How do diving seals prevent them from drowning? Marine biologists from Scottish University of St Andrews investigated. The marine mammals can immediately observe the oxygen content in their blood, suggest the results that this Thursday Science published.
And that is quite special, because most mammals, including people, mainly use the CO2-Content as an indicator for the amount of oxygen in their blood. When someone entails his breath – below or above water – the amount of oxygen in the blood decreases and the amount of carbon dioxide. Once the CO2-Increase in high, register chemoreceptors of cells. Receptors are proteins that are sensitive to chemical stimuli – CO2 In this case – in, among other things, the carotid arteries. They then send a signal to the breathing muscles through the brain: breathe!
Normally this mechanism works well, but for diving the CO is2-Registration not infallible. For example freediverswrite the researchers: people who dive deep for a single breath for minutes and tens of meters without diving equipment. By consciously hyperventilating for a dive, they can do it2-bring down level in their blood. As a result, they postpone the breath stimulus, which is inspired by a high amount of CO2 In the blood. This is useful to be able to dive longer, but it does entail the risk of unconsciousness and drowning. The diver does not notice on time that the oxygen content is dangerously low.
Only trusting the carbon dioxide content is not enough, according to the researchers. On the contrary: the marine biologists suspected that oxygen plays a more important role than carbon dioxide in the diving behavior of seals.
Six gray seals
To test this, they studied six young, prisoned in the wild, gray seals. The seals swam sixty meters under water in a basin from a breathing room to a sprot dining station under water and back. Only in the room could they come up to breathe. The seals could themselves determine the duration and frequency of their dives. Between the diving series, the biologists changed the percentages O2 and co2 In the room.
What turned out? The seals adapted their diving behavior to the amount of oxygen inhaled, but not to the carbon dioxide content. With more oxygen available than in normal ambient air, the seals dived longer, with less shorter. But even a co2-In content that was two hundred times higher than normal, had no influence on the duration of the dive. That is an indication that the seals can immediately perceive the amount of oxygen in their blood instead of relying on Co2-content. The research only shows this mechanism for gray seals, the researchers emphasize. Yet they suspect the same kind of oh2-Observation also prevents other species. That is an important evolutionary adjustment to prevent drowning for the fiddling Seed animals, according to the biologists.