| Saltwater butterflyfishes | |
|---|---|
_and_other_Chaetodon_Moorea.jpg) | |
| Various examples of butterflyfish | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Acanthuriformes |
| Family: | Chaetodontidae Rafinesque, 1810 |
| Genera | |
About 10, seetext | |
| Synonyms | |
Chaetodontinae(but seetext) | |
Thebutterflyfish are a group of conspicuoustropicalmarinefish of the familyChaetodontidae; thebannerfish andcoralfish are also included in this group. The approximately 129species in 12genera[1] are found mostly on thereefs of theAtlantic,Indian, andPacific Oceans. A number ofspecies pairs occur in the Indian and Pacific Oceans, members of the huge genusChaetodon.
Butterflyfish look like smaller versions of angelfish (Pomacanthidae), but unlike these, lackpreopercle spines at thegill covers. Some members of the genusHeniochus resemble theMoorish idol (Zanclus cornutus) of themonotypic Zanclidae. Among theparaphyleticPerciformes, the former are probably not too distantly related to butterflyfish, whereas the Zanclidae seem far less close.
Butterflyfish mostly range from 12 to 22 cm (4.7 to 8.7 in) in length. The largest species, thelined butterflyfish and thesaddle butterflyfish,C. ephippium, grow to 30 cm (12 in). The common name references the brightly coloured and strikingly patterned bodies of many species, bearing shades of black, white, blue, red, orange, and yellow. Other species are dull in colour. Butterflyfish are a boundless, different group of marine percoids with delegates on practically all coral reef frameworks and in every single tropical ocean. Their bright and color patterns have drawn in much consideration, creating an abundance of data about their conduct and environment.[2] Many haveeyespots on their flanks and dark bands across their eyes, not unlike the patterns seen onbutterfly wings.[3] Their deep,laterally narrow bodies are easily noticed through the profusion of reef life. The conspicuous coloration of butterflyfish may be intended for interspecies communication. Butterflyfish have uninterrupteddorsal fins withtail fins that may be rounded or truncated, but are never forked.
Generallydiurnal and frequenting waters less than 18 m (59 ft) deep (though some species descend to 180 m (590 ft), butterflyfish stick to particular home ranges. Thesecorallivores are especially territorial, forming pairs and staking claim to a specific coral head. Contrastingly, thezooplankton feeders form large conspecific groups. By night, butterflyfish hide in reef crevices and exhibit markedly different coloration.
Their coloration also makes them popularaquarium fish. However, most species feed oncoralpolyps andsea anemones. Balancing the relative populations of prey and predator is complex, leading hobby aquarists to focus on the few generalists and specialistzooplankton feeders.
Butterflyfish are pelagic spawners; that is, they release many buoyant eggs into the water, which become part of theplankton, floating with the currents until hatching. The fry go through a tholichthys stage, wherein the body of the postlarval fish is covered in large, bony plates extending from the head. They lose their bony plates as they mature.[3] Only one other family of fish, the scats (Scatophagidae) express such an armored stage.
The Chaetodontidae can be, but are not usually, divided into two lineages that arguably aresubfamilies. The subfamily nameChaetodontinae is a little-used leftover from the period when thePomacanthidae and Chaetodontidae were united under the latter name as a single family. Hence, Chaetodontinae is today considered ajunior synonym of Chaetodontidae. In any case, one lineage of Chaetodontidae (in the modern sense) contains the "typical" butterflyfish aroundChaetodon, while the other unites the bannerfish and coralfishgenera. As thePerciformes are highlyparaphyletic, the precise relationships of the Chaetodontidae as a whole are badly resolved.[4]
Chaetodontidae is classified within thesuborderPercoidei by the 5th edition ofFishes of the World, but they are placed in an unnamedclade which sits outside thesuperfamilyPercoidea. This clade contains 7 families which appear to have some relationship toAcanthuroidei,Monodactylidae, andPriacanthidae.[5] Other authorities have paced the family in the orderChaetodontiformes alongside the familyLeiognathidae.[6] Presently, based on the most recent phylogenetic analyses,Eschmeyer's Catalog of Fishes places it in the large, diverse orderAcanthuriformes.[7] Molecular analyses suggest that the Chaetodontidae shared a common ancestor with theScatophagidae andPomacanthidae that lived during theEarly Eocene (54 Ma).[8]
BeforeDNA sequencing, thetaxonomy was confused about whether to treat these as species orsubspecies. Also, numeroussubgenera have been proposed for splitting out ofChaetodon, and it is becoming clear how to subdivide the genus if that is desired.[9]
Thefossil record of this group is disputed and marginal. Their restriction tocoral reefs means their carcasses are liable to be dispersed byscavengers, overgrown bycorals, and any that do fossilize will not long surviveerosion. ManyEocene-aged fish such asPygaeus have been variously referred to Chaetodontidae in the past; if used for calibration, it can be deduced that most living genera were probably distinct by the end of thePaleogene 23 Mya.[10] However, these Eocene genera cannot be reliably referred to Chaetodontidae.[8]
The earliest confirmed fossil specimens of Chaetodontidae are an indeterminate larval specimen fromFrauenweiler, Germany, two tholichthys specimens from theMenilite Formation of Poland, as well as the extinct speciesChaetodon (Blumchaetodon) wattsi from Italy; all date to theEarly Oligocene. The occurrence of the first confirmed butterflyfish in the Early Oligocene is supported by molecular phylogenies indicating that the family may have arose during theLate Eocene.[8]
The bannerfish-coralfish lineage can be further divided in two groups; these might be consideredtribes, but have not been formally named. Genera are listed in order of the presumedphylogeny, from the most ancient to the youngest:[4][11]
Bannerfish/coralfish lineage 1:
Bannerfish/coralfish lineage 2:
The"typical" butterflyfishes may eventually come to contain more genera; seeChaetodon:
