Animal Diversity Web

Di­ver­sity

Scarids, which are widely known as par­rot­fishes be­cause of their beak-like jaws, in­clude ap­prox­i­mately nine gen­era and 83 species. They are abun­dant in trop­i­cal reefs around the world and well known to divers for their strik­ing col­oration and noisy feed­ing as they crunch on dead coral. Par­rot­fishes ex­hibit sev­eral types of com­plex mat­ing sys­tems that vary more by ge­o­graphic lo­ca­tion than by species (see Re­pro­duc­tion). They also have con­sid­er­able eco­log­i­cal im­pacts on coral reefs through her­bivory and bio­ero­sion (see Ecosys­tem Roles). (Choat and Bell­wood, 1998; Nel­son, 1994; Thresher, 1984)

Ge­o­graphic Range

Par­rot­fishes are found pri­mar­ily in trop­i­cal wa­ters through­out the At­lantic, In­dian, and Pa­cific oceans. How­ever, some species in­habit sub­trop­i­cal wa­ters, and some, such as Scarus ghob­ban, may ven­ture far from reef en­vi­ron­ments. (Choat and Bell­wood, 1998; Nel­son, 1994)

• Biogeographic Regions
• nearctic
  • native
• palearctic
  • native
• oriental
  • native
• ethiopian
  • native
• neotropical
  • native
• australian
  • native
• indian ocean
  • native
• atlantic ocean
  • native
• pacific ocean
  • native
• mediterranean sea
  • native

Habi­tat

Most par­rot­fishes ex­clu­sively in­habit off­shore coral reefs in trop­i­cal re­gions. How­ever, a few species feed pri­mar­ily on sea grasses and are most com­mon in the Caribbean. Two other species, Nicholsina den­tic­u­late and Spari­soma cretense, are com­mon over rocky reefs of the Gulf of Cal­i­for­nia and Mediter­ranean Sea, re­spec­tively. (Choat and Bell­wood, 1998; Nel­son, 1994)

• Habitat Regions
• saltwater or marine

• Aquatic Biomes
• pelagic
• reef
• coastal

Sys­tem­atic and Tax­o­nomic His­tory

Scarids are one of sev­eral re­cently de­rived fam­i­lies (Acan­thuri­dae, Monacan­thi­dae, Po­ma­cen­tri­dae, Blenni­idae, Siganidae) ca­pa­ble of ex­ploit­ing reef algae and small colo­nial in­ver­te­brates. Reef her­bivory was pri­mar­ily re­stricted to post-Cre­ta­ceous per­ci­formes until these fam­i­lies un­der­went rapid evo­lu­tion dur­ing the early Ter­tiary, 50 to 30 mil­lion years ago. The mod­i­fied pha­ryn­geal ap­pa­ra­tus , which par­rot­fishes use to grind dead corals into a di­gestible paste, is an im­por­tant adap­ta­tion that has al­lowed par­rot­fishes to ex­ploit reef algae and small colo­nial in­ver­te­brates (see Phys­i­cal De­scrip­tion and Food Habits for fur­ther in­for­ma­tion). Bru­cae and Ran­dall (1983 and 1985) (in Nel­son 1994) cre­ated two sub­fam­i­lies of par­rot­fishes: Scari­nae with four gen­era con­tain­ing ap­prox­i­mately 67 species, and Spari­so­mati­nae with five gen­era and 16 species. Ran­dall (1983 and 1985) (in Nel­son 1994) cre­ated two sub­fam­i­lies of par­rot­fishes: Scari­nae with four gen­era con­tain­ing ap­prox­i­mately 67 species, and Spari­so­mati­nae with five gen­era and 16 species. (Choat and Bell­wood, 1998; Harmelin-Vivien, 2002; Nel­son, 1994)

Phys­i­cal De­scrip­tion

Par­rot­fishes are char­ac­ter­ized by their dis­tinc­tive beak-like jaws, in which the teeth are fused to­gether in most species, and a pha­ryn­geal ap­pa­ra­tus , which acts as a sec­ond set of jaws in the throat. In the pha­ryn­geal ap­pa­ra­tus, the teeth are arranged in rows and are highly spe­cial­ized to grind, crop, and crush food as it is processed. Par­rot­fishes have large, cy­cloid scales , usu­ally with 22-24 scales along the lat­eral line. The dor­sal fin has nine spines and ten soft rays. The anal fin has three spines and nine soft rays, and the pelvic fins one spine and five soft rays. (Click here to see a fish di­a­gram). (Choat and Bell­wood, 1998; Nel­son, 1994)

Some par­rot­fishes have a com­plex so­cio-sex­ual (so­cially in­flu­enced sex­ual change) sys­tem punc­tu­ated by three phases, and each phase change re­sults in a dif­fer­ent color pat­tern (See Re­pro­duc­tion: Mat­ing Sys­tems for a de­scrip­tion of “phases” in par­rot­fishes). For in­stance, ju­ve­niles tend to have a drab mix­ture of browns, grays and blacks, but as they ma­ture a dis­tinct col­oration emerges with the ad­di­tion of red tones. A third set of col­ors is donned by males and by fe­males that have re­cently un­der­gone sex change into males. As these males ma­ture, they ex­hibit bright, in­tri­cate pat­terns of reds, greens, and blues. This type of color change has been doc­u­mented in Scarus, Spari­soma, Nicholsina, Bol­bometapon, and Cryp­to­to­mus, but there are some mono­chromic (fishes that do not ex­hibit sex­ual color change) species that ex­hibit dif­fer­ent types of sex­ual di­mor­phism. (Choat and Bell­wood, 1998; Thresher, 1984)

Scarus coelesti­nus and Scarus coeruleus in the east­ern Pa­cific and Scarus niger in the Indo-West Pa­cific ex­hibit no color dif­fer­ences. How­ever, ma­ture males of Scarus coelesti­nus and Scarus coeruleus de­velop more squared-off and promi­nent fore­heads than smaller fish, while Scarus niger ex­hibits no phys­i­cal dif­fer­ences other than size. Fi­nally, fleshy tips on the upper and lower lobes of the cau­dal fin can be ob­served in ma­ture males of Scarus rubrovi­o­laceus, but are poorly de­vel­oped on small males and fe­males. (Thresher, 1984; Wheeler, 1985)

• Other Physical Features
• ectothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently
• male more colorful
• sexes shaped differently
• ornamentation

De­vel­op­ment

Tidal cur­rents dis­perse par­rot­fish eggs, which begin to hatch ap­prox­i­mately 25 hours after fer­til­iza­tion. Newly hatched lar­vae begin to feed after three days but the length of the plank­tonic stage is un­known. Most par­rot­fish species de­velop rapidly and reach ma­tu­rity be­tween two and four years. (Choat and Bell­wood, 1998; Thresher, 1984)

Re­pro­duc­tion

Par­rot­fishes uti­lize some of the most com­plex and un­usual re­pro­duc­tion sys­tems known to fishes. Males can be ei­ther pri­mary, i.e. born male, or sec­ondary, i.e. fe­males that have un­der­gone sex change. In some species there are no sec­ondary males while in oth­ers all in­di­vid­u­als are born fe­male (mo­nan­dric) and change sex when nec­es­sary. In the most com­plex sys­tems, species are dian­dric – both pri­mary and sec­ondary males exist in the pop­u­la­tion. In these species, in­di­vid­u­als pro­ceed through three dis­tinct phases, marked by color dif­fer­ences. In fact, the color dif­fer­ences are so pro­nounced that for over 200 years re­searchers re­garded some phases as dis­tinct species. Sex­u­ally im­ma­ture and drab col­ored ju­ve­niles rep­re­sent the first phase. The sec­ond, known as the ini­tial, phase (IP) can in­clude sex­u­ally ma­ture males or fe­males, which are im­pos­si­ble to tell apart with­out in­ter­nal ex­am­i­na­tion or ob­ser­va­tion dur­ing spawn­ing. The ter­mi­nal phase (TP) in­cludes only ma­ture males, which dis­play bril­liant col­ors. TP males usu­ally dom­i­nate re­pro­duc­tive ac­tiv­ity through a harem-based so­cial sys­tem. The death of a TP male serves as a so­cial cue for an IP fe­male to change sex and be­hav­ior. The mor­phol­ogy and be­hav­ior of IP males may also change in re­sponse to the death of a TP male. In some cases IP males at­tempt to in­fil­trate a TP male’s harem by mas­querad­ing as a fe­male. In the so called “sneak spawn­ing” at­tempt IP males fol­low spawn­ing pairs into the water col­umn and re­lease a large cloud of ga­metes at peak spawn­ing in an at­tempt to over­whelm fer­til­iza­tion by the TP male. IP males are well equipped to per­form “sneak spawn­ing” as they have larger testes and so are able to pro­duce more ga­metes, while TP males have smaller testes and rely on ag­gres­sion to deter other males. (Choat and Bell­wood, 1998; Thresher, 1984)

The type of re­pro­duc­tive be­hav­ior de­scribed above and whether it in­volves paired, for­ag­ing group or mass spawn­ing de­pends on a com­plex set of be­hav­ioral and ge­o­graphic fac­tors. For in­stance, some species, such as Scarus iseri, ex­hibit a wide range of re­pro­duc­tive be­hav­iors de­pend­ing on the area in which they are found. In Panama, Scarus iseri em­ploys a sys­tem in­volv­ing three classes of in­di­vid­u­als: ter­ri­to­ri­als, sta­tioner­ies and for­agers. Ter­ri­to­ri­als are or­ga­nized into groups that con­sist of a dom­i­nant fe­male, sev­eral sub­or­di­nate fe­males and usu­ally, but not al­ways, a ter­mi­nal (TP) male. Paired spawn­ing oc­curs within the ter­ri­tory, which both males and fe­males de­fend. Sta­tion­ar­ies con­sis­tently use the same area for spawn­ing but do not de­fend it, and for­agers in­clude groups of up to 500 in­di­vid­u­als, mostly fe­males. In Puerto Rico, ini­tial phase (IP) and ter­mi­nal phase (TP) in­di­vid­u­als mi­grate to tem­po­rary spawn­ing areas in deep water, usu­ally in pairs. Fi­nally, in Ja­maica Scarus iseri em­pha­sizes as­pects of the for­ag­ing group sys­tem and spawn­ing only takes place in groups. The three pre­vi­ous ex­am­ples il­lus­trate the flex­i­bil­ity of the so­cio-sex­ual mat­ing sys­tems found in par­rot­fishes. The rea­sons that dif­fer­ent as­pects of the basic spawn­ing sys­tem man­i­fest in dif­fer­ent areas range from pop­u­la­tion den­sity to com­pe­ti­tion for spawn­ing sites and other re­sources to ge­o­graphic fac­tors like sea­sons and water tem­per­a­ture. (Thresher, 1984)

• Mating System
• polygynous
• polygynandrous (promiscuous)

In gen­eral, par­rot­fishes spawn year-round, usu­ally at dusk. How­ever, peak spawn­ing oc­curs in sum­mer for many species and there is ev­i­dence that some species have de­fined non-spawn­ing pe­ri­ods. As dis­cussed above, many species mi­grate to the outer edges of the reef to spawn but some spawn within de­fined ter­ri­to­ries. There is ev­i­dence that some scarids re­spond to the lunar cycle dur­ing spawn­ing, but in oth­ers, spawn­ing cor­re­lates closely with high tide, re­gard­less of the time of the lunar month. In species that spawn sev­eral times dur­ing the day, the tidal cycle is fol­lowed closely since this is the op­ti­mal time for egg dis­per­sal. (Choat and Bell­wood, 1998; Thresher, 1984)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• year-round breeding
• sequential hermaphrodite
  • protogynous
• sexual
• fertilization
  • external
• oviparous

There is no ev­i­dence of parental be­hav­ior in par­rot­fishes. (Thresher, 1984)

• Parental Investment
• no parental involvement

Lifes­pan/Longevity

The max­i­mum age of most par­rot­fishes is less than 20 years and most live less than five years. There is a gen­eral trend in the scarids for larger species to live longer. Sub­se­quently, the largest scarid, Bol­bome­to­pon muri­ca­tum, is the one ex­cep­tion to the 20 year max­i­mum age. (Choat and Bell­wood, 1998; Choat and Robert­son, 2002)

Be­hav­ior

Par­rot­fishes are most well known for their com­plex so­cial struc­tures. Most are or­ga­nized into male-dom­i­nated harems but oth­ers breed co­op­er­a­tively or in pairs (see Re­pro­duc­tion: Mat­ing Sys­tems & Gen­eral Be­hav­ior for more on so­cial sys­tems). Some par­rot­fishes are highly ter­ri­to­r­ial while oth­ers are mainly no­madic, with the home range in­creas­ing as the size of the fish in­creases. Large for­ag­ing groups of up to 500 in­di­vid­u­als form for spawn­ing and to deter preda­tors while feed­ing. Par­rot­fishes feed con­tin­u­ously through­out the day and seek shel­ter in reefs at night. (Böhlke and Chap­lin, 1994; Thresher, 1984)

• Key Behaviors
• natatorial
• diurnal
• motile
• territorial
• social
• colonial
• dominance hierarchies

Com­mu­ni­ca­tion and Per­cep­tion

Most known forms of com­mu­ni­ca­tion in par­rot­fishes are re­lated to re­pro­duc­tion and are dis­cussed in Re­pro­duc­tion: Mat­ing Sys­tems. How­ever, in some species male col­oration in­ten­si­fies when de­fend­ing its ter­ri­tory, which sug­gests that vi­sual cues are used to deter in­vaders. (Thresher, 1984)

• Communication Channels
• visual
• tactile

• Perception Channels
• visual
• tactile
• chemical

Food Habits

Par­rot­fishes are pri­mar­ily her­biv­o­rous, graz­ing in­ten­sively on dead, al­gae-coated coral, veg­etable ma­te­r­ial, and in some species sea grasses. Bump-headed par­rot­fishes, which con­sume sig­nif­i­cant amounts of live coral, are one ex­cep­tion. Key to the suc­cess of par­rot­fishes is their abil­ity to take up plant ma­te­r­ial, de­tri­tus and cal­care­ous sed­i­ment and process it through the ac­tion of the pha­ryn­geal jaw. This chew­ing mech­a­nism grinds in­gested ma­te­r­ial into a fine paste and breaks down algal cells, re­leas­ing the cel­lu­lar ma­te­r­ial for di­ges­tion. Like acan­thurids, par­rot­fishes form large feed­ing groups, some­times with mul­ti­ple species, to over­whelm ter­ri­to­r­ial fishes and deter preda­tors. (Choat and Bell­wood, 1998; Thresher, 1984)

• Primary Diet
• herbivore

Pre­da­tion

A unique fea­ture of some par­rot­fishes is the pro­duc­tion of a mu­cous en­ve­lope at night be­fore rest­ing. The en­ve­lope takes about 30 min­utes to con­struct and is open at both ends to allow water flow. The se­creted en­ve­lope is foul smelling and tast­ing, which may serve to deter night­time preda­tors that hunt by scent. Most par­rot­fishes seek out caves and ledges in the reef for pro­tec­tion at night, but par­rot­fishes in the genus Cryp­to­to­mus bury them­selves in the sand like wrasses. After cre­at­ing a hole in the sand Cryp­to­to­mus then pro­duces its mu­cous night­gown. (Böhlke and Chap­lin, 1994; Choat and Bell­wood, 1998; Nel­son, 1994)

• Known Predators

  • sharks (Chondrichthyes)
  • humans (Homo sapiens)

Ecosys­tem Roles

Par­rot­fishes have a major im­pact on coral reefs through in­ten­sive graz­ing and as­so­ci­ated bio­ero­sion. The graz­ing pat­terns of large schools of par­rot­fish have the ef­fect of se­lect­ing for cer­tain species of corals and algae, and pre­vent­ing algae from chok­ing out corals. Many par­rot­fishes feed on cal­care­ous algae (algae that are high in min­eral cal­cium) grow­ing on dead, ex­posed coral by bit­ing off chunks and turn­ing them into a fine paste. This type of graz­ing con­tributes sig­nif­i­cantly to the process of bio­ero­sion and the cre­ation of sed­i­ment on reefs. For in­stance, it has been cal­cu­lated that a sin­gle large par­rot­fish, Bol­bometapon muri­ca­tum (bump-head par­rot­fish), con­sumes ap­prox­i­mately one cubic meter of coral skele­tons per year, and turns it into fine sed­i­ment. In this way large schools of bump-head par­rot­fish de­ter­mine the fine-scale topog­ra­phy of coral reefs. (Choat and Bell­wood, 1998)

A sep­a­rate eco­log­i­cal con­se­quence of in­tense her­bivory in par­rot­fishes is the con­ver­sion of plant ma­te­r­ial into fish flesh. The suc­cess of par­rot­fishes in con­sum­ing plant ma­te­r­ial un­avail­able to most other fishes and the large size of par­rot­fish pop­u­la­tions makes them an im­por­tant part of the preda­tory food chain. (Choat and Bell­wood, 1998)

• Ecosystem Impact
• biodegradation

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

In the Ba­hamas, the scales of some par­rot­fishes are used for dec­o­rat­ing bas­ket­work and shell­flower arrange­ments, but the fish are not con­sumed. In other areas, par­rot­fishes are some­times taken as food, but their flesh can be dan­ger­ous to hu­mans as a re­sult of ac­cu­mu­lated ciguat­era tox­ins. (Böhlke and Chap­lin, 1994)

• Positive Impacts
• food
• body parts are source of valuable material
• research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Sev­eral species, such as blue par­rot­fish and one Indo-Pa­cific species, have caused ciguat­era (fish poi­son­ing sick­ness) in hu­mans, which can be fatal. (Böhlke and Chap­lin, 1994)

• Negative Impacts
• injures humans

Con­ser­va­tion Sta­tus

One scarid, Scarus gua­ca­maia (rain­bow par­rot­fish), is listed as vul­ner­a­ble to ex­tinc­tion. (The World Con­ser­va­tion Union, 2002)

• IUCN Red List [Link]

  Not Evaluated

Other Com­ments

The fos­sil his­tory of scarids dates back to the lower Ter­tiary and Eocene epochs. (Berg, 1958)

Con­trib­u­tors

R. Jamil Jonna (au­thor), An­i­mal Di­ver­sity Web.

Ref­er­ences

Berg, L. 1958. Sys­tem Der Rezen­ten und Fos­silen Fis­char­ti­gen und Fis­che. Berlin: VEB Deutscher Ver­lag der Wis­senschaften.

Böhlke, J., C. Chap­lin. 1994. Fishes of the Ba­hamas and Ad­ja­cent Trop­i­cal Wa­ters. Wyn­newood, Pa: Pub­lished for the Acad­emy of Nat­ural Sci­ences of Philadel­phia by Liv­ingston.

Choat, H., D. Bell­wood. 1998. Wrasses & Par­rot­fishes. Pp. 209-210 in W Es­chmeyer, J Pax­ton, eds. En­cy­clo­pe­dia of Fishes – sec­ond edi­tion. San Diego, CA: Aca­d­e­mic Press.

Choat, J., D. Robert­son. 2002. Age-Based Stud­ies. Pp. 63-67 in P Sale, ed. Coral Reef Fishes: Dy­nam­ics and Di­ver­sity in a Com­plex Ecosys­tem. San Diego, CA: Aca­d­e­mic Press.

Harmelin-Vivien, M. 2002. En­er­get­ics and Fish Di­ver­sity on Coral Reefs. Pp. 268-269 in P Sale, ed. Coral Reef Fishes: Dy­nam­ics and Di­ver­sity in a Com­plex Ecosys­tem. San Diego, CA: Aca­d­e­mic Press.

Nel­son, J. 1994. Fishes of the World – third edi­tion. New York, NY: John Wiley and Sons.

The World Con­ser­va­tion Union, 2002. "IUCN 2002" (On-line). IUCN Red List of Threat­ened Species. Ac­cessed Au­gust 02, 2003 at http://​www.​iucnredlist.​org/​.

Thresher, R. 1984. Re­pro­duc­tion in Reef Fishes. Nep­tune City, NJ: T.F.H. Pub­li­ca­tions.

Wheeler, A. 1985. The World En­cy­clo­pe­dia of Fishes - sec­ond edi­tion. Lon­don: Mac­don­ald.