Brett Smith for redOrbit.com – Your Universe Online
Clownfish became very popular 10 years ago when Disney released the animated feature film Finding Nemo, but the colorful fish are also famous among aquarium enthusiasts for their symbiotic relationship with the deadly sea anemone.
According to a new report in the Journal of Experimental Biology, a new aspect of this relationship has recently been uncovered: at night the fish oxygenate their partner anemone by agitating the water throughout the anemone´s tentacles.
Scientists had known that the anemone serves as refuge for the clownfish by selectively not stinging them with their deadly tentacles and in return the fish keeps the anemone free from parasites and would-be predators.
Marine biologist Joe Szczebak from Auburn University suspected that there might be more to the seemingly simplistic collaboration. After learning that coral reefs benefit from the oxygenating fins of the damselfish that waft water over corals at night, Szczebak wondered if clownfish conveyed a similar benefit to their anemone hosts.
“There had been almost no research done on the clownfish—anemone mutualism at night,” explains Szczebak.
To begin his investigation, Szczebak traveled to the Marine Science Station in Aqaba, Jordan where he and some colleagues collected specimens of both the colorful fish and their anemone partners.
The team then separated each fish from its anemone and measured the individual oxygen consumption rates of the two organisms. They found that the fish and anemone consumed 1.4 times more oxygen when they were united than when they were alone.
After releasing the Red Sea organisms back into their natural habitat, Szczebak and his team repeated the experiments back in his Auburn laboratory. However, this time separated the symbiants using a plastic mesh that allowed the clownfish to see and smell its partner.
Szczebak found that the oxygen consumption for the two organisms was still lower than when they were in direct contact.
“There was something about the physical contact between them that was the source of the increase,” said Szczebak.
The team also filmed the clownfish at night as they nestled in amongst their anemone’s tentacles. After studying the video, the researchers realized that the fish were more active than previously thought. The fish were seen fanning the anemone rapidly with their fins, burrowing deep into their host, and making 180-degree turns deep within the collection of tentacles. The team suspected that this activity helped to circulate fresher, or more oxygenated, water through the anemone.
To check this suspicion, Szczebak measured the oxygen consumption of the anemones as he flowed water through them at various speeds. He found that their oxygen consumption never increased by as much as it did when they were in contact with a clownfish, suggesting that the clownfish also add to the pair´s increased oxygen consumption.
“I think that I have found foundational evidence that, like similar symbioses on coral reefs, (clownfish) may actively modulate flow conditions surrounding their host to benefit them under low oxygen scenarios,” says Szczebak.
He added that current research is focused on finding out whether the fish also benefit from the additional water circulation.