Parrotfish

Source: Wikipedia, the free encyclopedia.

"Scarinae" and "Scarini" redirect here. For the group of leafhoppers formerly known by these names, see Gyponini.
Not to be confused with parrot cichlid.

Parrotfish
Temporal range: Miocene–present
Scarus frenatus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Labriformes
Family: Labridae
Tribe: Scarini
Rafinesque, 1810
Genera

Bolbometopon

Calotomus
Cetoscarus
Chlorurus
Cryptotomus

Hipposcarus
Leptoscarus

Nicholsina
Scarus
Sparisoma

Parrotfish (named for their mouths, which resemble a parrot's beak) are a clade of fish placed in the tribe Scarini of the wrasse family (Labridae).[1] Traditionally treated as their own family (Scaridae), genetic studies have found them to be deeply nested within the wrasses, and they are now treated as a subfamily (Scarinae) or tribe (Scarini) of them.[2] With roughly 95 species, this group's largest species richness is in the Indo-Pacific. They are found in coral reefs, rocky coasts, and seagrass beds, and can play a significant role in bioerosion.[3][4][5]

Taxonomy

Traditionally, the parrotfishes have been considered to be a

monophyletic
(unless split into several families).

The following taxonomic placement is based on Bellwood et al (2019):[6]

  • Tribe Scarini[6]
    • subtribe
      Scarina
      • genus
        Bolbometopon
         Smith, 1956 (1 species)
      • genus Cetoscarus Smith, 1956 (2 species)
      • genus Chlorurus Swainson, 1839 (18 species)
      • genus Hipposcarus Smith, 1956 (2 species)
      • genus Scarus Forsskål, 1775 (53 species)
    • subtribe Sparisomatina
      • genus Calotomus Gilbert, 1890 (5 species)
      • genus
        Cryptotomus
         Cope, 1870 (1 species)
      • genus
        Leptoscarus
         Swainson, 1839 (1 species)
      • genus Nicholsina Fowler, 1915 (3 species)
      • genus Sparisoma Swainson, 1839 (15 species)

Some sources retain the Scaridae as a family, placing it alongside the wrasses of the family Labridae and the weed whitings Odacidae in the order Labriformes, part of the Percomorpha. They also do not support the division of the Scaridae into two subfamilies.[8] However, as such a placement is paraphyletic, they are placed within the wrasses by Eschmeyer's Catalog of Fishes.[9]

Fossil remains of parrotfishes are known dating back to the Early Miocene of Java, Indonesia.[6]

Description

Parrotfish skeleton

Parrotfish are named for their

labrids. 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[11] (which contributes to the process of bioerosion
).

Maximum sizes vary within the group, with the majority of species reaching 30–50 cm (12–20 in) in length. However, a few species reach lengths in excess of 1 m (3 ft 3 in), and the

bluelip parrotfish (Cryptotomus roseus), which has a maximum size of 13 cm (5.1 in).[13][14][15]

Mucus

Scarus zelindae in its mucus cocoon

Some parrotfish species, including the queen parrotfish (Scarus vetula), secrete a mucus cocoon, particularly at night.[16] 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.[17][18] 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.[18] The skin itself is covered in another mucous substance which may have antioxidant properties helpful in repairing bodily damage,[16][18] or repelling parasites, in addition to providing protection from UV light.[16]

Feeding

Bolbometopon muricatum
is suited to 'excavating', grinding the sturdiest corals.
The beak of Calotomus japonicus is suited to 'browsing' on seagrass, macroalgae, and epilithic algae without touching the rocky substrate.

Most parrotfish species are

benthic species, as well as zooplankton), bacteria and detritus.[22] A few mostly larger species such as the green humphead parrotfish (Bolbometopon muricatum) feed extensively on living coral (polyps).[11][20][21] None of these are exclusive corallivores, but polyps can make up as much as half their diet[21] or even more in the green humphead parrotfish.[19] Overall it has been estimated that fewer than one percent of parrotfish bites involve live corals and all except the green humphead parrotfish prefer algae-covered surfaces over live corals.[21] Nevertheless, when they do eat coral polyps, localized coral death can occur.[21] Their feeding activity is important for the production and distribution of coral sands in the reef biome, and can prevent algal overgrowth of the reef structure. The teeth grow continuously, replacing material worn away by feeding.[14] Whether they feed on coral, rock or seagrasses, the substrate is ground up between the pharyngeal teeth.[21][23] After they digest the edible portions from the rock, they excrete it as sand, helping create small islands and the sandy beaches. The humphead parrotfish can produce 90 kg (200 lb) of sand each year.[24]
Or, on average (as there are so many variables i.e. size/species/location/depth etc.), almost 250 g (9 oz) per parrotfish per day. While feeding, parrotfish must be cognizant of predation by one of their main predators, the lemon shark.[25] On Caribbean coral reefs, parrotfish are important consumers of sponges.[26] An indirect effect of parrotfish grazing on sponges is the protection of reef-building corals that would otherwise be overgrown by fast-growing sponge species.[27][28]

Analysis of parrotfish feeding biology describes three functional groups: excavators, scrapers and browsers.

Leptoscarus, Nicholsina and Sparisoma.[19] Feeding modes reflect habitat preferences, with browsers chiefly living in the grassy seabed, and excavators and scrapers on coral reefs.[30][19]

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.[31]

Microscopy and molecular barcoding of coral reef substrate bitten by scraping and excavating parrotfish suggest that coral reef cyanobacteria from the order Nostocales are important in the feeding of these parrotfish.[32] Additional microscopy and molecular barcoding research indicates that some parrotfish may ingest microscopic biota associated with endolithic sponges.[33]

Life cycle

Terminal phase rusty parrotfish (Scarus ferrugineus) fighting.

Most tropical species form large schools when feeding and these are often grouped by size. Harems of several females presided over by a single male are normal in most species, with the males vigorously defending their position from any challenge.[citation needed] As pelagic spawners, parrotfish release many tiny, buoyant eggs into the water, which become part of the plankton. The eggs float freely, settling into the coral until hatching.[citation needed]

Sex change

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

The development of parrotfishes is complex and accompanied by a series of changes in sex and colour (

gonochorists. This means that some females do not change sex (they remain females throughout their lives), the ones that do change from female to male do it while still immature (reproductively functioning females do not change to males) and there are no males with female-like colors (the initial phase males in other parrotfish).[35][36][37] The marbled parrotfish (Leptoscarus vaigiensis) is the only species of parrotfish known not to change sex.[14] In most species, the initial phase is dull red, brown, or grey, while the terminal phase is vividly green or blue with bright pink, orange or yellow patches.[14][7] In a smaller number of species the phases are similar,[14][7] and in the Mediterranean parrotfish the adult female is brightly colored, while the adult male is gray.[38] In most species, juveniles have a different color pattern from adults. Juveniles of some tropical species can alter their color temporarily to mimic other species.[39] Where the sexes and ages differ, the remarkably different phases often were first described as separate species.[7] As a consequence early scientists recognized more than 350 parrotfish species, which is almost four times the actual number.[34]

Female Scarus psittacus (= initial phase)
Male Scarus psittacus (= terminal phase)

The sex change in parrotfishes is accompanied by changes in circulating steroids. Females have high levels of estradiol, moderate levels of T and undetectable levels of the major fish androgen 11-ketotestosterone. During the transition from initial to terminal coloration phases, concentrations of 11-ketotestosterone rise dramatically and estrogen levels decline. If a female is injected with 11-ketotestosterone, it will cause a precocious change in gonadal, gametic and behavioural sex.[citation needed]

Economic importance

A commercial

Mediterranean parrotfish.[40] Protecting parrotfishes is proposed as a way of saving Caribbean coral reefs from being overgrown with seaweed[41] and sponges.[27][28] Despite their striking colors, their feeding behavior renders them highly unsuitable for most marine aquaria.[14]

A new study has discovered that the parrotfish is extremely important for the health of the Great Barrier Reef; it is the only one of thousands of reef fish species that regularly performs the task of scraping and cleaning inshore coral reefs.[42]

Timeline of genera

QuaternaryNeogenePaleogeneHolocenePleist.Plio.MioceneOligoceneEocenePaleoceneScarusQuaternaryNeogenePaleogeneHolocenePleist.Plio.MioceneOligoceneEocenePaleocene

References

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  10. ^ Ostéologie céphalique de deux poissons perroquets (Scaridae: Teleostei) TH Monod, JC Hureau, AE Bullock - Cybium, 1994 - Société française d'ichtyologie
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  12. ^ Froese, Rainer; Pauly, Daniel (eds.). "Bolbometopon muricatum". FishBase. December 2009 version.
  13. ^ Froese, Rainer; Pauly, Daniel (eds.). "Cryptotomus roseus". FishBase. September 2015 version.
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  15. ^ Shah, A.K. (2016). Cryptotomus roseus (Slender Parrotfish). The Online Guide to the Animals of Trinidad and Tobago. The University of the West Indies. Accessed 11 March 2018.
  16. ^ a b c Cerny-Chipman, E. "Distribution of Ultraviolet-Absorbing Sunscreen Compounds Across the Body Surface of Two Species of Scaridae." DigitalCollections@SIT 2007. Accessed 2009-06-21.
  17. ^ Langerhans, R.B. "Evolutionary consequences of predation: avoidance, escape, reproduction, and diversification. Archived 14 June 2011 at the Wayback Machine" pp. 177–220 in Elewa, A.M.T. ed. Predation in organisms: a distinct phenomenon. Heidelberg, Germany, Springer-Verlag. 2007. Accessed 2009-06-21.
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  33. ^ Nicholson, G.M., Clements, K.D. A role for encrusting, endolithic sponges in the feeding of the parrotfish Scarus rubroviolaceus? Evidence of further trophic diversification in Indo-Pacific Scarini. Coral Reefs (2024). https://doi.org/10.1007/s00338-024-02482-z
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Further reading

Wikimedia Commons has media related to Scaridae.
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