Search Results (21)

This exploratory study evaluated plasma atrial natriuretic peptide (ANP) concentrations in four species of captive cetaceans and their associations with physiological and environmental factors, including husbandry conditions, diet, and management practices. Twenty-six individuals were voluntarily sampled, and blood samples were analyzed using a human-based chemiluminescent immunoassay. Transthoracic echocardiography was also attempted in several individuals but was technically challenging due to interference from the lung tissue and the sternum. The mean plasma ANP concentration in clinically healthy young animals was 44.12 ± 14.62 pg/mL, with no significant differences observed according to age, sex, species, or the presence of mild chronic disease. ANP was detectable across all species using human reagents. In addition, brain natriuretic peptide (BNP), a commonly used cardiac biomarker in humans and other animals, was evaluated for comparison; however, BNP concentrations remained below the detection threshold, possibly reflecting species-specific differences. Importantly, ANP concentrations were not evaluated in animals with clinically significant disease, and therefore the relevance of these findings to diseased populations remains unknown. These results demonstrate that plasma ANP can be measured using existing clinical assays and provide preliminary baseline data for multiple cetacean species. Overall, ANP may offer preliminary insights into physiological variation in managed cetaceans; however, its utility as a biomarker for cardiovascular or systemic health assessment remains to be determined. Full article

Candida albicans is currently considered one of the most significant fungal pathogens in cetaceans and pinnipeds and the spread of antifungal-resistant strains pose significant threats to animal health and One Health concerns. Although C. albicans is the most commonly detected species, non-albicans Candida (NAC) species, including C. tropicalis, C. parapsilosis and Nakaseomyces glabratus and the multidrug-resistant C. auris, have been recognized in captive dolphins. This review examines the clinical patterns observed in marine mammal taxa: cetaceans are most commonly vulnerable to respiratory and disseminated mycoses owing to their distinct anatomical characteristics, whereas mucocutaneous infections are the common manifestation in pinnipeds. Localized mucocutaneous infections may progress to fatal systemic disease, with mortality rates approaching 100% in severe cases, despite therapeutic treatment. The most important predisposing factors are immunosuppression, long-term antibiotic treatment, environmental stress factors, and the deterioration of water quality. Diagnostic methods are based on cytology, histopathology, culture, and molecular methods, and treatment is mostly composed of systemic azole antifungals although with high levels of therapeutic failure. Recent results showed that there are high levels of azole resistance in the isolates of marine mammals that had no history of exposure to antifungal agents, which points to the role of aquatic environments as sources of resistance genes. The lack of knowledge remains particularly evident in species-specific pharmacokinetics and the development of evidence-based treatment guidelines. These infections also have broader implications for ecosystem health surveillance and the protection of endangered marine mammal populations. The current review highlights the One Health approach with marine mammals being at the core of ocean health surveillance and identifies the potential for zoonotic transmission. Full article

This case report describes a male bottlenose dolphin (Tursiops truncatus) from a republic aquarium in Quanzhou City, Fujian Province, China, in 2024. The dolphin exhibited prolonged vomiting that did not improve despite extended antibiotic treatment, followed by progressive deterioration in physical condition until death. Antemortem biochemical analyses indicated hepatic dysfunction (ALT: 269.8 IU/L, AST: 1357.5 IU/L, LDH: 2913.3 IU/L) and renal impairment (TBIL: 55.84 μmol/L, BUN: 31.93 mmol/L, Cr: 200.2 μmol/L). Necropsy showed atrophy of coronary fat in the heart, hepatomegaly with extensive yellow discoloration, splenomegaly with congestion, diffuse dark-red discoloration of the lungs, renal atrophy, segmental dark-red discoloration of the intestines, and dark-red enlargement of intestinal lymph nodes. Histopathological examination revealed hepatic steatosis with necrosis, extensive pulmonary hemorrhage with foreign bodies in the trachea and alveoli, intestinal necrosis with visible fungus, and congestion and necrosis of intestinal lymph nodes with visible fungus present; the fungus hyphae were periodic acid–Schiff (PAS)-positive. Fungal PCR targeting the fungus internal transcribed spacer (ITS) region identified the intestine fungus as Cladosporium. Infection with Cladosporium is extremely rare, and this report highlights the potential risks of emerging infectious diseases in marine mammals. Full article

Imidazole dipeptides (IDPs), including anserine, carnosine, and balenine, are predominantly found in the skeletal muscles of vertebrates. Balenine is the major IDP in cetaceans. Serum amyloid A (SAA) is an acute phase protein released in response to damage or injury in various tissues, including skeletal muscles. A captive bottlenose dolphin (Tursiops truncatus) died due to rhabdomyolysis and subsequent acute kidney injury that probably originated from accidental muscle trauma. In this study, concentrations of IDPs and SAA were measured using stored serum collected from the affected dolphin with intermittent continuous damage of skeletal muscles to demonstrate the pathological relevance of these parameters and their usefulness as biomarkers for muscle damage in dolphins. The IDP concentration was measured using the high-performance liquid chromatography-ultraviolet method. The SAA concentration was measured using an enzyme-linked immunosorbent assay (ELISA) specific to dolphin SAA and a latex turbidimetric immunoassay (LTI) specific to human SAA. Herein, the IDP concentration was altered similarly to serum muscular enzymes, including creatinine kinase (CK) and aspartate aminotransferase (AST). However, IDP concentrations were elevated one day earlier than CK and AST levels at disease onset. Furthermore, IDP concentrations were similarly altered when assessed using both ELISA- and LTI-SAAs, and the change in IDP concentration coincided with that in LTI-SAA based on the statistical analysis. These data suggest that IDP concentration could detect muscle damage and injury, including necrosis and inflammation, in dolphins. Full article

Cetaceans are highly adapted to the underwater environment, which is very different from the terrestrial environment. For cetaceans with neither high visual acuity nor color vision, contrast may be an important cue for visual object recognition, even in the underwater environment. Contrast is defined as the difference in luminance between an object and its background and is known to be perceived as enhanced by the luminance contrast illusion in humans. The aim of this study was to experimentally investigate whether the enhancement of contrast by the luminance contrast illusion could be observed in killer whales. Luminance discrimination tasks were performed on two captive killer whales, which were required to compare the luminance of two targets presented in monitors through an underwater window and to choose the brighter one. After baseline training, in which the target areas were surrounded by black or white inducer areas, the test condition of gray inducer areas was added. Although there were some individual differences, both individuals showed higher correct response rates for gray inducer conditions than for black and white. The results suggest that contrast was perceived as enhanced by the illusion also in killer whales and may help them to extract the contours of objects. Full article

The pituitary gland regulates essential physiological processes in mammals. Despite its importance, research on its anatomy and ultrastructure in dolphins remains scarce. Using non-invasive imaging technology (MRI) and a novel skull-opening and dissection protocol, this study characterizes the dolphin pituitary through immunohistochemistry (IHC) and transmission electron microscopy (TEM). A total of 47 pituitaries were collected from stranded common bottlenose dolphins (Tursiops truncatus). common dolphins (Delphinus delphis), and Atlantic spotted dolphins (Stenella frontalis). as well as from captive common bottlenose dolphins. MRI allowed visualization of the gland’s anatomy and its spatial relationship with the hypothalamus and surrounding structures. A modified skull-opening and pituitary extraction protocol ensured the preservation of the adenohypophysis and neurohypophysis for detailed analysis. Histological, immunohistochemical, and ultrastructural studies confirmed the gland’s structural organization, identifying eight distinct adenohypophyseal cell types: corticotrophs (ACTH), somatotrophs (GH), gonadotrophs (FSH and LH), lactotrophs (LTH), melanotrophs (MSH), thyrotrophs (TSH), follicular cells, and capsular cells. This study presents the first immunolabelling of thyrotrophs in cetacean adenohypophysis and the first detailed ultrastructural characterization of adenohypophyseal cells in cetaceans, providing baseline data for future research. By integrating multidisciplinary techniques, it advances the understanding of dolphin neuroendocrinology and highlights broader implications for cetacean health, welfare, and conservation. Full article

The SEA LIFE Trust Beluga Whale Sanctuary (BWS) has been in operation for over five years and serves as a unique case study to evaluate the effectiveness of marine sanctuaries for cetaceans. While cetacean sanctuaries are often regarded as a middle-ground solution between captivity and release, evidence from the BWS highlights complexities in adapting cetaceans to these environments. Despite initial assumptions that natural conditions would inherently improve welfare, the belugas at the BWS spent the majority of the operational period (92.6%) in a conventional indoor pool, due to health and welfare concerns. Repeated delays, challenges in acclimatization, and distress-related conditions observed during periods in the bay suggest that natural environments alone may not guarantee improved welfare. Additionally, the lack of publicly accessible data on health and welfare outcomes hinders comprehensive evaluation of the sanctuary’s success and raises questions about transparency and evidence-based practices. This review underscores the need for refined sanctuary models, improved infrastructure, and structured adaptation programs tailored to species and individual cetaceans. It highlights the importance of robust planning, ongoing research, and transparency to meet the ambitious goals of marine sanctuaries in the best interests of the well-being of cetaceans under human care. These considerations also raise concerns about the decision to relocate captive cetaceans to marine sanctuaries, as the available evidence suggests that such environments may not inherently guarantee better welfare outcomes. Full article

Cetaceans, which are crucial in marine ecosystems, act as sentinels for ecosystem and human–environmental health. However, emerging fungal infections, particularly by Candida spp., pose a growing concern in these marine mammals. This review consolidates current knowledge on the prevalence, clinical manifestations, species distribution, and antifungal resistance of Candida infections in cetaceans. We detail the diverse pathogenic impacts of Candida, including respiratory, dermal, and systemic afflictions, underscoring diagnostic and treatment challenges amid rising antifungal resistance. Our analysis extends beyond health concerns in captive cetaceans, where confinement stress heightens vulnerability, to encompass substantial ecological risks in wild populations. The review emphasizes the One Health perspective, linking cetacean health with broader environmental and human public health issues. We particularly focus on the potential zoonotic transmission of emerging fungal pathogens such as Candida auris and the role of environmental changes in fostering antifungal resistance. The study underscores the need for concerted, interdisciplinary efforts in veterinary, medical, and environmental sciences to enhance understanding and management of Candida infections in cetaceans. We advocate for comprehensive monitoring and collaborative research initiatives to mitigate the rising challenge of these infections. Addressing Candida spp. in cetaceans is not just a conservation priority but a critical step in safeguarding overall marine health and, by extension, human health in the context of evolving infectious diseases. Full article

Society is showing a growing concern about the welfare of cetaceans in captivity as well as cetaceans in the wild threatened by anthropogenic disturbances. The study of the physiological stress response is increasingly being used to address cetacean conservation and welfare issues. Within it, a newly described technique of extracting cortisol from epidermal desquamation may serve as a non-invasive, more integrated measure of a cetacean’s stress response and welfare. However, confounding factors are common when measuring glucocorticoid hormones. In this study, we validated a steroid hormone extraction protocol and the use of a commercial enzyme immunoassay (EIA) test to measure cortisol concentrations in common bottlenose dolphin (Tursiops truncatus) and beluga (Delphinapterus leucas) epidermal samples. Moreover, we examined the effect of sample mass and body location on cortisol concentrations. Validation tests (i.e., assay specificity, accuracy, precision, and sensitivity) suggested that the method was suitable for the quantification of cortisol concentrations. Cortisol was extracted from small samples (0.01 g), but the amount of cortisol detected and the variability between duplicate extractions increased as the sample mass decreased. In common bottlenose dolphins, epidermal skin cortisol concentrations did not vary significantly across body locations while there was a significant effect of the individual. Overall, we present a contribution towards advancing and standardizing epidermis hormone assessments in cetaceans. Full article

Matching-to-sample tasks have been a useful method in visual cognitive studies on non-human animals. The use of touch panels in matching-to-sample tasks has contributed to cognitive studies on terrestrial animals; however, there has been a difficulty in using these devices underwater, which is one of the factors that has slowed the progress of visual studies on underwater animals. Cetaceans (e.g., dolphins and whales) are highly adapted to underwater environments, and further studies on their cognitive abilities are needed to advance our understanding of the interactions between environmental factors and the evolution of cognitive abilities. In this study, we aimed to develop a new experimental method in which a captive killer whale performed a matching-to-sample task using a monitor shown through an underwater window as if a touch panel were used. In order to confirm the usefulness of this method, one simple experiment on mirror image discrimination was conducted, and the pairs with mirror images were shown to be more difficult to identify than the pairs with other normal images. The advantages of using this method include (1) simplicity in the devices and stimuli used in the experiments, (2) appropriate and rigorous experimental control, (3) the possibility of increasing the number of individuals to be tested and interspecies comparisons, and (4) contributions to animal welfare. The use of this method solves some of the problems in previous visual cognitive studies on cetaceans, and it suggests the further possibility of future comparative cognitive studies. It is also expected to contribute to animal welfare in terms of cognitive enrichment, and it could help with the proposal of new exhibition methods in zoos and aquariums. Full article

Housing cetaceans in netted sea pens is not new and is common for many accredited managed-care facilities. Hence, the distinction between sanctuary and sea pen is more about the philosophies of those who run these sanctuary facilities, the effects of these philosophies on the animals’ welfare, and how proponents of these sanctuaries fund the care of these animals. Here, I consider what plans exist for cetacean sanctuaries and discuss the caveats and challenges associated with this form of activist-managed captivity. One goal for stakeholders should be to disregard the emotional connotations of the word “sanctuary” and explore these proposals objectively with the best interest of the animals in mind. Another focus should be related to gauging the public’s understanding of proposed welfare benefits to determine if long-term supporters of donation-based sanctuary models will likely see their expectations met as NGOs and their government partners consider moving forward with cetacean sanctuary experiments. Full article

Cetaceans, including beluga whales (Delphinapterus leucas), have high morbidity and mortality rates due to bacterial or fungal lower respiratory infections. Bronchoalveolar lavage fluid (BALF) collection by bronchoscopy is beneficial for detecting pathogenic microorganisms in the lower respiratory tract. Efficient and safe bronchoscopy requires characterizing the bronchial tree systems of beluga whales, as no reports exist on bronchial length and bifurcation. In this study, bronchoscopy was performed on five captive beluga whales (9–44 years old) to detect bronchial length and bifurcation. The lengths from the blowhole to the scope impassable points due to the minimized bronchi diameters of the left principal bronchus (LPB), right principal bronchus (RPB), and tracheal bronchus (TB) were 110–155, 110–150, and 80–110 cm, respectively, and were correlated with the body length. Bronchoscopy identified more than 10, 10, and 6 bifurcated bronchi from the LPB, RPB, and TB, respectively. This is the first report to clarify the differences in bronchial tree systems between beluga whales and other cetaceans, as well as the differences for each individual beluga whale. These results could be useful for obtaining BALF via bronchoscopy to detect pathogenic microorganisms causing infections in the lower respiratory tract of beluga whales. Full article

As people’s focus broadens from animals on farms to zoos and aquaria, the field of welfare science and the public’s concern for animal welfare continue to grow. In captive animals, stress and its causes are topics of interest in welfare issues, and the identification of an objective method that can be used to assess animals’ stress as a physiological state is essential. Both behavioral and physiological parameters can be used as indicators in order to assess animal stress quantitatively. To validate this approach, acoustic activity and the sloughed scrape skin cortisol concentration were used to evaluate the animal welfare of captive beluga whales (Delphinapterus leucas). The acoustic activity (5 min at 10:00 am) of three captive D. leucas was routinely recorded by a transducer and analyzed using audio editing software. The calls were separated into three main categories: whistles, pulses, and combo calls. The sloughed scrape skin samples were collected non-invasively once a week from all three animals’ fluke and/or flipper. Cortisol was extracted using a modified skin steroid extraction technique, and detected via commercially available enzyme immunoassays. The results showed that the cortisol concentration increased by varying levels when the whales encountered the same event. In addition, the number and distribution of the calls changed along with the events. This indicated that the changes in the cortisol concentration and acoustic behavior may have reflected the fluctuations in the environment and body condition. Therefore, the scrape cortisol measurement and acoustic recordings could be used to monitor stress levels in captive beluga whales. We recommend that aquaria consider incorporating skin scrape cortisol and acoustic activity monitoring into their standards for animal welfare. Full article

Genetic analysis is a conventional way of identifying and monitoring captive and wildlife species. Knowledge of statistical parameters reinforcing their usefulness and effectiveness as powerful tools for preserving diversity is crucial. Although several studies have reported the diversity of cetaceans such as Tursiops truncatus using microsatellites, its informative degree has been poorly reported. Furthermore, the genetic structure of this cetacean has not been fully studied. In the present study, we selected 15 microsatellites with which 210 dolphins were genetically characterized using capillary electrophoresis. The genetic assertiveness of this set of hypervariable markers identified one individual in the range of 6.927e¹³ to 1.806e¹⁶, demonstrating its substantial capability in kinship relationships. The genetic structure of these 210 dolphins was also determined regarding the putative capture origin; a genetic stratification (k = 2) was found. An additional dolphin group of undetermined origin was also characterized to challenge the proficiency of our chosen markers. The set of markers proposed herein could be a helpful tool to guarantee the maintenance of the genetic diversity rates in conservation programs both in Tursiops truncatus and across other odontocetes, Mysticeti and several genera of endangered and vulnerable species. Full article

Cetaceans are potentially at risk of poor welfare due to the animals’ natural reliance on sound and the persistent nature of anthropogenic noise, especially in the wild. Industrial, commercial, and recreational human activity has expanded across the seas, resulting in a propagation of sound with varying frequency characteristics. In many countries, current regulations are based on the potential to induce hearing loss; however, a more nuanced approach is needed when shaping regulations, due to other non-hearing loss effects including activation of the stress response, acoustic masking, frequency shifts, alterations in behavior, and decreased foraging. Cetaceans in managed-care settings share the same acoustic characteristics as their wild counterparts, but face different environmental parameters. There have been steps to integrate work on welfare in the wild and in managed-care contexts, and the domain of acoustics offers the opportunity to inform and connect information from both managed-care settings and the wild. Studies of subjects in managed-care give controls not available to wild studies, yet because of the conservation implications, wild studies on welfare impacts of the acoustic environment on cetaceans have largely been the focus, rather than those in captive settings. A deep integration of wild and managed-care-based acoustic welfare research can complement discovery in both domains, as captive studies can provide greater experimental control, while the more comprehensive domain of wild noise studies can help determine the gaps in managed-care based acoustic welfare science. We advocate for a new paradigm in anthropogenic noise research, recognizing the value that both wild and managed-care research plays in illustrating how noise pollution affects welfare including physiology, behavior, and cognition. Full article