Dusky spinefoot
Venomous rabbitfish that migrated from the Red Sea to the Mediterranean.
The dusky spinefoot (Siganus luridus), also called the squaretail rabbitfish, is a marine ray-finned fish in the family Siganidae. It is known for the venom in its fin spines and for migrating from the western Indian Ocean into the Mediterranean Sea through the Suez Canal—a Lessepsian migration. It is fished for food.
German naturalist Eduard Rüppell first described the species in 1829 as *Amphacanthus luridus*, with the Red Sea as the type locality. The specific name *luridus* means "pale yellow," given by collector Christian Gottfried Ehrenberg, who described the body as yellowish-brown with thin pale yellow lines. Rüppell, however, described the color as bluish black with irregular paler spots and a yellowish ring around the pupil.
The body is compressed, with a depth that fits 2.1 to 2.8 times into its standard length. The jaws have a single row of incisor-like teeth, each with one or two lateral cusps. The dorsal fin has 13–14 spines and 10 soft rays; the anal fin has 7 spines and 9 soft rays. The caudal fin is truncate. Maximum total length is 30 cm (12 in), though 20 cm (7.9 in) is typical. Color varies, usually olive green to dark brown with a mottled pattern. Pectoral fins are hyaline-yellow, and the caudal fin has dark bars.
The dusky spinefoot occurs along eastern Africa from Mozambique north to the Red Sea, and around the Comoros, Madagascar, and the Mascarene Islands. Its presence in the Persian Gulf is unconfirmed. It was first recorded in the Mediterranean off Israel in 1955, after entering via the Suez Canal, and has since spread across the eastern basin, reaching the French Mediterranean coast and the Adriatic Sea. It lives at depths of 2 to 40 m (6 ft 7 in to 131 ft 3 in) over hard substrates like coral and rocky reefs.
Spawning occurs in April and from June to August, when seawater temperatures are between 24 and 29 °C (75 and 84 °F). Eggs and larvae are planktonic; larvae stay near the surface and feed on phytoplankton and zooplankton from three days old. Adults are herbivorous, active during the day, and hide in cavities at night. They are often found in schools, though solitary individuals graze on algae from the substrate, feeding on larger brown algae and other macrophytes.
The fin spines produce venom. A study of a related rabbitfish found its venom similar to that of stonefishes.
Quick Facts
- Taxon
- Siganus luridus
Facts from the source article.
Lore & Background
The dusky spinefoot was first formally described in 1829 as Amphacanthus luridus by German naturalist Eduard Rüppell, with the type locality given as the Red Sea. The specific name luridus means 'pale yellow', given by the collector Christian Gottfried Ehrenberg, who described the body color as yellowish-brown with numerous very thin pale yellow lines. Rüppell, however, described the color as bluish black with irregular paler spots and a yellowish ring around the pupil.
This species has a compressed body with a depth 2.1 to 2.8 times into its standard length. It has a single row of incisor-like teeth with lateral cusps, a dorsal fin with 13-14 spines and 10 soft rays, an anal fin with 7 spines and 9 soft rays, and a truncate caudal fin. Its color is variable, normally olive green to dark brown with a mottled pattern, hyaline-yellow pectoral fins, and dark bars on the caudal fin. It is found over hard substrates such as coral and rocky reefs at depths between 2 and 40 m.
The dusky spinefoot spawns in April and from June to August when seawater temperature is between 24 and 29 °C. The eggs and larvae are planktonic; larvae feed on phytoplankton and zooplankton from 3 days old. Adults are herbivorous, active during the day, hiding in cavities at night, and frequently encountered in schools or solitary, grazing on larger brown algae and other macrophytes.
Reader's Guide
The dusky spinefoot is significant as a species that has successfully colonized the Mediterranean Sea following its entry via the Suez Canal, first recorded there in 1955 off Israel. It has since expanded across the eastern basin and now reaches as far west as the French Mediterranean coast and the Adriatic Sea. Its venomous fin spines, which produce venom similar to that of stonefishes, are used for defense; the fish erects its dorsal, anal, and pelvic spines to present a threat. Predation pressure is highest on planktonic and larval stages. Known parasites include the monogeneans Glyphidohaptor plectocirra and Tetrancistrum polymorphum, and the digeneans Hexangium brayi, Hexangium sigani, and Progyliauchen magnacetabulum. The species is caught using set fish traps, gillnets, and beach seines, sold fresh, and has become important for fisheries in the Mediterranean, while in areas like Kenya it is a bycatch. It has been implicated in cases of mild ciguatera-like poisoning when consumed.
Did You Know?
- The dusky spinefoot was first described in 1829 by Eduard Rüppell as Amphacanthus luridus.
- Its fin spines contain venom similar to that of stonefishes.
- It was first recorded in the Mediterranean Sea in 1955 off Israel, having entered via the Suez Canal.
- Adults are herbivores that feed on larger brown algae and other macrophytes.
Frequently Asked Questions
What is the Dusky spinefoot?
The Dusky spinefoot (Siganus luridus), often nicknamed the squaretail rabbitfish, is a ray-finned marine fish in the family Siganidae. It is native to the western Indian Ocean and has since established itself in the Mediterranean.
Is the Dusky spinefoot dangerous to handle?
Yes—like other members of Siganidae, it carries venom in its fin spines, so a careless grip can result in a painful, medically significant wound. This toxic spine defense is one of the species' most widely noted traits.
How did the Dusky spinefoot end up in the Mediterranean?
It moved from the Red Sea and western Indian Ocean into Mediterranean waters via the Suez Canal, a process ecologists call a Lessepsian migration. This canal-mediated dispersal has made it a well-documented introduced species in European seas.
Who first described the Dusky spinefoot and where was it found?
German naturalist Eduard Rüppell formally named the species in 1829 as Amphacanthus luridus, designating the Red Sea as the type locality. The specific epithet 'luridus,' meaning 'pale yellow,' was proposed by collector Christian Gottfried Ehrenberg to reflect the fish's yellowish-brown body color.
How big does the Dusky spinefoot get?
Adults typically measure around 20 cm (roughly 8 inches) in total length, with a maximum recorded size of about 30 cm (12 inches). It is a modestly sized reef fish that is also harvested by local fisheries for food.
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