We’ll talk about sea turtles in a bit, but first, let me ask you: have you ever tried to open your mouth underwater?
I tried doing that once in a swimming pool, and that was the last time I’ll try that. Not only did my mouth instantly fill with water (duh!), but I also panicked due to the sudden change in the ‘breathing dynamic’. Basically, I was holding my breath underwater and when I opened my mouth, I inhaled as a reflex, so my mouth flooded with water, scaring the bejesus out of me.
While I won’t repeat this little experiment, it later made me wonder: how do fish and aquatic creatures eat food underwater? Don’t they end up swallowing too much water when they ingest their food?
There must be some sort of biological mechanism in place that helps aquatic animals fill their bellies without swallowing too much water in the process.
How do fish eat underwater?
It’s a misconception that all fish can breathe underwater; there are certain fish, like dolphins, whose respiratory system is similar to ours. As such, those fish cannot breathe underwater. That’s why they resurface so frequently to inhale and boost the oxygen level in their system.
However, most fish can breathe underwater. They open their mouth to let both food and water fill their oral cavity. The ingested food then makes it way into the digestive system for further ‘processing’, while the water is used to extract breathable oxygen. You see, the main component of the respiratory system of a fish consists of its gills.
When water passes over the gill plates of a fish, the oxygen dissolved in water is extracted by the gill plates and the excess water is expelled. What this essentially means is that when fish need to breathe, they open their mouth and let it fill with water in order to extract breathable oxygen from that water!
How do turtles eat underwater without swallowing too much water?
Although many turtles spend a significant part of their lives underwater, they can only breathe air, so they have to resurface at regular intervals to refill their lungs. However, when they eat, do they end up swallowing a lot of water as well?
In fact, yes, they do!
It’s true that while swallowing food underwater, turtles end up swallowing a lot of water, but this doesn’t cause them any harm.
Think of it this way: while eating food, we end up swallowing a lot of air, don’t we? But does that cause any harm? No, it doesn’t, for the simple reason that the air we ‘swallow’ (or inhale) is used up for respiration and in the production of energy. In fact, we inhale all the time without even realizing that we’re doing it. However, note that doctors advise against breathing through the mouth, especially while eating food, as it may increase flatulence (Source).
Since turtles eat underwater, instead of in the air, they end up swallowing a lot of water while having their meals. This is good for them, as turtles do not produce saliva, which means that they can’t actually swallow without water; they basically need water in order to swallow food. Fortunately, their food pipe or esophagus is quite special, as turtles constrict their food pipe once food enters it. This causes the excess water to be expelled from it, allowing only food and a small amount of water to enter the stomach.
Furthermore, sea turtles have extremely salty tears, which help them expel all the excess salt (accumulated by consuming so much salt water) from within their bodies.
In a nutshell, both fish and turtles end up swallowing a lot of water while eating food underwater, but that doesn’t cause them any harm, as both types of creatures have their own special ways of dealing with this ‘excess water’ problem.