After many episodes that focused on the smaller and more cryptic marine life, in this „Take a Minute to Relax“ we’d like to introduce you to the largest fish in the ocean, the whale shark (Rhincodon typus). The name of this creature has confused people for many years, and unlike what it seemingly suggests, this creature is in no way related to whales.
The only reason this was added to its name, was to give people an idea about the immense size of this fish. Rhincodon typus can grow up to a size of around 18 metres when given the chance. Although most adults that are encountered by people are around 12 metres in length. Not only are these creatures very large, but they can live to be around 130 years!
Take a Minute to Relax XXXIX: Whale shark (Rhincodon typus)
Despite its enormous size, and the amount of research that’s been done on them, much of the whale sharks‘ life is still shrouded in mystery. This is probably due to the fact that whale sharks migrate and can easily travel great distances. One particular tagged specimen was recorded to travel nearly 15.000 kilometres, in a little over 3 years. On top of that Rhincodon typus can dive to a depth of around 1,500 metres. All of this makes it very hard for scientists to study this iconic creature.
How giants are born
As mentioned before, not everything is known about the reproductive behaviour and life cycle of whale sharks. But what we do know is that Rhincodon typus reaches sexual maturity around 30 years of age, and is ovoviviparous. Meaning that the female lays eggs and keeps them inside of her body. When fertilised, they will hatch, but remain safely inside until they are fully formed and strong enough to start their life outside of their mother’s body. A whale shark can give birth to about 300 pups that are about 40-60 cm in length, and already look like a miniature version of their parents.
How whale sharks (Rhincodon typus) feed
Although whale sharks are no threat to humans and are referred to as the gentle giants of the ocean, they do have teeth. In fact, they have more than 3,000 teeth stacked in 300-350 rows, which is more than any other shark species. Despite all these teeth in their enormous 1-1,5 metre mouths, these sharks are filter feeders. Meaning that these animals feed by straining suspended matter and food particles from water. They typically do so by letting the water pass over a specialized filtering structure. Due to the fact that they play such an important role in clarifying water, filter feeders are considered to be ecosystem engineers.
The whale shark also feeds by active suction feeding. This occurs when they are in a vertical position. The animal opens and closes its mouth, sucking in volumes of water, then expelled them through the gills. Rhincodon typus can process over 6,000 litres (1,500 gallons) of water each hour in this fashion! The whale shark’s most common diet consists of plankton, copepods, krill, fish eggs, jellyfish, red crab larvae and small nektonic life, such as small squid or fish. To eat, the whale shark opens its formidable sized jaws and passively filters everything in its path. This technique is called “cross-flow filtration”, and is similar to how some bony fish and baleen whales feed.
From species to individual
The distinct pattern of white spots on the whale shark’s back is unique, and no two are alike. Which makes them a bit like human fingerprints, and helps scientists identify individuals. Since swimming with this creature is high on the list of divers and snorkellers alike, we can all contribute by making our photos available to organisations and researchers that study this incredible creature.
How about some more marine life to relax with?
Scientific classification / Taxonomy: Rhincodon typus