The dusky spinefoot (''Siganus luridus''), also known as the squaretail rabbitfish, 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 native to the western

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

which has spread to the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

through the

Suez Canal The Suez Canal (; , ') is an artificial sea-level waterway in Egypt, Indo-Mediterranean, connecting the Mediterranean Sea to the Red Sea through the Isthmus of Suez and dividing Africa and Asia (and by extension, the Sinai Peninsula from the rest ...

(

Lessepsian migration The Lessepsian migration (or Erythrean invasion) is the migration of marine species along the Suez Canal, usually from the Red Sea to the Mediterranean Sea, and more rarely in the opposite direction. When the canal was completed in 1869, fish, ...

). Its fin spines contain venom. It is regarded as a food fish.

Taxonomy

The dusky spinefoot was first formally described in 1829 as ''Amphacanthus luridus'' by the German

naturalist Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...

and

explorer Exploration is the process of exploring, an activity which has some Expectation (epistemic), expectation of Discovery (observation), discovery. Organised exploration is largely a human activity, but exploratory activity is common to most organis ...

Eduard Rüppell Wilhelm Peter Eduard Simon Rüppell, also spelled Rueppell (20 November 1794 – 10 December 1884) was a German Natural history, naturalist and List of explorers, explorer, best known for his collections and descriptions of plants and animals from ...

with the type locality given as the

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

. 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 ...

''luridus'' means “pale yellow”, this name was given to it by the collector of the

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

Christian Gottfried Ehrenberg Christian Gottfried Ehrenberg (19 April 1795 – 27 June 1876) was a German Natural history, naturalist, zoologist, Botany, botanist, comparative anatomist, geologist, and microscopy, microscopist. He is considered to be one of the most famous an ...

, According to

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 ...

in 1835, Ehrenberg described the colour of the body as yellowish-brown, with numerous very thin pale yellow lines. However, Rüppell said that the colour was bluish black with some irregular, paler spots and a yellowish ring around pupil in his description.

Description

The dusky spinefoot has a compressed body which Has a depth which fits into its standard length 2.1 to 2.8 times. There is a single row of

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

-like teeth in the jaws, each with 1 or 2 lateral cusps. 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 ...

contains 13-14 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

caudal 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 only ...

is truncate. This species attains a maximum total length of , although is more typical. The colour is variable, it is normally olive green to dark brown with a mottled pattern. The

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

s are

hyaline A hyaline substance is one with a glassy appearance. The word is derived from , and . Histopathology Hyaline cartilage is named after its glassy appearance on fresh gross pathology. On light microscopy of H&E stained slides, the extracellula ...

-yellow and there are dark bars on the caudal fin

Distribution and habitat

The dusky spinefoot is found on the coast of eastern Africa from Mozambique northwards into the Red Sea, and also the Comoros, Madagascar, and the

Mascarene Islands The Mascarene Islands (, ) or Mascarenes or Mascarenhas Archipelago is a group of islands in the Indian Ocean east of Madagascar consisting of islands belonging to the Republic of Mauritius as well as the French department of Réunion. Their na ...

. Its presence in the

Persian Gulf The Persian Gulf, sometimes called the Arabian Gulf, is a Mediterranean seas, mediterranean sea in West Asia. The body of water is an extension of the Arabian Sea and the larger Indian Ocean located between Iran and the Arabian Peninsula.Un ...

needs to be confirmed. Recorded first in the

in 1955 off Israel, following entry via the Suez Canal, it fast expanded across the eastern Basin and now reaches westwards as far as the French Mediterranean coast and the

Adriatic Sea 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 ...

.Atlas of Exotic Fishes in the Mediterranean Sea (Siganus luridus). 2nd Edition. 2021. 366p. CIESM Publishers, Paris, Monaco.https://ciesm.org/atlas/fishes_2nd_edition/Siganus_luridus.pdf It is found at depths between in waters over hard substrates, such as coral and rocky reefs.

Biology

The dusky spinefoot spawns in April and from June to August when the seawater temperature is between , the eggs and larvae are planktonic. The larvae stay close to the surface where they feed on phytoplankton and zooplankton from 3 days old. The adults are herbivores which are active during the day, hiding in cavities during the hours of darkness. They are frequently encountered in schools but solitary individuals can also be seen, grazing on algae from the substrate. It feeds on larger

brown algae Brown algae (: alga) are a large group of multicellular algae comprising the class (biology), class Phaeophyceae. They include many seaweeds located in colder waters of the Northern Hemisphere. Brown algae are the major seaweeds of the temperate ...

species, as well as other macrophytes.

Venom

This species produces

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

in the spines of its fins. In a study of the venom of a congener it was found that rabbitfish venom was similar to the venom of stonefishes. This species has been observed stopping suddenly. erecting the dorsal, anal and pelvic to present a potential threat with an array of venomous spines around its body.

Predators and parasites

The venomous spines are used for defence against predators so the highest predation pressure is on the planktonic and larval stages. Known parasites of the dusky spinefoot included the

monogenean Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they ...

'' Glyphidohaptor plectocirra'' and '' Tetrancistrum polymorphum'' as well as the

digeneans Digenea (Gr. ''Dis'' – double, ''Genos'' – race) is a class of trematodes in the Platyhelminthes phylum, consisting of parasitic flatworms (known as ''flukes'') with a syncytial tegument and, usually, two suckers, one ventral and one or ...

'' Hexangium brayi'', '' Hexangium sigani'' and '' Progyliauchen magnacetabulum''.

Utilisation

The dusky spinefoot is caught using set

fish trap A fish trap is a animal trapping, trap used for fishing, catching fish and other aquatic animals of value. Fish traps include fishing weirs, lobster trap, cage traps, fish wheels and some fishing net rigs such as fyke nets. The use of traps ar ...

gillnet Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

s and beach seines, the catch is sold as fresh fish. This species has become an important species for fisheries in the Mediterranean while i other areas, such as Kenya, it is a

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

. This species has been implicated in cases of mild ciguatera like poisoning when consumed.

References

External links

* {{Taxonbar, from=Q2289387 Siganidae Fish described in 1829 Taxa named by Eduard Rüppell Western Indo-Pacific fauna