Relationships in which the partners do not harm each other bu rather make a substantial contribution to is other are called symbiotic relationships. These are close relationships between animals from different groups, in which both parties benefit from the partnership.
A classic example of a symbiotic relationship in the sea is the relationship between the orange clownfish, and various species of sea anemones. The orange clownfish takes refuge in the arms of the sea anemone, which no other animal would dare to penetrate, for fear of being injured by the anemones’ numerous stinging cells. The anemone in turn gets to occasionally enjoy a meal when a reckless predator chases an orange clownfish straight into the hunter’s arms.
Another symbiosis is a group of hermit crabs, they live with their stomachs in an empty shell, on top of which the crabs stick small sea anemones. The hermit crab enjoys dual protection; the empty shell serves as a refuge, and the sea anemones on the shell prevent the enemy from approaching. The anemones, on the other hand, are transported from place to place, refreshing the water around them, and multiplying the chances of finding food.
Some crabs stick sea anemones on their backs, and there is a species that grips two tiny sea anemones in its pincers, projecting them forward towards the enemy.
A different kind of symbiosis is: cleaning symbiosis. Most reef fish are cleaning symbiosis hosts, and many others live in open waters. Long belly crustaceans (crabs) are known to attract fish by waving their long white antennae, and moving their bodies from side to side. These crabs mount the fish that arrive to “be cleaned”, remove parasites and dirt particles, cleaning it – even cleaning between its teeth (for which the fish opens its mouth, and gill covers), and when they are finished they move on the next fish in line.
The cleaning phenomenon is also common between the fish themselves. The labroides cleaner fish is an example; this is a small fish that is identified by other fish as a cleaner because of its color, and twisting swimming movements.
The labroides cleaner fish removes parasites from other fish (on which it feeds), cleans wounds, and even removes harmful growths. Today, it is clear that the cleaning phenomenon is very important to the normal living of coral reef fish. When all the cleaners are removed from a specific coral reef area, most of the fish living there end up leaving the area, while, at the same time, the number of fish infected with fin and scale diseases increases. The fact that there are only approximately 45 known species of cleaners in the world increases their importance, and proves that what seems to be a coincidental connection between two animals is in actual fact a vital necessity in the normal lives of one, or both of the parties involved in this partnership.
We have seen, therefore, that symbiotic relationships can be defined as a close connection between different animals, both of which benefit mutually from the partnership. What is prominent is the physical connection between the two partners – the protection, the provision of refuge and food, as well as the transportation of one symbiote from place to place.
(By David Masry – The Marine Biology Laboratory, Eilat)