasmid was present. In conclusion, the properties presented by ACs-J5 make it a valuable biopreservative in food industries in avoiding pathogenic microorganisms such as L. monocytogenes and it should be a good candidate for probiotic application. Key words: Antimicrobial compounds, Enterococcus mundtii, wild fur seal, antilisterial activity.

Rapid postnatal development of myoglobin from large liver iron stores in hooded seals

Hooded seals (Cystophora cristata) rely on large stores of oxygen, either bound to hemoglobin or myoglobin (Mb), to support prolonged diving activity. Pups are born with fully developed hemoglobin stores, but their Mb levels are only 25-30% of adult levels. We measured changes in muscle [Mb] from birth to 1 year of age in two groups of captive hooded seal pups, one being maintained in a seawater pool and one on land during the first 2 months. All pups fasted during the first month, but were fed from then on. The [Mb] of the swimming muscle musculus longissimus dorsi (LD) doubled during the month of fasting in the pool group. These animals had significantly higher levels and a more rapid rise in LD [Mb] than those kept on land. The [Mb] of the shoulder muscle, m. supraspinatus, which is less active in both swimming and hauled-out animals, was consistently lower than in the LD and did not differ between groups. This suggests that a major part of the postnatal rise in LD [Mb] is triggered by (swimming) activity, and this coincides with the previously reported rapid early development of diving capacity in wild hooded seal pups. Liver iron concentration, as determined from another 25 hooded seals of various ages, was almost 10 times higher in young pups (1-34 days) than in yearling animals and adults, and liver iron content of pups dropped during the first month, implying that liver iron stores support the rapid initial rise in [Mb].

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.

Genetic characterization of mycobacteria from South American wild seals

Tuberculosis has been recently diagnosed in four wild seals found stranded in the Atlantic coast of Argentina. By bacteriological studies and IS6110 hybridization, these isolates were characterized as belonging to the Mycobacterium tuberculosis complex. A genetic characterization using RFLP (Restriction fragment length polymorphism) and a species-specific probe of M. tuberculosis, called mtp40, showed hybridization with this probe on a single band. A similar band was also found in M. tuberculosis H37Rv. This showed a relationship between M. tuberculosis and the wild seal isolates. However these would also seem to belong to a different genetic group in the M. tuberculosis complex, since they do not grow on glycerol-egg containing medium (Lowenstein-Jensen) as typical M. tuberculosis strains usually do. Repeated sequences pMBA2, pTNB12, DR and IS6110 were used as probes to evaluate the epidemiological relationships between the 4 cases of tuberculosis. A low degree of polymorphism was observed, that suggested that these isolates were epidemiologically related.

Structure of phenolic metabolites of p,p'-DDE in rat, wild seal and guillemot.

WE recently described the isolation and characterisation of metabolites of polychlorinated biphenyls from field-collected samples, that is faeces from guillemots and seals1. In addition to the PCB metabolites—hydroxychlorobiphenyls—we unexpectedly found two compounds which after treatment with diazomethane gave mass spectra consistent with p,p′-DDE (1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene) containing a methoxy group (M=346 a.m.u.). To verify these observations rats were given p,p′-DDE (about 20 mg per animal dissolved in peanut oil) and the faeces investigated for the presence of phenolic metabolites as described previously1. This report deals with the structure of three phenolic metabolites—compounds Ia–IIIa (Fig. 1)—of p,p′-DDE excreted by the rat.