Amphiprion ocellarisClown anemonefish(Also: Common clownfish; False clown anemonefish)

Geographic Range

Amphiprion ocellaris (Cuvier 1830), the false clownfish, is a tropical marine fish found in parts of Asia and Australia. Its range includes Northwest Australia, Southeast Asia, and as far north as the Ryukyu Islands of Japan (Allen 1997). (Allen, 1997)

Habitat

Amphiprion ocellaris inhabits coral reefs (Allen 1997) and sheltered lagoons up to a depth of 15 meters (Myers 1999). More specifically, it is mainly found in or near the anemones Heteractis magnifica, Stichodactyla gigantean, and Stichodactyla mertensii (Myers 1999) as part of a symbiotic relationship. (Allen, 1997; Myers, 1999)

  • Aquatic Biomes
  • reef
  • Range depth
    15 to 1 m
    49.21 to 3.28 ft

Physical Description

False clownfish are orange to reddish-brown with three white bands on the head and body. The white bands are outlined in black. Black A. ocellaris, with white bands and black coloring instead of orange, are found off the Northern Territory of Australia (Allen 1997). Amphiprion ocellaris has a rounded caudal fin and may grow up to 110 mm in length (Nelson et al. 1996). There are 11 dorsal spines and 17 pectoral rays that help to distinguish it from the closely related Amphiprion percula. Females are larger than males in this species. (Allen, 1997; Nelson, et al., 1996)

  • Sexual Dimorphism
  • female larger
  • Range length
    110 (high) mm
    4.33 (high) in
  • Average length
    80 mm
    3.15 in

Development

Amphiprion ocellaris hatches and enters a short larval stage where it resides close to the surface in a planktonic stage. As they change from larvae to juvenile fish, usually within a day, the fish moves from the surface to the bottom in search of a host anemone (Fautin and Allen 1992). (Fautin and Allen, 1992)

Reproduction

Information specifically for A. ocellaris mating habits is not available, but general behavior believed to be typical of all anemonefishes is documented. They are territorial to the specific anemone they inhabit and are monogamous (Thresher 1984). Prior to spawning, nest preparation is done by the male, where substrate is cleared to make a nest on bare rock, but near enough to the anemone to still have protection from the overhanging tentacles (Thresher 1984). Males will attract the female by extending fins, biting, and chasing (Fautin and Allen 1992). During spawning, the males are increasingly aggressive. (Fautin and Allen, 1992; Thresher, 1984; Fautin and Allen, 1992; Thresher, 1984)

Amphiprion ocellaris is part of a the subfamily Amphiprioninae, or anemonefishes. This group is characterized by being protandrous hermaphrodites, meaning that all individuals develop first into males and then possibly into females later (Myers 1999). An adult male and female and several juveniles may reside together in an anemone. If the female were to be removed or die, the largest male would then become the female, with the larger of the immature fish transforming into a male. Females control males with aggressive dominance, thus controlling the creation of other females (Fricke and Fricke 1977). The largest male will in turn dominate the juveniles and prevents other males from spawning (Fricke and Fricke 1977).

Amphiprion ocellaris is able to breed nearly year round because it inhabits tropical waters (Thresher 1984) but may be somewhat limited in the northern reaches of its distribution during winter months. Spawning is concentrated around the full moon and usually occurs in the morning. Possible reasons for this include: stronger water currents for larval distribution, greater food supplies due to invertebrate spawning at the same time, and overall increased visibility (Thresher 1984).

When spawning is about to occur, the male will chase the female to the nest, but the female actually begins the process. The female makes several passes over the nest and eventually lays orange eggs over the period of 1-2 hours before leaving the nest (Thresher 1984). Eggs are approximately 3-4 mm in length and range in number from 100-1000 depending on the age of the fish (Fautin and Allen 1992). The male then continues the process as he passes over the eggs, fertilizing them. Eggs are attached to the substrate with a fine thread. Incubation is affected by water temperature, the cooler the water, the longer incubation period, but in general it requires 6-8 days before hatching occurs (Thresher 1984). The planktonic larval stage lasts from 8-12 days and ends when the juvenile fish settle returns to the bottom and attempt to find an anemone to inhabit. (Fautin and Allen, 1992; Fricke and Fricke, 1977; Myers, 1999; Thresher, 1984)

  • Breeding season
    Spawing occurs year-round in the tropics, but only in warmer months in warm-temperate areas. Spawning occurs near the full moon.
  • Average time to hatching
    7 days

Prior to spawning, males prepare a nest where the eggs will be deposited. Males account for the majority of the egg care, but females are involved sporadically. Main duties include fanning the eggs and eating eggs that are infertile or damaged by fungus (Thresher 1984). Once the eggs hatch into the larval stage, they are independent of the parents. (Thresher, 1984)

  • Parental Investment
  • pre-fertilization
    • protecting
      • male
  • pre-hatching/birth
    • protecting
      • male

Lifespan/Longevity

Lifespan has not been studied fully in the wild, but it is believed that A. ocellaris may live 6-10 years (Fautin and Allen 1992). Larval fish are extremely susceptible to predation as they have no way of defending themselves and have high mortality rates. Captivity transfer experiments have been performed to address the possibility of restocking the fish in areas where they have been depleted; these find that survival among transferred fish is higher among smaller A. ocellaris (Nelson et al. 1996). (Fautin and Allen, 1992; Nelson, et al., 1996)

  • Typical lifespan
    Status: wild
    6 to 10 years

Behavior

Amphiprion ocellaris exists in a symbiotic relationship with sea anemones, specifically, Heteractis magnifica, Stichodactyla gigantean, and Stichodactyla mertensii (Myers 1999). These fish are dependent upon the anemone for shelter. In open waters these fish are more susceptible to predators and are poor swimmers. In addition, anemones provide protection for the nests (Fautin and Allen 1992). The anemones are observed to generally do better with a host fish and may also benefit possibly from fish consumption of parasites and increased water circulation from fanning (Fautin and Allen 1992). Anemonefishes are protected from the sting of the anemone by their mucus (Fautin and Allen 1992). There is a period of acclimatization that must occur before the fish is immune to the anemone sting. This involves a process in which the fish swims around the anemone rubbing its belly and ventral fins on the ends of the tentacles (MarineBio 1998).

As the juveniles search for an anemone, their survival is contingent upon finding an anemone to reside in, but this process is complicated by the dynamics within the anemone. Because of the hierarchical dynamics within the anemone, the new juvenile fish enters the system at the bottom and is exposed to the worst aggression and may be driven away (Thresher 1984). A. ocellaris are able to find one of the three species of sea anemones by olfactory clues, due to imprinting that occurred while in the nest (Arvedlund and Nielsen 1996). (Arvedlund and Nielsen, 1996; Fautin and Allen, 1992; MarineBio, 1998; Myers, 1999; Thresher, 1984)

Communication and Perception

Communication during mating occurs through the male biting, chasing, and extending his fins towards the female (Thresher 1984). The hierarchical system is communicated through aggression by the larger members residing in the anemone at the smaller individuals. Ampiprion ocellaris is able to find host anemones by olfactory imprinting that occurs while in the nest (Arvendlund and Nielsen 1996). (Arvedlund and Nielsen, 1996; Thresher, 1984)

Food Habits

Planktonic food such as zooplankton, copepods, and algae are the primary source of food for A. ocellaris (Myers 1999). They are classified as generalized omnivores as they feed on equal amounts of algae and animals (Sano et al. 1984). They are also reported to consume parasites from their host anemones (Thresher 1984). Feeding is also dominated by the hierarchical structure of the group dynamics in the anemone. Because the smaller fish receive the most aggression from the others, they have reduced energy for foraging great distances from the anemone and tend to stay close. Additionally, it is unsafe for the smaller fish to stray farther from the safety of the anemone (Fautin and Allen 1992). The large, dominant fish will forage at greater distances, but generally no farther than several meters from the anemone. (Fautin and Allen, 1992; Myers, 1999; Sano, et al., 1984; Thresher, 1984)

  • Plant Foods
  • algae

Predation

Predation on anemonefishes is greatly reduced due to the relationship with the host anemone, whose sting deters potential predators. The eggs are more susceptible to predation, mainly by other damselfishes (Pomacentridae) not including other anemonefishes, and wrasses (Labridae) (Arvedlund et al. 2000). Egg predation susceptibility increases at night as the male is not guarding them and they may fall victim to brittle stars (Ophiotrichidae) (Arvedlund et al. 2000). (Arvedlund, et al., 2000)

Ecosystem Roles

As mentioned previously (Behavior), A. ocellaris is part of a symbiotic relationship between three species of sea anemones, Heteractis magnifica, Stichodactyla gigantean, and Stichodactyla mertensii (Myers 1999). In this relationship, the fish receives protection from the anemone in the form of daily shelter and for its nest. The anemone receives protection too, as it has been documented that in the absence of a guest fish, the anemones may be attacked by butterfly fish or even turtles (MarineBio 1998). Additionally, in the presence of the fish, bulbs are found on the end of tentacles that are believed to increase surface area available to solar energy (Fautin and Allen 1992). The bulbs are not present in the absence of the fish. (Fautin and Allen, 1992; MarineBio, 1998; Myers, 1999)

Species Used as Host

Economic Importance for Humans: Positive

Amphiprion ocellaris are part of the tropical fish aquarium trade and certain rare colors of the species are specifically sought (Sadovy and Vincent 2002). They are easily bred in captivity and may be used in research (Thresher 1984). (Sadovy and Vincent, 2002; Thresher, 1984)

  • Positive Impacts
  • pet trade
  • research and education

Economic Importance for Humans: Negative

None known

Conservation Status

The high demand for the A. ocellaris in the aquarium trade has reduced the population size in some locations, leaving the local populations open to over-exploitation and other threats (Nelson et al. 1996). The species is not classified as threatened or endangered (IUCN 2003); however, as threats to coral reefs increase, A. ocellaris may face habitat degradation and possibly be threatened in the future. Coral reefs face many issues including sedimentation, eutrophication, exploitation of resources, and possible sea temperature increases due to global warming (Bhat 2004). (Bhat, 2004; IUCN, 2003; Nelson, et al., 1996)

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

Dani Newcomb (author), University of Michigan-Ann Arbor, William Fink (editor, instructor), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

planktivore

an animal that mainly eats plankton

protandrous

condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Allen, G. 1997. Marine Fishes of Tropical Australia and South-East Asia. Perth: Western Australian Museum.

Arvedlund, M., I. Bundgaard, L. Nielsen. 2000. Host imprinting in anemonefishes (Pisces: Pomacentridae): does it dictate spawning site preferences?. Environmental Biology of Fishes, 58: 203-213.

Arvedlund, M., L. Nielsen. 1996. Do the anemonefish Amphiprion ocellaris (Pisces: Pomacentridae) imprint themselves to their host sea anemone Heteractis magnifica (Athozoa: Actinidae)?. Ethology, 102: 197-211.

Bhat, A. 2004. Coral reefs and their fauna: An underwater fantasyland. Resonance, September: 62-73.

Fautin, D., G. Allen. 1992. Field Guide to Anemonefishes and their Host Sea Anemones. Perth: Western Australian Museum.

Fricke, H., S. Fricke. 1977. Monogamy and sex change by aggressive dominance in coral reef fish. Nature, 266: 830-832.

IUCN, 2003. "2003 IUCN Red List of Threatened Species" (On-line). Accessed October 22, 2004 at www.iucnredlist.org.

MarineBio, 1998. "False Clownfish" (On-line). Accessed October 21, 2004 at http://www.marinebio.com/species.asp?id=29.

Myers, R. 1999. Miconesian Reef Fish: A Field Guide for Divers and Aquarists. Barrigada: Territory of Guam: Coral Graphics.

Myrberg, Jr., A., L. Fuiman. 2002. The Sensory World of Coral Reef Fishes. Pp. 146 in P Sale, ed. Coral Reef Fishes. San Diego, California: Academic Press.

Nelson, J., P. Phang, L. Chou. 1996. Survival and growth rates of the anemonefish Amphiprion ocellaris: a transfer experiment. Journal of Fish Biology, 48: 1130-1138.

Sadovy, Y., A. Vincent. 2002. Ecological Issue and the Trade in Live Reef Fishes. Pp. 395 in P Sale, ed. Coral Reef Fishes. San Diego, California: Academic Press.

Sano, M., M. Shimizu, Y. Nose. 1984. Food habits of teleostean reef fishes in Okinawa Island, Southern Japan. Japan: University of Tokyo Press.

Thresher, R. 1984. Reproduction in Reef Fishes. New Jersey: T.F.H. Publications, Inc..