In 2003 the film Finding Nemo was made and Nemo shot to fame as the bravest little fish on the reef. Although we all love Nemo and his tales of bravery, he tends to steal the limelight when it comes to anemonefish (also known as clown fish). You see, alongside Nemo, there are 27 other species of anemonefish, each deserving its own 15 minutes of fame. So to restore the balance, although I cannot promise each species its own blockbuster movie, I am here to enlighten you on all things weird and wonderful about the anemonefish family.
Species: Clarks anemonefish (Amphiprion clarkii)
Where Do They Live?
As their name suggests anemonefish live in sea anemones. Anemones are animals related to jellyfish and are essentially a blob of tentacles surrounding a central mouth, attached to the reef. They are mostly sedentary, typically selecting a suitable spot on the reef and remaining there. However, they are also capable of movement, slowly crawling along the reef and taking their anemonefish along for the ride.
Life on the reef can be dangerous for small fish, with size not on your side you must find clever ways to survive. The tentacles of anemones are lined with stinging cells, for most fish this sting can be painful or even fatal but anemonefish can safely hide amongst the deadly tentacles without receiving a nasty sting. This immunity develops gradually. As the fish rubs against the anemone’s tentacles, the two exchange bacteria, allowing the clownfish to build a mucus layer on its skin that closely matches the anemone’s own. As a result, the anemone no longer recognises the fish as a foreign body. In effect, the clownfish becomes part of the anemone, and is spared from being stung.
Species: Skunk Anemonefish (Amphiprion akallopisos)
But as any true symbiotic relationship both must benefit. So the clown fish keeps busy doing the housekeeping, removing any debris, such as sand, that may land on the anemone. The fish’s excretions also provide the anemone with a nutrient rich food source. Additionally, if you are lucky enough to get up close and personal with an anemonefish, you will notice how aggressive it becomes when approached. This behavior is an attempt to appear threatening and to protect the anemone from predators, a challenging task when you are only a few centimetres long and as cute as a button.
Females Rule The Roost
Anemone fish have one of the most fascinating social systems in the animal kingdom. They’re protandrous hermaphrodites which means every anemone fish is born male, with the remarkable ability to change into a female later in life.
Inside each anemone, there’s a strict hierarchy. The largest fish is always the sole female, while all the others remain male. The second largest fish earns the title of dominant male and is the only one allowed to mate with her. But here’s where it gets really interesting: if the female disappears, the dominant male undergoes a complete sex change and becomes the new female. The next largest male then steps up, matures, and takes over as the dominant male. The remaining males form an orderly queue, patiently waiting for their chance to mate. One particular case study documented a single fish staying in the same anemone for an astonishing 14 years, gradually progressing from an immature male, to a mature male, and eventually becoming the female.
Species: True Clown Fish (Amphiprion ocellaris)
This clever system ensures every clownfish has a home and keeps conflict to a minimum. However, it’s not without its drawbacks: the wait can be long, and some males may spend their entire lives in line without ever getting their chance at mating.
Reproduction
Anemone fish can lay eggs as often as every two weeks if conditions are favorable. The female lays her eggs next to the anemone, on a hard substrate such as the bare limestone reef. The male takes it from there. He swims over the rows of eggs and fertilizes them. He then has the very important job of using his pectoral fin to meticulously fan the unhatched eggs until they mature.
Above: Clown Fish eggs attached to reef under anemone.
Below: Male anemone fish fanning its eggs.
Top Tip: If you ever find an anemone that seems empty, have a peek next to/underneath it and you might be lucky enough to see this behavior happening.
Fanning the eggs keeps them oxygenated but also plays a vital role in helping the young fish find their future home. Anemones release chemical cues secreted in the mucus of their tentacles. Each different species of anemone has its signature smell. As dad fans these chemicals over the eggs, the smell remains imprinted in the unhatched fish’s memories. It is the smell of home.
Once hatched the fish will have a brief larval stage where they free float over the reef. Not all will make it past this stage but the ones that do must now find their anemone home. Although there are over 1000 species of anemone, only 10 are capable of hosting anemonefish and not just any anemone species can host any fish species, the match must be just right. The juvenile clown fish will follow the smell of chemical cues released by nearby anemones to locate the same species of anemone they were born under and their forever home.
Photos by Kya Daly-Griffiths and Lydia Vavoula
