Known as either Clark’s anemonefish or yellowtail clownfish, this species is the most widely distributed anemonefish in the Indo West Pacific, ranging from the Persian Gulf to western Australia, throughout the Indo-Australian Archipelago, Melanesia, and Micronesia, and as far north as Taiwan, southern Japan, and the Ryukyu Islands. (Allen, 1997)
Clark's anemonefish inhabit coral reefs, sheltered lagoons, and steep edges of reefs up to a depth of 60 meters. This species is always found living within the tentacles of sea anemones (Class Anthozoa). Although they are often found near anemones such as Entacmaea quadricolor, Heteractis magnifica, and Stichodactyla gigantea, they are known to naturally associate with all 10 of the anemone species known to host clownfishes. (Allen, 1997; Fautin and Allen, 1992)
- Aquatic Biomes
- Range depth
- 1 to 60 m
- 3.28 to 196.85 ft
Clark’s anemonefish are colorful, although the exact pattern shows considerable geographical variation. The base body color is usually black but may range from a yellow to brown color, with varying amounts of orange on the head, ventral areas, and fins. A vertical, white to yellowish bar is located on the head, posterior to the eye, with two more on the body: one above the anus and the other at the base of the caudal fin. However, juveniles from all geographic regions and adults from Vanuatu and New Caledonia may be mainly or entirely orange-yellow with only the two most anterior white bars. The caudal fin may be white or yellow, but is always lighter than rest of body coloration. Male caudal fins are either yellow or white with yellow edges, whereas in some females, the caudal fin may change to a solid white as they mature. Both males and females have yellow pectoral fins. Individuals that reside within Stichodactyla mertensii are frequently black except for a pale snout, with white bars on the head and body, and a yellow or white tail. Coloration may differ in additional ways, depending on the species of host anemone that the fish inhabits. (Allen, 1997; Fautin and Allen, 1992)
This species has a total of 10 dorsal spines, 15 to 16 soft dorsal rays, 2 anal spines, and 13 to 14 total anal soft rays. The teeth are close-set, each resembling a typical incisor. These are used to defend its host anemone from invading fish, and can inflict harm to humans if the fish is provoked. (Allen, 1997; Fautin and Allen, 1992)
On rare occasions, these anemonefish will develop an interesting mutation within their eyes. A pale blue crescent will appear in the upper part of the iris, often referred to as “Pearl Eyes.” Individuals with this trait are highly desirable within the aquarium trade. (Allen, 1997; Fautin and Allen, 1992)
- Range length
- 14 (high) cm
- 5.51 (high) in
Eggs generally hatch 6 to 8 days after fertilization, depending on the surrounding water temperature; the cooler the water, the longer the incubation period. Once the eggs hatch, larvae are completely independent from their parents. The planktonic larval stage lasts between 7 to 9 days and ends when the juvenile fish returns to the bottom and finds a suitable host anemone to inhabit. (Breder and Rosen, 1966; Fautin and Allen, 1992; Fricke and Fricke, 1977; Myers, 1999; Thresher, 1984)
Clark's anemonefish, as part of the anemonefish subfamily Amphiprioninae, is a species characterized by protandrous hermaphrodism, meaning that all larvae develop as males and possibly change into females later in life. An adult male, female, and several juveniles may reside together within an anemone. If the female is removed or dies, the largest male becomes a female. Females control males with aggressive dominance, thus prohibiting the creation of other females. The largest male will in turn dominate the juveniles, preventing other males from spawning. This results in distinct monogamous pairings during the breeding season. (Breder and Rosen, 1966; Fricke and Fricke, 1977; Myers, 1999)
Prior to spawning, males prepare a nest where the female deposits her eggs. When spawning is about to occur, the male, extending his fins in a corralling gesture, chases the female into the nest. The female makes several passes over the nest and then begins to lay orange elliptical shaped eggs over a period of 1 to 2 hours before leaving the nest. The male then passes over the eggs and fertilizes them. (Breder and Rosen, 1966; Thresher, 1984)
- Mating System
Clark's anemonefish breed nearly year-round in tropical waters, typically spawning 2 to 3 times per month. Spawning frequency may be somewhat limited during winter months in the northern edge of its distribution. Females lay demersal eggs (adhering to the substrate) in a large nest containing of 600 to 700 elliptical eggs from multiple spawnings. The eggs are approximately 3 to 4 mm in length and are attached to the substrate with a fine thread. The number of eggs in a nest varies depending on the age and size of the female. (Breder and Rosen, 1966; Fautin and Allen, 1992; Moyer, 1980; Thresher, 1984)
Spawning is synchronized with the full moon and usually occurs in the early morning hours. Possible explanations for this include stronger water currents along the reef created by spring tides, which aid dispersal by transporting the anemonefish larvae greater distances, and a greater food supply and increased visibility of planktonic prey as a result of simultaneous spawning of invertebrates (such as corals and annelids) during the full moon. (Breder and Rosen, 1966; Thresher, 1984)
- Key Reproductive Features
- year-round breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sequential hermaphrodite
- Breeding interval
- Breeding occurs possibly 2 to 3 times per month, although spawning may be reduced (or cease completely) in the northern regions of their distribution during winter months.
- Breeding season
- Spawning occurs year-round in the tropics, but only in the warmer months (May-October) in northern regions. Spawning occurs near the full moon.
- Range number of offspring
- 600 to 700
- Range time to hatching
- 6 to 8 days
Males provide the majority of egg care, with the female involved only sporadically. Main duties of the male include fanning the eggs in a process that helps with incubation, and eating eggs that are infertile or that have been damaged during spawning. Once the eggs hatch, larvae are completely independent from their parents. (Thresher, 1984)
- Parental Investment
- male parental care
Data on longevity in wild Clark's anemonefish is limited to a single study, which estimated that a female under periodic observation over a period of 11 years was at least 13 years old at the time she disappeared from her host anemone, with other anemones hosting females with estimated ages of 10 and 12 years. Sexually functional males disappear from anemones more frequently, perhaps suggesting shorter average lifespans for males, although this pattern could also be due to increased mobility of males seeking dominance on other anemones. (Fautin and Allen, 1992; Moyer, 1986)
- Range lifespan
- 10 to 13 years
- Range lifespan
Clark's anemonefish form symbiotic relationship with at least 10 different anemone species. Since these fish are poor swimmers and are susceptible to predation, they are completely dependent upon the anemone for shelter and protection of their nests. In return, anemones with a host fish present are typically healthier, possibly due to the anemonefish’s consumption of parasites or increased water circulation that males create while they care for eggs. Although anemonefishes are protected from the stinging nematocysts found on the anemone by a thin layer of mucus that covers their bodies, there is a period of acclimatization that must occur before the fish becomes immune to the anemone sting. This occurs as the fish swims over the anemone, rubbing its belly and ventral fins on the ends of the tentacles until the fish begins producing the protective mucus covering. (Fautin and Allen, 1992; Lee, 2011; Myrberg and Fuiman, 2002)
A juvenile's search for an ideal host anemone is often a difficult process, since Clark's anemonefish are aggressive to other species, particularly when defending a host anemone from congeners. Fish in each anemone have an established dominance hierarchy that keeps individuals at a specific social rank. A newly-recruited juvenile is at the bottom of the hierarchy and receives the harshest aggression when it enters an anemone community. Some juveniles may be driven away, leaving them exposed and vulnerable to predation. (Buston, 2003; Thresher, 1984)
Since this species is completely dependent upon anemones for shelter, they never stray far from their respective host anemone. Home range and territory is essentially the area within the tentacles of the host anemone. (Fautin and Allen, 1992)
Communication and Perception
Hierarchical social structure is maintained through an array of aggressive tactics by larger fish towards the smaller individuals residing in the host anemone. Juvenile Clark's anemonefish are able to find host anemones through olfactory imprinting that occurs as the eggs develop in the nest. Anemone selection occurs as a ritualistic swimming pattern in which the fish will repeatedly brush up against the tentacles of the potential host anemone. If the anemone is found to be unsuitable in some way, the fish will move on to another anemone and repeat the process until a suitable host is found. Special chemicals contained within the mucus layer covering the skin of the clownfish have the capacity to block stings from the anemone’s nematocysts. (Fautin and Allen, 1992; Myers, 1999; Thresher, 1984)
Clark's anemonefish are able to perceive their environment using visual, olfactory, tactile, auditory, and vibrational (lateral line) sensory systems. (Fautin and Allen, 1992)
This species primarily consumes planktonic food such as zooplankton, copepods, and algae. In some cases, they have been observed to consume parasites found on their host anemone. Feeding behavior is affected by the hierarchical structure of the group within the host anemone. Smaller fish, which experience the greatest amount of aggression, have less energy to venture outside the anemone to forage, thus forcing them to remain within a close distance to their host. This may be beneficial to the overall survival of the population, as those smaller fish are better protected from the predation that the older and larger dominant fish are subjected to while foraging a few meters from their host anemone. (Fautin and Allen, 1992; Myers, 1999; Nose, 1985; Sano, et al., 1984; Thresher, 1984)
- Animal Foods
- aquatic crustaceans
- Plant Foods
- Other Foods
Larval anemonefish are extremely susceptible to predation as they are small, poor swimmers, resulting in very high mortality rates while in the planktonic stage. Predation on adult and juvenile anemonefishes is greatly reduced due to the protection conferred by the host anemone, whose sting deters potential predators. The eggs are more susceptible to predation, mainly by wrasses and pomacentrid damselfishes. Egg predation increases at night, when the male is not guarding them. (Thresher, 1984)
Clark's anemonefish form mutualistic symbiotic relationships with all anemone species that are known to host anemone- and clownfishes. In this relationship, the anemonefish receives shelter and a protected nesting location, while the host anemone receives defense from its resident anemonefishes. Anemones remain healthier while hosting anemonefish, developing terminal bulbs on the tips of the tentacles and thereby increasing the amount of surface area from which the photosynthetic algae housed within the anemone’s tentacles can capture solar energy. These bulbs do not develop in anemones lacking anemonefish. (Fautin and Allen, 1992; Gudgeon, 2011; Lee, 2011)
- tongue-eating copepod (Cymothoa exigua)
Economic Importance for Humans: Positive
Clark's anemonefish are found in the tropical fish aquarium trade and certain rare color morphs of the species are highly sought after. They are easily bred and grow relatively quickly in captivity, and thus make useful research animals. (Sadovy and Vincent, 2002; Thresher, 1984)
- Positive Impacts
- pet trade
- research and education
Economic Importance for Humans: Negative
There are no known negative impacts of this species on humans. Adults may nip at a SCUBA diver's fingers, if provoked.
- Negative Impacts
- bites or stings
Although the conservation status of this species has not been evaluated, the increased demand for Clark's anemonefish in the aquarium trade has reduced populations in some locations. As global degredation of coral reefs continues to increase, these anemonefish will undoubtably encounter decreases in suitable habitat availability, which may cause populations to become threatened in the future. ("2003 IUCN Red List of Threatened Species", 2003)
This species makes an execellent choice as an aquarium fish for hobbists who want a healthy and productive symbotic clownfish/anemone relationship due to its versatility in adapting to various host anemones.
Padgette' Steer (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Jeremy Wright (editor), University of Michigan-Ann Arbor.
- 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.
uses sound to communicate
- 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.
uses smells or other chemicals to communicate
- 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
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
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).
- male parental care
parental care is carried out by males
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
- native range
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats all kinds of things, including plants and animals
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.
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.
- saltwater or marine
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
associates with others of its species; forms social groups.
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.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
- year-round breeding
breeding takes place throughout the year
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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