Devil Scorpionfish

Inimicus filamentosus, commonly known as the filament-finned stinger, is a venomous fish belonging to the Inimicus genus. It is a member of the Scorpaeniformes order and the Synanceiidae family, which includes devilfishes, goblinfishes, and stonefishes. These benthic fish inhabit tropical coastal regions, specifically sandy or silty substrates of lagoon and seaward reefs in oceans.

This species, like others in the genus, is a demersal ambush predator. They are primarily active at night and tend to partially bury themselves in sandy seabeds during the day.

Inimicus filamentosus is found in the western 🌊 Indian Ocean, from the 🌊 Red Sea and East Africa to the 🇲🇻 Maldives. Adult individuals typically measure 13-25 centimeters in length and can weigh up to 480 grams. They have a dull yellow, gray, brown, or rust-colored body with light blotches, blending with the sandy or coral seabed that surrounds them. Their coloration acts as an effective camouflage, making them difficult to detect in their natural habitat. Their skin lacks scales, except along the lateral line, and is covered with venomous spines and wartlike glands, giving it a knobby appearance. The head is flattened, depressed, and concave, with upward and outward-projecting eyes, mouth, and nostrils. There is no known sexual dimorphism in this species.

The fin morphology of Inimicus filamentosus includes:

• Dorsal fin: Composed of 15 to 17 spines and 7 to 9 soft rays.
• Caudal fin: Composed of 2-4 spines and 4-14 soft rays, with dark bands at basal and subterminal positions.
• Pelvic fin: Composed of one spine and 3-5 soft rays.
• Pectoral fin: Composed of 10-12 rays. The two most caudal rays of each pectoral fin are detached from the rest of the fin and angled in a ventral direction. These two rays are used by the fish to support the forward part of its body and to "walk" along the substrate. The ventral surface of the pectoral fins bears broad black bands with 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. This distinction is crucial for distinguishing between the two species, as they are otherwise very similar.

Inimicus filamentosus is a nocturnal piscivorous ambush predator. It typically lies partially buried on the sea floor or coral heads during the day, disguising itself with sand and debris for further camouflage. This species has no known natural predators. When disturbed, it spreads out its brightly colored pectoral and caudal fins as a warning. It is reluctant to leave its hiding place once dug in. However, when it does move, it displays a unique subcarangiform locomotion, crawling slowly along the seabed using the lower rays of its pectoral fins as legs.