Adaptations to diving in mammals

In this section, you’ll learn how diving mammals can stay underwater for so long. Hi, I’m Dr. Christopher Clemente, and I’m a specialist in animal eco physiology at the University of the Sunshine Coast. Now the average person can hold their breath for about 30 to 90 seconds. The world record for breath holding is just under 12 minutes, which is incredible. But this really pales in comparison to what some marine mammals are capable of doing. For example, Weddell seals voluntarily dive to 600 metres for greater than 60 minutes. Sperm whales can dive to at least 1134 metres and can hold their breath for nearly two hours. So how have these marine mammals evolved the ability to dive underwater for so long?

Well, contrary to the way humans go about diving, most marine mammals don’t use their lungs. The reason they can’t use their lungs is that at really deep depths, the air in the lungs would be compressed and the volume available would not be very large at all. In fact, diving mammals have five key innovations that allow them to stay underwater for so long. The first is that diving mammals have greater oxygen stores per unit bodyweight than terrestrial mammals. It’s not just their lungs, they actually stored in their blood. Check out this plot. Their blood has a high oxygen carrying capacity and they have higher blood volumes.

They also have high concentrations of myoglobin in their muscles, which is similar to haemoglobin in your blood, but it’s capable of taking the oxygen from it. But even this is not enough. Let’s do a quick calculation from the amount of blood and muscle in our 450 kilogramme. Weddell seal, it has an oxygen store of about 38.8 litres. Now when it’s breathing air on the surface, it uses about two litres of oxygen per minute. So the seal could sustain its resting arterial rate of oxygen consumption for about 17 to 20 minutes during diving, it completely used up all its available oxygen stores. Now, most dives are aerobic, but not all of them.

As early as 1934, a scientist named Irving recognise that certain tissues for example, the central nervous system or the heart are dependent on aerobic metabolism and are quickly damaged by oxygen insufficiency. Others for example, the skeletal muscle can work anaerobically that is without oxygen, at least for a short period of time. So the second trick is to shut off the blood supply to non essential organs. How did they do this? Well, experiments have shown that circulation to many parts of the body is reduced by a visor constriction, a constriction of certain blood vessels, the heart pumps blood primarily between itself and the lungs and the head.

Early experiments showed small cuts that bled freely when seals were breathing air on the surface stopped completely when the seals were pushed underwater. So if you don’t have to pump as much blood around the body, you can save energy and oxygen in other ways, like reducing heart rate, which moves us to a third mechanism diving animals use diving Briar cardio, the heart rate is reduced during really long dogs. But it’s not just a breathing mammals that show this response. In fact, even fish like flying fish show the same response when they jump out of water. So it’s luckily this response evolved really early on. mechanism for involves diving metabolism are the fuel sources during ducts.

The body becomes metabolically subdivided during forced or protected dives. The parts of the body which have been shut off from the blood supply, like the muscles quickly deplete their oxygen store, while the circulating blood which serves the brain remains high. As the muscles use up their oxygen, they switch to anaerobic metabolism, which is metabolism without oxygen, and this produces lactic acid which accumulates in the muscles, but little leaks into that circulating blood. When a dive ends. The blood flow is promptly restored to these better constricted tissues and the lactic acid is washed out.

That washed out results in a rapid rise in the lactic As the concentration of the circulating blood, and it takes a little bit of time to remove it all. And this wash out limits the time that these diving mammals can have between the successive dots. Now the last mechanism is quite incredible. The nerves in our brain called neurons need oxygen to keep working, or the nerve membrane itself loses its ability to send messages. But seal neurons are more resistant to the loss of membrane potential when placed in low oxygen conditions than a mask neurons. This means that seals remain conscious when oxygen levels fall to a level that would cause blackout for most mammals.

This permits the seal to make almost complete use of their oxygen stores, especially during really long bucks. In the next section, we will look over an article which goes through these aspects in a little more detail. But before we do, how long can you hold your breath for? Leave a comment below and let’s see who is more seal than human