Sea Sirens' Secret: How Seals Sense Oxygen Levels to Survive Diving
- By: Nicole Simon
- Approx. Read Time: 3 minutes
- Resourceful survival tactic: Seals detect oxygen levels
Staying underwater without drowning is a tough task for marine mammals, who need oxygen to breathe. But seals might just have an ace up their flippers - they can sense their own blood oxygen levels!
Even though marine animals like us have some adaptations, such as increased oxygen storage and a certain tolerance for low oxygen levels, the risk of running out of oxygen during a dive is always there. For diving mammals, the greatest evolutionary challenge is not drowning.
Was There a Hidden Sensor All Along?
For a long time, it was thought that mammals couldn't directly measure oxygen levels. We and birds rely on a somewhat unreliable system - an increase in carbon dioxide (CO2) levels as a signal for oxygen deprivation. This is risky because our system can be fooled, as seen in freedivers.
But Chris McKnight, a researcher at the University of St Andrews, wondered if marine mammals possessed a fundamentally different sensory system, one that tracks oxygen rather than CO2. This week, his research team revealed just that, discovering that harbor seals (Halichoerus grypus) can withstand dramatic increases in CO2 levels - up to 200 times higher than normal - without altering their dive behavior. However, when they discovered fluctuations in oxygen levels, the length of their dives changed immediately.
Oxygen Regulation and Dive Strategy
Intrigued by their findings, McKnight and his colleagues conducted experiments with a few wild harbor seals. The animals were brought to a research station, where the scientists modified the air conditions in the diving tubes. Starting from a transparent tent-like chamber sticking out of the water, the seals dove about 60 meters to an underwater feeding station, ate some fish, and returned to the adapted breathing chamber.
The results were striking. Even when seals inhaled CO2 at concentrations 200 times higher than ambient air, their dive duration stayed the same. But when researchers varied the concentration of inhaled oxygen, the seals adjusted their dives accordingly. The seals dove longer when oxygen levels were higher, and vice versa, indicating that they're indeed able to perceive the amount of oxygen in their blood and plan their dive duration accordingly.
Can Whales and Dolphins Also Perceive Oxygen Levels?
The discovery raises questions about whether other marine mammals, such as whales and dolphins, might have a similar capacity. With their incredible deep-diving abilities, these species operate on a very thin margin for error.
Future research could help clarify if this capacity is shared among various marine mammal species. The results could also shed light on why humans lack this unique ability, if it's an ancestral trait that our terrestrial descendants gradually lost over time or a capability that we never had in the first place.
- Seals
- Marine mammals
- Diving
- Oxygen
Enrichment Data:While the research focused on gray seals, this ability to sense oxygen levels may be shared among other marine mammals that regularly engage in breath-hold diving. Gray seals possess a higher number of autonomic ganglion cells in their carotid bodies, suggesting that these structures are more sensitive in seals than in terrestrial mammals. This heightened sensitivity is thought to be enhanced by chronic intermittent hypoxia, a condition to which seals are regularly exposed during dives. However, further research is needed to determine if similar mechanisms exist in other marine mammals, such as whales and dolphins.
- Other fish, including fish of the species Gallus gallus, may not possess the ability to sense their own blood oxygen levels like seals do, as seals are unique among vertebrates in this regard.
- It's intriguing to consider if other marine mammals, such as whales and dolphins, might also have the capacity to perceive oxygen levels, given their impressive diving abilities and the thin margin for error they operate on.
- Deficiencies in tolerance to low oxygen levels during diving periods could potentially impact the behavior and survival of other vertebrates, including fish and marine mammals, as it directly affects their ability to manage their dive strategies effectively.
