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ho would have thought that a father and abducted son could make such an impact on our lives. The story of the Hollywood Pixar movie Finding Nemo so touched everyone, it became the biggest-selling DVD of all time. However, the lives of these (almost) comical and colourful fish is indeed stranger than the fictionalised story behind the movie. We are all now well acquainted with the anemonefish, with our closest encounters to be found in the Red Sea, thankfully now back on the diving menu after the lifting of COVID-19 travel restrictions. Being only a four-hour flight away from mainland Europe, the Red Sea is the closest tropical coral reef ecosystem available to us. The Red Sea anemonefish (Amphiprion bicinctus) is more commonly known to us as the clownfish and it is this remarkable little damselfish that so steals our hearts on almost every dive in the Red Sea. These clownfish are so obvious to us snorkellers and divers, not only because of their amazing flamboyant colours of orange/red overall, plus a couple of iridescent blue/white stripes which wrap the upper body, they also live exclusively within the grasp of an anemone’s tentacles. Anemones (as we all know) have stinging cells, called nematocysts, within their tentacles to snare any passing food bits, yet the clownfish manage to live their entire lives within this sticky embrace and manage to appear invincible to the deadly stinging cells of their host. It has taken various marine scientists many years of intense study to work out this relationship between the anemone and its clownfish and it is found that their relationship is entirely mutualistic, with both partners benefitting from the association. We know that clownfish help to protect their anemone by attacking any possible threats to their host (and that includes us divers), with clownfish readily leaving their protective host and swimming many metres into open waters to ward off anything and everybody. This is doubly so when the clownfish have laid their eggs under the skirt of the anemone and within the range of their tentacles. The clownfish also helps to ‘clean up’ debris from the feeding anemone, and also eats the anemone’s faecal matter. The most obvious of the relationship is the fact that the clownfish are not stung and ingested by their host. The clownfish appear to keep in almost constant contact to their host and continuously swim amid the tentacles and even the mouth, coating themselves in the anemone’s protective mucus, thus rendering them effectively ‘invisible’ to the
anemone’s toxins and stinging cells. Once the clownfish’s eggs are laid and fertilised, it is the male that cares for the brood by blowing fresh water over the eggs and removing any dead or diseased cells. Even the newborn hatchlings spend some small time amid the anemone’s tentacles before leaving the nest and finding (perhaps) their own anemone to start the cycle all over again. There are few predators while the clownfish is within the range of the anemone, but are prone to incidental attack if they venture too far, but they are prey to isopods such as species of the Cymothidae family, which attach themselves to the heads of the clownfish (as well as many other species), where they do little harm, rather than some skeletal deformities as they are scavengers, rather than parasites. Clownfish are able to reproduce all year and depending on the water temperature and constant current of the water, they can often form huge colonies with dozens of anemones and perhaps hundreds of clownfish, living alongside another damselfish, the juvenile three-spot damselfish (Dascyllus trimaculatus), which co-habit the anemones, and are usually in much greater numbers than the clownfish. In the Red Sea, two of the most obvious of these super colonies are the Anemone Gardens at Ras Mohammed at the tip of the Sinai Peninsula and Anemone City on Panorama Reef to the south of Marsa Alam, down Egypt’s African mainland. Other lovely small colonies can be found at El Quseir, Gubal and Tawila that are rarely, if ever dived, due to the heady excesses of other more popular dives nearby. If you look closely at the anemones, you will also find that they are inhabited by various species of small shrimps and even crabs and depending on the anemone species, there may be several species of shrimps co-habiting with the clownfish and three-spot Dascyllus. There is a similar-looking fish to the clownfish and can sometimes be confused, but this species lives on table corals and will certainly be killed if it touches an anemone. This is the citron or lemon coral goby (Gobiodon citrinus), which is an overall lemon yellow in colour with iridescent thin blue lines around the head and at the base of the dorsal fin.
Clownfish are relatively common in all tropical oceans, yet there are only 29 different species worldwide and perhaps around only a dozen host anemones. The greater number of different species can be found within the Coral Triangle in Indonesia
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