Clownfish or anemonefish are
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
es from the subfamily Amphiprioninae in the family
Pomacentridae. Thirty
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of clownfish are recognized: one in the genus ''
Premnas'', while the remaining are in the genus ''
Amphiprion
''Amphiprion'' is a genus of ray-finned fish which comprises all but one of the species of clownfish or anemonefish in the subfamily Amphiprioninae of the family Pomacentridae.
Species
The following species are classified in the genus ''Amphipri ...
''. In the wild, they all form
symbiotic mutualisms with
sea anemones. Depending on the species, anemonefish are overall yellow, orange, or a reddish or blackish color, and many show white bars or patches. The largest can reach a length of , while the smallest barely achieve .
Distribution and habitat
Anemonefish are endemic to the warmer waters of the Indian Ocean, including the
Red Sea
The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...
, and Pacific Ocean, the
Great Barrier Reef
The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, ...
, Southeast Asia, Japan, and the Indo-Malaysian region. While most species have restricted distributions, others are widespread. Anemonefish typically live at the bottom of shallow seas in sheltered
reef
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...
s or in shallow
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') ...
s. No anemonefish are found in the Atlantic.
Diet
Anemonefish are
omnivorous
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
and can feed on undigested food from their host anemones, and the
fecal
Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
matter from the anemonefish provides nutrients to the sea anemone. Anemonefish primarily feed on small
zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
from the water column, such as
copepods and
tunicate
A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...
larvae, with a small portion of their diet coming from algae, with the exception of ''
Amphiprion perideraion'', which primarily feeds on
algae.
Symbiosis and mutualism
Anemonefish and sea anemones have a symbiotic, mutualistic relationship, each providing many benefits to the other. The individual species are generally highly host specific. The sea anemone protects the anemonefish from predators, as well as providing food through the scraps left from the anemone's meals and occasional dead anemone tentacles, and functions as a safe nest site. In return, the anemonefish defends the anemone from its predators and parasites.
The anemone also picks up nutrients from the anemonefish's excrement. The nitrogen excreted from anemonefish increases the number of algae incorporated into the tissue of their hosts, which aids the anemone in tissue growth and regeneration.
The activity of the anemonefish results in greater water circulation around the sea anemone, and it has been suggested that their bright coloring might lure small fish to the anemone, which then catches them. Studies on anemonefish have found that they alter the flow of water around sea anemone tentacles by certain behaviors and movements such as "wedging" and "switching". Aeration of the host anemone tentacles allows for benefits to the metabolism of both partners, mainly by increasing anemone body size and both anemonefish and anemone respiration.
Bleaching of the host anemone can occur when warm temperatures cause a reduction in algal symbionts within the anemone. Bleaching of the host can cause a short-term increase in the metabolic rate of resident anemonefish, probably as a result of acute stress. Over time, however, there appears to be a down-regulation of metabolism and a reduced growth rate for fish associated with bleached anemones. These effects may stem from reduced food availability (e.g. anemone waste products, symbiotic algae) for the anemonefish.
Several theories are given about how they can survive the sea anemone poison:
* The mucus coating of the fish may be based on
sugars rather than
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s. This would mean that anemones fail to recognize the fish as a potential food source and do not fire their
nematocysts, or sting
organelles.
* The
coevolution of certain species of anemonefish with specific anemone host species may have allowed the fish to evolve an immunity to the nematocysts and toxins of their hosts. ''
Amphiprion percula
The orange clownfish (''Amphiprion percula'') also known as percula clownfish and clown anemonefish, is widely known as a popular aquarium fish. Like other clownfishes (also known as anemonefishes), it often lives in association with sea anemones. ...
'' may develop resistance to the toxin from ''
Heteractis magnifica'', but it is not totally protected since it was shown experimentally to die when its skin, devoid of mucus, was exposed to the nematocysts of its host.
Anemonefish are the best known example of fish that are able to live among the venomous sea anemone tentacles, but several others occur, including juvenile
threespot dascyllus, certain
cardinalfish
Cardinalfishes are a family, Apogonidae, of ray-finned fishes found in the Atlantic, Indian, and Pacific Oceans; they are chiefly marine, but some species are found in brackish water and a few (notably '' Glossamia'') are found in fresh water. A ...
(such as
Banggai cardinalfish
The Banggai cardinalfish (''Pterapogon kauderni'') is a small tropical cardinalfish in the family Apogonidae. It is the only member of its genus. This attractive fish is popular in the aquarium trade. It is among the relatively few marine fish ...
),
incognito (or anemone) goby, and juvenile
painted greenling.
Reproduction
In a group of anemonefish, a strict
dominance hierarchy
In biology, a dominance hierarchy (formerly and colloquially called a pecking order) is a type of social hierarchy that arises when members of animal social groups interact, creating a ranking system. A dominant higher-ranking individual is so ...
exists. The largest and most aggressive female is found at the top. Only two anemonefish, a male and a female, in a group reproduce – through
external fertilization
External fertilization is a mode of reproduction in which a male organism's sperm fertilizes a female organism's egg outside of the female's body.
It is contrasted with internal fertilization, in which sperm are introduced via insemination and then ...
. Anemonefish are protandrous
sequential hermaphrodites, meaning they develop into males first, and when they mature, they become females. If the female anemonefish is removed from the group, such as by death, one of the largest and most dominant males becomes a female. The remaining males move up a rank in the hierarchy. Clownfish live in a hierarchy, like Hyenas, except smaller and based on size not gender, and order of joining/birth. In a clownfish anemone only two clownfish get to mate, the male and the female. The other clownfish do not breed unless the female dies then one of them becomes the dominant male, while the old dominant male becomes the new breeding female.
Anemonefish lay eggs on any flat surface close to their host anemones. In the wild, anemonefish spawn around the time of the full moon. Depending on the species, they can lay hundreds or thousands of eggs. The male parent guards the eggs until they hatch about 6–10 days later, typically two hours after dusk.
Parental investment
Anemonefish colonies usually consist of the reproductive male and female and a few male juveniles, which help tend the colony. Although multiple males cohabit an environment with a single female,
polygamy
Crimes
Polygamy (from Late Greek (') "state of marriage to many spouses") is the practice of marriage, marrying multiple spouses. When a man is married to more than one wife at the same time, sociologists call this polygyny. When a woman is ...
does not occur and only the adult pair exhibits reproductive behavior. However, if the female dies, the social hierarchy shifts with the breeding male exhibiting protandrous sex reversal to become the breeding female. The largest juvenile then becomes the new breeding male after a period of rapid growth.
The existence of
protandry
Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...
in anemonefish may rest on the case that nonbreeders modulate their phenotype in a way that causes breeders to tolerate them. This strategy prevents conflict by reducing competition between males for one female. For example, by purposefully modifying their growth rate to remain small and submissive, the juveniles in a colony present no threat to the fitness of the adult male, thereby protecting themselves from being evicted by the dominant fish.
The reproductive cycle of anemonefish is often correlated with the lunar cycle. Rates of spawning for anemonefish peak around the first and third quarters of the moon. The timing of this
spawn
Spawn or spawning may refer to:
* Spawn (biology), the eggs and sperm of aquatic animals
Arts, entertainment, and media
* Spawn (character), a fictional character in the comic series of the same name and in the associated franchise
** '' Spawn: ...
means that the eggs hatch around the full moon or new moon periods. One explanation for this lunar clock is that spring tides produce the highest tides during full or new moons. Nocturnal hatching during high tide may reduce predation by allowing for a greater capacity for escape. Namely, the stronger currents and greater water volume during high tide protect the hatchlings by effectively sweeping them to safety. Before spawning, anemonefish exhibit increased rates of anemone and substrate biting, which help prepare and clean the nest for the spawn.
Before making the clutch, the parents often clear an oval-shaped clutch varying in diameter for the spawn. Fecundity, or reproductive rate, of the females, usually ranges from 600 to 1500 eggs depending on her size. In contrast to most animal species, the female only occasionally takes responsibility for the eggs, with males expending most of the time and effort. Male anemonefish care for their eggs by fanning and guarding them for 6 to 10 days until they hatch. In general, eggs develop more rapidly in a clutch when males fan properly, and fanning represents a crucial mechanism of successfully developing eggs. This suggests that males can control the success of hatching an egg clutch by investing different amounts of time and energy towards the eggs. For example, a male could choose to fan less in times of scarcity or fan more in times of abundance. Furthermore, males display increased alertness when guarding more valuable broods, or eggs in which paternity was guaranteed. Females, though, display generally less preference for parental behavior than males. All these suggest that males have increased parental investment towards the eggs compared to females.
Taxonomy
Historically, anemonefish have been identified by
morphological features and color pattern in the field, while in a laboratory, other features such as
scalation of the head, tooth shape, and body proportions are used. These features have been used to group species into six
complexes,
percula,
tomato
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...
,
skunk,
clarkii,
saddleback, and
maroon. As can be seen from the gallery, each of the fish in these complexes has a similar appearance.
Genetic analysis
Genetic analysis is the overall process of studying and researching in fields of science that involve genetics and molecular biology. There are a number of applications that are developed from this research, and these are also considered parts of ...
has shown that these complexes are not
monophyletic group
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
s, particularly the 11 species in the ''A. clarkii'' group, where only ''A. clarkii'' and ''A. tricintus'' are in the same
clade, with six species,''A. allardi'' ''A. bicinctus'', ''A. chagosensis'', ''A. chrosgaster'', ''A. fuscocaudatus'', ''A. latifasciatus'', and ''A. omanensis'' being in an Indian clade, ''A. chrysopterus'' having
monospecific
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
lineage, and ''A. akindynos'' in the Australian clade with ''A. mccullochi''. Other significant differences are that ''A. latezonatus'' also has monospecific lineage, and ''A. nigripes'' is in the Indian clade rather than with ''A. akallopisos'', the skunk anemonefish. ''A. latezonatus'' is more closely related to ''A. percula'' and ''Premnas biaculeatus'' than to the saddleback fish with which it was previously grouped.
Obligate
mutualism was thought to be the key innovation that allowed anemonefish to radiate rapidly, with rapid and convergent morphological changes correlated with the ecological niches offered by the host anemones. The complexity of
mitochondrial DNA structure shown by genetic analysis of the Australian clade suggested evolutionary connectivity among samples of ''A. akindynos'' and ''A. mccullochi'' that the authors theorize was the result of historical
hybridization and
introgression in the evolutionary past. The two evolutionary groups had individuals of both species detected, thus the species lacked reciprocal monophyly. No shared
haplotypes were found between species.
Phylogenetic relationships
Morphological diversity by complex
File:Blackandorangefalsepercs.JPG, '' A. percula'' (clown anemonefish) in a 'normal' orange and a melanistic blackish variant
File:Amphiprion clarkii.jpg, '' A. clarkii '' (Clark's anemonefish)
File:Amphiprion Species.JPG, '' A. polymnus'' (saddleback clownfish) off Sulawesi, Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
File:Amphiprion ephippium.jpg, '' A. ephippium'' (red saddleback anemonefish)
File:Pink Skunk Clownfish.jpg, '' A. perideraion'' (pink skunk anemonefish)
File:Clownfish (Papua New Guinea).jpg, Male '' P. biaculeatus'' (maroon anemonefish) in Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
In the aquarium
Anemonefish make up approximately 43% of the global marine ornamental trade, and approximately 25% of the global trade comes from fish bred in captivity, while the majority is captured from the wild, accounting for decreased densities in exploited areas. Public aquaria and captive-breeding programs are essential to sustain their trade as marine ornamentals, and has recently become economically feasible. It is one of a handful of marine ornamentals whose complete
lifecycle has been in closed captivity. Members of some anemonefish species, such as the maroon clownfish, become aggressive in captivity; others, like the false percula clownfish, can be kept successfully with other individuals of the same species.
When a sea anemone is not available in an
aquarium, the anemonefish may settle in some varieties of
soft coral
Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian corals", that produce a more or less hard skeleton, though quite different f ...
s, or large polyp stony
coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...
s.
Once an anemone or coral has been adopted, the anemonefish will defend it. Anemonefish, however, are not obligately tied to hosts, and can survive alone in captivity.
In popular culture
In
Disney
The Walt Disney Company, commonly known as Disney (), is an American multinational mass media and entertainment conglomerate headquartered at the Walt Disney Studios complex in Burbank, California. Disney was originally founded on October ...
Pixar
Pixar Animation Studios (commonly known as Pixar () and stylized as P I X A R) is an American computer animation studio known for its critically and commercially successful computer animated feature films. It is based in Emeryville, Californ ...
's 2003 film ''
Finding Nemo'' and its 2016 sequel ''
Finding Dory
''Finding Dory'' is a 2016 American computer-animated comedy-drama adventure film produced by Pixar Animation Studios and released by Walt Disney Pictures. Directed by Andrew Stanton, produced by Lindsey Collins and written by Stanton and Vict ...
'' main characters Nemo, his father Marlin, and his mother Coral are clownfish from the species ''
A. ocellaris''.
The popularity of anemonefish for aquaria increased following the film's release; it is the first film associated with an increase in the numbers of those captured in the wild.
Notes
References
Further reading
*
*
External links
*
Photo Gallery of ''Amphiprion ocellaris'' and their eggsMonterey Bay Aquarium: Video and informationAquaticcommunity.comTolweb.org
{{DEFAULTSORT:Amphiprioninae
Pomacentridae
Symbiosis
Articles containing video clips
Fish subfamilies
Fish of Saudi Arabia