The colors and patterns of the Clownfish
The mutualistic symbiotic relationship between clownfish and anemones has long been known, with each providing a number of benefits to the other.
Immune to the potent effects of the nematocysts in the anemone’s tentacles, the clownfish receives protection from predators, while at the same time the anemone provides clownfish with food scraps from the prey it captures.
In turn, the anemone absorbs nutrients from the waste this saltwater fish produces, aiding growth and regeneration. The continuous movement of the clownfish between the anemone increases the circulation of water around them, allowing for metabolic benefits and further growth.
Although clownfish are famous in our marine aquariums for their vibrant orange and white stripes, until now no one has really investigated a possible link between their markings and the toxicity of the anemones they call home.
The study on the relationship between the colors and patterns of clownfish and anemones
The in-depth study, published in the Journal of Evolutionary Biology, collects data on 27 species of clownfish and 10 known species of host anemone. They looked for associations between certain fish color/pattern traits and the degree of protection offered by the anemone, including tentacle length and degree of toxicity.
Interestingly, they found that clownfish with fewer stripes occupied fewer different anemone species and were more inclined to choose hosts with shorter tentacles.
Fish with additional stripes preferred to settle in a greater variety of anemone species, and these generally had longer tentacles. At the same time, they found that anemones with shorter tentacles tended to possess more potent nematocysts, all of which suggests a complex evolutionary relationship between clownfish rays and anemone type/toxicity.
It has long been recognized that vivid, aposematic coloration and patterns on an animal can be used to warn potential predators of danger before they attack.
But for one animal to use its coloration and pattern to warn predators of another species’ toxicity is especially rare, and perhaps due to the unique arrangement of this remarkable symbiotic relationship.
It suggests that the clownfish are alerting predators to the fact that they are in league with the poisonous anemones by using their bright colours/markings.
However, there is still much more to learn about this intriguing relationship: for example, how the striped clownfish’s patterns appear to predators when seen in front of the host anemone, and how this affects predatory behaviour.