Nudiantennarius

Nudiantennarius is a monospecific genus of marine ray-finned fish belonging to the family Antennariidae, the frogfishes. The only species in the genus is Nudiantennarius subteres, the deepwater frogfish. This fish is found in the Western Pacific Ocean.

Taxonomy
Nudiantennarius was first proposed as a genus in 1957 by the American ichthyologist Leonard Peter Schultz. Schultz designated Antennarius subteres as the type species of the new genus, as well as being its only species. Anetnnarius subteres has been first formally described in 1912 by Hugh McCormick Smith and Lewis Radcliffe with its type locality given as Lingayen Gulf in western Luzon in the Philippines. An unidentified frogfish from Lembeh was identified as this species in 2017. Within the family Antennariidae this taxon has been found to be most closely related to the sargassum fish (Histrio histrio). Some authorities classify this genus in the subfamily Antennariinae within the family Antennariidae. However, the 5th edition of Fishes of the World does not recognise subfamilies within the Antennariidae, classifying the family within the suborder Antennarioidei within the order Lophiiformes, the anglerfishes.

Etymology
Nudiantennarius is a combination of nudus, meaning "nude" or "naked", with the genus name Antennarius, the type genus of the frogfish family, Antennariidae. This is a references to the seemingly naked skin, it only has a scattering of small denticles embedded in the skin on the head and body. The specific name, subteres, prefixes teres, which means "cylindrical" or "tapering", as in the English word terete, with sub, meaning "less than". The authors did not explain what this was referring to but it is thought to be alluding to the shape of the body.

Description
Nudiantennarius is distinguished from other frogfishes by the reduced number of spinules in the skin, the skin has only a partial covering of bifurcate dermal spinules, so few that the body has the appearance of being naked. The spinules are each no longer than the distance between their tips. The first dorsal spine, or illicium, has a distinct esca, or lure, and is naked without spinules. The illicium is around half the length of the second dorsal spine which is unusually long in comparison to other frogfishes, slender and is not connected to the skin of the head by a posterior membrane. The lobe of the pectoral fin is thin and is somewhat separated from the sides. This species has a caudal peduncle and the rear margins of the dorsal and anal fins are clearly attached to the just in front of the outer rays of the caudal fin. The dorsal fin has 12 soft rays while the anal fin has 7. There is typically at least one large ocellus on the base of the dorsal fin. The esca is small and round, has short filaments and fits in a thin groove beside the second dorsal spine. The deepwater frogfish has a maximum published standard length of 7.5 cm.

Distribution and habitat
Nudiantennarius is found in the Western Pacific Ocean in the Philippines and Indonesia, and off Japan. This species is usually encountered on substrates of brown or black sand, silt or mud, where there may be some soft coral, gorgonians and sponges but where there is very little hard coral. The deepwater frogfish has also been found on pier pilings and rarely among small patches of seaweed. Other records have come from areas dominated by leaf litter and refuse, particularly in areas near human habitation. Others have been recorded in habitats mainly made up of very coarse sand or fine coral rubble, with a few hard corals and gorgonians. In this habitat there were many small cephalopods, numerous decapods and other crustaceans, and a variety of fishes, largely juveniles such as small species of shark, burrowing snake eels, Rhinopias eschmeyeri and R. frondosa, as well as a number of other species of scorpionfishes and waspfishes. At another site this species and the striated frogfish (Antennarius striatus]] were observed on coarse sand and rubble covered slopes with scatterred encrusting sponges, hydroids and litter covered in organic growth. This species is found at depths between 3 and 128 m.

Biology
Nudiantennarius is most commonly observed on night dives off Bali. Dark coloured fishes are most numerous on coarse sand or gravel, frequently where there are patches of green algae, at depths between 4 and 20 m whereas the lighter and more colourful individuals are typically found in association with small sponges, similar in colour to the frogfish, at rather greater depths, between 12 and 30 m. This is an oviparous species.