genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
ray-finned fish
Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species.
The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...
in the family
Pomacentridae
Pomacentridae is a family of ray-finned fish, comprising the damselfishes and clownfishes. This family were formerly placed in the order Perciformes but are now regarded as being ''incertae sedis'' in the subseries Ovalentaria in the clade Perco ...
. Members of this genus are marine coastal fishes except for ''S. otophorus'', which also occurs in brackish water. These fish are known by the names of damselfish, gregory and major. They are small tropical fish associated with coral and rocky reefs in the Atlantic, Indian and Pacific Oceans. They are sometimes found in the aquarium trade where they are an easy-to-keep fish, but they do not mix well with other fish of their own or other species because of their territorial habits and aggressiveness.
Description
The largest species in the genus is ''S. acapulcoensis'', which grows to a maximum length of , while the smallest is ''S. pictus'' at .
Members of this genus are deep-bodied and laterally flattened fish with forked tails. The head has a blunt snout, a small, terminal mouth, a nostril on each side of the face, and large eyes. The
lateral line
The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...
does not run the full length of the body and has gaps in it. A single large dorsal fin is present and the anal fin has two, or rarely three, spines. The colour varies with the species and sometimes varies in different parts of the fish's range. Juvenile fish tend to have bright colours which are completely different from the appearance of adults of that species.
Behaviour
These damselfish feed on filamentous algae which make up about 90% of their diet, although they may consume
detritus
In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...
and some
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
material, possibly ingesting it accidentally with the algae. They are
territorial
A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal.
In international politics, a territory is usually either the total area from which a state may extract power resources or a ...
and cultivate the algae, guarding their garden from other fish. Most species of ''Stegastes'' live a solitary existence, though some live in association with a member of the opposite sex and a few form loose aggregations of a small number of individuals. They tend not to face too much competition from other fish because of the very shallow water in which they live and because their habitat is not actually on reefs, but is near them, among boulders, dead branching corals, man-made structures, and junk. Most species are very aggressive and attack anything that moves into their territory, including nipping divers to drive them away.
Their behaviour changes somewhat during the breeding season. The male prepares a nesting site by cleaning a smooth piece of rock, removing algae and debris, and removing or driving away from the vicinity unwanted invertebrates such as
starfish
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ...
and
sea urchin
Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...
s. He then signals his readiness to breed by changing hue and displaying his brighter colours. A female that accepts his advances lays a single layer of eggs which she attaches to the prepared rock. The male fertilises them and then stays to guard them, removing any debris that lands on them or unfertilised eggs and fanning the developing
embryo
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
s with his fins to keep them well oxygenated. The eggs hatch in about a week, the larvae drifting away as part of the
plankton
Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...
. About a month later, they settle to the seabed and undergo
metamorphosis
Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...
into juveniles, well away from the territories occupied by the adults.
In the aquarium
''Stegastes'' species may be offered to new aquarists on the grounds that they are easy to care for. They will indeed tolerate poor water quality and feed on the algae which is often a nuisance in reef tanks, but because of their aggressive behaviour, they should not be kept with other fish, especially smaller ones.
Species
FishBase
FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.
lists these species:
*''
Stegastes acapulcoensis
''Stegastes acapulcoensis'', commonly called the Acapulco major, the Acapulco damselfish, or the Acapulco gregory, is a species of damselfish of the family Pomacentridae. It is native to the eastern Pacific Ocean.
Distribution and habitat
''S. ...
'' (Fowler, 1944)
*''
Stegastes adustus
''Stegastes adustus'', also known as the dusky damselfish or scarlet-backed demoiselle, is a species of damselfish in the family Pomacentridae. It is found at one- to three-meter depths on surging and wavy coral reefs in the Caribbean Sea, the t ...
'' (Troschel in Müller, 1865)
*''
Stegastes albifasciatus
''Stegastes albifasciatus'', known commonly as the whitebar gregory or white-banded gregory, is a damselfish of the family Pomacentridae native to the western Indo-Pacific. Its range extends from the Seychelles and Réunion to the Ryukyu Islands ...
'' (Schlegel and Müller, 1839)
*''
Stegastes altus
''Stegastes apicalis'', commonly known as the Japanese gregory, is a damselfish of the family Pomacentridae.
It is native to the northwestern Pacific Ocean in the seas around Japan and the Ryukyu Islands. It has also been reported from Taiwan a ...
'' (Okada and Ikeda, 1937)
*''
Stegastes apicalis
''Stegastes apicalis'', commonly known as the Australian gregory or yellowtip gregory, is a damselfish of the family Pomacentridae. It is native to the Western Pacific where it occurs on the east coast of Australia, the Great Barrier Reef, Queen ...
'' (De Vis, 1885)
*''
Stegastes arcifrons
''Stegastes arcifrons'', the island major or Galapagos gregory, is a damselfish of the family Pomacentridae native to the eastern Pacific Ocean. Its range extending from Costa Rica to the Cocos Islands, Malpelo Island, and the Galapagos Island ...
'' (Heller and Snodgrass, 1903)
*''
Stegastes aureus
''Stegastes aureus'', the golden gregory, is a damselfish of the family Pomacentridae native to islands in the tropical Pacific Ocean, its range including New Caledonia, the Gilbert Islands, Line Island, Phoenix Island, Samoa, the Tuamotu Arch ...
'' (Fowler, 1927)
*''
Stegastes baldwini
''Stegastes baldwini'', is a damselfish of the family Pomacentridae.
It is endemic to the waters surrounding Clipperton Island
Clipperton Island ( or ; ) is an uninhabited, coral atoll in the eastern Pacific Ocean. It is from Paris, Franc ...
'' Allen and Woods, 1980
*''
Stegastes beebei
''Stegastes beebei'' (Galapagos ringtail damselfish or southern whitetail major), is a species of damselfish found on coral and rocky reefs at depths between 0 and 15 m. They are somewhat territorial, and chase away small intruders. They ar ...
'' (Nichols, 1924)
*''
Stegastes diencaeus
''Stegastes diencaeus'', the longfin damselfish, is a damselfish in the family Pomacentridae from the Western Atlantic. It occasionally makes its way into the aquarium trade. It grows to a size of 12.5 cm in length. Longfin damselfish have b ...
'' (Jordan and Rutter, 1897)
*''
Stegastes emeryi
''Stegastes'' is a genus of ray-finned fish in the family Pomacentridae. Members of this genus are marine coastal fishes except for ''S. otophorus'', which also occurs in brackish water. These fish are known by the names of damselfish, gregory ...
'' (Allen and Randall, 1974)
*''
Stegastes fasciolatus
''Stegastes fasciolatus'', commonly called the Pacific gregory, is a species of damselfish in the family Pomacentridae. It is native to the tropical western Indo-Pacific. It feeds on filamentous algae.
Distribution and habitat
''Stegastes fasci ...
'' (Ogilby, 1889)
*''
Stegastes flavilatus
''Stegastes flavilatus'', commonly known as beaubrummel, is a damselfish of the family Pomacentridae. It is native to the tropical eastern Pacific Ocean, its range extends from Mexico, Baja California and the Gulf of California southwards to the ...
'' (Gill, 1862)- Beaubrummel
*''
Stegastes fuscus
''Stegastes fuscus'', the dusky damselfish, is a species of bony fish in the Family (biology), family Pomacentridae found near the seabed in shallow waters on the western fringes of the Atlantic Ocean.Stegastes gascoynei'' (Whitley, 1964)- Coral Sea gregory
*''
Stegastes imbricatus
''Stegastes imbricatus'', commonly called the Cape Verde gregory, is a damselfish of the family Pomacentridae. It is native to the tropical eastern Atlantic Ocean.
Distribution and habitat
''Stegastes imbricatus'' is native to the tropical easte ...
Stegastes leucostictus
''Stegastes leucostictus'' is a species of damselfish found near the sea bed in shallow waters on the western fringes of the Atlantic Ocean. It is commonly known as the beau gregory or beaugregory.Stegastes limbatus
''Stegastes'' is a genus of ray-finned fish in the family Pomacentridae. Members of this genus are marine coastal fishes except for ''S. otophorus'', which also occurs in brackish water. These fish are known by the names of damselfish, gregory a ...
'' (Cuvier in Cuvier and Valenciennes, 1830)
*''
Stegastes lividus
''Stegastes'' is a genus of ray-finned fish in the family Pomacentridae. Members of this genus are marine coastal fishes except for ''S. otophorus'', which also occurs in brackish water. These fish are known by the names of damselfish, gregory ...
'' (Forster in Bloch and Schneider, 1801)
*''
Stegastes lubbocki
''Stegastes'' is a genus of Actinopterygii, ray-finned fish in the family Pomacentridae. Members of this genus are marine coastal fishes except for ''S. otophorus'', which also occurs in brackish water. These fish are known by the names of damse ...
'' Allen and Smith, 1992
*''
Stegastes nigricans
''Stegastes nigricans'', the dusky farmerfish, is a species of damselfish found around coral reefs at a depth of one to 12 meters, in tropical climates between 30°S and 30°N. They are known for farming monocultures of algae such as cyanophores ...
Stegastes otophorus
''Stegastes'' is a genus of Actinopterygii, ray-finned fish in the family Pomacentridae. Members of this genus are marine coastal fishes except for ''S. otophorus'', which also occurs in brackish water. These fish are known by the names of damse ...
'' (Poey, 1860)- freshwater gregory
*''
Stegastes partitus
''Stegastes partitus'' or the bicolor damselfish is a species of bony fish in the family Pomacentridae found near the sea bed on shallow rocky and coral reefs in the Caribbean Sea, the Gulf of Mexico and off the coasts of Florida.
'' (Poey, 1868)
*''
Stegastes pelicieri
''Stegastes pelicieri'', commonly known as the Mauritian gregory, is a damselfish of the family Pomacentridae. It is native to the islands of Mauritius and Réunion in the western Indian Ocean
The Indian Ocean is the third-largest of the wor ...
Stegastes redemptus
''Stegastes redemptus'', commonly known as the clarion major, clarion damselfish or clarion gregory, is a damselfish of the family Pomacentridae. It is native to the tropical eastern Pacific Ocean, its range extending from the Revillagigedo Islan ...
'' (Heller and Snodgrass, 1903)
*''
Stegastes rocasensis
''Stegastes rocasensis'', commonly known as the Rocas gregory, is a damselfish of the family Pomacentridae. It is native to the tropical West Atlantic Ocean where it is found at depths between . It is known only from the coast of Brazil including ...
Stegastes sanctipauli
''Stegastes sanctipauli'' is a species of fish in the family Pomacentridae. It is endemic to Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Lat ...
'' Lubbock and Edwards, 1981
*''
Stegastes uenfi
''Stegastes uenfi'', the grizzed gregory, is a damselfish of the family Pomacentridae. It is native to the tropical West Atlantic Ocean where it is found at depths of about . It is known only from the coast of Brazil. The specific nae derives fr ...
'' Novelli, Nunan and Lima, 2000
*''
Stegastes variabilis
''Stegastes variabilis'' (cocoa damselfish) is a damselfish in the family Pomacentridae, found on coral and rocky reefs in the Caribbean Sea and neighboring areas of the Atlantic Ocean and Gulf of Mexico. They are often solitary fish.
Descripti ...