Clownfish need their anemones, every child knows that since “Finding Nemo”. A new study shows how close this connection is. Because the size of the fish depends on the anemone.
Clownfish grow to match the size of their native sea anemones. Researchers found this out with the help of experimental laboratory studies in which they observed clownfish in anemones of different sizes. The study was published in the journal Scientific Reports.
‘We first found a close correlation between sizes in a wild population in Papua New Guinea, and then experimentally in the laboratory explored the mechanisms behind this correlation,’ said lead author Theresa Rueger of the University of Newcastle. “To do this, we raised young anemone fish of the same size on anemones of very different sizes.”
Fish that live in larger sea anemones grow faster than those that live in smaller ones. This would optimize the animals’ ability to reproduce, it said. Bigger fish can produce more offspring. However, if they are too big for their anemones, they are less able to hide from predators. Therefore, the adaptation is important for the fish, according to a statement from the university.
“The difference could not be explained by different food intake, since we gave all the fish the same amount of food,” says Rueger. The available space alone was not a reason either, since the effect could not be observed to the same extent with artificial anemones made of silicone.
The experiment shows that the fish actively regulate their growth to adapt to their anemone host. “This is the first time that this plasticity of growth in a vertebrate has been found to be dependent on a reciprocal partner, and it shows the importance of reciprocity.” How exactly the adaptation to the anemone size works is now to be clarified by further studies.