Decompression sickness (DCS, also known as “the bends”, is the result of the formation of gas bubbles (often nitrogen) in the blood and/or the tissues when the sum of the dissolved gas tension exceeds the absolute pressure. Stemming from a rapid change in pressure, scuba divers can suffer DCS if they ascend too rapidly from deep to shallow waters. In the past, it was thought that diving air-breathing vertebrates, like cetaceans and pinnipeds, were protected against DCS through physiological, anatomical and behavioral adaptations.
Veterinary scientists at the University of Las Palmas de Gran Canaria in Spain, have described an acute systemic gas and fat embolic syndrome in beaked whales, whose pathology was similar to that of human DCS. Fernándex et al (2017) were investigating Risso’s dolphins, Grampus griseus, that stranded in temporal and spatial association with military exercises involving high-powered sonar.
In two of the necropsied whales they found abundant systemic gas-filled vascular dilations (gas bubbles) in the mesenteric epigastric, splenic, diaphragmatic, inter-renicular veins as well as in the lumbo-caudal plexus. In the mesenteric veins, gas bubbles coalesced and obliterated large vessel segments. Extravascular gas bubbles were also detected beneath the renal capsule and in the heart coronary fat depots. Other findings included evidence of interactions with squid, the distil segment of a squid tentacles fixed to the whales, mandible and whole squid with the digestive tract.
Histopathological findings of Risso’s dolphins with acute decompressive pathology. Round non-staining spaces among groups of red cells are consistent with gas bubbles
in liver (a), lung (b) and cerebellum (c). Scattered gas bubbles in the spinal cord
white matter (d).
The author’s ruled out Deadly systemic, inflammatory, infectious, or neoplastic diseases, ship collision, military sonar, fisheries interaction or other types of lethal inducing associated trauma. Instead they hypothesized considering the systemic gas embolism, the high nitrogen2content of the gas bubbles, the presence of entire undigested squid and the related lesions, the most possible explanation of the DCS pathology may have been the result of abnormal diving behaviour and physiology while struggling with their squid prey.
Risso's dolphin with segment of squid tentacle attached to mandibular skin a), gss bubbles in the mesenteric veins d). Mild multifocal haemorrhages following the vascular tracts (arrowheads). Inset: GFVD in the coronary veins associated to petechial haemorrhages e)
Please see the full article Fernandez A., Sierra E., Diaz-Delgado J., Sacchini S., Sanches-Paz Y., Suarez-Sanatan C., Arregui M, Arbelo M., Bernaldo de Quiros Y. (2017) Deadly acute Decompression Sickness in Risso’s dolphins. Scientific Reports 7, Article number: 13621 doi:10.1038/s41598-017-14038-z
https://www.nature.com/articles/s41598-017-14038-z
