''Stomias boa boa'', also called the scaly dragonfish or boa dragonfish, is a

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

abyssal The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of , this zone remains in perpetual darkness. It covers 83% of the total area of the ocean a ...

barbeled dragonfish Stomiidae is a family of deep-sea ray-finned fish, including the barbeled dragonfishes. They are quite small, usually around 15 cm, up to 26 cm. These fish are apex predators and have enormous jaws filled with fang-like teeth. They are ...

of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Stomiidae Stomiidae is a family of deep-sea ray-finned fish, including the barbeled dragonfishes. They are quite small, usually around 15 cm, up to 26 cm. These fish are apex predators and have enormous jaws filled with fang-like teeth. They are ...

. It is found at great depths worldwide in tropical to temperate oceans but is absent from the northern

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

and northwest

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

Description

''Stomias boa boa'' is a long, slender fish. The head is small, and the mouth has a protuberant lower jaw and sharp, pointed teeth. It is very scary looking due to its "sharp fangs," say local fishermen. There is a large fleshy barbel projecting from the chin with a pale stalk, a dark spot at the base of the bulb and a dark filament. The dorsal fin has no spines and 17 to 22 soft rays and the anal fin has 18 to 22 soft rays. The dorsal and anal fins are positioned on the slender caudal peduncle and the caudal fin is forked. The skin is covered in small hexagonal scales. The maximum length of this fish is about . Like many fish of deep oceans, it has large eyes and is transparent and silvery in appearance with iridescent speckles.

Distribution and habitat

''Stomias boa boa'' has a wide distribution, being found in the eastern Atlantic Ocean, the western Mediterranean Sea, the west coast of Africa as far south as Mauritania and southern Africa from Angola to the

Cape of Good Hope The Cape of Good Hope ( af, Kaap die Goeie Hoop ) ;''Kaap'' in isolation: pt, Cabo da Boa Esperança is a rocky headland on the Atlantic coast of the Cape Peninsula in South Africa. A common misconception is that the Cape of Good Hope is t ...

. On the other side of the Atlantic it is found from the

Northwest Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...

of Canada to Argentina. It is also known from Chile and the sub-Antarctic region of the Indian Ocean south to

Heard Island The Territory of Heard Island and McDonald Islands (HIMI) is an Australian external territory comprising a volcanic group of mostly barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall size ...

. It usually inhabits waters deeper than in the daytime but migrates upwards towards the surface during the night.

Ecology

''Stomias boa boa'' is a

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

and mainly feeds on fish. It is itself preyed on by the deepwater hakes ''

Merluccius paradoxus ''Merluccius paradoxus'', the deep-water Cape hake, is a merluccid hake of the genus '' Merluccius'', found in the south-eastern Atlantic Ocean, along the coast of Southern Africa, south of Angola. Its range extends in decreasing abundance around ...

'' and ''

Merluccius capensis ''Merluccius capensis'' (shallow-water Cape hake or South African hake) is a ray-finned fish in the genus '' Merluccius'', found in the south-eastern Atlantic Ocean, along the coast of South Africa. It is a long, lean fish with a large head, simi ...

'', the blackmouth catshark ''

Galeus melastomus The blackmouth catshark (''Galeus melastomus'') is a species of catshark, and part of the family Scyliorhinidae, common in the northeastern Atlantic Ocean from Iceland to Senegal, including the Mediterranean Sea. It is typically found over the c ...

'' and the swordfish '' Xiphias gladius''. ''Stomias boa boa'' has large light-producing

photophore A photophore is a glandular organ that appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors, ...

s behind the eyes and other smaller ones scattered across the body in a geometrical pattern, mostly on the ventral surface. Special organs near the eyes detect the amount of illumination in the surrounding water and this enables the fish to adjust the amount of light its photophores emit. The

bioluminescence Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some b ...

can be turned on and off at will and may confuse potential

predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

. Other species of fish emit light in a similar way, and the particular arrangement of photophores in the scaly dragonfish permits individuals to identify other fish of the same species.

References

* Tony Ayling & Geoffrey Cox, ''Collins Guide to the Sea Fishes of New Zealand'', (William Collins Publishers Ltd, Auckland, New Zealand 1982) {{Taxonbar, from=Q3753776 Stomiidae Fish described in 1810