Latin name

Inimicus didactylus

Other name

Demon stinger, devil stinger, bearded ghoul.

Identification

The sea goblin's skin is scaleless except on the lateral line and is covered with spines and wart-like glands, giving it a bumpy appearance. The head is flattened, depressed and concave. The eyes, mouth and nostrils protrude upward and outward from the dorsal part of the head. Sexual dimorphism is thought to be absent in this species.

Features of fish fins

Dorsal fin of these fish: consists of 15-17 spines and 7-9 soft rays. Caudal fin: Consists of 2-4 spines and 4-14 soft rays, with dark stripes in the basal and subterminal parts. Pelvic fin: Consists of one spine and 3-5 soft rays. Pectoral fin: Consists of 10-12 rays. 

The two most caudal rays of each pectoral fin are separated from the rest of the fin and bent towards the ventral part. Fish use these two rays to support the front of the body and to "walk" along the bottom of the substrate. 

Fish colouring

Their body colour is red or sandy yellow with light spots, very similar to the surrounding sandy or coral seabed on which they live. This colouration serves as camouflage, making them extremely difficult to detect in their natural habitat. 

There are broad black stripes on the ventral surface of the pectoral fins, with smaller and lighter spots at the basal and distal ends. In I. filamentosus these stripes are attenuated, while I. sinensis has yellow spots on the stripes. This is the main feature that distinguishes these two species, which are otherwise almost identical.

Distribution

Widespread in the Indo-West Pacific: from Thailand to Vanuatu, north to the Ryukyu Islands and south-east China, south to Australia.

Habitat

Marine tropical species that prefer brackish water. Associated with reefs, depths from 5 to 80 m.

Size

The body length of this fish can reach 25 centimetres.

Behavior

Sea Goblins are solitary nocturnal creatures that spend the day partially hidden on the seabed or on a coral outcrop, covered in sand and other debris. They camouflage well on sandy and coral bottoms.

When disturbed, they spread their brightly coloured pectoral and caudal fins as a warning. They are very reluctant to leave their hiding place. When they do move, they exhibit an unusual mechanism of subcarangiform locomotion - slowly crawling along the seabed using the four lower rays (two on each side) of their pectoral fins as legs.

Food and feeding habits

They are fish-eating predators that live in ambush. They have no known predators in the wild. 

Reproduction

Reproduction oocytes in pairs. Some of the eggs hatch as a compact clutch surrounded by sperm, which only break up into individual eggs after fertilisation.

Fishing

This species is commercially important for fishing and aquarium sales.

Relationship with a person

Venomous. The fish has poisonous spikes that scare away enemies. This fish's venom can be fatal to humans.