No abstract

Decompression sickness (DCS; ‘the bends’) is a disease associated with gas uptake at pressure. The basic pathology and cause are relatively well known to human divers. Breath-hold diving marine mammals were thought to be relatively immune to DCS owing to multiple anatomical, physiological and behavioural adaptations that reduce nitrogen gas (N2) loading during dives. However, recent observations have shown that gas bubbles may form and tissue injury may occur in marine mammals under certain circumstances. Gas kinetic models based on measured time-depth profiles further suggest the potential occurrence of high blood and tissue N2 tensions. We review evidence for gas-bubble incidence in marine mammal tissues and discuss the theory behind gas loading and bubble formation. We suggest that diving mammals vary their physiological responses according to multiple stressors, and that the perspective on marine mammal diving physiology should change from simply minimizing N2 loading to management of the N2 load. This suggests several avenues for further study, ranging from the effects of gas bubbles at molecular, cellular and organ function levels, to comparative studies relating the presence/absence of gas bubbles to diving behaviour. Technological advances in imaging and remote instrumentation are likely to advance this field in coming years.

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.

The vascular system of Cuvier's beaked whales (CBW) (Ziphius cavirostris; family Ziphiidae), an extremely deep, prolonged-diving cetacean, is increasingly receiving anatomic and physiologic study due to possible anthropogenic interactions; however, vascular pathology rarely has been reported in this species. Thirteen CBW stranded in the Canary Islands from June 2008 to June 2014 were autopsied. A careful dissection of the thoracic and abdominal vasculature was performed on these animals. All had moderate to severe and extensive chronic fibrosing arteritis with aneurysms, hemorrhages, and thrombosis primarily involving the mesenteric and gastroepiploic arteries and the thoracic and abdominal aorta. Microscopically, the lesions varied from subacute subintimal hemorrhages and severe neutrophilic, eosinophilic, and histiocytic dissecting arteritis with intralesional nematode larvae to marked, chronic, fibrosing arteritis with thickening and distortion of the vascular wall with calcification and occasional cartilage metaplasia. In addition, adult nematodes in renal arteries and veins, renal parenchyma and/or ureter were identified morphologically as Crassicauda sp. Nucleic acid sequenced from renal nematodes from 2 animals yielded closest nucleotide identity to C. magna The pathogenesis is proposed to involve a host response to larval migration from the intestine to the kidney through the mesenteric arteries, abdominal aorta, and renal arteries. Severe consequences for such lesions are possible and could vary from reduced vascular compliance to chronic renal disease and predisposition to the development of disseminated intravascular coagulation and multiorgan failure. Severe chronic arteritis in CBW is associated with renal parasitism by Crassicauda spp.

Diving air-breathing vertebrates have long been considered protected against decompression sickness (DCS) through anatomical, physiological, and behavioural adaptations. However, an acute systemic gas and fat embolic syndrome similar to DCS in human divers was described in beaked whales that stranded in temporal and spatial association with military exercises involving high-powered sonar. More recently, DCS has been diagnosed in bycaught sea turtles. Both cases were linked to human activities. Two Risso’s dolphin (Grampus griseus) out of 493 necropsied cetaceans stranded in the Canary Islands in a 16-year period (2000–2015), had a severe acute decompression sickness supported by pathological findings and gas analysis. Deadly systemic, inflammatory, infectious, or neoplastic diseases, ship collision, military sonar, fisheries interaction or other type of lethal inducing associated trauma were ruled out. Struggling with a squid during hunting is discussed as the most likely cause of DCS.

The challenge of identifying cause of death in discarded bycaught marine mammals stems from a combination of the non-specific nature of the lesions of drowning, the complex physiologic adaptations unique to breath-holding marine mammals, lack of case histories, and the diverse nature of fishing gear. While no pathognomonic lesions are recognized, signs of acute external entanglement, bulging or reddened eyes, recently ingested gastric contents, pulmonary changes, and decompression-associated gas bubbles have been identified in the condition of peracute underwater entrapment (PUE) syndrome in previous studies of marine mammals. We reviewed the gross necropsy and histopathology reports of 36 cetaceans and pinnipeds including 20 directly observed bycaught and 16 live stranded animals that were euthanized between 2005 and 2011 for lesions consistent with PUE. We identified 5 criteria which present at significantly higher rates in bycaught marine mammals: external signs of acute entanglement, red or bulging eyes, recently ingested gastric contents, multi-organ congestion, and disseminated gas bubbles detected grossly during the necropsy and histologically. In contrast, froth in the trachea or primary bronchi, and lung changes (i.e. wet, heavy, froth, edema, congestion, and hemorrhage) were poor indicators of PUE. This is the first study that provides insight into the different published parameters for PUE in bycatch. For regions frequently confronted by stranded marine mammals with non-specific lesions, this could potentially aid in the investigation and quantification of marine fisheries interactions.

During an investigation into the microbiota of beaked whales (Mesoplodon bidens), nine isolates were obtained from different organs of four animals. The isolates were Gram-positive-staining, catalase-negative, short rod-shaped or coccoid organisms. A phylogenetic analysis based on 16S rRNA gene sequences of these isolates allocated them to the genus Weissella, showing 96.3 % and 96.0 % 16S rRNA gene sequence similarity with Weissella viridescens NRIC 1536 T and Weissella minor NRIC 1625 T , respectively. On the basis of phenotypic, physiological and phylogenetic evidence, it is proposed that the new isolates from whales represent a novel species of the genus Weissella, Weissella ceti sp. nov. The type strain of Weissella ceti is 1119-1A-09 T (5CECT 7719 T 5CCUG 59653 T ).Micro-organisms of the genus Weissella have been isolated from a wide variety of habitats such as soil, fresh vegetables and fermented foods or meat and meat products (Björkroth et al., 2002;Magnusson et al., 2002;De Bruyne et al., 2010;Padonou et al., 2010). In addition, some species have been isolated from human or animal sources. Thus, Weissella cibaria was isolated from human gall and faeces and Weissella confusa was isolated from faeces of children with bacteraemia (Green et al., 1990), from liver transplants (Green et al., 1991) and from the peritoneal fluid and abdominal wall of two patients (Riebel & Washington, 1990). In animals, W. confusa has been isolated from a primate (Cercopithecus mona) with a systemic infection (Vela et al., 2003b), from an autopsied dog and from the ear of a dog with otitis (Björkroth et al., 2002), and from intestines of farmed Asian seabass (Lates calcarifer) (Cai et al., 1998;Rengpipat et al., 2008). W. cibaria and Weissella hellenica have been isolated from the livers of canaries and from the ears of dogs with otitis and from the intestinal contents of flounder (Paralichthys olivaceus), respectively (Cai et al., 1998; Björkroth et al., 2002). Recently, members of the genus Weissella were isolated from diseased rainbow trout (Oncorhynchus mykiss) at a commercial fishery in China (Liu et al., 2009), although they were not identified to species level.Other species of the genus Weissella isolated from animals have not been formally described. In this article, we report the phenotypic and phylogenetic characterization of an unusual Weissella-like organism isolated from stranded beaked whales (Mesoplodon bidens).During an investigation into the microbiota of beaked whales, nine unidentified Gram-positive-staining, rodshaped or coccoid organisms were recovered from muscle tissue (strains 1119-2B-09, 1121-2A-09 and 1122-2A-09), brain (1120-7A-09), kidney (1119-4A-09 and 1121-4A-09), lymph nodes (1121-8A-09), spleen (1119-1A-09 T and 1121-1A-09) of four different animals. None of these animals showed organic lesions associated with these unidentified bacteria after post-mortem studies (gross and histological examination). Strains were isolated on Columbia blood agar plates (bioMérieux) incubated for 24 h at 37 u C...

Gas-bubble lesions were described in cetaceans stranded in spatio-temporal concordance with naval exercises using high-powered sonars. A behaviourally induced decompression sickness-like disease was proposed as a plausible causal mechanism, although these findings remain scientifically controversial. Investigations into the constituents of the gas bubbles in suspected gas embolism cases are highly desirable. We have found that vacuum tubes, insulin syringes and an aspirometer are reliable tools for in situ gas sampling, storage and transportation without appreciable loss of gas and without compromising the accuracy of the analysis. Gas analysis is conducted by gas chromatography in the laboratory. This methodology was successfully applied to a mass stranding of sperm whales, to a beaked whale stranded in spatial and temporal association with military exercises and to a cetacean chronic gas embolism case. Results from the freshest animals confirmed that bubbles were relatively free of gases associated with putrefaction and consisted predominantly of nitrogen.