A small group of divers, mostly camera pros, filmed this stunning 4K footage in the waters of Koh Tao, Thailand. The subject is a whale shark, a filter-feeding gentle giant that’s also the largest known extant fish species.
The whale shark is covered with (what looks to be) remora suckerfish. Remoras attach themselves to larger marine creatures in a symbiotic arrangement: For the ride, protection, and food, they clean bacteria and parasites from the skin of their hosts.
• The largest accurately measured whale shark was 61.7 feet (18.8 m).
• The whale shark has a huge mouth, which can reach up to 4 feet (1.4 m) across, located at the front of the head.
• Each whale shark has its own individual spot pattern; like human fingerprints, no two are exactly alike.
• Can only swallow small prey because its throat is very narrow, often compared to the size of a quarter.
• A whale shark filters food from the water by “cross-flow filtration,” which means the particles do not catch on the filter. Rather, water is directed away through the gills while particles (which have more momentum) carry on towards the back of the mouth in an ever more concentrated stream. A bolus or spinning ball of food grows in diameter at the back of the throat until it triggers a swallowing reflex. This is very efficient and does not clog the filters.
Related reading at CBC Radio: How remora ‘sucker fish’ use physics to surf on their whale hosts.