Clownfish and anemones both benefit from their relationship Enlarge

Clownfish boost oxygen flow around their anemone hosts at night, scientists have found.

The relationship between the reef animals is well known, with the fish hiding in the anemone's stinging tentacles to avoid predators.

But US researchers have discovered the anemones also benefit from the night-time presence of the fidgety fish.

As clownfish move around, they boost water flow over the anemone and increase its oxygen consumption.

The findings are published in the Journal of Experimental Biology.

At night there is less oxygen available on the reef because photosynthesis ceases once the sun goes down. But night is also when the main predators of clownfish hunt.

"While many reef organisms can pick up and move to other areas with more oxygen, clownfish stick by their anemones; retreat is not an option," explained Dr Joseph Szczebak from Auburn University, Alabama, US who led the study.

To understand more about the nocturnal relationship of the clownfish and anemone, Dr Szczebak and colleagues travelled to the Marine Science Station in Aqaba, Jordan.

Diving in the nearby Red Sea, the scientists were able to record how oxygen levels changed when the fish were in the anemones and when they were separated.

They found that both the fish and anemones consumed 1.4 times more oxygen when they were together than when apart.

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