“Gas and Fat Embolic Syndrome” Involving a Mass Stranding of Beaked Whales (Family Ziphiidae) Exposed to Anthropogenic Sonar Signals

Platelet phosphatidylserine exposure and microparticle production as health bioindicators in marine mammals

In human medicine, various pathologies, including decompression sickness, thrombocytopenia, and rheumatoid arthritis, have been linked to changes in cellular microparticles (MP) formation, particularly platelet microparticles (PMP). Similar disorders in marine mammals might be attributed to anthropogenic threats or illnesses, potentially impacting blood PMP levels. Thus, detecting platelet phosphatidylserine (PS) exposure and PMP formation could serve as a crucial diagnostic and monitoring approach for these conditions in marine mammals. Our group has developed a methodology to assess real-time PS exposure and PMP formation specifically tailored for marine mammals. This method, pioneered in species such as bottlenose dolphins, beluga whales, walruses, and California sea lions, represents a novel approach with significant implications for both clinical assessment and further research into platelet function in these animals. The adapted methodology for evaluating PS exposure and PMP formation in marine mammals has yielded promising results. By applying this approach, we have observed significant correlations between alterations in PMP levels and specific pathologies or environmental factors. These findings underscore the potential of platelet function assessment as a diagnostic and monitoring tool in marine mammal health. The successful adaptation and application of this methodology in marine mammals highlight its utility for understanding and managing health concerns in these animals.

Osteolytic Lesions in a Sub-Adult Loggerhead Sea Turtle (Caretta caretta): A Case Report

Osteolytic lesions in loggerhead sea turtles (Caretta caretta) during rehabilitation are attributed to multiple causes, including gas embolism, hypothermia, and osteomyelitis due to bacterial or fungal infection. This study reports the appearance of osteolytic lesions in a sub-adult loggerhead sea turtle with involvement of the right fore and hind flippers, visible swelling of the elbow and knee joints, and accompanied by lameness after 45 days of rehabilitation. Radiographs and computed tomography revealed multiple lytic bone lesions. This was the fourth rehabilitation admission of the turtle after being accidentally captured by trawler ships (bycatch) in 2019, 2020, 2022, and 2023. Potential causes were dysbaric osteonecrosis due to a past decompression sickness event and hypothermia with osteomyelitis from bacterial infection. Blood cultures and antibiotic susceptibility testing led to the isolation of Ewingella americana responsive to enrofloxacin. This study investigates extensive fore and hind flipper involvement in a sub-adult loggerhead turtle, aiming to determine causes and risk factors. The pathogenesis and significance of these lesions is discussed.

Transcriptomic analysis reveals the immune response mechanisms of sea cucumber Apostichopus japonicus under noise stress from offshore wind turbine

As an important form of renewable energy, offshore wind power can effectively reduce dependence on traditional energy sources and decrease carbon emissions. However, operation of wind turbines can generate underwater noise that may have negative impacts on marine benthic organisms in the surrounding area. Sea cucumbers are slow-moving invertebrates that inhabit the ocean, relying on their immune system to adapt to their environment. To evaluate the frequency range of characteristic noise produced by offshore wind turbines, we conducted a field survey. Additionally, we utilized sea cucumbers in simulated experiments to assess their response to the noise produced by offshore wind turbines. We established a control group, a low-frequency noise group simulating offshore wind turbine noise at 125 Hz and 250 Hz, and a high-frequency noise group at 2500 Hz, each lasting for 7 days. Results from measuring immune enzyme activity in the coelomic fluid suggest that noise can reduce the activity of superoxide dismutase enzymes, which may make sea cucumbers more susceptible to oxidative damage caused by free radicals. Exposure to low-frequency noise can have the effect of diminishing the activity of catalase, and this decrease in catalase activity could potentially increase the susceptibility of the sea cucumber's coelom to inflammation. In order to elucidate the hypothetical mechanism of immune response, intestinal tissue was extracted for transcriptome sequencing. The results showed that under 125 Hz low-frequency noise stress, the number of differentially expressed genes was the highest, reaching 1764. Under noise stress, sea cucumber's cell apoptosis and cell motility are reduced, interfering with lipid metabolism process and membrane synthesis. This research provides theoretical support for the environmental safety assessment of offshore wind power construction.

Biomarkers related to gas embolism: Gas score, pathology, and gene expression in a gas bubble disease model

Fish exposed to water supersaturated with dissolved gas experience gas embolism similar to decompression sickness (DCS), known as gas bubble disease (GBD) in fish. GBD has been postulated as an alternative to traditional mammals' models on DCS. Gas embolism can cause mechanical and biochemical damage, generating pathophysiological responses. Increased expression of biomarkers of cell damage such as the heat shock protein (HSP) family, endothelin 1 (ET-1) or intercellular adhesion molecule 1 (ICAM-1) has been observed, being a possible target for further studies of gas embolism. The GBD model consisted of exposing fish to supersaturation in water with approximately 170% total dissolved gas (TDG) for 18 hours, producing severe gas embolism. This diagnosis was confirmed by a complete histopathological exam and the gas score method. HSP70 showed a statistically significant upregulation compared to the control in all the studied organs (p <0.02). Gills and heart showed upregulation of HSP90 with statistical significance (p = 0.015 and p = 0.02, respectively). In addition, HSP70 gene expression in gills was positively correlated with gas score (p = 0.033). These results suggest that gas embolism modify the expression of different biomarkers, with HSP70 being shown as a strong marker of this process. Furthermore, gas score is a useful tool to study the abundance of gas bubbles, although individual variability always remains present. These results support the validity of the GBD model in fish to study gas embolism in diseases such as DCS.

How chronic anthropogenic noise can affect wildlife communities

Anthropogenic noise is a major pollutant in terrestrial and aquatic ecosystems. Since the industrial revolution, human activities have become increasingly noisy, leading to both acute and chronic disturbance of a wide variety of animals. Chronic noise exposure can affect animals over their lifespan, leading to changes in species interactions and likely altering communities. However, the community-level impacts of chronic noise are not well-understood, which impairs our ability for effective mitigation. In this review, we address the effects of chronic noise exposure on communities and explore possible mechanisms underlying these effects. The limited studies on this topic suggest that noise can affect communities by changing the behavior and/or physiology of species in a community, which results in direct or knock-on consequences for other species in the ecosystem. Major knowledge gaps remain due to the logistically complex and financially expensive nature of the long-term studies needed to address these questions. By identifying these gaps and suggesting approaches to answer them, we provide a road map toward mitigating the effects of a noisy world.

Multimodal Assessment of Bottlenose Dolphin Auditory Nuclei Using 7-Tesla MRI, Immunohistochemistry and Stereology

The importance of assessing neurochemical processes in the cetacean brain as a tool for monitoring their cognitive health and to indirectly model human neurodegenerative conditions is increasingly evident, although available data are largely semiquantitative. High-resolution MRI for post-mortem brains and stereology allow for quantitative assessments of the cetacean brain. In this study, we scanned two brains of bottlenose dolphins in a 7-Tesla (7T) MR scanner and assessed the connectivity of the inferior colliculi and ventral cochlear nuclei using diffusion tensor imaging (DTI). Serial thick sections were investigated stereologically in one of the dolphins to generate rigorous quantitative estimates of identifiable cell types according to their morphology and expression of molecular markers, yielding reliable cell counts with most coefficients of error <10%. Fibronectin immunoreactivity in the dolphin resembled the pattern in a human chronic traumatic encephalopathy brain, suggesting that neurochemical compensation for insults such as hypoxia may constitute a noxious response in humans, while being physiological in dolphins. These data contribute to a growing body of knowledge on the morphological and neurochemical properties of the dolphin brain and highlight a stereological and neuroimaging workflow that may enable quantitative and translational assessment of pathological processes in the dolphin brain in the future.

Remarkable consistency of spinal cord microvasculature in highly adapted diving odontocetes

Odontocetes are breath-hold divers with a suite of physiological, anatomical, and behavioral adaptations that are highly derived and vastly different from those of their terrestrial counterparts. Because of these adaptations for diving, odontocetes were originally thought to be exempt from the harms of nitrogen gas embolism while diving. However, recent studies have shown that these mammals may alter their dive behavior in response to anthropogenic sound, leading to the potential for nitrogen supersaturation and bubble formation which may cause decompression sickness in the central nervous system (CNS). We examined the degree of interface between blood, gases, and neural tissues in the spinal cord by quantifying its microvascular characteristics in five species of odontocetes (Tursiops truncatus, Delphinus delphis, Grampus griseus, Kogia breviceps, and Mesoplodon europaeus) and a model terrestrial species (the pig-Sus scrofa domesticus) for comparison. This approach allowed us to compare microvascular characteristics (microvascular density, branching, and diameter) at several positions (cervical, thoracic, and lumbar) along the spinal cord from odontocetes that are known to be either deep or shallow divers. We found no significant differences (p < 0.05 for all comparisons) in microvessel density (9.30-11.18%), microvessel branching (1.60-2.12 branches/vessel), or microvessel diameter (11.83-16.079 µm) between odontocetes and the pig, or between deep and shallow diving odontocete species. This similarity of spinal cord microvasculature anatomy in several species of odontocetes as compared to the terrestrial mammal is in contrast to the wide array of remarkable physio-anatomical adaptations marine mammals have evolved within their circulatory system to cope with the physiological demands of diving. These results, and other studies on CNS lipids, indicate that the spinal cords of odontocetes do not have specialized features that might serve to protect them from Type II DCS.

Age- and sex-specific survivorship of the Southern Hemisphere long-finned pilot whale (Globicephala melas edwardii)

Biodiversity loss is a major global challenge of the 21st century. Ultimately, extinctions of species are determined by birth and death rates; thus, conservation management of at-risk species is dependent on robust demographic data. In this study, data gathered from 381 (227 females, 154 males) long-finned pilot whales (Globicephala melas edwardii) that died in 14 stranding events on the New Zealand coast between 2006 and 2017 were used to construct the first age- and sex-specific life tables for the subspecies. Survivorship curves were fitted to these data using (1) a traditional maximum likelihood approach, and (2) Siler's competing-risk model. Life table construction and subsequent survival curves revealed distinct differences in the age- and sex-specific survival rates, with females outliving males. Both sexes revealed slightly elevated rates of mortality among the youngest age-classes (<2 years) with postweaning mortality rates decreasing and remaining relatively low until the average life expectancy is reached; 11.3 years for males and 14.7 years for females. Overall (total) mortality is estimated to be 8.8% and 6.8% per annum for males and females, respectively. The mortality curve resembles that of other large mammals, with high calf mortality, lower postweaning mortality, and an exponentially increasing risk of senescent mortality. An accelerated mortality rate was observed in mature females, in contrast to the closely related short-finned pilot whale (G. macrorhynchus), which selects for an extension to the postreproductive life span. The reason for the observed differences in the mortality rate acceleration and postreproductive life span between the two pilot whale species have not been established and warrant further investigation. Obtaining robust information on the life history of long-lived species is challenging, but essential to improve our understanding of population dynamics and help predict how future pressures may impact populations. This study illustrates how demographic data from cetacean stranding events can improve knowledge of species survival rates, thus providing essential information for conservation management.

Budd-Chiari-like pathology in dolphins

Nearly two decades ago, pathologic examination results suggested that acoustic factors, such as mid-frequency active naval military sonar (MFAS) could be the cause of acute decompression-like sickness in stranded beaked whales. Acute systemic gas embolism in these whales was reported together with enigmatic cystic liver lesions (CLL), characterized by intrahepatic encapsulated gas-filled cysts, tentatively interpreted as “gas-bubble” lesions in various other cetacean species. Here we provide a pathologic reinterpretation of CLL in odontocetes. Among 1,200 cetaceans necropsied, CLL were only observed in four striped dolphins (Stenella coeruleoalba), with a low prevalence (2%, N = 179). Together, our data strongly suggest that CLL are the result of the combination of a pre-existing or concomitant hepatic vascular disorder superimposed and exacerbated by gas bubbles, and clearly differ from acute systemic gas embolism in stranded beaked whales that is linked to MFAS. Budd-Chiari-like syndrome in dolphins is hypothesized based on the present pathologic findings. Nonetheless, further researched is warranted to determine precise etiopathogenesis(es) and contributing factors for CLL in cetaceans.

Microscopic Findings in the Cardiac Muscle of Stranded Extreme Deep-Diving Cuvier's Beaked Whales (Ziphius cavirostris)

Considerable information has been gained over the last few decades on several disease processes afflicting free-ranging cetaceans from a pathologist's point of view. Nonetheless, there is still a dearth of studies on the hearts of these species. For this reason, we aimed to improve our understanding of cardiac histological lesions occurring in free-ranging stranded cetaceans and, more specifically, in deep-diving Cuvier's beaked whales. The primary cardiac lesions that have been described include vascular changes, such as congestion, edema, hemorrhage, leukocytosis, and intravascular coagulation; acute degenerative changes, which consist of contraction band necrosis, wavy fibers, cytoplasmic hypereosinophilia, and perinuclear vacuolization; infiltration of inflammatory cells; and finally, the presence and/or deposition of different substances, such as interstitial myoglobin globules, lipofuscin pigment, polysaccharide complexes, and intra- and/or extravascular gas emboli and vessel dilation. This study advances our current knowledge about the histopathological findings in the cardiac muscle of cetaceans, and more specifically, of Cuvier's beaked whales.

Establishment of a fish model to study gas-bubble lesions

Decompression sickness (DCS) is a clinical syndrome caused by the formation of systemic intravascular and extravascular gas bubbles. The presence of these bubbles in blood vessels is known as gas embolism. DCS has been described in humans and animals such as sea turtles and cetaceans. To delve deeper into DCS, experimental models in terrestrial mammals subjected to compression/decompression in a hyperbaric chamber have been used. Fish can suffer from gas bubble disease (GBD), characterized by the formation of intravascular and extravascular systemic gas bubbles, similarly to that observed in DCS. Given these similarities and the fact that fish develop this disease naturally in supersaturated water, they could be used as an alternative experimental model for the study of the pathophysiological aspect of gas bubbles. The objective of this study was to obtain a reproducible model for GBD in fish by an engineering system and a complete pathological study, validating this model for the study of the physiopathology of gas related lesions in DCS. A massive and severe GBD was achieved by exposing the fish for 18 h to TDG values of 162-163%, characterized by the presence of severe hemorrhages and the visualization of massive quantities of macroscopic and microscopic gas bubbles, systemically distributed, circulating through different large vessels of experimental fish. These pathological findings were the same as those described in small mammals for the study of explosive DCS by hyperbaric chamber, validating the translational usefulness of this first fish model to study the gas-bubbles lesions associated to DCS from a pathological standpoint.

Molecular Diagnosis of Cetacean Morbillivirus in Beaked Whales Stranded in the Canary Islands (1999–2017)

A retrospective survey for detecting the cetacean morbillivirus (CeMV) was carried out in beaked whales (BWs) stranded in the Canary Islands (1999–2017). CeMV is responsible for causing worldwide epizootic events with the highest mass die-offs in cetaceans, although the epidemic status of the Canarian Archipelago seems to be that of an endemic situation. A total of 319 tissue samples from 55 BWs (35 Cuvier’s BWs and 20 specimens belonging to the Mesoplodon genus) were subjected to the amplification of a fragment of the fusion protein (F) and/or phosphoprotein (P) genes of CeMV by means of one or more of three polymerase chain reactions (PCR). RNA integrity could not be demonstrated in samples from 11 animals. Positivity (dolphin morbillivirus strain (DMV)) was detected in the skin sample of only a subadult male Cuvier’s BW stranded in 2002, being the earliest confirmed occurrence of DMV in the Cuvier’s BW species. The obtained P gene sequence showed the closest relationship with other DMVs detected in a striped dolphin stranded in the Canary Islands in the same year. A phylogenetic analysis supports a previous hypothesis of a cross-species infection and the existence of the circulation of endemic DMV strains in the Atlantic Ocean similar to those later detected in the North-East Atlantic, the Mediterranean Sea and the South-West Pacific.

Pulmonary and Systemic Skeletal Muscle Embolism in a Beaked Whale with a Massive Trauma of Unknown Aetiology

Simple Summary

A severe trauma of unknown aetiology was suspected as the cause of death in an adult female Sowerby’s beaked whale found floating dead in the Canary Islands in December 2016. Many bruises in the skin and muscles (contusions) were observed in the chest wall and bone fractures, mainly located in the mandible and ribs. The broken rib bones also affected thoracic muscles, which escaped into the blood circulation once ruptured, reaching several organic locations, including the lungs, where they became trapped within the small lumen of pulmonary blood vessels, leading to a systemic and pulmonary skeletal muscle embolism. An embolism occurs when a piece of intravascular internal or foreign material obstructs the lumen of a blood vessel, starving tissues of blood and oxygen. An embolism necessarily needs cardiac function, indicating a survival time after trauma. This case report aimed to include the diagnosis of skeletal muscle embolism as a routine tool to determine if the traumatic event occurred before or after death. This is especially valuable when working with dead animals because no other evidence of traumatic injury may be recorded if carcasses are in advanced decay.

Abstract

An adult female Sowerby’s beaked whale was found floating dead in Hermigua (La Gomera, Canary Islands, Spain) on 7 December 2016. Severe traumas of unknown aetiology were attributed, and the gross and microscopic findings are consistent with catastrophic trauma as a cause of death. Rib fractures affected the intercostals, transverse thoracis skeletal muscles, and thoracic rete mirabile. Degenerated muscle fibres were extruded to flow into vascular and lymphatic vessels travelling to several anatomic locations into the thoracic cavity, including the lungs, where they occluded the small lumen of pulmonary microvasculature. A pulmonary and systemic skeletal muscle embolism was diagnosed, constituting the first description of this kind of embolism in an animal. The only previous description has been reported in a woman after peritoneal dialysis. Skeletal pulmonary embolism should be considered a valuable diagnostic for different types of trauma in vivo in wild animals. This is especially valuable when working with decomposed carcasses, as in those cases, it is not always feasible to assess other traumatic evidence.

Methodology and Neuromarkers for Cetaceans’ Brains

Cetacean brain sampling may be an arduous task due to the difficulty of collecting and histologically preparing such rare and large specimens. Thus, one of the main challenges of working with cetaceans’ brains is to establish a valid methodology for an optimal manipulation and fixation of the brain tissue, which allows the samples to be viable for neuroanatomical and neuropathological studies. With this in view, we validated a methodology in order to preserve the quality of such large brains (neuroanatomy/neuropathology) and at the same time to obtain fresh brain samples for toxicological, virological, and microbiological analysis (neuropathology). A fixation protocol adapted to brains, of equal or even three times the size of human brains, was studied and tested. Finally, we investigated the usefulness of a panel of 20 antibodies (neuromarkers) associated with the normal structure and function of the brain, pathogens, age-related, and/or functional variations. The sampling protocol and some of the 20 neuromarkers have been thought to explore neurodegenerative diseases in these long-lived animals. To conclude, many of the typical measures used to evaluate neuropathological changes do not tell us if meaningful cellular changes have occurred. Having a wide panel of antibodies and histochemical techniques available allows for delving into the specific behavior of the neuronal population of the brain nuclei and to get a “fingerprint” of their real status.

Crassicaudiasis in three geographically and chronologically distant Cuvier's beaked whales (Ziphius cavirostris) stranded off Brazil

The Cuvier's beaked whale (CBW; Ziphius cavirostris) is a cosmopolitan marine mammal found in deep tropical and temperate waters of all oceans. CBW strandings have been recorded sporadically in Brazil; however, there is lack of information available regarding their causes of stranding and/or death. Herein, we report the epidemiologic, pathologic, morphologic parasitologic features and molecular identification of arterial and renal crassicaudiasis by Crassicauda sp. in three geographically and chronologically distant CBW stranded off Brazil. CBW-1 was an adult male stranded dead in Rio Grande do Sul State. CBW-2 was an adult female that stranded alive in Sergipe State and died shortly after. CBW-3 was and adult male that stranded dead in Santa Catarina State. The most relevant pathologic findings in these three CBW were severe, chronic proliferative mesenteric and caudal aortic endarteritis and chronic granulomatous and fibrosing interstitial nephritis with renicular atrophy and loss, and numerous intralesional Crassicauda sp. nematodes. Furthermore, CBW-1 had concomitant gram-negative bacterial pneumonia and pulmonary and hepatic thromboembolism. Morphologic analysis of renal adult nematodes identified Crassicauda sp. in the three CBW. Molecular analyses targeting the 18S and ITS-2 ribosomal loci of renal nematodes in CBW-2 and CBW-3 identified C. anthonyi. It is believed that severe arterial and renal crassicaudiasis likely resulted or contributed significantly to morbidity and death of these animals. These results expand the known geographical range of occurrence of crassicaudiasis in CBW. Specifically, the present study provides the first accounts of arterial and renal crassicaudiasis in CBW off the southern hemisphere, specifically in CBW off Brazil, and to the authors' knowledge, it is the first record of C. anthonyi in the southern Atlantic Ocean.

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First record of Crassicauda anthonyi in cetaceans off the southern Atlantic Ocean.

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Arterial and renal crassicaudiasis may be fatal in Ziphius cavirostris.

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ITS-2 gene sequence analysis enables Crassicauda species identification.

Towards a better characterisation of deep-diving whales' distributions by using prey distribution model outputs?

In habitat modelling, environmental variables are assumed to be proxies of lower trophic levels distribution and by extension, of marine top predator distributions. More proximal variables, such as potential prey fields, could refine relationships between top predator distributions and their environment. In situ data on prey distributions are not available over large spatial scales but, a numerical model, the Spatial Ecosystem And POpulation DYnamics Model (SEAPODYM), provides simulations of the biomass and production of zooplankton and six functional groups of micronekton at the global scale. Here, we explored whether generalised additive models fitted to simulated prey distribution data better predicted deep-diver densities (here beaked whales Ziphiidae and sperm whales Physeter macrocephalus) than models fitted to environmental variables. We assessed whether the combination of environmental and prey distribution data would further improve model fit by comparing their explanatory power. For both taxa, results were suggestive of a preference for habitats associated with topographic features and thermal fronts but also for habitats with an extended euphotic zone and with large prey of the lower mesopelagic layer. For beaked whales, no SEAPODYM variable was selected in the best model that combined the two types of variables, possibly because SEAPODYM does not accurately simulate the organisms on which beaked whales feed on. For sperm whales, the increase model performance was only marginal. SEAPODYM outputs were at best weakly correlated with sightings of deep-diving cetaceans, suggesting SEAPODYM may not accurately predict the prey fields of these taxa. This study was a first investigation and mostly highlighted the importance of the physiographic variables to understand mechanisms that influence the distribution of deep-diving cetaceans. A more systematic use of SEAPODYM could allow to better define the limits of its use and a development of the model that would simulate larger prey beyond 1,000 m would probably better characterise the prey of deep-diving cetaceans.

Contribution to Herpesvirus Surveillance in Beaked Whales Stranded in the Canary Islands

Simple Summary

Herpesviruses (HVs) are a large family of DNA viruses infecting animals (including insects and mollusks) and humans. Cetaceans can be also infected by HVs presenting different range of lesions, from dermatitis to meningoencephalitis, or being asymptomatic. Several studies have addressed the question of HVs in cetaceans, although no previous systematic survey of HV in beaked whales (BWs) (Ziphiidae family) has been previously performed. The family Ziphiidae, which includes 22 species in 6 genera, is one of the most widespread families of cetaceans, with a strict oceanic habitat pattern. Beaked whales, Cuvier’s BW in particular, are one of the deepest diving whales and are of particular interest because of a notable relationship between military operations employing mid-frequency sonar and the mass stranding of BWs in different geographic areas, including the Canary Islands. In this study, we analyzed 55 BWs (294 samples) stranded in the Canary Islands from 1990 to 2017 by molecular methods (conventional nested polymerase chain reaction). Our results showed that 8 BWs were infected by HVs, although only three animals displayed lesions indicative of active viral replication. Phylogenetic analysis suggests that HV-BW sequences are species-specific, although more studies are needed to better address this question.

Abstract

Herpesviruses (HVs) (Alpha- and Gammaherpesvirinae subfamilies) have been detected in several species of cetaceans with different pathological implications. However, available information on their presence in beaked whales (BWs) is still scarce. In this study, a total of 55 BWs (35 Ziphius cavirostris and 20 animals belonging to the Mesoplodon genus) were analyzed. Samples (n = 294) were obtained from BWs stranded along the coasts of the Canary Islands (1990–2017). Molecular detection of HV was performed by means of a conventional nested PCR based on the DNA polymerase gene. Herpesvirus was detected in 14.45% (8/55) of the analyzed BWs, including 2 positive animals from a previous survey. A percentage positivity of 8.57% was found within the Cuvier’s BW group, while the percentage of positivity rose to 25% within the Mesoplodon genus group (three M. densirostris, one M. europaeus, and one M. bidens). All the obtained sequences from this study belonged to the Alphaherpesvirinae subfamily, from which three are considered novel sequences, all of them within the Mesoplodon genus group. In addition, to our knowledge, this is the first description of HV infection in Gervais’ and Sowerby’s BWs. Three out of eight HV-positive BWs displayed histopathological lesions indicative of active viral replication.

Decompressive Pathology in Cetaceans Based on an Experimental Pathological Model

Decompression sickness (DCS) is a widely known clinical syndrome in human medicine, mainly in divers, related to the formation of intravascular and extravascular gas bubbles. Gas embolism and decompression-like sickness have also been described in wild animals, such as cetaceans. It was hypothesized that adaptations to the marine environment protected them from DCS, but in 2003, decompression-like sickness was described for the first time in beaked whales, challenging this dogma. Since then, several episodes of mass strandings of beaked whales coincidental in time and space with naval maneuvers have been recorded and diagnosed with DCS. The diagnosis of human DCS is based on the presence of clinical symptoms and the detection of gas embolism by ultrasound, but in cetaceans, the diagnosis is limited to forensic investigations. For this reason, it is necessary to resort to experimental animal models to support the pathological diagnosis of DCS in cetaceans. The objective of this study is to validate the pathological results of cetaceans through an experimental rabbit model wherein a complete and detailed histopathological analysis was performed. Gross and histopathological results were very similar in the experimental animal model compared to stranded cetaceans with DCS, with the presence of gas embolism systemically distributed as well as emphysema and hemorrhages as primary lesions in different organs. The experimental data reinforces the pathological findings found in cetaceans with DCS as well as the hypothesis that individuality plays an essential role in DCS, as it has previously been proposed in animal models and human diving medicine.

Lipid signature of neural tissues of marine and terrestrial mammals: consistency across species and habitats

Marine mammals are exposed to O₂-limitation and increased N₂ gas concentrations as they dive to exploit habitat and food resources. The lipid-rich tissues (blubber, acoustic, neural) are of particular concern as N₂ is five times more soluble in lipid than in blood or muscle, creating body compartments that can become N₂ saturated, possibly leading to gas emboli upon surfacing. We characterized lipids in the neural tissues of marine mammals to determine whether they have similar lipid profiles compared to terrestrial mammals. Lipid profiles (lipid content, lipid class composition, and fatty acid signatures) were determined in the neural tissues of 12 cetacean species with varying diving regimes, and compared to two species of terrestrial mammals. Neural tissue lipid profile was not significantly different in marine versus terrestrial mammals across tissue types. Within the marine species, average dive depth was not significantly associated with the lipid profile of cervical spinal cord. Across species, tissue type (brain, spinal cord, and spinal nerve) was a significant factor in lipid profile, largely due to the presence of storage lipids (triacylglycerol and wax ester/sterol ester) in spinal nerve tissue only. The stability of lipid signatures within the neural tissue types of terrestrial and marine species, which display markedly different dive behaviors, points to the consistent role of lipids in these tissues. These findings indicate that despite large differences in the level of N₂ gas exposure by dive type in the species examined, the lipids of neural tissues likely do not have a neuroprotective role in marine mammals.

Challenges in the Assessment of Bycatch: Postmortem Findings in Harbor Porpoises (Phocoena phocoena) Retrieved From Gillnets

Bycatch is considered one of the most significant threats affecting cetaceans worldwide. In the North Sea, bottom-set gillnets are a specific risk for harbor porpoises (Phocoena phocoena). Methods to estimate bycatch rates include on-board observers, remote electronic monitoring, and fishermen voluntarily reporting; none of these are systematically conducted. Additionally, necropsies of stranded animals can provide insights into bycatch occurrence and health status of individuals. There are, however, uncertainties when it comes to the assessment of bycatch in stranded animals, mainly due to the lack of diagnostic tools specific for underwater entrapment. We conducted a literature review to establish criteria that aid in the assessment of bycatch in small cetaceans, and we tested which of these criteria applied to harbor porpoises retrieved from gillnets in the Netherlands (n = 12). Twenty-five criteria were gathered from literature. Of these, "superficial incisions," "encircling imprints," and "recent ingestion of prey" were observed in the vast majority of our confirmed bycatch cases. Criteria like "pulmonary edema," "pulmonary emphysema," and "organ congestion" were also frequently observed, although considered unspecific as an indicator of bycatch. Notably, previously mentioned criteria as "favorable health status," "absence of disease," or "good nutritional condition" did not apply to the majority of our bycaught porpoises. This may reflect an overall reduced fitness of harbor porpoises inhabiting the southern North Sea or a higher chance of a debilitated porpoise being bycaught, and could result in an underestimation of bycatch rates when assessing stranded animals.

First assessment of POPs and cytochrome P450 expression in Cuvier's beaked whales (Ziphius cavirostris) skin biopsies from the Mediterranean Sea

The Cuvier's beaked whale (Ziphius cavirostris) is one of the least known cetacean species worldwide. The decreasing population trend and associated threats has led to the IUCN categorising the Mediterranean subpopulation as Vulnerable on the Red List of Threatened Species. This study aimed to investigate for the first time the ecotoxicological status of Cuvier's beaked whale in the NW Mediterranean Sea. The study sampled around the 20% of the individuals belonging to the Ligurian subpopulation, collecting skin biopsies from free-ranging specimens. The levels of polychlorinated biphenyl (PCBs), polybrominated diphenyl ethers (PBDEs) and induction of cytochrome's P450 (CYP1A1 and CYP2B isoforms) were evaluated. Results highlighted that the pattern of concentration for the target contaminants was PCBs > PBDEs and the accumulation values were linked to age and sex, with adult males showing significantly higher levels than juvenile. Concerns raised by the fact that 80% of the individuals had PCB levels above the toxicity threshold for negative physiological effects in marine mammals. Therefore, these findings shed light on this silent and serious threat never assessed in the Mediterranean Cuvier’s beaked whale population, indicating that anthropogenic pressures, including chemical pollution, may represent menaces for the conservation of this species in the Mediterranean Sea.

Amyloid-beta peptide and phosphorylated tau in the frontopolar cerebral cortex and in the cerebellum of toothed whales: aging versus hypoxia

Hypoxia could be a possible risk factor for neurodegenerative alterations in cetaceans' brain. Among toothed whales, the beaked whales are particularly cryptic and routinely dive deeper than 1000 m for about 1 h in order to hunt squids and fishes. Samples of frontal cerebral and cerebellar cortex were collected from nine animals, representing six different species of the suborder Odontoceti. Immunohistochemical analysis employed anti-β-amyloid (Aβ) and anti-neurofibrillary tangle (NFT) antibodies. Six of nine (67%) animals showed positive immunolabeling for Aβ and/or NFT. The most striking findings were intranuclear Aβ immunopositivity in cerebral cortical neurons and NFT immunopositivity in cerebellar Purkinje neurons with granulovacuolar degeneration. Aβ plaques were also observed in one elderly animal. Herein, we present immunohistopathological findings classic of Alzheimer's and other neurodegenerative diseases in humans. Our findings could be linked to hypoxic phenomena, as they were more extensive in beaked whales. Despite their adaptations, cetaceans could be vulnerable to sustained and repetitive brain hypoxia.

Effects of marine noise pollution on Mediterranean fishes and invertebrates: A review

Marine noise pollution (MNP) can cause a multitude of impacts on many organisms, but information is often scattered and general outcomes difficult to assess. We have reviewed the literature on MNP impacts on Mediterranean fish and invertebrates. Both chronic and acute MNP produced by various human activities - e.g. maritime traffic, pile driving, air guns - were found to cause detectable effects on intra-specific communication, vital processes, physiology, behavioral patterns, health status and survival. These effects on individuals can extend to inducing population- and ecosystem-wide alterations, especially when MNP impacts functionally important species, such as keystone predators and habitat forming species. Curbing the threats of MNP in the Mediterranean Sea is a challenging task, but a variety of measures could be adopted to mitigate MNP impacts. Successful measures will require more accurate information on impacts and that effective management of MNP really becomes a priority in the policy makers' agenda.

Postnatal development of diving physiology: implications of anthropogenic disturbance for immature marine mammals

Marine mammals endure extended breath-holds while performing active behaviors, which has fascinated scientists for over a century. It is now known that these animals have large onboard oxygen stores and utilize oxygen-conserving mechanisms to prolong aerobically supported dives to great depths, while typically avoiding (or tolerating) hypoxia, hypercarbia, acidosis and decompression sickness (DCS). Over the last few decades, research has revealed that diving physiology is underdeveloped at birth. Here, I review the postnatal development of the body's oxygen stores, cardiorespiratory system and other attributes of diving physiology for pinnipeds and cetaceans to assess how physiological immaturity makes young marine mammals vulnerable to disturbance. Generally, the duration required for body oxygen stores to mature varies across species in accordance with the maternal dependency period, which can be over 2 years long in some species. However, some Arctic and deep-diving species achieve mature oxygen stores comparatively early in life (prior to weaning). Accelerated development in these species supports survival during prolonged hypoxic periods when calves accompany their mothers under sea ice and to the bathypelagic zone, respectively. Studies on oxygen utilization patterns and heart rates while diving are limited, but the data indicate that immature marine mammals have a limited capacity to regulate heart rate (and hence oxygen utilization) during breath-hold. Underdeveloped diving physiology, in combination with small body size, limits diving and swimming performance. This makes immature marine mammals particularly vulnerable to mortality during periods of food limitation, habitat alterations associated with global climate change, fishery interactions and other anthropogenic disturbances, such as exposure to sonar.

Lipids of lung and lung fat emboli of the toothed whales (Odontoceti)

Lipids are biomolecules present in all living organisms that, apart from their physiological functions, can be involved in different pathologies. One of these pathologies is fat embolism, which has been described histologically in the lung of cetaceans in association with ship strikes and with gas and fat embolic syndrome. To assess pathological lung lipid composition, previous knowledge of healthy lung tissue lipid composition is essential; however, these studies are extremely scarce in cetaceans. In the present study we aimed first, to characterize the lipids ordinarily present in the lung tissue of seven cetacean species; and second, to better understand the etiopathogenesis of fat embolism by comparing the lipid composition of lungs positive for fat emboli, and those negative for emboli in Physeter macrocephalus and Ziphius cavirostris (two species in which fat emboli have been described). Results showed that lipid content and lipid classes did not differ among species or diving profiles. In contrast, fatty acid composition was significantly different between species, with C16:0 and C18:1ω9 explaining most of the differences. This baseline knowledge of healthy lung tissue lipid composition will be extremely useful in future studies assessing lung pathologies involving lipids. Concerning fat embolism, non-significant differences could be established between lipid content, lipid classes, and fatty acid composition. However, an unidentified peak was only found in the chromatogram for the two struck whales and merits further investigation.

Long-term and large-scale spatiotemporal patterns of soundscape in a tropical habitat of the Indo-Pacific humpback dolphin (Sousa chinensis)

Little is known about the characteristics of ambient sound in shallow waters southwest of Hainan Island, China, a tropical habitat of the Indo-Pacific humpback dolphin. The spatiotemporal patterns of soundscape in this area were thus studied and described here. Acoustic data collected from February 2018 to February 2019 at ten monitoring sites, spanning ~200 km of the coastline, were analyzed. The ambient sound characteristics in the investigated area showed significant spatiotemporal variations. Sound levels centered at 0.5 and 1 kHz were higher during dusk and night than other times of the day at all monitoring sites except for one. Higher sound levels at frequencies above 8 kHz were documented during autumn and winter at all sites except for three of them. Biological and anthropogenic sound sources including soniferous fishes, snapping shrimps, dolphins, ships, pile-driving activities, and explosions were identified during spectrogram analyses of a subsample of the dataset. The shipping noise was frequently detected throughout the monitoring sites. Spatiotemporal variations of the soundscape in the investigated waters provided baseline information on the local marine environment, which will be beneficial to the protection of the vulnerable Indo-Pacific humpback dolphin population recently discovered in the investigated waters.

Comparison of Three Histological Techniques for Fat Emboli Detection in Lung Cetacean's Tissue

Fat embolism is the mechanical blockage of blood vessels by circulating fat particles. It is frequently related to traumas involving soft tissues and fat-containing bones. Different techniques have been used for decades to demonstrate histologically fat emboli, being the extremely toxic post-fixation with osmium tetroxide one of the most used techniques in the last decades. In the present study, the osmium tetroxide technique was compared qualitatively and quantitatively, for the first time, with chromic acid and Oil Red O frozen techniques  for histological fat emboli detection in the lungs of eight sperm whales that died due to ship strikes. This was also the first time that chromic acid technique was tested in cetaceans. Results showed that the three techniques were valuable for the histological detection of fat embolism in cetaceans, even when tissues presented advanced autolysis and had been stored in formaldehyde for years. Although quantitative differences could not be established, the Oil Red O frozen technique showed the lowest quality for fat emboli staining. On the contrary, the chromic acid technique was proven to be a good alternative to osmium tetroxide due to its slightly lower toxicity, its equivalent or even superior capacity of fat emboli detection, and its significantly lower economic cost.

Comparison of Methods for the Histological Evaluation of Odontocete Spiral Ganglion Cells

Cetaceans greatly depend on their hearing system to perform many vital activities. The spiral ganglion is an essential component of the auditory pathway and can even be associated with injuries caused by anthropogenic noise. However, its anatomical location, characterized by surrounding bony structures, makes the anatomical and anatomopathological study of the spiral ganglion a difficult task. In order to obtain high-quality tissue samples, a perfect balance between decalcification and the preservation of neural components must be achieved. In this study, different methodologies for spiral ganglion sample preparation and preservation were evaluated. Hydrochloric acid had the shortest decalcification time but damaged the tissue extensively. Both formic acid and EDTA decalcification solutions had a longer decalcification time but exhibited better preservation of the neurons. However, improved cell morphology and staining were observed on ears pretreated with EDTA solution. Therefore, we suggest that decalcifying methodologies based on EDTA solutions should be used to obtain the highest quality samples for studying cell morphology and antigenicity in cetacean spiral ganglion neurons.

Effects of acoustic stimulation on biochemical parameters in the digestive gland of Mediterranean mussel Mytilus galloprovincialis (Lamarck, 1819)

Underwater sounds generated by anthropogenic activity can cause behavior changes, temporary loss of hearing, damage to parts of the body, or death in a number of marine organisms and can also affect healing and survival. In this study, the authors examined the effects of high-frequency acoustic stimulations on a number of biochemical parameters in the Mediterranean mussel, Mytilus galloprovincialis. During the experiment, animals were placed in a test tank and exposed to acoustic signals [a linear sweep ranging from 100 to 200 kHz and lasting 1 s, with a sound pressure level range of between 145 and 160 dBrms (re 1μParms)] for 3 h. Total haemocyte count was assessed and glucose levels, cytotoxic activity and enzyme activity (alkaline phosphatase, esterase and peroxidase) in the digestive gland were measured. For the first time, this study suggests that high-frequency noise pollution has a negative impact on biochemical parameters in the digestive gland.

Fatty acid composition and N2 solubility in triacylglycerol-rich adipose tissue: the likely importance of intact molecular structure

Diving tetrapods (sea turtles, seabirds and marine mammals) are a biologically diverse group, yet all are under similar constraints: oxygen limitation and increased hydrostatic pressure at depth. Adipose tissue is important in the context of diving because nitrogen gas (N₂) is five times more soluble in fat than in blood, creating a potential N₂ sink in diving animals. Previous research demonstrates that unusual lipid composition [waxes and short-chained fatty acids (FA)] in adipose tissue of some whales leads to increased N₂ solubility. We evaluated the N₂ solubility of adipose tissue from 12 species of diving tetrapods lacking these unusual lipids to explore whether solubility in this tissue can be linked to lipid structure. Across all taxonomic groups, the same eight FA accounted for 70-80% of the entire lipid profile; almost all adipose tissues were dominated by monounsaturated FA (40.2-67.4 mol%). However, even with consistent FA profiles, there was considerable variability in N₂ solubility, ranging from 0.051±0.003 to 0.073±0.004 ml N₂ ml^-1 oil. Interestingly, differences in N₂ solubility could not be attributed to taxonomic group (P=0.06) or FA composition (P>0.10). These results lead to two main conclusions: (1) in triacylglycerol-only adipose tissues, the FA pool itself may not have a strong influence on N₂ solubility; and (2) samples with similar FA profiles can have different N₂ solubility values, suggesting that 3D arrangement of individual FA within a triacylglycerol molecule may have important roles in determining N₂ solubility.

Endocrine response to simulated U.S. Navy mid-frequency sonar exposures in the bottlenose dolphin (Tursiops truncatus)

Little information exists on endocrine responses to noise exposure in marine mammals. In the present study, cortisol, aldosterone, and epinephrine levels were measured in 30 bottlenose dolphins (Tursiops truncatus) before and after exposure to simulated U.S. Navy mid-frequency sonar signals (3250-3450 Hz). Control and exposure sessions, each consisting of ten trials, were performed sequentially with each dolphin. While swimming across the experimental enclosure during exposure trials, each dolphin received a single 1-s exposure with received sound pressure levels (SPLs, dB re 1 μPa) of 115, 130, 145, 160, 175, or 185 dB. Blood samples were collected through behaviorally conditioned, voluntary participation of the dolphins approximately one week prior to, immediately following, and approximately one week after exposure were analyzed for hormones via radioimmunoassay. Aldosterone was below detection limits in all samples. Neither cortisol nor epinephrine showed a consistent relationship with received SPL, even though dolphins abandoned trained behaviors after exposure to the highest SPLs and the severity of behavioral changes scaled with SPL. It remains unclear if dolphins interpret high-level anthropogenic sound as stressful, annoying, or threatening and whether behavioral responses to sound can be equated to a physiological (endocrine) response.

Deiminated proteins and extracellular vesicles - Novel serum biomarkers in whales and orca

Peptidylarginine deiminases (PADs) are a family of phylogenetically conserved calcium-dependent enzymes which cause post-translational protein deimination. This can result in neoepitope generation, affect gene regulation and allow for protein moonlighting via functional and structural changes in target proteins. Extracellular vesicles (EVs) carry cargo proteins and genetic material and are released from cells as part of cellular communication. EVs are found in most body fluids where they can be useful biomarkers for assessment of health status. Here, serum-derived EVs were profiled, and post-translationally deiminated proteins and EV-related microRNAs are described in 5 ceataceans: minke whale, fin whale, humpback whale, Cuvier's beaked whale and orca. EV-serum profiles were assessed by transmission electron microscopy and nanoparticle tracking analysis. EV profiles varied between the 5 species and were identified to contain deiminated proteins and selected key inflammatory and metabolic microRNAs. A range of proteins, critical for immune responses and metabolism were identified to be deiminated in cetacean sera, with some shared KEGG pathways of deiminated proteins relating to immunity and physiology, while some KEGG pathways were species-specific. This is the first study to characterise and profile EVs and to report deiminated proteins and putative effects of protein-protein interaction networks via such post-translationald deimination in cetaceans, revealing key immune and metabolic factors to undergo this post-translational modification. Deiminated proteins and EVs profiles may possibly be developed as new biomarkers for assessing health status of sea mammals.

Advances in research on the impacts of anti-submarine sonar on beaked whales

Mass stranding events (MSEs) of beaked whales (BWs) were extremely rare prior to the 1960s but increased markedly after the development of naval mid-frequency active sonar (MFAS). The temporal and spatial associations between atypical BW MSEs and naval exercises were first observed in the Canary Islands, Spain, in the mid-1980s. Further research on BWs stranded in association with naval exercises demonstrated pathological findings consistent with decompression sickness (DCS). A 2004 ban on MFASs around the Canary Islands successfully prevented additional BW MSEs in the region, but atypical MSEs have continued in other places of the world, especially in the Mediterranean Sea, with examined individuals showing DCS. A workshop held in Fuerteventura, Canary Islands, in September 2017 reviewed current knowledge on BW atypical MSEs associated with MFAS. Our review suggests that the effects of MFAS on BWs vary among individuals or populations, and predisposing factors may contribute to individual outcomes. Spatial management specific to BW habitat, such as the MFAS ban in the Canary Islands, has proven to be an effective mitigation tool and mitigation measures should be established in other areas taking into consideration known population-level information.

Skeletal and Cardiac Rhabdomyolysis in a Live-Stranded Neonatal Bryde's Whale With Fetal Distress

The main objective of wildlife forensic investigation is to recognize pathologic changes and cause of death. Even though it may not always be possible to determine the specific illness and/or etiology, the description and subsequent interpretation of the injuries provide an invaluable understanding of pathology in cetacean post-mortem investigations. Although pathological studies have been previously reported in various cetacean species, such descriptions of the infraorder Mysticeti remain rare. A live-stranded neonatal Bryde's whale (Balaenoptera edeni) which subsequently died soon after the stranding, was assessed by physical exam, blood examination, gross necropsy evaluation, histopathology, and immunohistochemistry. It presented with elevated serum levels of creatine kinase, cardiac troponin I, urea, and creatinine. Microscopically, we observed keratin spicules (squamous epithelial cells) and areas of atelectasis in the lungs. Acute degeneration in the myocytes and cardiomyocytes were comparable to the findings previously described in cases of capture myopathy in live-stranded cetaceans. Immunohistochemistry biomarkers such as myoglobin, fibrinogen, and troponin were analyzed. Skeletal and myocardial damage has been documented in several cetacean species. However, this is the first reported case of skeletal and cardiac rhabdomyolysis associated with live-stranding in a newborn Bryde's whale that suffered from fetal distress.

Gross and histopathologic diagnoses from North Atlantic right whale Eubalaena glacialis mortalities between 2003 and 2018

Seventy mortalities of North Atlantic right whales Eubalaena glacialis (NARW) were documented between 2003 and 2018 from Florida, USA, to the Gulf of St. Lawrence, Canada. These included 29 adults, 14 juveniles, 10 calves, and 17 of unknown age class. Females represented 65.5% (19/29) of known-sex adults. Fourteen cases had photos only; 56 carcasses received external examinations, 44 of which were also necropsied. Cause of death was determined in 43 cases, of which 38 (88.4%) were due to anthropogenic trauma: 22 (57.9%) from entanglement, and 16 (42.1%) from vessel strike. Gross and histopathologic lesions associated with entanglement were often severe and included deep lacerations caused by constricting line wraps around the flippers, flukes, and head/mouth; baleen plate mutilation; chronic extensive bone lesions from impinging line, and traumatic scoliosis resulting in compromised mobility in a calf. Chronically entangled whales were often in poor body condition and had increased cyamid burden, reflecting compromised health. Vessel strike blunt force injuries included skull and vertebral fractures, blubber and muscle contusions, and large blood clots. Propeller-induced wounds often caused extensive damage to blubber, muscle, viscera, and bone. Overall prevalence of NARW entanglement mortalities increased from 21% (1970-2002) to 51% during this study period. This demonstrates that despite mitigation efforts, entanglements and vessel strikes continue to inflict profound physical trauma and suffering on individual NARWs. These cumulative mortalities are also unsustainable at the population level, so urgent and aggressive intervention is needed to end anthropogenic mortality in this critically endangered species.

Re-evaluating the significance of the dive response during voluntary surface apneas in the bottlenose dolphin, Tursiops truncatus

The dive response is well documented for marine mammals, and includes a significant reduction in heart rate (f_H) during submersion as compared while breathing at the surface. In the current study we assessed the influence of the Respiratory Sinus Arrhythmia (RSA) while estimating the resting f_H while breathing. Using transthoracic echocardiography we measured f_H, and stroke volume (SV) during voluntary surface apneas at rest up to 255 s, and during recovery from apnea in 11 adult bottlenose dolphins (Tursiops truncatus, 9 males and 2 females, body mass range: 140–235 kg). The dolphins exhibited a significant post-respiratory tachycardia and increased SV. Therefore, only data after this RSA had stabilized were used for analysis and comparison. The average (±s.d.) f_H, SV, and cardiac output (CO) after spontaneous breaths while resting at the surface were 44 ± 6 beats min⁻¹, 179 ± 31 ml, and 7909 ± 1814 l min⁻¹, respectively. During the apnea the f_H, SV, and CO decreased proportionally with the breath-hold duration, and after 255 s they, respectively, had decreased by an average of 18%, 1–21%, and 12–37%. During recovery, the f_H, SV, and CO rapidly increased by as much as 117%, 34%, and 190%, respectively. Next, f_H, SV and CO rapidly decreased to resting values between 90–110 s following the surface apnea. These data highlight the necessity to define how the resting f_H is estimated at the surface, and separating it from the RSA associated with each breath to evaluate the significance of cardiorespiratory matching during diving.

Impact of pile-driving on Hector's dolphin in Lyttelton Harbour, New Zealand

Several dolphin species occur close inshore and in harbours, where underwater noise generated by pile-driving used in wharf construction may constitute an important impact. Such impacts are likely to be greatest on species such as the endangered Hector's dolphin (Cephalorhynchus hectori), which has small home ranges and uses this habitat type routinely. Using automated echolocation detectors in Lyttelton Harbour (New Zealand), we studied the distribution of Hector's dolphins using a gradient sampling design over 92 days within which pile-driving occurred on 46 days. During piling operations, dolphin positive minutes per day decreased at the detector closest to the piling but increased at the mid-harbour detector. Finer-grained analyses showed that close to the piling operation, detections decreased with increasing sound exposure level, that longer piling events were associated with longer reductions in detections, and that effects were long-lasting - detection rates took up to 83 h to return to pre-piling levels.

Ventilation and gas exchange before and after voluntary static surface breath-holds in clinically healthy bottlenose dolphins, Tursiops truncatus

We measured respiratory flow (V̇), breathing frequency (f _R), tidal volume (V _T), breath duration and end-expired O₂ content in bottlenose dolphins (Tursiops truncatus) before and after static surface breath-holds ranging from 34 to 292 s. There was considerable variation in the end-expired O₂, V _T and f _R following a breath-hold. The analysis suggests that the dolphins attempt to minimize recovery following a dive by altering V _T and f _R to rapidly replenish the O₂ stores. For the first breath following a surface breath-hold, the end-expired O₂ decreased with dive duration, while V _T and f _R increased. Throughout the recovery period, end-expired O₂ increased while the respiratory effort (V _T, f _R) decreased. We propose that the dolphins alter respiratory effort following a breath-hold according to the reduction in end-expired O₂ levels, allowing almost complete recovery after 1.2 min.

The Possible Effects of High Vessel Traffic on the Physiological Parameters of the Critically Endangered Yangtze Finless Porpoise (Neophocaena asiaeorientalis ssp. asiaeorientalis)

Background: Poyang is the largest freshwater lake in China, where the acoustic environment and space for the critically endangered Yangtze finless porpoises (YFPs) has been altered by heavy vessel traffic and dredging activities. The density of vessel and the rate of dredging increases annually, especially in the area with the highest density of YFPs. The heavy vessel traffic can cause an increase in the physical activities and direct physical injuries to the YFPs. Furthermore, noise is a potent stressor to all cetaceans irrespective of age and can compromise all their physiological functions. The objective of this study was to examine the possible effects of heavy vessel traffic and dredging on the biochemistry, hematology, adrenal, thyroid, and reproductive hormones of two different YFP populations. One population was living in Poyang Lake and the second living in the Tian-E-Zhou Oxbow which is a semi-natural resserve. Results: The results showed statistically significantly higher levels of serum cortisol, fT3, fT4, and lowered testosterone in both adult and juvenile YFPs living in Poyang Lake vs. adult YFPs living in the Tian-E-Zhou Oxbow. The serum biochemical parameters (Aspartate Amino Transferase, Alkaline Phosphatase, High Density Lipoprotein cholesterol ratio, Globulin, Uric acid, Glucose, K+, and Amylase) and the hematology parameters (Red Blood Cells, Hematocrit, Mean Corpuscular Volume, White Blood Cells, and Eosinophils) were statistically significantly higher in the adult Poyang Lake YFPs vs. adult Tian-E-Zhou Oxbow YFPs. On the other hand, adult males of the Tian-E-Zhou Oxbow also showed significantly higher levels of the serum biochemical parameters (Total Cholesterol, Light Density Lipoprotein cholesterol, Direct Bilirubin, Albumin, Lactate Dehydrogenase, CO2, and Na+) and the blood parameters (Mean Corpuscular Hemoglobin and Mean Corpuscular Hemoglobin Concentration). In Poyang Lake YFPs, various parameters showed significantly positive (fT4, amylase, neutrophil, Ca+2) or negative (total protein, lymphocyte) correlations with cortisol levels. Conclusions: The hyperactivity of adrenal glands in response to heavy vessel traffic and dredging resulted in significantly elevated cortisol levels in Poyang Lake YFPs. The higher cortisol level could possibly have affected various hormonal, hematological, and biochemical parameters, and ultimately the YFPs physiology.

Pathologic findings and causes of death of stranded cetaceans in the Canary Islands (2006-2012)

This study describes the pathologic findings and most probable causes of death (CD) of 224 cetaceans stranded along the coastline of the Canary Islands (Spain) over a 7-year period, 2006-2012. Most probable CD, grouped as pathologic categories (PCs), was identified in 208/224 (92.8%) examined animals. Within natural PCs, those associated with good nutritional status represented 70/208 (33.6%), whereas, those associated with significant loss of nutritional status represented 49/208 (23.5%). Fatal intra- and interspecific traumatic interactions were 37/208 (17.8%). Vessel collisions included 24/208 (11.5%). Neonatal/perinatal pathology involved 13/208 (6.2%). Fatal interaction with fishing activities comprised 10/208 (4.8%). Within anthropogenic PCs, foreign body-associated pathology represented 5/208 (2.4%). A CD could not be determined in 16/208 (7.7%) cases. Natural PCs were dominated by infectious and parasitic disease processes. Herein, our results suggest that between 2006 and 2012, in the Canary Islands, direct human activity appeared responsible for 19% of cetaceans deaths, while natural pathologies accounted for 81%. These results, integrating novel findings and published reports, aid in delineating baseline knowledge on cetacean pathology and may be of value to rehabilitators, caregivers, diagnosticians and future conservation policies.

Beached bachelors: An extensive study on the largest recorded sperm whale Physeter macrocephalus mortality event in the North Sea

Between the 8^th January and the 25^th February 2016, the largest sperm whale Physeter macrocephalus mortality event ever recorded in the North Sea occurred with 30 sperm whales stranding in five countries within six weeks. All sperm whales were immature males. Groups were stratified by size, with the smaller animals stranding in the Netherlands, and the largest in England. The majority (n = 27) of the stranded animals were necropsied and/or sampled, allowing for an international and comprehensive investigation into this mortality event. The animals were in fair to good nutritional condition and, aside from the pathologies caused by stranding, did not exhibit significant evidence of disease or trauma. Infectious agents were found, including various parasite species, several bacterial and fungal pathogens and a novel alphaherpesvirus. In nine of the sperm whales a variety of marine litter was found. However, none of these findings were considered to have been the primary cause of the stranding event. Potential anthropogenic and environmental factors that may have caused the sperm whales to enter the North Sea were assessed. Once sperm whales enter the North Sea and head south, the water becomes progressively shallower (<40 m), making this region a global hotspot for sperm whale strandings. We conclude that the reasons for sperm whales to enter the southern North Sea are the result of complex interactions of extrinsic environmental factors. As such, these large mortality events seldom have a single ultimate cause and it is only through multidisciplinary, collaborative approaches that potentially multifactorial large-scale stranding events can be effectively investigated.

Multidisciplinary studies on a sick-leader syndrome-associated mass stranding of sperm whales (Physeter macrocephalus) along the Adriatic coast of Italy

Mass strandings of sperm whales (Physeter macrocephalus) are rare in the Mediterranean Sea. Nevertheless, in 2014 a pod of 7 specimens stranded alive along the Italian coast of the Central Adriatic Sea: 3 individuals died on the beach after a few hours due to internal damages induced by prolonged recumbency; the remaining 4 whales were refloated after great efforts. All the dead animals were genetically related females; one was pregnant. All the animals were infected by dolphin morbillivirus (DMV) and the pregnant whale was also affected by a severe nephropathy due to a large kidney stone. Other analyses ruled out other possible relevant factors related to weather conditions or human activities. The results of multidisciplinary post-mortem analyses revealed that the 7 sperm whales entered the Adriatic Sea encountering adverse weather conditions and then kept heading northward following the pregnant but sick leader of the pod, thereby reaching the stranding site. DMV infection most likely played a crucial role in impairing the health condition and orientation abilities of the whales. They did not steer back towards deeper waters, but eventually stranded along the Central Adriatic Sea coastline, a real trap for sperm whales.

Resting Metabolic Rate and Lung Function in Wild Offshore Common Bottlenose Dolphins, Tursiops truncatus, Near Bermuda

Diving mammals have evolved a suite of physiological adaptations to manage respiratory gases during extended breath-hold dives. To test the hypothesis that offshore bottlenose dolphins have evolved physiological adaptations to improve their ability for extended deep dives and as protection for lung barotrauma, we investigated the lung function and respiratory physiology of four wild common bottlenose dolphins (Tursiops truncatus) near the island of Bermuda. We measured blood hematocrit (Hct, %), resting metabolic rate (RMR, l O₂ ⋅ min^-1), tidal volume (V_T, l), respiratory frequency (f_R, breaths ⋅ min^-1), respiratory flow (l ⋅ min^-1), and dynamic lung compliance (C_L, l ⋅ cmH₂O^-1) in air and in water, and compared measurements with published results from coastal, shallow-diving dolphins. We found that offshore dolphins had greater Hct (56 ± 2%) compared to shallow-diving bottlenose dolphins (range: 30–49%), thus resulting in a greater O₂ storage capacity and longer aerobic diving duration. Contrary to our hypothesis, the specific C_L (sC_L, 0.30 ± 0.12 cmH₂O^-1) was not different between populations. Neither the mass-specific RMR (3.0 ± 1.7 ml O₂ ⋅ min^-1 ⋅ kg^-1) nor V_T (23.0 ± 3.7 ml ⋅ kg^-1) were different from coastal ecotype bottlenose dolphins, both in the wild and under managed care, suggesting that deep-diving dolphins do not have metabolic or respiratory adaptations that differ from the shallow-diving ecotypes. The lack of respiratory adaptations for deep diving further support the recently developed hypothesis that gas management in cetaceans is not entirely passive but governed by alteration in the ventilation-perfusion matching, which allows for selective gas exchange to protect against diving related problems such as decompression sickness.

Modeling Tissue and Blood Gas Kinetics in Coastal and Offshore Common Bottlenose Dolphins, Tursiops truncatus

Bottlenose dolphins (Tursiops truncatus) are highly versatile breath-holding predators that have adapted to a wide range of foraging niches from rivers and coastal ecosystems to deep-water oceanic habitats. Considerable research has been done to understand how bottlenose dolphins manage O2 during diving, but little information exists on other gases or how pressure affects gas exchange. Here we used a dynamic multi-compartment gas exchange model to estimate blood and tissue O2, CO2, and N2 from high-resolution dive records of two different common bottlenose dolphin ecotypes inhabiting shallow (Sarasota Bay) and deep (Bermuda) habitats. The objective was to compare potential physiological strategies used by the two populations to manage shallow and deep diving life styles. We informed the model using species-specific parameters for blood hematocrit, resting metabolic rate, and lung compliance. The model suggested that the known O2 stores were sufficient for Sarasota Bay dolphins to remain within the calculated aerobic dive limit (cADL), but insufficient for Bermuda dolphins that regularly exceeded their cADL. By adjusting the model to reflect the body composition of deep diving Bermuda dolphins, with elevated muscle mass, muscle myoglobin concentration and blood volume, the cADL increased beyond the longest dive duration, thus reflecting the necessary physiological and morphological changes to maintain their deep-diving life-style. The results indicate that cardiac output had to remain elevated during surface intervals for both ecotypes, and suggests that cardiac output has to remain elevated during shallow dives in-between deep dives to allow sufficient restoration of O2 stores for Bermuda dolphins. Our integrated modeling approach contradicts predictions from simple models, emphasizing the complex nature of physiological interactions between circulation, lung compression, and gas exchange.

Cadhla O, Berrow S. Signals from the deep: Spatial and temporal acoustic occurrence of beaked whales off western Ireland

Little is known of the spatio-temporal occurrence of beaked whales off western Ireland, limiting the ability of Regulators to implement appropriate management and conservation measures. To address this knowledge gap, static acoustic monitoring was carried out using eight fixed bottom-mounted autonomous acoustic recorders: four from May to December 2015 on Ireland’s northern slope and four from March to November 2016 on the western and southern slopes. Recorders ran for 205 to 230 days, resulting in 4.09 TB of data sampled at 250 kHz which could capture beaked whale acoustic signals. Zero-crossing-based automated detectors identified beaked whale clicks. A sample of detections was manually validated to evaluate and optimize detector performance. Analysis confirmed the occurrence of Sowerby’s and Cuvier’s beaked whales and Northern bottlenose whales. Northern bottlenose whale clicks occurred in late summer and autumn, but were too few to allow further analysis. Cuvier’s and Sowerby’s clicks occurred at all stations throughout the monitoring period. There was a significant effect of month and station (latitude) on the mean daily number of click detections for both species. Cuvier’s clicks were more abundant at lower latitudes while Sowerby’s were greater at higher latitudes, particularly in the spring, suggesting a spatial segregation between species, possibly driven by prey preference. Cuvier’s occurrence increased in late autumn 2015 off northwest Porcupine Bank, a region of higher relative occurrence for each species. Seismic airgun shots, with daily sound exposure levels as high as 175 dB re 1 μPa²·s, did not appear to impact the mean daily number of Cuvier’s or Sowerby’s beaked whale click detections. This work provides insight into the significance of Irish waters for beaked whales and highlights the importance of using acoustics for beaked whale monitoring.

If technological intelligent extraterrestrials exist, what biological traits are de rigueur

If extraterrestrials exist in the depths of cosmic space, and are capable of interstellar communications, even space flight, there is no requirement that they be humanoid in form. However, certain humanoid capabilities would be advantageous for tool fashioning and critical to operating space craft as well as functioning under the disparate extreme conditions under which they may be forced to operate. They would have to be "gas breathing". The reasonable assumption that life based upon the same elements as Earth life requiring water stems from the unique properties of water that no other similar low molecular weight nonmetal hydride offers. Only water offers the diversity of chemical properties and reactivity, including the existence of the three common physical states within a limited temperature range of service to life, avoiding the issues presented by any alternatives. They must, like us, possess a large, abstract-thinking brain, and probably possess at least all the fundamental senses that humankind possess. They would also be carbon-based life, using oxygen as the electron sink of their biochemistry for the reasons considered. They most likely are homeothermic as us, though they may not necessarily be mammalian as we are. Their biochemistry could differ some from ours, perhaps presenting contact hazards for both species as discussed.

Pulmonary ventilation-perfusion mismatch: a novel hypothesis for how diving vertebrates may avoid the bends

Hydrostatic lung compression in diving marine mammals, with collapsing alveoli blocking gas exchange at depth, has been the main theoretical basis for limiting N2 uptake and avoiding gas emboli (GE) as they ascend. However, studies of beached and bycaught cetaceans and sea turtles imply that air-breathing marine vertebrates may, under unusual circumstances, develop GE that result in decompression sickness (DCS) symptoms. Theoretical modelling of tissue and blood gas dynamics of breath-hold divers suggests that changes in perfusion and blood flow distribution may also play a significant role. The results from the modelling work suggest that our current understanding of diving physiology in many species is poor, as the models predict blood and tissue N2 levels that would result in severe DCS symptoms (chokes, paralysis and death) in a large fraction of natural dive profiles. In this review, we combine published results from marine mammals and turtles to propose alternative mechanisms for how marine vertebrates control gas exchange in the lung, through management of the pulmonary distribution of alveolar ventilation ([Formula: see text]) and cardiac output/lung perfusion ([Formula: see text]), varying the level of [Formula: see text] in different regions of the lung. Man-made disturbances, causing stress, could alter the [Formula: see text] mismatch level in the lung, resulting in an abnormally elevated uptake of N2, increasing the risk for GE. Our hypothesis provides avenues for new areas of research, offers an explanation for how sonar exposure may alter physiology causing GE and provides a new mechanism for how air-breathing marine vertebrates usually avoid the diving-related problems observed in human divers.