This is the first installment on a three-part blog series about Clownfish written by our Aquarium Biologist.
Symbiosis: a relationship where both parties benefit from their association with each other. These relationships are particularly prominent in coral reef ecosystems and are essential to its functionality. One of the most iconic symbiotic relationships involves the charismatic clownfish and its protective sea anemone home. But how does such an essential relationship evolve in nature?
The anemone with its toxic properties offers protection the small clownfish (anemonefish), who in return provides additional nutrients and oxygenation to the anemone. Clownfish are also fiercely defensive of their anemone and will fight off predators such as other fish species and even Sea Turtles to protect their home! Through toxic mimicry, the clownfish is able to develop an immunity to the sting of the anemone, allowing it to be the only species who can pass through the anemones tentacles. Anemonefish incorporate some elements of the anemones toxin into a mucus layer over its body, making the anemone think the fish is its ‘self’ and therefore not firing its toxin.
Anemones are very special in that they have a three-way symbiosis. A symbiotic alga, zooxanthellae lives inside their tissues providing additional energy and nutrients through photosynthesis. The algae gives the anemone its unique colours and allows the anemone to invest less energy into sourcing food for itself and more into toxin production.
There are 28 species of anemonefish and they form a symbiosis with only 10 host anemone species, despite there being around 1000 different anemone species. It is thought that there is an optimal range of toxicity that these 10 anemones fit, allowing for the best cost/benefit ratio for the clownfish. Throughout the Maldives there is only 2 species of anemonefish:
Anemonefish will generally be found in pairs, with the larger of the two fish being the dominate and protective female. Her smaller male partner takes on the submissive role in their relationship and is responsible for cleaning and caring for their eggs. Any other juveniles present are all males, as all clownfish are born male and only one fish per anemone group will make the transition into the dominate female to produce offspring.
Anemones and clownfish can be found on reefs all throughout the Maldives at depths from 3-12m and can be viewed by both snorkeling and diving. The one of most famous and abundant locations in the Maldives for seeing this symbiosis in action is Anemone Thila in the Lhaviyani Atoll.
Stay tuned for more upcoming blogs about clownfish and anemones!
By Cassie Hoepner