Abstract
Parrotfishes (Perciformes: Scaridae) represent a critical functional group on coral reefs because their intense herbivory activity helps in avoiding coral overgrowth by algae. Although feeding preferentially on algae and detritus, some parrotfish species also consume live corals, leading to detrimental effects that may offset the benefits of removing competitive seaweeds. Parrotfish species differ markedly in terms of jaw morphology, foraging activity and extent of substratum excavation, and are typically divided into three functional groups: browsers, scrapers and excavators. The recognition of species within each functional group helps to understand their relative effects in terms of bioerosion, coral fitness and survival, habitat alteration and ecosystem dynamics. Here we report on live coral predation by the Brazilian endemic parrotfishes Scarus trispinosus and Sparisoma amplum in the largest coral reefs of the South Atlantic (Abrolhos Bank, eastern Brazil) and comment on their classification into functional groups based on direct behavioral observations. Scarus trispinosus and Sp. amplum allocated 0.8% and 8.1% of their bites to live corals respectively. Sparisoma amplum fed at lower rates, took shorter feeding forays and larger bites than Sc. trispinosus. Bite rates and foray size were negatively correlated to body size for Sc. trispinosus, but not for Sp. amplum. Our results indicate that Sp. amplum may be primarily recognized as an excavating species, as well as the most specialized parrotfish coral predator in Brazil, while Sc. trispinosus may be recognized as a scraper or excavator depending on its body size. This functional classification corresponds to the classification used for the putative sister taxa of Sc. trispinosus (Sc. coeruleus) and the sister taxa of Sp. amplum (Sp. viride) in the Caribbean, indicating that these two congeneric species pairs play similar ecological roles in different geographic regions.
Highlights
IntroductionParrotfishes (family Scaridae) are primarily herbivorous reef fishes that use their fused beak-like jaws to remove algae and detritus from the substratum
Parrotfishes are primarily herbivorous reef fishes that use their fused beak-like jaws to remove algae and detritus from the substratum
These fishes play a critical functional role in coral reefs because their intense herbivory activity helps in avoiding coral overgrowth by algae (Hughes, 1994; Bellwood et al, 2004)
Summary
Parrotfishes (family Scaridae) are primarily herbivorous reef fishes that use their fused beak-like jaws to remove algae and detritus from the substratum. The separation of species into functional groups is critical for understanding their effects in terms of bioerosion, coral fitness and survival, habitat modification and ecosystem dynamics (Bellwood & Choat, 1990; Bellwood et al, 2004). Browsers use their discrete teeth to remove food from the substrata without scarring it. With two parallel scrapes made by each dental plate, while scars are approximately half as wide as long and usually possess 4-6 deep grooves running along their length (Bellwood & Choat, 1990)
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