A member of the Pomacentridae family, the Chagos anemonefish (Amphiprion chagosensis) belongs to a group of 28 species of small reef fish which are often referred to as clownfish (3). A deep-bodied and brightly coloured species, the Chagos anemonefish is yellow-orange to light brown, with two dark-edged white bars. The dorsal, anal and pelvic fins are dusky brown, and the caudal fin is whitish (3)(4).
This species is very similar in appearance and morphology to Amphiprion akindynos from the Great Barrier Reef and Coral Sea Region, and the closely related Amphiprion nigripes from the Maldives and Sri Lanka, although A. nigripes only has a single white bar on the body (3)(4).
Along with the other species of the family Pomacentridae, the Chagos anemonefish has developed a complex symbiotic relationship with sea anemones (3)(7)(8). The small fish lives within the tentacles of a ‘host’ anemone. However, there is currently very little information available about the specific anemone species with which the Chagos anemonefish associates.
Most species of anemonefish are adapted to live with only a single or few species of sea anemone (3). While the tentacles of sea anemones can deliver a nasty sting to most fish and potential predators, anemonefish are thought to be protected by a thick mucus coating which covers the skin, although the exact mechanism is unknown (3)(7)(9)(10). Individual anemonefish usually remain within a few metres of their host anemone and return quickly when threatened, being particularly vulnerable to predation without the protection of their host. In return for this protection, the anemonefish feeds on small invertebrates which would otherwise prey on the host anemone, hence providing mutual protection (7).
Members of the genusAmphiprion have an unusual social structure. Generally, an adult female and an adult male form a pair and defend a small territory around their host anemone. Several sexually immature juveniles are also usually found close to the adult pair. These immature, non-breeding fish are prevented from developing into adults by the dominant adult male, and may only reach maturity if one of the adult pair dies. Juvenile fish always develop into males. If the adult male dies, one of the juveniles, usually the largest, will develop into an adult male. If the adult female dies, the adult male changes sex to become female, while one of the larger juveniles replaces the adult male (11).
Generally restricted to shallow coral reefs at depths of less than 15 metres (6), the Chagos anemonefish is primarily found on seaward reef slopes, but is occasionally observed on lagoon reefs and reef tops (2).
There are currently no conservation measures targeted directly at the Chagos anemonefish. Furthermore, the Chagos Archipelago has suffered relatively little in terms of direct human impact due to its isolated position and limited access, making it one of the most important island and coral reef wilderness areas in the Indian Ocean (12).
In 2010, the Chagos Archipelago, also known as the British Indian Ocean Territory, was designated as the world’s largest Marine Protected Area (MPA). This near pristine ocean ecosystem now represents 16 percent of the world’s fully protected coral reef and 60 percent of the world’s no-take protected areas (5).
ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra
In fish, an unpaired fin on the under surface of a fish, behind the anus.
The tail fin of a fish.
The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
A species or taxonomic group that is only found in one particular country or geographic area.
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.
Referring to the visible or measurable characteristics of an organism.
In fish, the pair of fins found on the underside of the body.
Relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).
An area occupied and defended by an animal, a pair of animals or a colony.
Koldewey, H.J., Curnick, D., Harding, S., Harrison, L.R. and Gollock, M. (2010) Potential benefits to fisheries and biodiversity of the Chagos Archipelago/British Indian Ocean Territory as a no-take marine reserve. Marine Pollution Bulletin, 60(11): 1899-1901.
Carpenter, K.E. (2002) The Living Marine Resources of the Western Central Atlantic. Volume 3: Bony Fishes. Part 2 (Opistognathidae to Molidae), Sea Turtles and Marine Mammals. Food and Agriculture Organisation of the United Nations, Rome.
Fautin, D.G. (1991) The anemonefish symbiosis: what is known and what is not. Symbiosis, 10: 23-46.
Buston, P.M. (2004) Territory inheritance in clownfish. Proceedings of the Royal Society London B (Suppl.), 271: S252-S254.
Burnie, D. (2001) Animal. Dorling Kindersley, London.
Campbell, A. and Dawes, J. (2004) Encyclopedia of Underwater Life. Oxford University Press, Oxford.
Reiss, M. and Sants, H. (1987) Behaviour and Social Organisation. Cambridge University Press, Cambridge.
Sheppard, C. and Spalding, M. (2003) Chagos Conservation Management Plan. British Indian Ocean Territory Administration, London.
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