OBLIGATE RAM VENTILATION: WHEN SHARKS HAVE TO SWIMīut about two dozen species are in the category of sharks that can’t switch and do require constant forward motion to breathe – “obligate ram ventilation. This young whale shark rushed through plankton-rich water at Nigaloo Reef, off the west coast of Australia, sweeping in a meal – and also ram-ventilating. When swimming fast enough, they can cease buccal pumping and rely on ram ventilation. Most sharks, like tiger sharks, sand tiger sharks (a different species) and lemon sharks can alternate breathing techniques. This is “ram ventilation,” as in “ramming” water into their gas exchange systems. For them, it took less energy to let water pass over their gills as they swam than to rely on buccal pumping. Over time, more active species evolved, prizing speed, pelagic seafaring and aggressive pursuit of prey over sedentary lifestyles. They’re re aided by the presence of spiracles, openings on the tops of their heads that they can use to pump water over their gills even when still. Some sharks – prime example: the angel shark – that have a habit of not just lingering on the seafloor but hiding in the sand.
#Sharks dont sleep tv#
As sharks that don’t have to swim continuously, they spend much time resting on the seafloor – not a good strategy for TV ratings. These are animals that receive far less cable television attention, probably because they tend to be less active. Skates and most rays flourish via buccal pumping, as well (as do bony fishes). Sharks have been around for more than 400 million years, and the earliest sharks drew water into their mouths and through their gills for the gas exchange by pumping cheek muscles called buccal muscles.īuccal pumping has survived in many species of modern sharks, particularly in bottom-dwelling sharks like the nurses and carpets. Like all fish, sharks breathe by extracting oxygen from water that passes through their gills. Checking out divers and “ramming” in oxygen-bearing water, a Caribbean reef shark passes by in the Bahamas.ĭO SHARKS HAVE TO SWIM CONSTANTLY IN ORDER TO BREATHE? The answer is yes – for the relatively small number of shark species that excite us the most, like great whites and hammerheads.īut it’s not the case with most of the 400-plus species of sharks in the oceans, like the familiar nurse shark and lesser-known species like bullhead, angel and carpet sharks.
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