20+ Interesting Facts About Clownfish

1. Clownfish are marine fish, present in the Indo-Pacific region. These reef fish are famous for their bright colors, white stripes, and relationship to sea anemones.
2. Clownfish are one of few animals that can change gender after birth. Every clownfish in a group is born male. In every group, the largest and most dominant fish becomes female, while the next biggest male becomes her breeding partner.
3. If the female clownfish in a group dies or is removed, her partner becomes female. Afterwards, the next largest fish takes the role of a dominant male fish and this cycle continues.
4. Various clownfish species differ in their colors and number of white stripes. These fish naturally have orange, yellow, brown, or, black skin colors, while the number of stripes is from zero to three. Red saddleback clownfish is famous for having no stripes during adulthood. Common clownfish, depicted in the animated film “Finding Nemo,” have three white stripes. (Source)

   

   Adult red saddleback clownfish are without stripes

   
   
5. Clownfish are famous for white stripes on their bright-colored skin. However, various clownfish species differ in their coloration and stripes. Clownfish choose one or more specific sea anemones as their hosts and the color difference is due to their unique host. According to a study, clownfish that live inside a more venomous sea anemone have less white stripes. Clownfish use white stripes to camouflage, while a more striking color functions as a warning signal. Therefore, less stripes clearly indicates to potential predators that the animal lives with a venomous anemone. (Source)
6. A female clownfish lays hundreds or thousands of eggs on a flat surface near their host anemone. The male fertilizes these eggs, fan them with his fins, and stands guard. This allows the female to return to the anemone.
7. The male clownfish eat some eggs while guarding them. The primary reason behind this filial cannibalism is to remove unfertilized or weak eggs that may spread harmful bacteria or fungi to healthy eggs. Sometimes, males may eat eggs to fulfill their dietary requirements or under noise stress.
8. Clownfish can’t hatch eggs in the presence of artificial light. Exposure to artificial lights during night doesn’t impact spawning and fertilization of eggs. However, it halts the egg hatching process altogether. Clownfish mostly inhabit shallow water, within 30 feet of the ocean surface. Therefore, they face this threat in their natural habitat also due to the coastal human population. (Source)
9. Unlike most fish that vocalize through swim bladders and bones, clownfish use their teeth, jaws, and bones in the oral cavity to communicate. They use these chirps and pops, produced by grinding of the teeth, to lure mates or warn rivals. (Source)
10. Due to their relationship to sea anemones, clownfish are also called anemonefish. Sea anemones are invertebrate marine animals that spend most of their lives attached to hard rocks or corals. Clownfish spend almost all their adult life inside or near sea anemone reef.
11. Sea anemones have venomous tentacles to sting their prey. However, clownfish live inside their hosts safely. Clownfish avoid stings from sea anemones due to the lack of sialic acid in their skin mucus. This sugar molecule triggers firing of toxic stings from sea anemones. (Source)
12. Clownfish and sea anemones benefit and protect each other to survive in the ocean. In this mutualism, sea anemones protect clownfish and their eggs from carnivorous fish through their venomous tentacles. On the other hand, clownfish also assist sea anemones in several ways. They protect their hosts from predators, remove debris, increase water circulation, exchange oxygen, and provide nutrients. (Source)
13. According to estimates, at least 10 sea anemone species host nearly all 30 clownfish species. Currently, sea anemones host clownfish only in the western Pacific and the Indian Ocean. However, research proves that sea anemones had hosted clownfish three times in the past in different locations. Sea anemones initially hosted clownfish during the Mesozoic era, around 65 million years ago, and then nearly 20 million years ago. On both these occasions, the two animals came together in the ancient tethys sea near the Arabian Peninsula. Researchers believe their third partnership also occurred at an unknown location before starting their recent collaboration in the Indo-Pacific Ocean. (Source)
14. Thyroid hormones play a major role in speeding the formation of white stripes in clownfish. However, these hormones are higher only in clownfish living in specific sea anemones. Research has proved that clownfish in the giant carpet anemone, a more toxic one, have higher thyroid hormones compared to those present in the magnificent sea anemone. (Source)
15. Baby clownfish spend their early life in the open ocean before moving to their sea anemone reef. During this journey, these small fish breathe faster and take more oxygen per breath than any other fish. This extraordinary feat enables larvae clownfish to swim up to 50 body lengths per second and complete nearly 64 km in a few weeks or months. These tiny fish complete this journey unstopped even if the water current moves in forward or opposite direction. (Source)
16. Clownfish assist sea anemones to breath at night by transporting more oxygen-rich water to its host. A study shows that clownfish move in a specific way during night while in contact with sea anemones. This increases flow of water, thus enhancing the oxygen consumption of up to 40% in both animals. (Source)
17. Tomato clownfish have two or three white stripes at juvenile stage. During adulthood, they lose most of these stripes except a single bar at the back of their eyes. Studies have confirmed that social pressure from adult clownfish plays a part in removing extra stripes from baby tomato clownfish. A baby fish retains its stripes for longer before entering a sea anemone reef with adults because they consider other adults a threat for their roles. Once a clownfish becomes part of a reef, it immediately loses additional stripes. Therefore, the timing of losing their white bars is from a month to 12 months after birth. (Source)
18. Clownfish recognize other clownfish on the basis of the number and type of their stripes. These fish react aggressively to clownfish of their own species as they consider them rivals. On the other hand, they remain peaceful to other clownfish species because they don’t pose a threat to their position inside sea anemone reefs. (Source)
19. Clownfish may inhabit one or more other clownfish species in the same anemone reef. Scientists have observed nearly 25% of species that live peacefully with other species in a single anemone throughout the Indo-Pacific Ocean. (Source)
20. Clownfish recognize and choose their specific sea anemone by smelling its chemical signature. Clownfish store this smell inside eggs even before their birth. When the juvenile fish decides to return to the reef from the ocean, they use the same smell to recognize their specific sea anemone.
21. Clownfish are named so due to their skin colors and swimming style. Bold colors and white stripes on the fish look like a clown's painted face. Moreover, their clumsy and bouncing swimming style is similar to doing funny acrobats.