Amphiprion akindynos, also known as the Barrier Reef anemonefish or clownfish, is native to the Western Pacific. Amphiprion akindynos is primarily found in the waters of the Great Barrier Reef of Australia and in the adjacent Coral Sea. It has also been found in waters off of northern New South Wales, New Caledonia, sections of the Indian Ocean and around the Loyalty Islands. There is some question as to whether A. akindynos also inhabits the waters around Sri Lanka. (Randall, et al., 1990)
Amphiprion akindynos inhabits reef waters and lagoons between 1 and 25 meters deep with temperatures ranging from 10 to 32 degrees Celsius. They are found in nature swimming in and closely around the tentacles of their host anemone. They are able to live and make shelter among the tentacles of anemones without being harmed by the nematocysts (stinging cells) present on the anemone’s tentacles. According to Allen (1980), A. akindynos are protected from possible stings by a special substance which is present in their external mucous covering. This substance does not actually protect them from the stinging cells. “Instead, it lowers the threshold of nematocyst discharge. In other words, it prevents the stinging cells from firing.” Host species of anemone for A. akindynos are: Entacmaea quadricolor, Heteractis aurora, H. crispa, H. magnifica, Stichodactyla haddoni, and S. mertensii. (Allen, 1980; Allen, 1991; Fautin and Allen, 1992; Froese and Pauly, 2002; Randall, et al., 1990)
The body and head of adult A. akindynos are both a brownish orange color. Two black-edged white bars encircle the body. The first bar runs across the top of the head just behind the eye and can be discontinuous and constricted (thin). The second stripe runs around the body at the mid portion of the dorsal fin. The caudal peduncle and caudal fin are both white. Amphiprion akindynos individuals have 10 to 11 dorsal spines, 14 to 17 dorsal soft rays, 2 anal spines, and 13 to 14 soft anal rays.
Juveniles are usually brown with three thick white bars. Sub-adults are usually yellow with two thin white bars. Both adults and juveniles and are often confused with A. clarkii and A. chrysopterus. However, A. clarkii have a more distinct color difference between their body and tail than adult A. akindynos and A. chrysopterus tend to have a darker orange color with bluish bars. (Allen, 1991; Fautin and Allen, 1992; Froese and Pauly, 2002)
The larval period of A. akindynos ranges from about 8 to 12 days. Although not known for certain, many believe that during this period the larvae are planktonic, “living in the surface waters of the ocean, where they are passively transported by currents” (Fautin and Allen, 1992). At the end of this period, the fish will descend to the bottom of the sea and begin to acquire the color patterns associated with juveniles. Once they get to the bottom, the young will begin to search for a host anemone. Without the protection of the anemone there is a high likelihood that a fish will be eaten by its predators and there is evidence that there is a high mortality rate at this stage of development (Fautin and Allen, 1992).
Arvedlund et. al. (2000) have found evidence that A. akindynos imprint onto their host anemone during their larval stage and are able to follow a trail of chemicals released by this host anemone, thus allowing these fish to return to the same species of host anemone to live and spawn. However, once returning to their host anemone a fish cannot simply swim into the anemone because it may get stung. According to Fautin and Allen (1992) it can take several hours to become fully acclimated to the anemone once it is located. The acclimation process consists of a series of progressively longer contacts with the tentacles. A. akindynos are initially protected from nematocyst stings by a thick mucus coat. However, over the acclimation process, the clownfish incorporates anemone mucus into its own coat until the anemone no longer stings it, apparently recognizing the fish as part of itself.
Even once a fish locates a host anemone it is not guaranteed a place to live. Within the anemone, there is an intricate social hierarchy. All A. akindynos begin life as males. Within a given anemone, the largest fish is the female and the next largest fish is her mate. There can be several other males in this structure; however, they generally do not have much chance of mating. If the female dies, the next largest male will become a female and the second largest male will become the new mate. In this structure the female is the dominant fish and her mate is the second most dominate. The remainder of the fish must compete and fight for a place in the anemone.
Mated pairs occupy the same anemone. Several days prior to spawning, there is increased social interaction between A. akindynos males and females. Usually the male becomes more aggressive and will pursue and bite his mate. He also displays himself either in front of his mate or beside her by fully extending his dorsal, anal, and pelvic fins. During this time, the male also selects a nest site, usually on bare rock adjacent to the host anemone. The male will spend considerable time clearing the site of algae and debris using his mouth. Sometimes the female will join in. Spawning usually occurs during the morning hours and can last from about 30 minutes to more than two hours. The female will swim in a zig-zag path over the nest with her belly brushing its surface. This brushing causes several eggs from her ovipositor to be dislodged. The male will follow behind the female and fertilize the eggs as they are laid. This will continue until all eggs have been dislodged. (Arvedlund, et al., June 2000; Fautin and Allen, 1992; Froese and Pauly, 2002; Richardson, et al., 1997)
The number of eggs deposited can range from about 100 to over 1000, depending on the size of the fish and on previous experience. The eggs are elliptical and are about 3 to 4 mm in length. They adhere to the nest surface by a tuft of short filaments. The eggs will incubate six to seven days before hatching. (Arvedlund, et al., June 2000; Fautin and Allen, 1992; Froese and Pauly, 2002; Richardson, et al., 1997)
Barrier reef anemonefish are hermaphroditic, with young developing into males first and only later into females if conditions are appropriate.
Individuals generally live between 6 and 10 years in the wild. However, as noted earlier, there is a high mortality rate during the larval, fry, and juvenile stages, which correspond to life stages when the fish do not necessarily have the protection of a host anemone.
They have been known to live up to 18 years in captivity. (Fautin and Allen, 1992; Froese and Pauly, 2002)
As noted before, Amphiprion akindynos has a very interesting social structure. There is a single dominant female in each social group who is the largest of all the fish inhabiting an anemone. She has a single male mate who is the second largest fish. Between two and four other smaller males can also live in the anemone. There is generally an amicable relationship between the female and her mate, and any aggression by the female is displayed as ritualized, non-harmful behaviors. However, aggression is more pronounced between the all of the males. There is a distinct pecking order where the largest male spends time chasing and bullying the next largest male, who in turn bullies the smaller fishes. Attacks may be so severe as to drive away the smallest fish (generally the newest member of the hierarchy) who must find another anemone to live in or die. Again, as noted before, when the female dies, the largest male will assume her position. Almost immediately after she is gone, the largest male will begin displaying behaviors similar to the previous female. Within days the male will actually change sexes and become female and the next largest male will become the mate. (Fautin and Allen, 1992; Carver, 2002)
Barrier Reef anemonefish use visual cues to communicate among themselves. Chemical communication via their protective mucous covering is essential to their symbiosis with anemones.
Barrier Reef anemonefish primarily eat algae and zooplankton. Copepods and larval tunicates are among the most common items found when their stomach contents are analyzed. The adult pair of fish (the female and her mate) are the largest fish in the social hierarchy. They tend to stray further from the host anemone to gather food than do the smaller non-dominate fish. It is speculated that one reason for the rapid growth of the mate and the second dominate male when the female dies is that the fish can spend more time feeding and less time competing for a place to live. (Fautin and Allen, 1992; Froese and Pauly, 2002)
Amphiprion akindynos avoid being preyed on by other larger fish by staying in and around their host anemone. As described above, they have a substance in the mucous covering their bodies, making it possible for them to touch the tentacles and not get stung. Predators will avoid getting stung by the tentacles of the host anemone and thus A. akindynos will be safe from larger fish. They may occasionally be preyed on when they are away from a host anemone, either as juveniles looking for a host, or when ejected from their host territory by another anemonefish. (Allen, 1980)
Amphiprion akindynos have a mutualistic symbiotic relationship with their host anemones. This arrangement works for both Amphiprion akindynos and their host. Without the anemone’s protection and shelter, Amphiprion akindynos are quickly consumed. Conversely Amphiprion akindynos fight off intruders, such as anemone-eating butterflyfish that would otherwise prey on the anemone. Additionally there may be some benefit to the anemone from the fishes’ feeding. Bits of food may drop onto the host and help feed it. It has also been suggested that the fish assists in keeping the anemone clean. The fish moving in and out of the anemone helps to create currents of water, which assist bringing food to the anemone and also in keeping it free of debris. (Allen, 1980; Fautin and Allen, 1992; Froese and Pauly, 2002; Randall, et al., 1990)
Amphiprion akindynos is popular in the aquarium trade and is an important member of the ecosystems in which they live. They contribute to the color and interest of reef ecosystems, thereby attracting tourism. Amphiprion species are important as research organisms in understanding mutualism.
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.
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.
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
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).
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
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.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
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
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
Carver, L. "PBS Evolution Series" (On-line). Accessed October 20, 2002 at http://www.pbs.org/wgbh/evolution.