Parrotfish

Bolbometopon Calotomus Cetoscarus Chlorurus Cryptotomus Hipposcarus Leptoscarus Nicholsina Scarus Sparisoma Parrotfish are a group of fish species traditionally regarded as a family (Scaridae), but now often treated as a subfamily (Scarinae) or tribe (Scarini) of the wrasses (Labridae).

Their numerous teeth are arranged in a tightly packed mosaic on the external surface of their jaw bones, forming a parrot-like beak with which they rasp algae from coral and other rocky substrates[6] (which contributes to the process of bioerosion).

[11] Prior to going to sleep, some species extrude mucus from their mouths, forming a protective cocoon that envelops the fish, presumably hiding its scent from potential predators.

[12][13] This mucus envelope may also act as an early warning system, allowing the parrotfish to flee when it detects predators such as moray eels disturbing the membrane.

[13] The skin itself is covered in another mucous substance which may have antioxidant properties helpful in repairing bodily damage,[11][13] or repelling parasites, in addition to providing protection from UV light.

[14][15][16] A wide range of other small organisms are sometimes eaten, including invertebrates (sessile and benthic species, as well as zooplankton), bacteria and detritus.

[17] A few mostly larger species such as the green humphead parrotfish (Bolbometopon muricatum) feed extensively on living coral (polyps).

[16][18] After they digest the edible portions from the rock, they excrete it as sand, helping create small islands and the sandy beaches.

[14] Feeding modes reflect habitat preferences, with browsers chiefly living in the grassy seabed, and excavators and scrapers on coral reefs.

[25][14] Recently, the microphage feeding hypothesis challenged the prevailing paradigm of parrotfish as algal consumers by proposing that: Most parrotfishes are microphages that target cyanobacteria and other protein-rich autotrophic microorganisms that live on (epilithic) or within (endolithic) calcareous substrata, are epiphytic on algae or seagrasses, or endosymbiotic within sessile invertebrates.

[citation needed] As pelagic spawners, parrotfish release many tiny, buoyant eggs into the water, which become part of the plankton.

In many species, for example the stoplight parrotfish (Sparisoma viride), a number of individuals develop directly to males (i.e., they do not start as females).

Although phylogenetic and evolutionary analyses of parrotfishes are ongoing, they are now accepted to be a clade in the tribe Cheilini, and are now commonly referred to as scarine labrids (subfamily Scarinae, family Labridae).

[1] Some authorities have preferred to maintain the parrotfishes as a family-level taxon,[33] resulting in Labridae not being monophyletic (unless split into several families).

Parrotfish skeleton
Scarus zelindae in its mucus cocoon
The strong beak of Bolbometopon muricatum is able to grind the sturdiest corals.
The bicolor parrotfish ( Cetoscarus bicolor ) was described by Eduard Rüppell in 1829. In 1835, he mistakenly described the terminal phase, featured on this photo, as a separate species, C. pulchellus