''Siganus virgatus'', the barhead spinefoot, doublebar rabbitfish or doublebar spinefoot is a species of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

, a

rabbitfish Rabbitfishes or spinefoots, genus ''Siganus'', are perciform fishes in the family (biology), family Siganidae. It is the only Extant taxon, extant genus in its family and has 29 species. In some now obsolete classifications, the species having ...

belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Siganidae Siganidae, the rabbitfishes, are a small family of ray-finned fishes in the order Perciformes. The only extant genus is '' Siganus'', the rabbitfish and spinefoot. However, a number of genera are known from fossils. The extant species are marine ...

. It is found in the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

region.

Taxonomy

''Siganus virgatus'' was first formally described in 1835 as ''Amphacanthus virgatus'' by the French

zoologist Zoology ( , ) is the scientific study of animals. Its studies include the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. Zoology is one ...

Achille Valenciennes Achille Valenciennes (9 August 1794 – 13 April 1865) was a French zoology, zoologist. Valenciennes was born in Paris, and studied under Georges Cuvier. His study of parasitic worms in humans made an important contribution to the study of parasi ...

with the type locality given as

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''virgatus'' was not explained by Valenciennes but it means "striped", this is presumed to be a reference to the two oblique brown bands on the front part of the body and head of this fish. ''Siganus virgatus'' is closely related to '' S. doliatus'', with which it is apparently hybridized in the Indo-Malay region.

Description

''Siganus virgatus'' has a deep and laterally compressed body which has a depth which fits 1.8 to 2.3 times into its

standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

. The dorsal profile of the head is bulging and the front nostril has a high flange, slightly higher and pointed to the rear. There is a recumbent spine to the front of the

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

. Like all rabbitfishes, the dorsal fin has 13 spines and 10 soft rays while the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

has 7 spines and 9 soft rays. The fin spines hold venom glands. The caudal fin is emarginate in juveniles and slightly forked in adults. This species attains a maximum total length of , although is more typical. The body of this species is pale with a silvery white belly. There are two wide diagonal dark bands on the head and the anterior part of body. The head and the front part of the body are marked with light bluish spots and lines. The caudal and dorsal fins are yellow and they normally have a yellow back and caudal peduncle. Siganus virgatus Tulamben.jpg, ''S. virgatus'' has dots and stripes in the upper half of the body, and the base of the yellow dorsal radiuis Siganus doliatus, pareja.jpg, ''S. doliatus'' has stripes all over the body and no rear yellow spot

Distribution and habitat

''Siganus virgatus'' is found in the

region from southern India and Sri Lanka eastwards to West Papua and Western Australia, north to the

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Geography of Taiwan, Taiwan: the Ryukyu Islands are divided into the Satsunan Islands (Ōsumi Islands, Ōsumi, Tokara Islands, Tokara and A ...

. An individual was collected off the

Adriatic The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans, Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Se ...

island of

Cres Cres is an Adriatic island in Croatia. It is one of the northern islands in the Kvarner Gulf and can be reached via ferry from Rijeka, Krk island or from the Istrian peninsula (line Brestova-Porozina). With an area of , Cres has the same si ...

, but it thought that this is the result of deliberate introduction or transportation in ships ballast. In Australia they are found from the

Ningaloo Reef The Ningaloo Coast is a World Heritage Site located in the north west coastal region of Western Australia. The heritage-listed area is located approximately north of Perth, along the East Indian Ocean. The distinctive Ningaloo Reef that frin ...

and

Kimberley region The Kimberley is the northernmost of the nine regions of Western Australia. It is bordered on the west by the Indian Ocean, on the north by the Timor Sea, on the south by the Great Sandy Desert, Great Sandy and Tanami Desert, Tanami deserts in t ...

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

along the northern coast to the Wessell Islands of the

Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

. They inhabit in tropical waters, associated with coastal

coral reefs A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. ...

, in lagoons and outer reefs. They frequent rocky and

hard coral Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mo ...

areas with patches of sand. They are tolerant of turbid waters. Large juveniles and adults occur in pairs on slopes of reefs and estuaries. Small juveniles inhabit mangroves, moving to reefs in small groups, protected by

. They are found at depths down to .

Biology

''Siganus virgatus'' is oviparous and the eggs are fertilized externally, laying sticky eggs.

Spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...

occurs at dusk, in the hot months, coinciding with the lunar cycle, in the first quarter of the moon. They possess a

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic larval state, and develop a post-larval state, characteristic of the suborder

Acanthuroidei Acanthuroidei , is a group of ray finned fishes which is a suborder of the Acanthuriformes, although older classifications regarded it as a suborder of the Perciformes, the largest order (biology), order of fish, The suborder includes the surgeonf ...

, called acronurus, in which the individuals are transparent, and they remain in

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

state during an extended period before establishing in the definitive habitat, and adopt then the shape and color of adults. They are mainly herbivores, in 84% of their nourishment. They progress from feeding on

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...

and

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

, like larvae, to feeding on

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

macroalgae Seaweed, or macroalgae, refers to thousands of species of Macroscopic scale, macroscopic, Multicellular organism, multicellular, ocean, marine algae. The term includes some types of ''Rhodophyta'' (red), ''Brown algae, Phaeophyta'' (brown) and ...

and small invertebrates. They are diurnal. At night they sleep in cracks, developing a specific coloration of camouflage, in brown tones, and turning off their lively colors, in an exercise of

crypsis In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be part of a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean life ...

, that also develop when they are stressed.

References

External links

* {{Taxonbar, from=Q2299723 Siganidae Fish described in 1835