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 Moon wrasse, Thalassoma lunare, a typical wrasse
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The wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with about 500 species in 60 genera.
They are typically small fish, with most less than 20 centimetres (7.9 in) long, although the largest, the Humphead wrasse, can measure up to 2.5 metres (8.2 ft). They are efficient carnivores, feeding on a wide range of small invertebrates. Many smaller wrasses follow the feeding trails of larger fish, picking up invertebrates disturbed by their passing.1
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Distribution
Wrasses are exclusively marine in distribution. They are found in the Atlantic, Indian, and Pacific Oceans, usually in shallow water habitats such as coral reefs and rocky shores where they live close to the substrate.
Anatomy
Wrasses have protractile mouths, usually with separate jaw teeth that jut outwards. The dorsal fin has 8–21 spines and 6–21 soft rays, usually running most of the length of the back. Wrasse are typically brightly coloured and sexually dimorphic. Many species are capable of changing sex: juveniles are a mix of males and females (known as Initial Phase or IP individuals) but the largest adults becoming territory-holding (Terminal Phase or TP) males.
The wrasses have become a primary study species in the biomechanics of fish-feeding due to their jaw structure. The nasal and mandibular bones are connected at their posterior ends to the rigid neurocranium, and the superior and inferior articulations of the maxilla are joined to the anterior tips of these two bones, respectively, creating a loop of 4 rigid bones connected by moving joints. This "4-bar linkage" has the interesting property of having numerous possible arrangements to achieve a given mechanical result (fast jaw protrusion or a forceful bite), thus decoupling morphological diversity from functional diversity. The actual morphology of wrasses reflects this, with many lineages displaying different jaw morphology that results in the same functional output and a similar or identical ecological niche.2
Cleaner wrasse
Some wrasses are widely known for their role as symbiotic fish, similar to the actions and those ascribed to the Egyptian plover: other fish will congregate at wrasse cleaning stations and wait for wrasses to swim into their open mouths and gill cavities to have gnathiid parasites removed. The cleaner wrasses are best known for feeding on dead tissue and scales and ectoparasites, although they are also known to 'cheat' through the removal of healthy tissue and mucus, which is costly for the client fish to produce. The bluestreak cleaner wrasse, Labroides dimidiatus is one of the most common cleaners found on tropical reefs. Few cleaner wrasses have been observed being eaten by predators, possibly because the removal of parasites from the predator fish is more important for the survival of the predator than the short-term gain of eating the cleaner.3
Other species of wrasse, rather than having fixed cleaning stations, specialize in making "house calls"—that is, their "clientele" are those fish that are too territorial or shy to go to a cleaning station.
Significance to humans
Wrasse are utilised as food in many parts of the world. In the western Atlantic, the most commonly eaten is the tautog.dubious Wrasse are widely kept in both public and home aquaria, with some species being small enough to be considered reef safe.
 Yellowtail coris wrasse, Coris gaimardi is being cleaned by Labroides phthirophagus. The picture was taken in Hawaii |
 Bluehead wrasse, Belize Barrier Reef |
 Clown wrasse, Coris aygula, Red Sea |
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 Yellowtail wrasse, Coris gaimard, Hawaii |
 Pearl wrasse, Anampses cuvieri, Hawaii |
 Humphead wrasse, Cheilinus undulatus, Melbourne Aquarium |
 Bluestreak wrasse, Labroides dimidiatus |
Genera
References
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This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (November 2008) |
- ^ Choat, J.H. & Bellwood, D.R. (1998). in Paxton, J.R. & Eschmeyer, W.N.: Encyclopedia of Fishes. San Diego: Academic Press, 211. ISBN 0-12-547665-5.
- ^ Wainwright et al. (2005) "Many-to-One Mapping of Form to Function: A General Principle in Organismal Design?" Intergrative & comparative biology 45:256–262.
- ^ Trivers, R. L. 1971
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- This page was last modified on 9 November 2008, at 18:49.
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