The exchange of bacteria can help the fish 'Nemo & # 39; to coexist with deadly anemones

Nemo, the adorable clownfish in the movie The world of Nemo, rubs on the anemone in which he lives to prevent him from biting and eating it as he does for most fish. According to a new study, this friction leads to the composition of microbes covering the clownfish.

Common bacterial coagulation with anemones can help clownfish comfortably nest in the poisonous tentacles of anemones, a strange symbiosis that life scientists – now including a team from the Georgia Institute of Technology – are trying to understand. Marine researchers have studied microbes on clownfish mixed with deadly anemones.

"It's the iconic mutualism between a host and a partner, and we knew that microbes were present on every surface of every animal," said Frank Stewart, associate professor at the Georgia Tech School of Biological Sciences. "In this particular mutualism, these surfaces are covered with a substance that microbes love to eat: mucus."

Clownfish and anemones exchange a lot of mucus when they rub. The researchers gathered clownfish and anemones and analyzed the microbes present in the mucus covering the fish when they were hosted by anemones or not.

"Their microbiome has changed," said Zoe Pratte, a postdoctoral researcher at Stewart's lab and first author of the new study. "Two bacteria that we have followed in particular have multiplied with contact with anemones."

"In addition, there have been radical changes," said Stewart, the study's lead investigator. "If you looked at the total number of microbe assemblies, their appearance was quite different for a clown fish hosted by an anemone and for another one that was not."

The researchers hunted 12 clownfish in six aquariums for eight weeks to buffer their mucus and identify the microbes by gene sequencing. They published their results in the journal Coral reefs. The research was funded by the Simons Foundation.

Here are some questions and answers about the experience, which have produced amusing anecdotes, as well as fascinating facts about anemones and clownfish. For example: fish that piss on anemones reinforce them. The clown fish changes gender. And it was particularly difficult to catch a fish that the researchers named "Houdini".

No, but it's a new approach to the fish-clown-anemone puzzle.

"It's a first step that begs the question:" Is there any part of the microbial relationship that's changing? ", Said Stewart. The study provided the answer from the clownfish side, which was "yes".

According to an earlier hypothesis on the riddle, the clownfish mucus was too thick to be stung. Current thinking considers that mucus exchange also overlaps clownfish with anemone antigens, ie its own immune proteins, or that fish and fish killer can exchange chemical messages.

"The anemone could recognize a chemical on the clownfish that prevents it from biting," Stewart said. "And that could involve microbes, microbes are great chemists."

In the future, researchers want to analyze the chemistry of mucus. They also do not know how the microbes present on the fish are changing because of the bacteria that the fish gleans from the anemone. It is possible that the fish mucus microbiome develops differently on fish due to contact.

Kill them and eat them.

"The anemone has evolved to kill the fish, it pulls small darts of poison into the skin of a fish to kill it and then pulls it into its mouth," Stewart said. "The clownfish gets out of it as it should."

By the way, tentacles are not harmful to people.

"If you touch an anemone, you will feel like sucking your finger," said Pratte. "Their little harpoons feel like you stick to it, it does not hurt."

For starters, they protect each other from potential prey. But there is a lot more. Some clownfish even change sex by living in an anemone.

"When they start to be housed, the fish make a big change in development," said Stewart. "The first fish of a group that establishes in a wild transition anemone from a male to a female grows much larger and becomes the dominant member of the group."

She is then the only woman in a school of smaller male comrades.

Anemones appear to be growing and healthier, partly because clownfish urinate there.

"When the fish pee, the anemone algae will absorb nitrogen, then secrete sugars that feed the anemone and grow it," Pratte said. "Sometimes the fish drops its food and it falls into the anemone that eats it."

Many: It was a simple but laborious scientific process, partly because the researchers took meticulous care of the fish at the same time.

"You have to put fish and anemones together, and the fish can be housed somewhere else, like corners in the rock," said Pratte.

"Clownfish are smarter than other fish, so they're harder to catch, especially when we want to minimize animal stress," said Alicia Caughman, research assistant at the undergraduate program of Fast Track to Research. the School of Biological Science. "We named a fish" Houdini "It could sneak between nets and confined spaces and be smarter than anyone else trying to catch it."

"We also had" Bubbles ", which blew a lot of bubbles," Biggie "and" Smalls "," Broad "," Sheila "," Earl "and" Flounder ", who liked to flap," Pratte said. Clownfish have different sizes and details in their bands, which allows people to distinguish them.

The anemone side of the microbial issue may be more difficult to answer because, for all of Houdini's tricks, the anemones, which are non-vertebrates, are even more trying. They can sneak into uncomfortable niches or plug the aquarium drainage. They also have microbiomes of temperament.

###

The following researchers co-authored the paper: Nastassia V. Patin, Mary E. McWhirt and Darren J. Parris, all of Georgia Tech. DOI: 10.1007 / s00338-018-01750-z. The research was funded by the Simons Foundation (price 346253). All conclusions, opinions or recommendations are those of the authors and not necessarily those of the Simons Foundation.