First, we’ll be understanding how lungs work and how mammals breathe. Us humans are ‘unconscious’ breathers; this means we breathe without telling ourselves to do so. We also breathe through our nostrils and mouth, however, mammals with a blowhole such as cetaceans have to tell themselves to breathe just the same as they have to consciously send a message from their brain to swallow. This makes them ‘conscious’ breathers.
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Cetaceans need to manipulate the muscle in front of their melon to open their blowhole to breathe. However, the muscles in a cetacean's forehead automatically close the blowhole. Cetaceans, of course, live underwater and therefore they breathe out first to clear the water away from their blowhole when they have surfaced: this prevents them from inhaling any water. After blowing out first, that’s when they then breathe in. This gives the illusion of cetaceans blowing water out of their blowhole. The Orcinus orca can hold their breath for up to 20 minutes! When a cetacean, such as a dolphin, will exhibit a behaviour known as the ‘chuff’ when unwanted debris enters the lungs; like a cough!
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Now you know how mammals breathe, now it’s time for you to understand how lungs work. Inside a mammal’s body will be 2 lungs which will be coated in a thin layer of red blood cells on the inside. These red blood cells will extract oxygen from the gasp of breath the body inhales then the oxygen will travel through blood vessels around the body, especially the brain.
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How about how fish breathe? If you’ve ever seen a fish before, you would’ve noticed that they continuously open and close their mouth. This creates a ‘vacuum’ like effect; when their mouth opens, water will be pulled into their mouths, this technique is named the ‘buccal pumping’. Fish do this to not only catch and eat food debris, but they also do this to pull oxygen towards the inside of their gills and over the lamella to breathe.
Some fish, known as Osteichthyes, have a skeleton made of bone (just like us humans). These fish have adapted to vacuum water into their mouths (as explained earlier). Whereas fish known as cartilaginous (Chondrichthyes), such as sharks, have cartilage as their skeleton material (the same tissue that our ears and nose are made up of). These animals have not evolved to obtain this adaption and therefore need to constantly be swimming in order to breathe and survive. More recently, some species of sharks, such as the Nurse shark, have adapted the technique called ‘buccal pumping’.
If you’ve ever caught sight of the inside of a fish’s mouth, you’d have noticed that the inside of their gills are red: this is due to a thin layer of red blood cells that will also extract oxygen through many blood vessels, similarly to lungs! You’ll notice that man-made fish species such as Goldfish will open and close their mouth more often than others since being ‘man-made’ their genetics are a lot weaker which can disrupt their oxygen intake more than naturally evolved species. However, any fish you buy from a common pet shop will have this issue from being bred badly. When unwanted debris enters a fish’s body, the fish will simply expel the unwanted debris or object back out the mouth. This means that fish can indeed drown as they breathe oxygen just like us; not water as once thought.
Scientific research has concluded that gills and lungs are just as equally efficient.
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Written by Ellie Davies
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