''Inimicus didactylus'', also known as sea goblin, demon stinger or devil stinger, is a Western Pacific member of the ''

Inimicus ''Inimicus'' is a genus of marine ray-finned fishes, it is one of two genera in the tribe Choridactylini, one of the three tribes which are classified within the subfamily Synanceiinae within the family Scorpaenidae, the scorpionfishes and their ...

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 venomous fishes, closely related to the true

stonefish ''Synanceia'' is a genus of ray-finned fish belonging to the subfamily Synanceiinae, the stonefishes, which is classified within the family Scorpaenidae, the scorpionfishes and relatives. Stonefishes are venomous, dangerous, and fatal to huma ...

es. It can reach a body length of 25 cm (10 in) and is irregularly surfaced with spines and a knobby appearance. The fish has venomous spines to ward off enemies. The fish are

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

, and often dig themselves partially into the sandy seabed during the day. The body is red or sandy yellow and well camouflaged on sandy and coral seabeds.

Taxonomy

''Inimicus didactylus'' was first formally described as ''Scorpaena didactyla'' in 1769 by the German naturalist Peter Simon Pallas, with the type locality given as the Indian Ocean, thought to be Indonesia. 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 ...

''didactylus'' means "two fingered", an allusion to the two detached, lowest pectoral fin rays.

Physical description

''Inimicus didactylus'' adults can attain a body length of up to 26 centimeters in length. The body color is red or sandy yellow with light blotches, and very similar to that of the surrounding sandy or coral seabed in which they are found. This coloration acts as a

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...

which renders them extremely difficult to detect in their natural habitat. The skin is without scales except along 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 ...

, and is covered with venomous spines and wartlike glands which give it a knobby appearance. The head is flattened, depressed and concave. The eyes, mouth and nostrils project upwards and outwards from the dorsal aspect of the head.

Sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

is not believed to occur in this species. Fin morphology: *

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

: composed of 15 to 17 spines and 7 to 9 soft rays. *

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

: composed of 2–4 spines and 4-14 soft rays, with dark bands at basal and subterminal positions. *

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

: composed of one spine and 3–5 soft rays. *

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

: composed of 10–12 rays. The two most

caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into the ...

rays of each pectoral fin are detached from the rest of the fin, and angled in a ventral direction. The fish employ these two rays to prop up the forward part of their body, as well as to "walk" along the bottom of the substrate.World Database of Marine Species
Spiny devil fish
. Accessed 03-22-2010.WetWebMedia.com

by Bob Fenner. Accessed 03-27-2010. The ventral surface of the pectoral fins bears broad black bands containing smaller, lighter spots at the basal and distal ends. In ''I. filamentosus'', these bands are attenuated, while the bands of ''I. sinensis'' have yellow spots on them. This is a key feature for distinguishing the two species, which are otherwise nearly identical.

Behavior

''Inimicus didactylus'' is a

piscivorous A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evoluti ...

ambush predator. It is

and typically lies partially buried on the sea floor or on a coral head during the day, covering itself with sand and other debris to further camouflage itself. It has no known natural predators. When disturbed by a

scuba diver Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface air supply. The name "scuba", an acronym for "Self-Contained Underwater Breathing Apparatus", was coined by Chris ...

or a potential predator, it fans out its brilliantly colored pectoral and caudal fins as a warning. Once dug in, it is very reluctant to leave its hiding place. When it does move, it displays an unusual mechanism of subcarangiform locomotion — it crawls slowly along the seabed, employing the four lower rays (two on each side) of its pectoral fins as legs. Its dorsal spines are venomous.

References

External links

* Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2008. The Animal Diversity Web (online)
Inimicus
Accessed March 21, 2010 at http://animaldiversity.org. * * Longsnout Stingerfish @ Fishes of Australia
/small> {{Taxonbar, from=Q538518 didactylus Fish of the Indian Ocean Marine fish of Western Australia Fish described in 1769 Taxa named by Peter Simon Pallas

Taxonomy

Physical description

Behavior

See also

References

External links