A corallivore is an animal that feeds on coral. Corallivores are an important group of reef organism because they can influence coral abundance, distribution, and community structure. Corallivores feed on coral using a variety of unique adaptations and strategies. Known corallivores include certain mollusks, annelids, fish, crustaceans, flatworms and echinoderms. The first recorded evidence of corallivory was presented by Charles Darwin in 1842 during his voyage on HMS Beagle in which he found coral in the stomach of two Scarus parrotfish.

While visiting the Cocos (Keeling) Islands in 1842, Charles Darwin was told by an Englishman living on the islands that there were large shoals of parrotfish that subsisted entirely on coral.^[1] Darwin dissected several parrotfish and found pieces of coral and finely ground calcareous material in their stomach.^[1][2] This led Darwin to correctly theorize that some species of parrotfish consume coral and contribute sediment to the environment by passing finely ground particles from coral skeletons.^[1]

In 1952, the first descriptions of organisms actively consuming coral were written by Jacques Cousteau and published in National Geographic.^[2][3] During his trip to the Red Sea aboard RV Calypso, Cousteau swam with a pair of green humphead parrotfish and watched them take regular bites and leaving white scars on the coral around them.^[3] Like Darwin, Cousteau also noticed the sediment particles that were produced in the parrotfishs' waste and settled to the seafloor.^[3] Cousteau noted the leisurely speed with which the parrotfish consumed the coral and remarked that they appeared "unhurried" and like "sea cows, browsing on stone pastures."^[3]

The term "corallivore" comes from the Latin word corallum for coral and -vora for to eat or devour.^{[4][failed verification]}

Approximately one-third of known corallivores are obligate corallivores, while the remaining three-fourths are facultative corallivores.^[5] Obligate corallivory is defined as having a diet which is at least 80% coral.^[5] Obligate corallivores are present in all tropical oceans, except the Caribbean.^[5] Facultative corallivores are defined as organisms that regularly consume coral without it comprising a large percentage of their diet.^[5]

It is thought that some facultative corallivores, such as some damselfish, eat coral to promote algal growth. Many facultative corallivores also graze on algae, which competes with coral for space and resources. By grazing coral, it may provide better conditions for algal growth.^[2] Aggressive grazing may keep the algal community in a state of accelerated growth, effectively preventing the transition to a slower growing community.^[6]

Organisms display different strategies for consuming coral. The majority of corallivores feed on stony coral, however, a few species feed on soft coral.^[5] There are no known obligate soft coral feeder; soft coral is estimated to be a small percentage of the diet of soft coral feeders.^[5] The most common genera of coral consumed are Acropora, Pocillopora, Montipora, and Porites.^[2][7] Only 18 out of the 111 described coral genera are known to be consumed by corallivores.^[2]

Corallivory is relatively rare in nature; less than 3% of known fish species, four families of crustaceans, four families of gastropods, and a few echinoderm genera have been identified as corallivores.^[8] Corallivores are present in all tropical reef regions. The region with the highest proportion of corallivorous organisms is the tropical eastern Pacific Ocean.^[9]

Corallivory often results in damage to coral or loss of coral biomass, and sometime directly causes coral death.^[16] Corals divert energy and resources towards repairing damage, which has shown to suppress additional growth.^{[2][11][5][6]} The ability for a coral to repair itself is partially based on the size of the lesion; since not all damage can be healed, superfluous damage can result in permanent change to the reef.^[2] Corals have shown to energetically prioritize repairing damage over reproducing, so corallivory can have a negative effect on coral reproduction.^{[2][11][5][6]} Additionally, studies have shown that grazing by corallivores can be associated with reduced zooxanthellae densities.^[5]

Scientists believe that excessive fishing of predators to corallivores, like large piscivorous fish, may result in an increase in corallivore abundance. This increase in corallivory may have a future negative effect on coral health and density.^[16]

Corallivory can indirectly cause an increase in growth of competitive organisms, such as algae and sponges.^[2] Additionally, some corallivores have been implicated in the spread of coral diseases.^[2] Some studies have shown that corallivores can have an influence on the competitive abilities of coral colonies.^[5]

Corallivory is not always detrimental to coral reefs. If the species of coral being consumed is spatially dominant, grazing can help control growth and promote greater reef diversity.^[5]

Corallivores are often sensitive to declines in coral health and population size, and are negatively affected during periods of high coral loss.^[5] In particular, obligate corallivores have been reported to experience high population declines following instances of coral loss.^[5] Studies have shown that corallivores suffer during bleaching events, suggesting that bleached coral is not as nutritional as healthy coral.^[5] Scientific investigation into the nutritional value of healthy and bleached coral is lacking. However, it has been determined that the disparity in nutritional value is not related to the concentration of zooxanthellae.^[5]

This list contains the majority of known corallivores, as research is actively ongoing.