A trio of marine biologists from the University of Western Australia have discovered that some whale sharks slow their swim to allow researchers to scrape groups of copepods from their sensitive areas. In their study, reported in the journal fishBrendon Osorio, Grzegorz Skrzypek, and Mark Meekan note that in recent years, whale sharks have become more cooperative as researchers try to collect samples of the parasites.
Marine scientists have been collecting samples of skin and/or parasites from whale sharks for many years. Sharks are the largest known living fish and the largest living non-mammalian vertebrate. They are sharks, not whales, and got their name because of their large size – the largest confirmed size is 18.8 meters in length. Sharks are filter feeders, and therefore pose little risk of biting. However, its large size poses a risk of infecting other creatures that venture near it. Scientists are studying them to learn more about them and the environment they live in – the open sea.
Researchers have been studying sharks for nearly a decade, collecting skin samples and tissue samples to learn more about what sharks can eat and how deep they dive. In recent years, they’ve found that they can get roughly the same data by collecting copepods (a type of small, parasitic crustacean) that attach themselves to the skin of sharks. They also note that suckerfish, which cling to sharks, do so as a means of eating copepods, but tend only to remove copepods on the flat, easily accessible parts of the skin. The copepods cling to the areas around the mouth, leaving the fins intact. For this reason, the researchers began targeting those areas with a small plastic knife to remove and encapsulate the parasites.
Over time, the researchers collected samples from the same shark more than once, and the sharks seemed to remember those encounters fondly—they began slowing their swimming rate as the researchers got closer, and in some cases stopped swimming altogether, making it easier for them to swim. researchers to do their work. They suggest that removing the parasites reduces irritation and makes swimming more efficient.
Brendon James Osorio et al, Parasitic copepods as biochemical tracers of foraging patterns and dietary transitions in whale sharks (Rhincodon typus Smith, 1828), fish (2023). DOI: 10.3390 / FISH 8050261
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