Tuna use sharks as back scratchers despite risk of being eaten

Large food similar to scrape against sharks implicit members of their ain species, perchance to pry disconnected parasites

Life 19 October 2022

By Corryn Wetzel

Large food similar tuna whitethorn usage sharks’ unsmooth tegument to escaped themselves of irritating parasites

Christopher D. H. Thompson

Fish opt to scrape themselves against sharks implicit members of their ain species, perchance due to the fact that shark tegument offers an perfect texture for sloughing disconnected outer parasites.

“Shark tegument is truly creaseless successful 1 absorption and it’s similar sandpaper successful the other,” says Chris Thompson astatine the University of Western Australia. By scraping against a unsmooth surface, food tin dislodge achy parasites clinging to their head, eyes and gills.

To larn much astir the interactions betwixt sharks and different fishes, Thompson and his squad deployed floating, baited underwater cameras into 36 antithetic regions of the Pacific, Indian and Atlantic oceans, each of which recorded 2 to 3 hours of footage. During much than 6000 deployments of the cameras, the squad documented 117,000 idiosyncratic animals from 261 antithetic species.

The thousands of hours of footage revealed that yellowfin tuna (Thunnus albacares) were doing astir 44 per cent of the scraping. Blue sharks (Prionace glauca) were astir apt to beryllium scraped against, being the rasp of prime 58 per cent of the time.

In astir each interactions, the food scraped against the rear fractional of the shark, often on its tail. Scraped sharks appeared unbothered by the activity. “I was benignant of amazed astatine however nonchalant the sharks were,” says Thompson.

In 17 per cent of scraping events, food rubbed up connected members of their ain species. Smaller fishes were little apt to usage sharks arsenic a idiosyncratic pumice stone, which the researchers enactment could beryllium due to the fact that tiny food person a higher hazard of being eaten during the little encounter.

“What makes this insubstantial truly absorbing is the sheer fig of [scraping] observations and… that they’ve got truly precocious prime video recording,” says Iain Barber astatine Nottingham Trent University successful the UK.

Barber notes that the enactment suggests that the global diminution of shark species could person knock-on consequences for food anxious to escaped themselves of harmful parasites.

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0275458

More connected these topics:

• animals
• oceans
• sharks