Researchers discovered that whale sharks slowed down to let them remove parasites.

Some whale sharks will slow down their swimming, according to a trio of marine biologists from the University of Western Australia, allowing researchers to collect copepod collections from sensitive areas. Brendon Osorio, Grzegorz Skrzypek, and Mark Meekan found in their study, which was published in the journal Fishes, that researchers have been able to collect parasite samples from whale sharks more successfully in recent years.

For many years, marine biologists have been collecting samples of whale shark skin and/or parasites. Sharks are both the largest nonmammalian vertebrate and the largest known fish. They are sharks, not whales, and the fact that they are so large gave them their name—the largest one has been confirmed to be 18.8 meters long. The sharks are channel feeders and, in this way, present little risk of gnawing. However, due to their size, other animals that approach them too closely run the risk of being injured. They are studied by scientists to learn more about them and the open sea in which they live.

The specialists have been reading up on the sharks for almost 10 years, gathering skin and tissue tests to get familiar with what the sharks may be eating and the way that they jump. In more recent times, they discovered that collecting copepods, which are small parasitic crustaceans that adhere to the sharks’ skin, allowed them to obtain approximately the same amount of data. They likewise noticed that suckerfish, which grip the sharks, do so as a way to eat the copepods; however, they tend just to clear copepods on level, simple to arrive at parts of the skin. The copepods that are clinging to the mouth and fins are preserved. Using a small plastic knife, the researchers began targeting those areas to remove and bag the parasites.

The sharks seemed to remember the encounters fondly, as the researchers collected samples from the same shark multiple times. When the researchers approached, the sharks slowed their swimming rate and, in some instances, stopped swimming altogether, making it easier for the researchers to complete their work. They suggest that getting rid of the parasites makes swimming easier and less irritating.

More information: Brendon James Osorio et al, Parasitic Copepods as Biochemical Tracers of Foraging Patterns and Dietary Shifts in Whale Sharks (Rhincodon typus Smith, 1828), Fishes (2023). DOI: 10.3390/fishes8050261

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