Aquarium of the Pacific - Online Learning Center - Species Print Sheet
The false clown’s other common names are common clownfish, false clown anemonefish, false anemonefish, and, the much more familiar, Nemo from the movie Finding Nemo in which Marlin was correctly shown as being immune to the sting of a sea anemone. Like other anemonefish, false clowns have a symbiotic relationship with selected sea anemones that provide their habitats.
At the Aquarium
There is a special habitat for two year old juvenile false clown anemonefish in the Aquarium’s Tropical Pacific Gallery. They are fed krill (a small shrimp-like animal) and pieces of finely chopped seafood. When the juveniles grow too large for this habitat, they are moved to other locations in the gallery
Anadam and Nicobar Islands in the Indian Ocean, Indo-Malaysan Archipelago, Philippines, northwest coast and Northern Territory of Australia, coast of southeast Asia north to the Ryukyu Islands
These anemonefish live on coastal reefs, in shallow and sheltered lagoons, and waters of reef faces and fore reef slopes at depths of 1-15 m (3.3-49.2 ft). They have three anemone hosts on which there are very dependent: magnificent anemone Heteractis magnifica, giant carpet anemone Stichodactyla gigantea, and Merten’s sea anemone S. mertensii.
Their body shape is perch-like—oval and laterally compressed with an interrupted lateral line. The caudal fin is rounded. They are usually orange to reddish-brown with three white bars that have thin black borders that may be almost invisible. The bars are located on the head, in the middle of the body, and at the base of the tail. The middle bar has a bulge or widening in the center. Not all false clowns are orange. There is a population off Darwin, Australia that has white bands on a black body
This species can grow to a length of 11 cm (4.3 in); however, the average length is 8 cm (3.15 in).
These fish are carnivorous omnivores. They eat zooplankton, bottom dwelling invertebrates, and algae with copepods being their primary food item. They also nibble on the tentacles of their host anemones at times.
Anemonefish are protandrous hermaphrodites, which means that they all mature as males but have the ability to change their sex to female. A typical harem living in the host anemone consists of a breeding pair and up to 20 juveniles. The larger fish of the pair is the female. She controls the dominant male from becoming a female while he controls the juveniles from becoming mature males. Should something happen to the female, the male of the breeding pair changes to a female, rapidly increasing in size. The next largest male usually becomes the breeding male.
Courtship begins three to five days before spawning and includes substrate biting (biting rocks and corals), extension of fins, and chasing. Initially the male prepares a nesting site on a bare rock or coral pavement substrate close to the host anemone, often just under its tentacles or at its base. As spawning nears, the female helps clean off debris and algae. The nest can cover an area of 4-10 cm (1.5-3.9 in). The breeding pair nips at the anemone’s tentacles that are near the spawning site, causing them to partially retract so the nest area is more open. The female makes several runs over the nest, swimming with her belly brushing against the site. Eventually she pushes her belly against the site and moving herself over the nest with her pectoral fins, releases a trail off eggs. Tiny filaments on the end of the eggs attach them to the substrate. The male swims behind the female and fertilizes the eggs. Between 100 and 1000 eggs are laid in several spawning passes. The initial pink to orange coloration of the eggs will gradually change to a dull gray or brown and shortly before hatching, to silver.
For the next six to seven days the male tends the nest, rarely helped by the female. He fans the eggs with his pectoral fins to aerate and clean them of settled debris, eats any that are infertile or damaged, and aggressively chases away predators. Hatching occurs shortly after sunset. After hatching, the larvae swim into the water column where their larval phase will last for 8-12 days. They then become bottom dwellers looking for their own host anemone. If lucky enough to find one before being consumed by a predator or chased by the anemone’s current inhabitants, they will become the youngest and lowest member of a community, perhaps with hopes of eventually becoming the dominant female.
False clownfish are found singly, in pairs, and in small groups. They rarely move more than 30 cm (12 in) from the protection of their host anemone. They are territorial, aggressively defending their host and an area around it. Aggression consists of tail beating, chasing, and biting at the intruder’s head, abdomen, and fins.
These fish aerate the water around the tentacle of their host anemone, remove waste from its oral disc, and provide nitrogenous waste that the anemone uses as food. Contrary to popular belief, they do not capture food for the anemone.
Some researchers believe that the mucus layer covering an anemonefish’s body has a special biochemical makeup that provides the fish with protection from the anemone’s stinging cells, its nematocysts. It is believed the anemone fails to recognize the fish as a food source because of this chemical composition, so it does not fire its nematocysts. Other researchers theorize the mucus contains the same chemical signature as the host anemone, so that the stinging cells never fire. It is known that if an anemonefish leaves its host for a period of time, it has to re-adapt to the host stinging cells. To do this the fish returning to the host goes through an elaborate dance-like ritual. It tentatively touches the anemone’s tentacles with only its ventral fins, then its entire belly. Acclimation takes several hours.
The ability of juvenile anemonefishes to locate the same host anemones preferred by their parents is believed to be due to an olfactory (smell) stimulus imprinted at the time of egg incubation. With the eggs in the nest site located close to the host anemone, imprinting occurs due to exposure to the odor of host species-specific mucus released from the anemone’s oral disc and tentacles. At the present time sight recognition is not believed to be a factor in recognizing the host anemone.
False clown anemonefish live 6-10 years in the wild and as long as 12 years in a protected environment.
Over-collection of this species for the aquarium trade has impacted the populations in some areas. Degradation of their coral reef habitats as a result of development, natural disasters, and global climate change is an ongoing and future threat. Predators include other damselfishes, wrasses, and at night, brittle stars. They are not listed on the IUCN Red List; however, some governments are controlling the numbers harvested for the aquarium trade.
This species has a more rounded caudal fin than other anemonefishes that makes it a naturally slow swimmer; however, the fin’s shape also allows it to make quick darting movements.
These fish are often found living with the anemone shrimp Periclimenes holthuisi in the same host anemone.