Marbled spinefoot, Rivulated rabbitfish, Surf parrotfish
Siganus rivulatus, the marbled spinefoot, rivulated rabbitfish or surf parrotfish, is a gregarious, largely herbivorous ray-finned fish of the family Siganidae. Its natural range encompasses the western Indian Ocean and the Red Sea from where it colonised the Mediterranean Sea by Lessepsian migration through the Suez Canal. It is the type species of the genus Siganus.
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PlanktivoreA planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton. Phytoplankton are usually photosynthet...
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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CongregatoryCongregatory animals tend to gather in large numbers in specific areas as breeding colonies, for feeding, or for resting.
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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SocialNo
Not a migrantAnimals that do not make seasonal movements and stay in their native home ranges all year round are called not migrants or residents.
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starts withSiganus rivulatus has a laterally compressed body which has a standard length of 2.7-3.4 times the greatest body depth. The dorsal fin has 14 spines and 10 soft rays, the anal fin has 7 spines and 9 soft rays, there are 23 vertebrae and the caudal fin is slightly forked. The longest spine in the dorsal fin is shorter than the distance between the front of the eye and the posterior edge of the operculum while the length of the longest dorsal ray is equal to or less than the length of the snout. The slender spines are barbed and bear venom. The teeth are incisor-like with lateral cusps and are arranged in a single row in the jaws. The body is covered in small embedded scales, except of the midline of the underside. The colour is variable and it usually shows some darks spots and yellow wavy lines along the sides. The upper body tends to be grey-green to brown with a yellow abdomen or silvery white underside. It usually grows to around 10–20 centimetres (3.9–7.9 in), sometimes up to 27 cm in standard length but the maximum recorded size is 40 cm.
Siganus rivulatus has a natural range which extends along the east African coast from South Africa to the Red Sea, including the Comoros, Madagascar and the Seychelles. It was first recorded in the Mediterranean off the coast of Israel in 1924, following entry through the Suez Canal, and is now very common in the entire eastern Basin reaching as far as the Sicily channel and parts of the Adriatic Sea.
Siganus rivulatus occurs in shallow waters over substrates clothed with algae, including rocky and sandy as well as areas where the algae grows among sea grass beds at depths of less than 15m. It sometimes enters estuarine environments and so can be described as euryhaline. It is normally found in schools of 50 to several hundred fish; it prefers sheltered areas. It feeds mainly by grazing on algae.
The newly hatched fish larvae are planktonic feeders on small diatoms, as they grow they also feed on zooplankton such a copepods. The adults are mainly herbivorous, feeding mainly on algae including Polysiphonia spp and Sphacelaria spp. but have been observed feeding on ctenophores and scyphozoans in the Spring and early summer within the northern Red Sea, attacking relatively large ctenophores until the disintegrate and on the schypozoan moon jellyfish Aurelia aurita until it sinks to the bottom.
S. rivulatus reaches sexual maturity at a length of 13.7 cm. The spawning season of S. rivulatus takes place when the water temperature reaches 24–27 °C and is later in the Mediterranean, May to July, than it is in the Red Sea when the season runs through March, April and May. Spawing takes place at dusk, they are oviparous and the eggs are fertilised externally, the eggs are small, 0.5–0.6 mm in diameter and are adhesive, the adults show no parental care for the brood after spawning. The larvae are planktonic and do not feed for three days after hatching, when they are about three weeks old they undergo metamorphosis and congregate in schools which migrate into deeper water.
S. rivulatus, like other rabbitfish, has venom glands associated with the spines in the fins and these spines can envenomate a human if the fish is handled incorrectly. The effect is very painful but there are no records of fatalities. The venom is a heat labile protein and any site where the body has been envenomated should be treated at as high a temperature as possible, 43-46 °C. Anyone so envenomated should also be treated for possible infection too.
Social animals are those animals that interact highly with other animals, usually of their own species (conspecifics), to the point of having a rec...