While living in the anemone only indirectly, tongue-eating isopods are a resident straight out of a horror movie. In some areas, particularly Lembeh Strait, Indonesia, many anemonefish have these creepy parasites living in their mouths.
Attaching to their tongues, the isopod feeds partly off the fish’s meals and also slowly devours its tongue until the isopod in effect becomes the tongue. Sometimes you can see two beady eyes looking back at you from inside a fish’s mouth.
Spoiler alert: Nemo wasn’t actually a clownfish, but a false clownfish. There are more than 30 species of anemonefish that are subtypes of damselfish that live in anemones.
Anemonefish can be found in the Red Sea, and in the Indian and Pacific Oceans.
They usually live in a group with one female and several males. In fact, they are all born males and, if the female dies, the alpha male will change into a female.
So in real life Nemo’s dad would likely have changed into his new mum and Nemo probably would have grown up to mate with his father (now mother).
Did I just ruin the movie for you?
Anemonefish are not naturally immune to the anemone’s toxins. When moving into a new home they slowly acclimatise by touching small parts of their body for short periods.
Sometimes, if you’re lucky, you can see anemonefish eggs, usually laid on a solid surface near the base of an anemone.
While they blend in quite well, what usually gives them away is that the anemonefish will continuously go from the anemone to the eggs to care for them.
They blow on them and wave their fins over the eggs to circulate water and clean them of algae. As the eggs develop, the tiny eyes of babies can be seen. It usually takes 8-14 days for them to hatch.
Sometimes when the fish are protecting eggs they get very aggressive, and charge divers who get too close.
Clockwise, from top left: The jewelled anemone crab places anemones on its shell for protection; a shrimp provides its cleaning services; a spinecheek; and a skunk anemonefish; anemone in the process of bleaching.
Anemones that host fish have sometimes been shown to be larger and healthier. The presence of the fish is like a home having good tenants that protect it from thieves – perhaps butterflyfish that try to eat the tentacles – and acting as good housekeepers to clean the anemone of debris.
A larger anemone has more surface area to collect light, which keeps the symbiotic algae that live within happy too. The anemone also gets a free snack from the fish occasionally.
The symbiotic algae photosynthesise and provide part of the anemones’ food, in exchange getting a safe place to live.
It’s the algae that give the anemones their colour, and they suffer from bleaching just as corals do.
If the water is too warm for the algae they will either leave on their own or be expelled, leaving behind a bright white anemone.
This is bad news for Nemo and his friends, as they stand out dramatically in a pure white anemone and are more easily seen (and eaten) by predators.
The news isn’t all bad for anemones, however. Because they also eat plankton and fish, they don’t depend on algae for food. They also tend to survive bleaching better and for longer than corals.
Once the water returns to the correct temperature the anemones can take on new algae and the colour returns (although it might be a different one).
Often they come back smaller after bleaching events, so multiple events can lead to major damage. Some studies have shown that anemonefish living in bleached anemones produce fewer eggs after bleaching.
Nemo might still be the star of the show, but his amazing home deserves respect in its own right, as do the many other creatures that live there.