Did you know that true anemone clownfish (Amphiprion percula) which live in groups are non-related? Scientists originally believed group members were relatives, helping the group as a family to spread their genes to future generations. A recent discovery tells a different story...

Scientists recently discovered that true anemone clownfish (Amphiprion percula), which live in groups, are non-related. It was originally believed that group members were relatives, helping the group as a family to spread its genes to future generations. A recent discovery tells a different story... Scientists performed a study on Amphiprion percula individuals from Madang Lagoon, Papua New Guinea. They investigated 79 Heteractis magnifica anemones and their symbiont fish. The A. percula groups consisted of one breeding pair and 0-4 non-breeding fish (these fish can replace one or both of the breeding individuals after predation or natural death). After the field study, they collected 32 individuals from 9 groups.  

 
Amphiprion occelaris with their host anemone. Copyright the Wikimedia Foundation. 

They extracted DNA from the fish tissue, and analyzed it for comparison between individuals.  For comparison, they made use of DNA microsatellites .They found that individuals from the same groups did not share more genes compared to individuals from different groups. This means that anemone fish, at least this species, create random groups and that families don't stay together. 

Anemone fishes are an interesting species to study, as they would make good candidates for the formation of kin groups in the marine environment. They live in groups with a breeding pair and some non-breeders, just like cooperatively breeding birds and mammals.  It is interesting to find that these fish do not form these breeding families. The scientists explain their results by stating that newly hatched larvae spread out over the reef and simply choose the first suitable anemone to make their new host (if the group accepts the individual). Next to this, avoiding family inbreeding lowers the risk of disease.

 
 Amphiprion sp, possibly percula, photograph: Tim Wijgerde

It has been found that these extra non-breeding fish probably help keep the host anemone healthy. Anemone fish, like all animals, have to protect their territory, and keeping their host anemone healthy is a very smart thing to do. This could be the reason why the fish in each group tolerate each other, because together they keep the anemone healthy. On average, A. percula breeding pairs live 22 years! This means they live long enough to reap the fruits of the group cooperation.

Next time when you see a group of anemone fish in a tank or in the wild, you'll look at them from a whole new perspective... 

References: 

Buston PM, Bogdanowicz SM, Won A and Harrison RG, Are clownfish groups composed of close relatives? An analysis of microsatellite DNA variation in Amphiprion percula, Molecular Ecology, 2007, 16 pp 3671–3678

Buston PM, Does the presence of non-breeders enhance the fitness of breeders? An experimental analysis in the clown anemonefish Amphiprion percula, Behavioural Ecology and Sociobiology, 2004, 57, 23–31.