HISTOLOGIC LESIONS IN PLACENTAS OF NORTHERN FUR SEALS (CALLORHINUS URSINUS) FROM A POPULATION WITH HIGH PLACENTAL PREVALENCE OF COXIELLA BURNETII

Coxiella burnetii is an intracellular bacterial pathogen that can be associated with significant reproductive disease or acute mortality in livestock and wildlife. A novel marine mammal-associated strain of C. burnetii has been identified in pinnipeds of the northwestern Pacific Ocean. Little is known about C. burnetii infection in regard to reproductive success or population status. Our objective was to characterize the severity and extent of histologic lesions in 117 opportunistically collected placentas from presumed-normal northern fur seals (Callorhinus ursinus) in July 2011 on St. Paul Island, Alaska, US, where a high placental prevalence of C. burnetii had been reported. Sections were examined by histology and immunohistochemistry and impression smears with modified acid-fast stain. The nature and frequency of histologic changes were compared with target COM1 PCR-confirmed C. burnetii positive and negative placentas. Overall, histologic changes were similar to placental lesions described in aborting ruminants; however, changes were variable within and between placentas. Vasculitis and occasional intracellular bacteria were seen only in C. burnetii PCR-positive placentas. Dystrophic mineralization, edema, and inflammation were seen in PCR-positive and negative placentas, although they were statistically more common in PCR-positive placentas. Results suggest that C. burnetti and associated pathologic changes are multifocal and variable in placentas from these presumably live-born pups. Therefore, multiple sections of tissue from different placental areas should be examined microscopically, and screened by PCR, to ensure accurate diagnosis as the genomes per gram of placenta may not necessarily represent the severity of placental disease. These limitations should inform field biologists, diagnosticians, and pathologists how best to screen and sample for pathogens and histopathology in marine mammal placental samples.

Longitudinal study of northern fur seal (Callorhinus ursinus) hematology

Although the causes have not been specified yet, wild populations of northern fur seals (Callorhinus ursinus) have been decreasing, which is why conservation techniques such as captive breeding and health maintenance should be established. Hematological parameters can be used to maintain the health status of northern fur seals kept in captivity for artificial reproduction and public education. Year-round fluctuations of blood parameters have not been examined for northern fur seals due to the difficulties in obtaining serial blood samples from wild animals during the oceanic migration period from late autumn to spring. In this study, blood samples were collected from four captive northern fur seals and analyzed monthly for more than three years to clarify the seasonal fluctuation patterns in 14 hematological parameters. Many hematological parameters seemed to be seasonal patterns: summer–autumn and winter–spring; leukocyte-related parameters were higher in summer and autumn than in winter and spring; erythrocyte-related parameters were lower in summer and autumn than in winter and spring. Significant seasonal differences in nine of the 14 parameters were observed using a generalized linear mixed model (GLMM) analysis. These results have improved our understanding of the seasonal patterns of hematological characteristics in the northern fur seal and can contribute to the health care of protected or captive northern fur seals.

Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis

Information about the reproductive status of free-ranging pinnipeds provides useful insight into their population dynamics, which is essential to their management and conservation. To determine the reproductive status of individual animals, blood sampling is often required despite being impractical to collect in open water. Hair as an endocrine marker has been used to less invasively assess the reproductive status of terrestrial animals. However, it is unknown whether pinniped reproductive status can be assessed from hair samples. Here, we examine testosterone levels in hair obtained from 57 male northern fur seals and used it to compare their age class and spermatogenesis during the non-breeding season off Hokkaido. We isolated testosterone from the samples using gas chromatography and measured testosterone levels using time-resolved fluoroimmunoassay. Testosterone levels in hair increased towards the breeding season. In May, testosterone levels were the highest in seals aged between 4 and 7 years, followed by those over the age of 8 years and under the age of 4 years. Spermatids, the final phase of spermatogenesis, were present in the seals sampled between April and June, even though testosterone levels were low in April. The seals with spermatids in May showed the highest testosterone levels. Our results demonstrate that seals with higher testosterone levels in May are likely to be mature males (≥4 years). Since hair can be collected using biopsy darts in the field, it will be possible to less invasively determine testosterone levels of male seals in the future.

Factors affecting energy expenditure in a declining fur seal population

Quantifying metabolic rates and the factors that influence them is key to wildlife conservation efforts because anthropogenic activities and habitat alteration can disrupt energy balance, which is critical for reproduction and survival. We investigated the effect of diving behaviour, diet and season on field metabolic rates (FMR) and foraging success of lactating northern fur seals (Callorhinus ursinus) from the Pribilof Islands during a period of population decline. Variation in at-sea FMR was in part explained by season and trip duration, with values that ranged from 5.18 to 9.68 W kg^-1 (n = 48). Fur seals experienced a 7.2% increase in at-sea FMR from summer to fall and a 1.9% decrease in at-sea FMR for each additional day spent at sea. There was no effect of foraging effort, dive depth or diet on at-sea FMR. Mass gains increased with trip duration and were greater in the fall compared with summer, but were unrelated to at-sea FMR, diving behaviour and diet. Seasonal increases in at-sea FMR may have been due to costs associated with the annual molt but did not appear to adversely impact the ability of females to gain mass on foraging trips. The overall high metabolic rates in conjunction with the lack of any diet-related effects on at-sea FMR suggests that northern fur seals may have reached a metabolic ceiling early in the population decline. This provides indirect evidence that food limitation may be contributing to the low pup growth rates observed in the Pribilof Islands, as a high metabolic overhead likely results in less available energy for lactation. The limited ability of female fur seals to cope with changes in prey availability through physiological mechanisms is particularly concerning given the recent and unprecedented environmental changes in the Bering Sea that are predicted to have ecosystem-level impacts.

Complete mitochondrial genome and phylogenetic analysis of Callorhinus ursinus: an endangered species from South Korea

We present the complete mitochondrial genome and a phylogenetic analysis of Callorhinus ursinus, the northern fur seal, determined using Illumina next-generation sequencing (NGS) technology. The total length of the mitogenome was 17,154 bp, which consisted of 13 protein-coding genes, two ribosomal RNA genes, 22 tRNA genes, and one control region. The base composition of the entire mitogenome was 33.5% (A), 26.3% (C), 13.9% (G), and 26.3% (T) with an A + T bias of 59.8%. The control region contained two types of tandem repeats. A neighbour-joining (NJ) tree was constructed and comprised two clades with C. ursinus forming a monophyletic group. Data produced in this study will aid exploration of the genetic diversity of endangered C. ursinus and contribute to molecular identification of this species.

Normal hematology and serum chemistry of northern fur seals (Callorhinus ursinus) in captivity

Northern fur seals (Callorhinus ursinus) are endemic to the North Pacific Ocean. They were hunted for their fur and became endangered in the late 1800s, but their populations recovered following the introduction of protection laws. Recently, populations have been decreasing again, although the reasons are unclear. For individuals that are bred and reared in captivity as part of ex situ conservation projects, details of blood characteristics are essential to ensure good health. However, the normal ranges of hematology and serum chemistry of captive northern fur seals have not been defined. This study determined the normal ranges of hematology and serum chemistry of captive fur seals. Blood samples were collected every month for 2 years from four captive northern fur seals in Japan (three born in an aquarium and one kept in the same aquarium following rescue). Fifteen blood characteristics and 29 serum chemistry properties were compared with those previously reported for wild northern fur seals in the USA. Several parameters were not within the normal ranges reported previously in wild northern fur seals. In particular, levels of alkaline phosphatase was outside of the normal ranges previously reported. The hematological and serum chemistry ranges in this study can help provide a guideline for understanding the health of northern fur seals in captivity.

Activity-specific metabolic rates for diving, transiting, and resting at sea can be estimated from time-activity budgets in free-ranging marine mammals

Time and energy are the two most important currencies in animal bioenergetics. How much time animals spend engaged in different activities with specific energetic costs ultimately defines their likelihood of surviving and successfully reproducing. However, it is extremely difficult to determine the energetic costs of independent activities for free-ranging animals. In this study, we developed a new method to calculate activity-specific metabolic rates, and applied it to female fur seals. We attached biologgers (that recorded GPS locations, depth profiles, and triaxial acceleration) to 12 northern (Callorhinus ursinus) and 13 Antarctic fur seals (Arctocephalus gazella), and used a hierarchical decision tree algorithm to determine time allocation between diving, transiting, resting, and performing slow movements at the surface (grooming, etc.). We concomitantly measured the total energy expenditure using the doubly-labelled water method. We used a general least-square model to establish the relationship between time-activity budgets and the total energy spent by each individual during their foraging trip to predict activity-specific metabolic rates. Results show that both species allocated similar time to diving (~29%), transiting to and from their foraging grounds (~26-30%), and resting (~8-11%). However, Antarctic fur seals spent significantly more time grooming and moving slowly at the surface than northern fur seals (36% vs. 29%). Diving was the most expensive activity (~30 MJ/day if done non-stop for 24 hr), followed by transiting at the surface (~21 MJ/day). Interestingly, metabolic rates were similar between species while on land or while slowly moving at the surface (~13 MJ/day). Overall, the average field metabolic rate was ~20 MJ/day (for all activities combined). The method we developed to calculate activity-specific metabolic rates can be applied to terrestrial and marine species to determine the energetic costs of daily activities, as well as to predict the energetic consequences for animals forced to change their time allocations in response to environmental shifts.

A NOVEL GAMMAHERPESVIRUS IN NORTHERN FUR SEALS (CALLORHINUS URSINUS) IS CLOSELY RELATED TO THE CALIFORNIA SEA LION (ZALOPHUS CALIFORNIANUS) CARCINOMA-ASSOCIATED OTARINE HERPESVIRUS-1

Otarine herpesvirus 1 (OtHV1) is strongly associated with California sea lion (CSL, Zalophus californianus) urogenital carcinoma, the most common cancer documented in marine mammals. In addition to CSL, OtHV1 has also been found in association with carcinoma in South American fur seals (Arctocephalus australis), demonstrating it can infect related species. Northern fur seals (NFS, Callorhinus ursinus) are sympatric with CSL, and copulation between these species has been observed; yet, there are no reports of urogenital carcinoma in NFS. We describe a new Otarine herpesvirus found in vaginal swabs from NFS, herein called OtHV4. Partial sequencing of the polymerase gene and the glycoprotein B gene revealed OtHV4 is closely related to OtHV1, with 95% homology in the region of polymerase sequenced, and phylogenetic analyses demonstrate that they are sister taxa. An OtHV4-specific hydrolysis probe quantitative PCR was developed and validated, and its use on vaginal swabs revealed 16 of 50 (32%) wild adult female NFS were positive for OtHV4. The identification of a virus highly similar to the carcinoma-associated OtHV1 in a sympatric species without carcinoma suggests that comparative genomics of OtHV1 and OtHV4 may identify candidate viral oncogenes.

Dental and Temporomandibular Joint Pathology of the Northern Fur Seal (Callorhinus ursinus)

Skulls from 145 northern fur seals (Callorhinus ursinus) were examined macroscopically according to predefined criteria. The museum specimens were acquired from strandings along the west coast of the USA between 1896 and 2008. Seventy-one skulls (49.0%) were from male animals, 56 (38.6%) from female animals and 18 (12.4%) from animals of unknown sex. Their age varied from juvenile to adult, with 58 adult animals (40.0%) and 87 juvenile animals (60.0%). The majority of teeth were available for examination (95.1%); 3.4% of teeth were artefactually absent, 0.8% were deemed absent due to acquired tooth loss and 0.6% were deemed congenitally absent. Males were no more likely than females to have either acquired tooth loss (P = 0.054) or congenitally absent teeth (P = 0.919). Adults had significantly more acquired tooth loss than juveniles (P = 0.0099). Malformations were seen in 11 teeth (0.2% of all 4,699 teeth available for examination). Two roots, instead of the typical one root, were found on 14 teeth (0.3%). Supernumerary teeth were associated with 14 normal teeth (0.3%) in eight specimens (5.5% of the total number of specimens). A total of 22 persistent deciduous teeth were found, 19 of which were associated with the maxillary canine teeth. Attrition/abrasion was seen on 194 teeth (3.9%); the canine teeth were most often affected, accounting for 39.7% of all abraded teeth. Adults were found to have a greater prevalence of abraded teeth than juveniles (P <0.0001). No significant difference was found in the appearance of attrition/abrasion between males and females (P = 0.072). Tooth fractures were found in 24 specimens (16.6%), affecting a total of 54 teeth (1.1%). Periapical lesions were found in two skulls (1.4%). None of the specimens showed signs of enamel hypoplasia. About a fifth (18.6%) of alveoli, either with or without teeth, showed signs of alveolar bony changes consistent with periodontitis. A total of 108 specimens (74.5%) had at least one tooth associated with mild periodontitis. Lesions consistent with temporomandibular joint osteoarthritis (TMJ-OA) were found in 29 specimens (20.0%). Both periodontal disease and TMJ-OA were significantly more common in adults than in juveniles (P <0.0001). Periodontitis was found to be more common in males than in females (P <0.012). Although the significance of the high incidence of periodontitis and TMJ-OA in the northern fur seal remains unknown, the occurrence and severity of these diseases found in this study may play an important role in this species morbidity and mortality.

Evidence of localized resource depletion following a natural colonization event by a large marine predator

For central place foragers, forming colonies can lead to extensive competition for prey around breeding areas and a zone of local prey depletion. As populations grow, this area of reduced prey can expand impacting foraging success and forcing animals to alter foraging behaviour. Here, we examine a population of marine predators, the northern fur seal (Callorhinus ursinus), which colonized a recently formed volcanic island, and assess changes in foraging behaviour associated with increasing population density. Specifically, we measured pup production and adult foraging behaviour over a 15-year period, during which the population increased 4-fold. Using measures of at-sea movements and dive behaviour, we found clear evidence that as the population expanded, animals were required to allot increasing effort to obtain resources. These changes in behaviour included longer duration foraging trips, farther distances travelled, a larger foraging range surrounding the island and deeper maximum dives. Our results suggest that as the northern fur seal population increased, local prey resources were depleted as a result of increased intraspecific competition. In addition, the recent slowing of population growth indicates that this population may be approaching carrying capacity just 31 years after a natural colonization event. Our study offers insight into the dynamics of population growth and impacts of increasing population density on a large marine predator. Such data could be vital for understanding future population fluctuations that occur in response to the dynamic environment, as natural and anthropogenic factors continue to modify marine habitats.

Regional differences in cortical electroencephalogram (EEG) slow wave activity and interhemispheric EEG asymmetry in the fur seal

Slow wave sleep (SWS) in the northern fur seal (Callorhinus ursinus) is characterized by a highly expressed interhemispheric electroencephalogram (EEG) asymmetry, called 'unihemispheric' or 'asymmetrical' SWS. The aim of this study was to examine the regional differences in slow wave activity (SWA; power in the range of 1.2-4.0 Hz) within one hemisphere and differences in the degree of interhemispheric EEG asymmetry within this species. Three seals were implanted with 10 EEG electrodes, positioned bilaterally (five in each hemisphere) over the frontal, occipital and parietal cortex. The expression of interhemispheric SWA asymmetry between symmetrical monopolar recordings was estimated based on the asymmetry index [AI = (L-R)/(L+R), where L and R are the power in the left and right hemispheres, respectively]. Our findings indicate an anterior-posterior gradient in SWA during asymmetrical SWS in fur seals, which is opposite to that described for other mammals, including humans, with a larger SWA recorded in the parietal and occipital cortex. Interhemispheric EEG asymmetry in fur seals was recorded across the entire dorsal cerebral cortex, including sensory (visual and somatosensory), motor and associative (parietal or suprasylvian) cortical areas. The expression of asymmetry was greatest in occipital-lateral and parietal derivations and smallest in frontal-medial derivations. Regardless of regional differences in SWA, the majority (90%) of SWS episodes with interhemispheric EEG asymmetry meet the criteria for 'unihemispheric SWS' (one hemisphere is asleep while the other is awake). The remaining episodes can be described as episodes of bilateral SWS with a local activation in one cerebral hemisphere.

Apoptosis in normal and Coxiella burnetii-infected placentas from Alaskan northern fur seals (Callorhinus ursinus)

In 2010, Coxiella burnetii was identified in 75% of northern fur seal placentas from a single rookery in Alaska, but nothing was known about the significance of this organism in the population. Although many infectious organisms cause increased cell death, C. burnetii has been shown to suppress apoptosis of the host macrophages as an intracellular survival mechanism. To determine if infection induces a similar functional change in the placenta, immunohistochemistry for antibodies to cleaved caspase-3 (activated caspase-3) and the (TDT)-mediated dUTP-digoxigenin nick end labeling (TUNEL) technique were used to compare the amount of placental apoptosis in infected and noninfected placentas. There was a statistically significant difference in the frequency of apoptotic cells between infected and uninfected placentas, with more apoptosis identified in the uninfected placentas. This finding suggests that the survival mechanism of C. burnetii in host macrophages to reduce apoptosis may also be utilized in trophoblasts. The significance of decreased trophoblastic apoptosis for the northern fur seal fetus requires further investigation.