True clown anemonefishes (Amphiprion percula) are native only to the Indo-Pacific Region (Rosenberg and Cruz, 1988). The species ranges from Northern Queensland to Melanesia, which comprises New Guinea, New Britain, New Ireland, the Solomon Islands, and Vanuatu (Fautin and Allen, 1992). (Fautin and Allen, 1992; Rosenberg and Cruz, 1988)
Like all anemonefishes, A. percula forms symbiotic relationships with sea anemones. It uses its host as both shelter and protection from predators. Because of this close relationship, the distribution of suitable host anemone species dictates the habitat of A. percula. Associations involving A. percula and the sea anemone species Heteractis magnifica, Stichodactyla gigantean, and Stichodactyla mertensii are usually found in nature (Elliott and Mariscal, 1996). Both symbionts reside in shallow coastal waters of the tropics where depth rarely exceeds 12 meters and water temperature ranges from 25-28 degrees C. (Randall et al., 1997; Fautin and Allen, 1992). The distribution of sea anemones themselves is limited by the photosynthetic activity of golden-brown algae that occupy the anemones’ tentacles (Fautin and Allen, 1992). The fish and anemone pair generally occurs on coral reefs where the latter is anchored securely and the former can be seen swimming in and out of the protective tentacles of its host.
When several species of anemonefishes occur together in similar habitats, they tend to partition themselves according to microhabitats and available species of sea anemones. A. percula, for example will typically occupy H. magnifica in nearshore zones while Amphiprion perideraion will occupy the same species in offshore zones. Intense competition for limited resources undoubtedly affects the territorial nature of these fishes. Niche differentiation is caused by distribution, abundance, and recruitment patterns of competing species (Elliott and Mariscal, 2001). (Elliott and Mariscal, 1996; Elliott and Mariscal, 2001; Fautin and Allen, 1992; Randall, et al., 1997)
A. percula can grow to 110 mm in length and is often distinguished by three white vertical bars on a bright orange body. The anterior white bar occurs just behind the eye; the middle bar bisects the fish; the posterior bar occurs near the caudal fin. An anterior projecting bulge further characterizes the middle bar. In addition to the white coloring, black edging outlines each fin with varying thickness (Fautin and Allen, 1992; Grant, 1999). Although A. percula’s vibrant colors are eye catching, it is easily confused with Amphiprion ocellaris (false clown anemonefish). One may distinguish the two by counting the number of dorsal-fin spines. A. percula usually has 10 dorsal-fin spines, while A. ocellaris usually has 11. Also, the latter never has thick black margins outlining the fins (Fautin and Allen, 1992)
There is no difference in color patterns among sexes. Nonetheless, dimorphic variation is present, since the female is larger than the male. Polymorphism, although present in other species of anemonefishes, does not occur in A. percula. Such is the case with melanistic (black pigmentation) variation in some anemonefish species. This is generally absent in A. percula (Fautin and Allen, 1992). (Fautin and Allen, 1992; Grant, 1999)
After incubating for 6-7 days, the eggs of A. percula are ready to hatch. Just before then, however, the embryo is visible through the transparent egg membrane. The two noticeable features at this stage are the silvery pupils contained within the large eyes and the red-orange yolk sac (Fautin and Allen, 1992). After hatching, the larva is about 3-4 mm total length and transparent except for the eye, yolk sac, and a few scattered pigments. The newly hatched individual initially sinks to the benthic environment but quickly swims to the upper surface of the water column using a process called phototaxis. Essentially, the larva is able to orient itself using the shine from a moonlit night. At this point, the larva spends a week floating among the plankton and is passively transported by ocean currents (Fautin and Allen, 1992). The larval stage of A. percula ends when the young anemonefish settles to the sea bottom approximately 8-12 days after hatching (DAH). Compared to other coral reef species, this is a relatively short period (Wellington and Victor 1989).
The juvenile stage of A. percula is characterized by a rapid development of color schemes. The white barring pattern that is unique to this species begins to form around 11 DAH and may correspond to the fish’s first association with its host anemone (Elliott et al., 1995). Consequently, contact with the anemone stimulates A. percula to produce its protective mucous coat (Elliott and Mariscal, 1996) (See Behavior section for a complete elaboration on acclimation and protection from anemone nematocysts). The entire metamorphosis from larva to juvenile is usually completed in a day (Fautin and Allen, 1992).
Development from juvenile to adult is highly dependent on the social hierarchy of the “family group.” Each host anemone is often occupied by a mating pair plus two to four smaller fish (Fautin and Allen, 1992). Aggression between the dominant female and her mate is minimal, thereby causing little expenditure in energy. Each male, however, bullies and chases the next male of smaller successive size until the smallest individual is driven away from the host anemone. As a result, energy that could be used for growth is instead appropriated for competitive encounters. The adult pair essentially stunts the growth of juveniles (Myers, 1999).
Like other anemonefishes, the uniqueness of A. percula development lies in adult metamorphosis from male to female (protandrous hermaphroditism). All anemonefishes are born as males (Wood and Aw, 2002; Fautin and Allen, 1992; Rosenberg and Cruz, 1988), and the largest of the group reverses sex to become the dominant female. The second largest male subsequently becomes the dominant male. In instances when the female dies, the dominant male reverses sex and all other subordinate males move up in the hierarchical ladder. (Elliott and Mariscal, 1996; Elliott, et al., 1995; Fautin and Allen, 1992; Myers, 1999; Rosenberg and Cruz, 1988; Wellington and Victor, 1989; Wood and Aw, 2002)
Monogamous pair-bond formations between male and female individuals of A. percula are very strong and correlated with the small territory size that this species occupies. Despite being restricted to the immediate vicinity of its host anemone, A. percula can breed/spawn year round due to the perpetually warm tropical waters they inhabit.
Initiation of courtship is highly correlated with the lunar cycle. The moonlight serves to maintain a high level of alertness in the male, which then leads to increased social interaction with the female. Several days before spawning, the male will show morphological and behavioral changes: fin erection, chasing, nest preparation, and “signal jumping.” This last trait is depicted with rapid up and down swimming motions. Finally, extensions of anal, dorsal, and pelvic fins accompany the aggressiveness of the male (Fautin and Allen, 1992)
The choice of nest site is important for later survival of the eggs. It is usually located under the tentacles of the host anemone and securely positioned on a patch of cleared rock (Myers, 1999). The male has been known to nip at the bottom edges of the tentacles in order to cause retraction, and thus providing enough clearance to clean the area (Rosenberg and Cruz, 1988). Initially, the male clears algae and debris with its mouth only later to be joined by its mate (Fautin and Allen, 1992). There is clear emphasis, then, on male parental care, and this will be crucial when the eggs become vulnerable to predation.
Actual spawning procession takes place during the morning hours, and generally lasts about 30 minutes to more than two hours. At this stage, the conical ovipositor of the female becomes visible. Several eggs are extruded through this structure with each slow and deliberate pass as the belly gently brushes the nest surface. Following closely behind is her mate, who externally fertilizes the eggs as they are laid. The number of total passes during each spawning session is high, and the amount of deposited eggs range from 100 to over 1000, depending on fish size and previous experience. Older, more experienced mating pairs will produce more eggs. The eggs of A. percula are about 3-4 mm in length (Fautin and Allen, 1992).
After egg deposition has finished, the incubation period begins. At this time, the male actively mouths and fans the eggs, while simultaneously being on guard against any predators (Rosenberg and Cruz, 1988). Because the eggs are attached to the bottom substrate via adhesive strands, additional protection is provide by the overhanging tentacles of the host anemone (Allen, 1997). Removal of dead eggs and debris is also important in keeping a well-oxygenated nest and is accomplished by the male. The female, in contrast, is occupied with feeding during this time (Fautin and Allen, 1992). (Allen, 1997; Fautin and Allen, 1992; Myers, 1999; Rosenberg and Cruz, 1988)
There is very little longevity data for many species of anemonefishes. However, some are recorded to have lived at least 6-10 years in nature. In captivity, the record is 18 years for Amphiprion frenatus and Amphiprion perideraion. (Fautin and Allen, 1992)
In anemonefishes particular attention has been given to behavioral components of the symbiotic relationship with sea anemones. Reliance on a host has effects at every particular life stage. A. percula lays its eggs under the overhang of an anemone’s tentacles (leeward side). Arvedlund et al. (2000) believed that this was a predator-deterrence and an olfactory imprinting mechanism. The latter plays an important role in directing juveniles to the appropriate sea anemone species later on. With a leeward placement, a maximum amount of imprinting mucous can transfer between the tentacles and eggs.
Once a juvenile, A. percula must locate and inhabit a suitable anemone host. Its poor swimming ability makes it an easy target for predators. Certain chemical cues are used, and they differ among anemonefishes; this causes preferential selection for certain anemone species (Fautin and Allen, 1992). Elliott et al. (1995) found that ocean currents facilitate the locating process and that visual cues were never used. Even when a targeted anemone is already occupied, the approaching A. percula does not avoid it; however, the territorial nature of anemonefishes causes the resident to chase away its intruder.
Habitation of a chosen anemone generally requires a period of acclimation (Davenport and Norris, 1958; Fautin and Allen, 1992, Elliott and Mariscal, 1997). The protective mucous of A. percula is developed with repeated interactions with the host anemone. Two theories exist about how the mucous layer forms. Either the fish acquires it after contact with the tentacles (a behavioral process), or it is developed physiologically (a biochemical process). Both explanations have been supported, and both are believed to be equally important. During its first encounter with the sea anemone, A. percula will engage in a swimming dance, gingerly touching tentacles first to its ventral fins and then to its entire body. It may be stung a number of times before full acclimation occurs. The whole procedure may take as little as a few minutes to several hours. Once acclimated, though, the mucous protection may disappear upon extended separation between host and fish. Continued contact with the tentacles appears to reactivate the mucous coat on A. percula. (Arvedlund, et al., 2000; Davenport and Norris, 1958; Elliott and Mariscal, 1997; Elliott, et al., 1995; Fautin and Allen, 1992)
A. percula feeds mainly on zooplankton, such as copepods and larval tunicates. Possibly, it consumes algae from the surrounding coral reef or even leftover food portions from its host anemone. The former strategy is commonly used by A. perideraion (Fautin and Allen, 1992). Frequently, A. percula will carry large pieces of food to its host anemone, presumably to store it for later use. The anemone, however, devours the accessible food item in most cases (Grant, 1999).
Optimal juvenile growth rate was discovered at a ration of approximately 6% body weight per day (Johnston et al., 2000). Juveniles are under considerable pressure from the hierarchical structure. The individual is harassed and chased by bigger males of the “family group,” which results in stunted growth. Consequently, the smaller fish has a more restricted feeding area, and more energy must be placed on evasion. Only when a larger male is removed (e.g. death) will the smaller juvenile experience an acceleration in growth rate. It is believed that less time being harassed translates into more time spent on feeding (Fautin and Allen, 1992).
Due to the increased aquarium trade for A. percula (See Economic Importance for Humans) and a continued depletion of coral reef habitats, there have been tremendous developments in rearing of marine fishes using aquaculturing techniques. One of the most challenging obstacles is providing an economical, yet effective, feed in an artificial environment. Hoff (1996) found that A. percula larvae and juveniles could be successfully reared on highly integrated and diverse feeds, such as rotifers, small particulate dry feed, Artemia, and krill meal. Unfortunately, this proved too expensive to be practical, and a regime solely based on artificial feed decreased survival and growth rates in young fishes. If, however, juveniles were weaned from live Artemia 15 to 20 days after hatching and fed a fish meal/casein-based substitute, survival and growth rates showed no difference from juveniles fed entirely on live feed (Gordon et al., 2000). (Fautin and Allen, 1992; Gordon, et al., 1998; Grant, 1999; Hoff, 1996; Johnston, et al., 2000)
The symbiosis between A. percula and its host anemone serves as an effective anti-predation measure. Protected within the tentacles of the sea anemone, A. percula belongs to a unique group of fishes that are not stung by the nematocysts. It is believed that a thick mucous layer cloaks the fish from detection and response by anemone tentacles (Rosenberg and Cruz, 1988). Fish species lacking in this physiological adaptation are captured and devoured by the sea anemone. It is no surprise, then, that A. percula has very few predatory foes as adults. Presence of danger immediately elicits a response to seek shelter deep within its host. Although adults are relatively safe from predation, the eggs of A. percula are susceptible and must be guarded by the dominant male. The most common day predators are wrasses (family Labridae) and other damselfishes (family Pomacentridae). Night predators of eggs are generally not fishes but invertebrates like brittle stars (Ophiotrichidae, Ophiochimidae, and Ophiodermatidae) (Arvedlund et al., 2000). (Arvedlund, et al., 2000; Rosenberg and Cruz, 1988)
A. percula interacts with its sea anemone host and other anemonefish species. The symbiotic relationship is well documented to benefit the fish, but equal rewards exist for the anemone. In exchange for protection, A. percula may feed, oxygenate, and remove waste material from its host (Rosenberg and Cruz, 1988). In addition, it may prevent certain coelenterate feeders, such as butterfly fishes, from preying on the anemone (Allen, 1997). Because anemonefishes are highly territorial, A. percula drives away intruders, including those that harm its symbiotic host. Whether these actions are self-serving or altruistic is not known, but both species gain advantage. (Allen, 1997; Rosenberg and Cruz, 1988)
A. percula and other anemonefishes are some of the most colorful fish species available for the aquarium trade. They also demonstrate interesting behaviors and are easily adaptable to captivity (Fautin and Allen, 1992). Consequently, these characteristics make them good reference fishes for scientific research, especially when conducting nutritional studies and determining egg and larval quality (Gordon et al., 2000). (Fautin and Allen, 1992; Gordon, et al., 1998)
The depletion of coral reef habitats and marine aquarium fishes has presented a relatively new market in aquaculture. It is possible to rear A. percula in controlled conditions (Gordon et al., 2000), and it may eventually play a significant role in maintaining stable populations. At present, this species is not threatened or endangered. (Gordon, et al., 1998)
William Fink (editor), University of Michigan-Ann Arbor.
Jeff Lee (author), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
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.
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
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.
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).
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.
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the business of buying and selling animals for people to keep in their homes as pets.
an animal that mainly eats plankton
condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products
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.
mainly lives in oceans, seas, or other bodies of salt water.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
places a food item in a special place to be eaten later. Also called "hoarding"
uses touch to communicate
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
breeding takes place throughout the year
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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.
Davenport, D., K. Norris. 1958. Observations on the symbiosis of the sea anemone *Stoichactis* and the pomacentrid fish, *Amphiprion percula*. Biological Bulletin, 115(3): 397-410.
Elliott, J., J. Elliott, R. Mariscal. 1995. Host selection, location, and association behaviors of anemonefishes in field settlement experiments. Marine Biology, 122: 377-389.
Elliott, J., R. Mariscal. 1997. Acclimation or innate protection of anemonefishes from sea anemones?. Copeia, 2: 284-289.
Elliott, J., R. Mariscal. 2001. Coexistence of nine anemonefish species: differential host and habitat utilization, size and recruitment. Marine Biology, 138: 23-36.
Elliott, J., R. Mariscal. 1996. Ontogenetic and interspecific variation in the protection of anemonefishes from sea anemones. Journal of Experimental Marine Biology and Ecology, 208: 57-72.
Ern, G. 1999. Grant's Guide to Fishes. Scarborough: E.M. Grant Pty Ltd..
Fautin, D., G. Allen. 1992. Field Guide to Anemonefishes and their Host Sea Anemones. Perth: Western Australian Museum.
Gordon, A., H. Kaiser, P. Britz, T. Hecht. 1998. Effect of feed type and age-at-weening on growth and survival of clownfish *Amphiprion percula* (Pomacentridae). Aquarium Sciences and Conservation, 2: 215-226.
Grant, E. 1999. Grant's Guide to Fishes. Scarborough: E.M. Grant Pty Ltd..
Hoff, F. 1996. Conditioning, Spawning and Rearing of Fish with Emphasis on Marine Clownfish. Dade City: Aquaculture Consultants, Inc..
Johnston, G., T. Hetcht, L. Oellermann, H. Kaiser. 2000. Effect of feeding frequency and ration on the growth of juvenile clownfish (*Amphiprion percula*). 10th Southern African Marine Science Symposium (SAMSS 2002): Land, Sea and People in the New Millennium--Abstracts.
Myers, R. 1999. Micronesian Reef Fishes. Guam: Coral Graphics.
Randall, J., G. Allen, R. Steene. 1997. Fishes of the Great Barrier Reef and Coral Sea. Bathurst: Crawford House Publishing.
Rosenberg, S., G. Cruz. 1988. The anemonefishes of the Indo-Pacific. Sea Frontiers, 34: 16-21.
Wellington, G., B. Victor. 1989. Planktonic larval duration of one hundred species of Pacific and Atlantic damselfishes (Pomacentridae). Marine Biology, 101: 557-567.
Wood, E., M. Aw. 2002. Reef Fishes: Corals and Invertebrates of The South China Sea. United Kingdom: New Holland Publishers.