A team of researchers, led by J. Chris McKnight of the University of St. Andrews, used a new wearable device based on near-infrared spectroscopy (NIRS) to investigate how voluntarily diving seals manage their oxygen supply to their brains and blubber, and properly distribute blood, before diving into the depths of the ocean.
McKnight and his team hypothesized that the NIRS technology could provide high-resolution measures of oxygenated and deoxygenated hemoglobin within certain tissues, and therefore be used to estimate blood volume changes before a dive, specifically for this study, published in PLOS Biology, within the brain and blubber.
Before, only invasive technology was available to track such measurements. However, this new device, dubbed the PortaSeal, can simply be attached to the animal’s fur on either the head or shoulder to monitor cerebral blood or peripheral circulation.
The PortaSeal revealed that seals are able to constrict their peripheral blood vessels, and increase cerebral blood volume, about 15 seconds before they dive. They are also able to increase cerebral oxygenation at a consistent time throughout each dive. These circulation adjustments are under somewhat of a cognitive control and not simply a reflex.
“Discovering that seals, which are physiologically fascinating animals, can seemingly actively exert control over their circulatory systems is really exciting,” McKnight said. “It gives a new perspective on the capacity to control the body’s fundamental physiological responses. Getting this insight with non-invasive wearable technology from the bio-medical field offers many exciting future research avenues. We can start to study organs, like the brain, of seals in the open ocean performing exceptional feats like diving to 2000m for 2hrs with heart rates as low as 2bpm, and yet somehow avoid brain trauma.”
Using NIRS to track blood volume and oxygenation in different tissues is vital for tracking and understanding physiological plasticity within diving mammals.
Image Credit: Monica Arso Civil, Sea Mammal Research Unit