Anemonefish are also known as Clownfish or Nemo Fish and there are at least 28 different species of them. It is almost guaranteed that you will see some anemonefish during a tropical water scuba dive. One of the most common that you will encounter on your diving excursion is the Pink Skunk Clownfish whos species is widespread and not considered threatened.
Clownfish appear to get some protection from predators by hiding amongst the stinging tentacles of their host anemone, but how are they able to do this?
One theory is that the clownfish have a mucus coating on their body that prevents them from getting stung. Another theory is that they gradually build up a resistance to the stinging cells by gently rubbing themselves against the tentacles of the anemone.
The exact science behind it is unknown but, either way, they are sufficiently protected from the stinging cells of the anemone.
Another interesting species that fascinates scuba divers is the Saddleback Anemonefish that are named after their center white coloured area which is shaped like a saddle. They reside on Carpet Anemones which can be found on coral reefs or out on the sand away from the reef.
The anemonefish depend on the anemone for protection so they will spend almost all of their life amongst them. In return, the anemone will feed on the waste of its residents. The defensive nature of the anemonefish also helps protect the anemone itself in case other fish try to attack.
The largest fish living in the anemone is the female with the next largest being the breeding male. The largest breeding male which is also the most aggressive will keep its body mass up by taking control of any food and preventing the juveniles from fully developing. They feed on algae and small organisms such as zooplankton.
The female can lay up to 1000 eggs. The male will prepare a nesting space and entice the female to mate with him. The eggs will hatch about one week later.
All anemonefish are born as males although they do possess both male and female sex organs. If the female leaves the anemone then the breeding male will turn into a female. The next largest will then take its place as the breeding male.
They are known as Sequential Hermaphrodites but once they have changed sex they cannot change back. This bizarre evolutionary process is not unique to anemonefish as it also occurs in some other fish species.
Sea anemones have a central opening surrounded by stinging tentacles that are used to capture prey. The opening is used as a mouth and for waste.
In reproduction, the anemone’s central orifice is where the newborn larvae will emerge from. They will spend their first few months growing within their parent anemone but eventually, they will find their way out and begin life on the sea bed.
Anemones do move around but they do so at an extremely slow pace. Mostly they remain in the same area for long periods. They can also inflate or retract their bodies if required.
Anemones can be affected by coral bleaching where the anemone itself can turn completely white. During this bleaching period, the anemonefish may leave and look for a new host.
If You look closely you might find some other creatures in the anemone such as Ghost Shrimps or Cleaner Shrimps. They are mostly transparent with some trace violet colouring so they are not always easy to see. Some fish seem to identify the anemone as a cleaning station where the Ghost Shrimp will come out to clean the parasites from the fish.
Some species of crab can also be found living amongst the anemone. How are these other creatures also able to reside in and around the stinging cells of the anemone?
Sea Anemones can be found in all oceans and especially around tropical coral reefs. Next time you see one during your scuba dive, take a minute and have a closer look at what is going on inside that anemone.