Innovation and Speciation: aquatic mammals avoid bends (Evolution)

by David Turell , Saturday, November 28, 2020, 20:35 (1246 days ago) @ David Turell

Dolphins can control heart rate b fore a deep dive:

https://www.sciencedaily.com/releases/2020/11/201125091446.htm

"New evidence indicates that dolphins are able to consciously slow down their heart rates when preparing to dive, and can even adjust their heart rates according to the length of their intended dive. This allows them to conserve oxygen and adjust their body to the changing pressure as they dive, therefore avoiding issues such as ''the bends''.

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"The authors worked with three male bottlenose dolphins (Tursiops truncatus), specially trained to hold their breath for different lengths of time upon instruction. "We trained the dolphins for a long breath-hold, a short one, and one where they could do whatever they want," explains Dr Andreas Fahlman of Fundación Oceanogràfic, Valencia, Spain. "When asked to hold their breath, their heart rates lowered before or immediately as they began the breath-hold. We also observed that the dolphins reduced their heart rates faster and further when preparing for the long breath-hold, compared to the other holds."

"'The results reveal that dolphins, and possibly other marine mammals, may consciously alter their heart rate to suit the length of their planned dive. "Dolphins have the capacity to vary their reduction in heart rate as much as you and I are able to reduce how fast we breathe," suggests Fahlman. "This allows them to conserve oxygen during their dives, and may also be key to avoiding diving-related problems such as decompression sickness, known as "the bends." '"

Comment: Another physiological adjustment land-to-water mammals must learn or be given by design. It doesn't seem to be possible to learn by diving. The bends can kill if there are too many nitrogen bubbles that are retained..