July 17, 2018, Frontiers
For the first time, researchers
have explored the physiological adaptations that enable different populations
of the same species of dolphin to vary in diving ability by almost 1000m. The
research, published in two complementary studies in Frontiers in
Physiology, compared the lung mechanics and metabolic rates of bottlenose
dolphin populations known for their different hunting depths. Using theoretical
estimates of gas management, the results support a new hypothesis that lung
architecture and the management of blood flow allow the dolphins to access
oxygen in the lungs while preventing uptake of nitrogen, thereby avoiding
decompression sickness.
Bottlenose dolphin populations
are often found close to land in shallow coastal environments, making short,
shallow dives of less than 10m for their prey. However, some populations—such
as the Bermudian population in this study—frequently dive to depths of up to
400m, and as deep as 1000m on occasion, spending up to 13 minutes underwater in
search of food on a single breath.
"How can a single species
have such extremely different life styles?" This question motivated Dr. Andreas Fahlman of
the Fundación Oceanográfic in Valencia, Spain, who led both studies with his
international team. "We wanted to measure what kind of differences are
responsible for these huge variations. This allows us to determine how far the
physiology can change within a single species and understand the threat that
stressors may have on these deep diving dolphins."
Anyone who has previously
scuba-dived will know about decompression sickness, commonly known as 'the
bends'. This painful and potentially life-threatening condition is caused from
surfacing too quickly at the end of a dive. The rapid expansion of nitrogen
bubbles—which form in the bloodstream and tissues during the dive—are not given
enough time to diffuse from the body naturally during the ascent.
Dolphins run the same risks when
diving to great depths. The team measured the physiology of the lungs and
energy consumption of several bottlenose dolphins known
to make deep dives to understand how these problems are avoided.
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