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How paraste-eating cleaner fish keep sea fish healthy and sharp

The relationship between a fish and its parasite-eating cleaner fish counterpart is a crucial one. The cleaner fish helps keep other fish parasite-free, and now, a new study has found that fish who are healthy are better at problem-solving.

A team of researchers led by Sandra Binning from the Université de Montréal’s Department of Biological Sciences discovered that when a fish is infected by parasites, its cognitive abilities decrease and the fish is unable to solve tests as well as healthy fish.

The study was conducted at the Lizard Island Research Station in Australia, and the findings were published in the Proceedings of the Royal Society B: Biological Sciences.

The results highlight the importance of cleaner fish and the effect that parasites can have on a fish’s mental capabilities.  

If a fish is infected with parasites, it can seek out species like the blue-streaked “cleaner wrasse” that eats parasites off an infected host.

Once the parasites have been removed, the fish is healthy and able to function properly again.

“We collected wild damselfish with or without access to cleaner wrasse and tested their ability to solve a feeding test in the lab,” said Binning. “We then compared their performance to fish that we infected with parasites experimentally.”

Binning said that the fish who were infected with parasites in high numbers were not able to perform as well as the healthy fish.

Similar effects of parasites have been shown in humans as well.

“Studies have found that schoolchildren with stomach worms perform worse on standardized tests than their parasite-free peers,” said Binning. “Treating these kids with anti-parasite medication improves their performance.”

The cleaner fish play such a vital role in the health and wellbeing of seafish that Binning compared them to veterinarians.

“Cleaner wrasse act like the vets of the sea,” Binning said. “Clients visit cleaners to get their parasites removed, and this helps boost their ability to think and solve the test.”

Cleaner fish are critical to reef vitality and the health of seafish but unfortunately, they are a popular aquarium pet. The researchers hope their study will show the essential role that cleaner fish play and the need to conserve their numbers in reef habitats.

“It’s important that we understand the impacts of reduced access to cleaners on client fishes,” said Binning. “Cleaners may not be the largest or most abundant fish on the reef, but they affect the well-being of thousands of their clients. This needs to be taken into consideration when setting collection limits and managing marine parks.”

By Kay Vandette, Staff Writer

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