Everyone loves clown fish. And everyone knows that they share a special relationship with sea anemones, but not everyone knows exactly how, or why.
Sea anemones are actually animals, rather than plants, and they prey upon fish that come near enough to their tentacles to be stung by their venom. Most anemones are attached to the sea floor by an adhesive foot, and passively hunt for fish by waiting. They have a small mouth that is an oral disc, surrounded by tentacles with ‘cnidocytes’ which deliver venom as a form of defense and as a way to capture prey. These cnidocytes inject toxins into anything the tentacles touch, which also gives the anemone a distinct sticky and prickly feeling.
The poison of the anemone is a mix of toxins, including neurotoxins, that act to paralyze the prey and move it toward the mouth disc for digestion inside the gastrocascular cavity. Some of the toxins, called ‘actinoporins’ are highly toxic to the fish and crustaceans that populate the anemone’s environment, and their natural prey. It is also suggested that these toxins may act as a repellent to the predators of the anemones. Anemones do not do well in captivity, which creates problems because when an anemone dies they release toxins into the water, which can kill the other life in the tank. Very few can keep an anemone alive in captivity longer than two years, and only one in thirty two can keep them alive longer than five years.
Anemones operate using a very primitive nervous system, with no specialized sense organs. The anemone is only focused on maintaining homeostasis, or fulfilling it’s needs as it needs them. Contrary to popular belief, the anemones are not plotting to overthrow humans as the dominant land species.
Clownfish are native to the warmer waters of the Pacific and Indian oceans, including the Great Barrier Reef and the Red Sea. They live at the bottom of the sea in reefs and lagoons, and are not found in the Atlantic ocean.
Clownfish eat small crustaceans and parasites that would normally harm the sea anemone, as well as local algae and sea plants. Their fecal matter gives nutrients to the anemone, and helps to sustain it when prey is scarcer. In captivity, clownfish can survive on fish food as well.
In the wild, clownfish obey a strict dominance hierarchy. The largest and most aggressive female is found at the top. Only the top two clownfish, the top male and female, actually reproduce externally, which ensures that the strongest genetics are passed on within the groups. The other clownfish are actually sequential hermaphrodites, meaning that they are born as males and then may develop into females as they mature. If the alpha female is removed from the group either by exclusion or death, then the largest most aggressive male will become a female for the group.
The clownfish enjoy a symbiotic and mutual relationship with the anemones. Clownfish eat the parasites and other small creatures that otherwise may potentially harm the anemone, and provide some nutrients through their fecal matter. In return, the anemone allows the clownfish to live within it, and provides shelter and protection for the fish. The reason that the clownfish aren’t harmed by the toxins of the anemone is that they have adapted to resist it. They do this by a special mucus secreted by their skin, which is specific varying based upon the species of anemone that they live in. This mucus is theorized to neutralize the toxins of the anemone, being based upon sugars rather than proteins which may cause the anemone to not recognize the clownfish as an item of prey or a predator, and therefore not sting it. Also, the fish and anemone may have evolved and adapted together, and thus the fish are immune to it as an evolutionary advantage.
The clownfish lay their eggs on a flat surface close to their host anemone for protection. The male parent clownfish will protect the eggs until they hatch 6 to 10 days later. The clownfish reproduce during the time of the full moon, and the eggs hatch usually close to 2 hours after dusk.
We can learn a lot from how the clownfish and anemones exist together. In a normal circumstance, they are predator and prey, diametrically opposed to each other. They would naturally be enemies, but they coexist and work together in order to help each other. In their symbiosis, they are stronger than they would be alone, and if we can adapt in a similar way to live with our environment, then many of our previous problems may find solutions we never though would be there.