Vancouver Aquarium

ABSTRACT Sea otters ( Enhydra lutris ) exhibit morphological and physiological adaptations supporting a mass‐specific resting metabolic rate (RMR) 2.9‐fold higher than predicted for terrestrial mammals of similar size. Their elevated metabolism results primarily from thermogenic mitochondrial proton leak to compensate for heat loss in the marine environment because of their high surface‐area‐to‐volume ratio, combined with their reliance on fur insulation rather than blubber. Key respiratory adaptations include an enlarged lung volume, 3.5‐fold greater than predicted allometrically, and a proportionately elevated tidal volume, enabling efficient oxygen uptake and carbon dioxide elimination. Complementary cardiovascular adaptations include a heart mass 1.3‐fold greater than the allometric prediction, a correspondingly elevated stroke volume, normal heart rate, increased hemoglobin concentration, and enhanced arterial oxygen content. Together, these adaptations result in an elevated cardiac output and enhanced convective oxygen transport to support the elevated RMR. These multi‐level adaptations, present even in young animals, likely evolved under selective pressures favoring thermogenesis over increased insulation by blubber, representing a convergent evolutionary strategy consistent with the principle of symmorphosis, similar to terrestrial athletic mammals adapted for sustained aerobic performance rather than energy conservation. Additional benefits of enlarged lungs, such as enhanced buoyancy and pulmonary oxygen stores, may also have contributed to their evolution.

Marine mammals may develop kidney stones, which can be challenging to treat. We describe burst wave lithotripsy (BWL) and ultrasonic propulsion to treat ureteral calculi in a 48-year-old female bottlenose dolphin (Tursiops truncatus) and to reduce renal stone burden in a 23-year-old male harbor seal (Phoca vitulina). BWL and ultrasonic propulsion were delivered transcutaneously in sinusoidal ultrasound bursts to fragment and reposition stones. Targeting and monitoring were performed with real-time imaging integrated within the BWL system. Four dolphin stones were obtained and fragmented ex vivo. The dolphin case received a 10-min and a 20-min BWL treatment conducted approximately 24 h apart to treat two 8–10 mm partially obstructing right mid-ureteral stones, using oral sedation alone. For the harbor seal, while under general anesthesia, retrograde ureteroscopy attempts were unsuccessful because of ureteral tortuosity, and a 30-min BWL treatment was targeted on one 10-mm right kidney stone cluster. All 4 stones fragmented completely to < 2-mm fragments in < 20 min ex vivo. In the dolphin case, the ureteral stones appeared to fragment, spread apart, and move with ultrasonic propulsion. On post-treatment day 1, the ureteral calculi fragments shifted caudally reaching the ureteral orifice on day 9. On day 10, the calculi fragments passed, and the hydroureter resolved. In the harbor seal, the stone cluster was observed to fragment and was not visible on the post-operative computed tomography scan. The seal had gross hematuria and a day of behavior indicating stone passage but overall, an uneventful recovery. BWL and ultrasonic propulsion successfully relieved ureteral stone obstruction in a geriatric dolphin and reduced renal stone burden in a geriatric harbor seal.

Magnesium chloride in high concentration is used for euthanasia of jellyfish to limit overpopulation and for predatory species consumption, but its use could lead to magnesium bioaccumulation and subsequent negative effects in consumers. Two species of scyphozoan jellyfish (Cassiopea andromeda and Aurelia aurita) were subjected to freezing (control), or magnesium chloride baths (144 g/L), with subsequent 30 min baths (one or two) in fresh artificial saltwater and submitted for inductively coupled plasma analysis to determine tissue concentration. Frozen jellyfish consistently yielded the lowest magnesium concentrations, while magnesium chloride euthanized individuals contained the highest concentrations in both species. C. andromeda displayed a significantly higher (p < .05) magnesium absorption capacity than A. aurita in both trials. Single and double baths significantly decreased magnesium concentrations (p < .05) in both species, however, magnesium remained consistently elevated compared to frozen specimens. This study demonstrated species-specific magnesium accumulation in jellyfish posteuthanasia and that rinsing was an effective method to limit excessive magnesium that could be deleterious to animals in public display aquaria. Magnesium concentrations of tissue and receiving water should be tested if magnesium chloride euthanasia is utilized for dietary supplementation in small bodies of water.

Harbor porpoise in the North Pacific are found in coastal waters from southern California to Japan, but population structure is poorly known outside of a few local areas. We used multiplexed amplicon sequencing of 292 loci and genotyped clusters of single nucleotide polymoirphisms as microhaplotypes (N=271 samples) in addition to mitochondrial (mtDNA) sequence data (N=413 samples) to examine the genetic structure from samples collected along the Pacific coast and inland waterways from California to southern British Columbia. We confirmed an overall pattern of strong isolation-by-distance, suggesting that individual dispersal is restricted. We also found evidence of regions where genetic differences are larger than expected based on geographical distance alone, implying current or historical barriers to gene flow. In particular, the southernmost population in California is genetically distinct (FST =0.02 [microhaplotypes]; 0.31 [mtDNA]), with both reduced genetic variability and high frequency of an otherwise rare mtDNA haplotype. At the northern end of our study range, we found significant genetic differentiation of samples from the Strait of Georgia, previously identified as a potential biogeographical boundary or secondary contact zone between harbor porpoise populations. Association of microhaplotypes with remotely sensed environmental variables indicated potential local adaptation, especially at the southern end of the species' range. These results inform conservation and management for this nearshore species, illustrate the value of genomic methods for detecting patterns of genetic structure within a continuously distributed marine species, and highlight the power of microhaplotype genotyping for detecting genetic structure in harbor porpoises despite reliance on poor-quality samples.

A 1.5 kg, male, wild-caught tiger rat snake (Spilotes pullatus) presented with an externally visible distension of the body wall at the level of the heart. Ultrasound examination showed marked pericardial effusion. Pericardial fluid showed no bacterial or fungal growth, few leukocytes, and few suspected reactive mesothelial or neoplastic cells. Therapeutic pericardiocentesis was successfully performed, removing most of the fluid from the pericardial sac. The snake had mild lethargy and weakness immediately after the procedure but returned to normal behavior within 2 wk. Repeat pericardiocentesis was performed 6 mo after the initial presentation when moderate refilling of the pericardial sac was seen. The snake died 4 days after the second procedure with acute hemorrhage. Pericardial mesothelioma was diagnosed by histopathology after postmortem examination. This report provides the first documented case of mesothelioma in a tiger rat snake and the first description of the disease in colubrids.

Primary fungal diseases in marine mammals are rare. Mucormycosis, a disease caused by fungi of the order Mucorales, has been documented in few cetaceans and pinnipeds. In 2012, the first case of mucormycosis in the Pacific Northwest was documented in a dead stranded harbor porpoise (Phocoena phocoena) in Washington state. Since then, mucormycosis has been detected in a total of 21 marine mammals; fifteen harbor porpoises, five harbor seals (Phoca vitulina), and one southern resident killer whale (Orcinus orca). Infected animals were predominately found in the inland waters of Washington and British Columbia, and one harbor seal was recovered in northern Oregon. Fungal hyphae were detected histologically in a variety of tissues, including brain, lung, spleen, pancreas, kidneys, muscle, lymph nodes, and skin. Three fungal species were identified from seven cases by PCR screening or fungal culture; Rhizomucor pusillus (four cases), Lichtheimia corymbifera (two cases), and Cunninghamella bertholletiae. Underlying conditions such as emaciation, current or recent pregnancy, multisystemic parasitism, protozoal infection, and herpesvirus were found in several affected animals. Reasons for the appearance and subsequent increase of these fungal infections in marine mammals are unknown. The emergence of this disease as a source of marine mammal mortality in the Pacific Northwest is of particular concern for endangered southern resident killer whales that spend time in this region. Current population-level stressors such as insufficient prey, high levels of contaminants, and noise pollution, could predispose them to these fatal infections.

In the current study, we used breath-by-breath respirometry to evaluate respiratory physiology under voluntary control in a male beluga calf [Delphinapterus leucas, body mass range (Mb): 151–175 kg], an adult female (estimated Mb = 500–550 kg) and a juvenile male (Mb = 279 kg) false killer whale (Pseudorca crassidens) housed in managed care. Our results suggest that the measured breathing frequency (fR) is lower, while tidal volume (VT) is significantly greater as compared with allometric predictions from terrestrial mammals. Including previously published data from adult bottlenose dolphin (Tursiops truncatus) beluga, harbor porpoise (Phocoena phocoena), killer whale (Orcinus orca), pilot whale (Globicephala scammoni), and gray whale (Eschrichtius robustus) show that the allometric mass-exponents for VT and fR are similar to that for terrestrial mammals (VT: 1.00, fR: −0.20). In addition, our results suggest an allometric relationship for respiratory flow (), with a mass-exponent between 0.63 and 0.70, and where the expiratory was an average 30% higher as compared with inspiratory . These data provide enhanced understanding of the respiratory physiology of cetaceans and are useful to provide proxies of lung function to better understand lung health or physiological limitations.

One spotted pike-characin Boulengerella maculata, managed in a public display aquarium for 7 yr, developed a small unilateral pink growth associated with the right nare. The growth eventually extended through both nares after 5 mo. B. maculata is a species of piscivorous fish that relies on visual acuity when hunting prey. The rapidly-growing bilateral tumor would have impeded vision if left untreated. The fish was managed for over 10 mo using only surgical debulking, topical liquid nitrogen, and occasional nonsteroidal anti-inflammatory medications as needed to reduce tumor size and restore sight. Diagnosis proved challenging due to superimposed inflammation, neoplasm cellular inconsistencies, and a lack of proven immunohistochemical stains or other diagnostic stains. Using tumor location and appearance, histopathology, advanced imaging, electron microscopy, special staining, and immunohistochemistry, the ultimate diagnosis confirmed olfactory neuroblastoma, or esthesioneuroblastoma. Although long-term prognosis is poor, hunting strategy of the affected species may dictate quality of life, as appetite, body condition, and behavior remained largely unchanged in this animal until time of euthanasia.

Recent studies of stranded marine mammals indicate that exposure to underwater military sonar may induce pathophysiological responses consistent with decompression sickness (DCS). However, DCS has been difficult to diagnose in marine mammals. We investigated whether blood microparticles (MPs, measured as number/μl plasma), which increase in response to decompression stress in terrestrial mammals, are a suitable biomarker for DCS in marine mammals. We obtained blood samples from trained Steller sea lions (Eumetopias jubatus, 4 adult females) wearing time-depth recorders that dove to predetermined depths (either 5 or 50 meters). We hypothesized that MPs would be positively related to decompression stress (depth and duration underwater). We also tested the effect of feeding and exercise in isolation on MPs using the same blood sampling protocol. We found that feeding and exercise had no effect on blood MP levels, but that diving caused MPs to increase. However, blood MP levels did not correlate with diving depth, relative time underwater, and presumed decompression stress, possibly indicating acclimation following repeated exposure to depth.