Parrotfishes: Characteristics, Behavior, Mucus and Sand-Creating Teeth

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blunthead parrotfish (Chlorurus microrhinos)

Parrotfish are fish that live around coral reefs that get their name from their beak-like mouths, which they use to bite off chunk of coral. The mouths have plates "edged like a concrete-cutter's saw" for teeth. The fish scrapes and bite off pieces of coral with its beak and chews them with a powerful jaws and set of molarlike teeth deep in its throat. Their second of jaws help extract algae growing in the coral polyps and grind down the coral into sand. The fish are often brightly colored.

Most parrotfish are “medium-sized” reef dwelling fish with multiple bright coloured patterns on their bodies. Residing in relatively near the surface in shallow sections of the reef’s waters, they one of the most visible species on reefs and are commonly seen by snorkelers as well as divers. The fish contribute to the development and growth of ocean land forms by grinding up coral and excreting it as sand which over time helps create islands and sandy beaches. [Source: Great Barrier]

Humans utilize parrotfish for food and their body parts are sources of valuable materials research and education. Although often caught along with other reef fish, they are not important to the fishing industry. 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. Several species, such as blue parrotfish and one Indo-Pacific species, have caused ciguatera (fish poisoning sickness) in humans, which can be fatal.One scarid, Scarus guacamaia (rainbow parrotfish), is listed as vulnerable to extinction. (The World Conservation Union, 2002). The International Union for Conservation of Nature (IUCN) Red List has not evaluated the fish. [Source: Animal Diversity Web (ADW)]

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase ; Encyclopedia of Life ; Smithsonian Oceans Portal ; Woods Hole Oceanographic Institute ; Cousteau Society ; Monterey Bay Aquarium ; MarineBio

Parrotfish Habitat and Where They Are Found

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Parrotfishes associated with coral reefs and found primarily in tropical waters throughout the Atlantic, Indian, and Pacific oceans and in the Caribbean and Mediterranean Sea, with the most number of species in the Indo-Pacific region. Some species inhabit subtropical waters, and some, such as the blue-barred parrotfish (Scarus ghobban), may venture into the open ocean far from reef environments. [Source: R. Jamil Jonna, Animal Diversity Web (ADW) /=]

Most parrotfish inhabit offshore coral reefs in tropical regions. Those that feed primarily on sea grasses are most common in the Caribbean. Two other species, the loose-tooth parrotfish (Nicholsina denticulate) and Mediterranean parrotfish (Sparisoma cretense), are common over rocky reefs of the Gulf of California and Mediterranean Sea, respectively. /=\

Their main known predators of parrotfish are sharks. 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 produces a mucous envelope to rest in.

Parrotfish Taxonomy and History

Parrotfish belong to the Scaridae family of fish, Scarids include approximately nine genera and 83 species. They are well represented in tropical reefs around the world and well known to divers for their striking coloration and noisy feeding habits as they crunch on dead coral. Parrotfishes exhibit several types of complex mating systems that vary more by geographic location than by species. They also have considerable ecological impacts on coral reefs and the ocean environment in general. [Source: R. Jamil Jonna, Animal Diversity Web (ADW) /=]

The fossil history of scarids dates back to the Lower Tertiary Period (66 million to 56 million years ago) and Eocene Period (56 million to 33.9 million years ago). 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. /=\

parrotfish teeth

According to Animal Diversity Web: Scarids are one of several recently derived families (Acanthuridae, Monacanthidae, Pomacentridae, Blenniidae, Siganidae) capable of exploiting reef algae and small colonial (living together in groups or in close proximity to each other), invertebrates. Reef herbivory was primarily restricted to post-Cretaceous (145 million to 66 million years ago) 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. Brucae and Randall (1983 and 1985) 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) created two subfamilies of parrotfishes: Scarinae with four genera containing approximately 67 species, and Sparisomatinae with five genera and 16 species. /=\

Parrotfish Physical Characteristics and Teeth

Parrotfishes are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature and bilateral symmetry (both sides of the animal are the same). Sexual Dimorphism (differences between males and females) is present: Males are larger than females. Sexes are colored or patterned differently with the male being more colorful. Males and females have different shapes. Ornamentation is different. [Source: R. Jamil Jonna, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: 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 and9 soft rays, and the pelvic fins one spine and five soft rays. /=\

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coral eaten by parrotfish
Each parrotfish has roughly 1,000 teeth, lined up in 15 rows and cemented together to form the beak structure, which they use for biting into the coral. According to When the teeth wear out, they fall to the ocean floor. This isn't a problem for the parrotfish, because another row of teeth sits behind the first and quickly replaces the missing teeth. [Source:]

Parrotfish teeth have an intricate crystal structure. They are made of a material called fluorapatite which contains calcium, fluorine, phosphorous and oxygen, and is the second-hardest biomineral in the world. Fluorapatite scores a five on the Mohs' hardness scale and is harder than copper. No biomineral in the world is stiffer than the tips of parrotfish teeth. The teeth can also withstand a lot of pressure. One square inch of parrotfish teeth can tolerate 530 tons of pressure-equivalent to the weight of about 88 elephants. The structure of parrotfish teeth is unique. The crystals are oriented in interwoven bundles, which form a chainmail pattern — a structure which could have application in the to creation of abrasion-resistant moving parts,

Parrotfish Colors and Mucus

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. According to Animal Diversity Web: 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. [Source: R. Jamil Jonna, Animal Diversity Web (ADW) /=]

In some species male coloration intensifies when defending its territory, which suggests that visual cues are used to deter invaders. 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. /=\

A unique feature of some parrotfishes is the production of a mucous envelope at night before resting. The envelope takes about 30 minutes to make and is open at both ends to allow water flow. The envelopes have a nasty smell and taste. At night parrotfish that use the filmy, mucus envelopes enter into a sleep-like state inside cocoons that covers them from head to foot. Scientist once thought the cocoon hid the parrotfish's scent from nocturnal predators. But that doesn't seem to be the case and scientists now are not sure why they have the cocoon.

This mucus envelope may also serve as an early warning system, allowing the parrotfish to flee when it detects predators such as moray eels disturbing the membrane. The skin itself is covered in another mucous substance which may have antioxidant properties helpful in repairing bodily damage, repelling parasites, and providing protection from UV light. [Source: Wikipedia]

Comparison of colour patterns in sympatric and allopatric sister species parrotfish, showing three patterns of divergence: I) terminal phase colour patterns: 1A) Scarus rivulatus; 1B) Scarus globiceps; 2A) Scarus altipinnis; 2B) Scarus niger; 3A) Chlorurus bleekeri; 3B) Chlorurus bowersi. Allopatric sister species: 4A) Scarus schlegeli; 4B) Scarus russelii; 4C) Scarus fuscopurpureus; 5A Chlorurus capistratoides; 5B Chlorurus japanensis. II) divergence of initial phase colour patterns in sympatric and allopatric Indo-Pacific species. Sympatric sister species: 6A) Scarus forsteni; 6B) Scarus tricolor. Allopatric sister species: 7A) Scarus schlegeli; 7B) Scarus russelii; 7C) Scarus fuscopurpureus. III) loss of one colour phase. Sympatric tropical Atlantic species: 8A) Scarus guacamaia; 8B) Scarus coelestinus.

Parrotfish Behavior

Parrotfish are diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), territorial (defend an area within the home range), social (associates with others of its species; forms social groups), colonial (living together in groups or in close proximity to each other), and have dominance hierarchies (ranking systems or pecking orders among members of a long-term social group, where dominance status affects access to resources or mates). [Source: R. Jamil Jonna, Animal Diversity Web (ADW) /=]

Parrotfish sometimes change sex (See Colors Above). Some are sequential hermaphrodites in which individuals change their sex at some point in their lives and typically produces eggs and sperm at different stages their lives, with many being protogynous (the condition of hermaphrodites that have female organs and eggs before male organs and sperm). /=\

According to Animal Diversity Web: Parrotfishes are most well known for their complex social structures. Most are organized into male-dominated harems but others breed cooperatively or in pairs Some parrotfishes are highly territorial, while others are mainly nomadic (move from place to place, generally within a well-defined range),, 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. /=\

Parrotfish communicate with vision and touch and sense using vision, touch and chemicals usually detected with smell. Most known forms of communication in parrotfishes are related to reproduction.

Parrotfish Food and Eating Behavior

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. "Coral eating" fish such as parrotfish, triggerfish and surgeon fish feed on the algae rather than the coral polyps themselves. Many do this by eating the rocky coral itself, extracting the food the need and grinding up rocky material and expelling it as sand. The source of much of the recently made sand sediments around the reef is from parrotfish and other coral eaters. Not all coral-eaters use this method. The leatherjacket is bright green fish with orange spots. It feeds on coral by clamping its mouth around the entrance of a polyps chamber and sucking out the polyp.

Coral's limestone exoskeletons passes through the parrotfish's body, and is ground into sand by more plates in the fish's throat, and defecated as a slurry of coral. It is estimated that one parrot fish transforms 200 pounds of coral to sand each year. Their bodies make a crunching sound when they sleep. [Source: David Doubilet, National Geographic, November 1987 ┭]

According to Animal Diversity Web (ADW): 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 (defend an area within the home range), fishes and deter predators. /=\

Parrotfish, Sand and Reef Ecosystems

Parrotfish help the reef ecosystem by creating habitat and fostering biodegradation and bioerosion. Their scraping, biting and excreting of coralline algae and coral debris recycles the materials needed for new coral production. Bioerosion can be potentially detrimental to reefs in areas where erosion exceeds construction, however, the activity of parrotfish is generally beneficial. Parrotfish also create habitat for smaller organisms within the coral, increasing reef diversity and productive biomass. Moderate mechanical interference by parrotfish and other bioeroders can also aid in coral reproduction, weakening the coral just enough so that other bioeroding processes can break off fragments, which propagate the reef.

Scientists estimate that up to 70 percent of the sand on white sandy beaches in the Caribbean and Hawaii has been excreted by parrotfish. A large adult parrotfish can excrete over a ton of sand per year. Areas that have parrotfish produce more sand than similar areas with few or no parrotfish. This sediment production rate is especially important in areas like Hawai‘i, where there is little terrestrial input, and almost all of the sand is of biogenic origin.

Parrotfish use fused tooth plates in their beak and a gristmill in their throat to chisel off and pulverize reef rock to get nutrients from algae that coat and bore into coral. This can keep coral from being suffocated by algae allowed to grow unchecked, but on the other hand overgrazing by the fish can destroy corals.

According to the University of Hawaii: Parrotfish are mostly herbivorous grazers. They and other reef herbivores help to maintain the structure and function of coral reefs by grazing algae that might smother coral. Parrotfish have unique teeth that allow them to play an integral role on coral reefs, especially in the Caribbean and Indo-Pacific. Parrotfish teeth are fused together This fusion enables them to scrape off fine, filamentous algae that grow within coral skeletons and on dead coral substrates. During this scraping while foraging for algae, parrotfish often ingest chunks of coral. Parrotfish have a special set of toothplates in their throat called a pharyngeal mill (pharyngeal = relating to the pharynx or throat) that acts like additional teeth to assist in grinding up the hard coral. The ground-up coral is passed through their digestive tract and expelled as fine-grain white sand The sand that is produced by parrotfish forms beaches and provides valuable habitat for benthic organisms like crabs and shrimp. [Source: University of Hawaii]

One of the main ecological roles played by parrotfish is biodegradation through their intensive grazing and associated bioerosion. According to Animal Diversity Web: 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. 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. /=\

Parrotfish Mating, Reproduction and Offspring

Parrotfish are oviparous (young are hatched from eggs), iteroparous (offspring are produced in groups) and generally polygynous (males having more than one female as a mate at one time) but are sometimes polygynandrous (promiscuous), with both males and females having multiple partners.. Reproduction is external, meaning the male’s sperm fertilizes the female’s egg outside her body. They engage in seasonal breeding and year-round breeding. There is no parental involvement in the raising of offspring.

According to Animal Diversity Web: 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. /=\

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: territorial (defend an area within the home range),s, stationeries and foragers. Territorial (defend an area within the home range),s 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. /=\

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. 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. /=\

Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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