Aphyonidae is a family of eel-like fishes in the order Ophidiiformes

Ophidiiformes

Ophidiiformes is an order of ray-finned fish that includes the cusk eels , pearlfishes , brotulas , and others....

. They are found in tropical and subtropical waters throughout the world. They are deep-sea fishes, living between 2000 metres (6,561.7 ft) and 6000 metres (19,685 ft) depth.

Description and biology

Aphyonids are small fishes, typically about 10 centimetres (3.9 in) long when fully grown. They have transparent, gelatinous skin, which lacks any scales. The dorsal, caudal, and anal fins are united into a single ribbon. Most species are neotenic

Neoteny

Neoteny , also called juvenilization , is one of the two ways by which paedomorphism can arise. Paedomorphism is the retention by adults of traits previously seen only in juveniles, and is a subject studied in the field of developmental biology. In neoteny, the physiological development of an...

, showing a number of features as adults that are more commonly associated with fish larvae. For example, the skeleton is only partially calcified, and the muscles and gills are underdeveloped. The eyes, nasal organ, and lateral line

Lateral line

The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

 are also reduced, and they lack a swim bladder.

The aphyonids are viviparous, giving birth to live young. The males bundle their sperm into small sacs (spermatophore

Spermatophore

A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...

s), so that they can be stored for extended periods. This allows them to mate with immature females, which can there store the sperm inside the ovaries until they reach sexual maturity, and the eggs are ready to be fertilised. This unusual adaptation is likely a response to the difficulty of finding a mate in their dark and sparsely inhabited deep-sea environment.

Species

There are 22 species in six genera:

• Genus Aphyonus
  • Aphyonus bolini Nielsen, 1974.
  • Aphyonus brevidorsalis Nielsen, 1969.
  • Gelatinous blindfish, Aphyonus gelatinosus Günther, 1878.
  • Aphyonus rassi Nielsen, 1975.
• Genus Barathronus
  • Barathronus affinis Brauer, 1906.
  • Barathronus bicolor Goode
    George Brown Goode
    George Brown Goode , was an ichthyologist, although most of his time was spent as a museum administrator and he was very interested in the history of science, especially the history of the development of science in America. Goode graduated from Wesleyan University and studied at Harvard University...
    
     & Bean
    Tarleton Hoffman Bean
    Tarleton Hoffman Bean was an American ichthyologist, born at Bainbridge, Pennsylvania on 8 October 1846. He died in Albany, New York on 28 December 1916.-FAMILY AND EDUCATION :...
    
    , 1886.
    
  • Barathronus bruuni Nielsen, 1969.
  • Barathronus diaphanus Brauer, 1906.
  • Barathronus maculatus Shcherbachev, 1976.
  • Barathronus multidens Nielsen, 1984.
  • Barathronus pacificus Nielsen & Eagle, 1974.
  • Barathronus parfaiti (Vaillant
    Léon Vaillant
    Léon Louis Vaillant was a French zoologist. He is most famous for his work in the areas of herpetology, malacology, and ichthyology...
    
    , 1888).
    
  • Barathronus unicolor Nielsen, 1984.
• Genus Meteoria
  • Meteoria erythrops Nielsen, 1969.
• Genus Nybelinella
  • Nybelinella brevidorsalis (Nielsen, 1969).
  • Nybelinella erikssoni (Nybelin, 1957).
• Genus Parasciadonus
  • Parasciadonus brevibrachium Nielsen, 1984.
  • Parasciadonus pauciradiatus Nielsen, 1997.
• Genus Sciadonus
  • Sciadonus cryptophthalmus (Zugmayer
    Erich Zugmayer
    Erich Johann Georg Zugmayer was an Austrian zoologist and ichthyologist-Species described by Zugmayer:* Benthalbella infans Zugmayer, 1911* Cetostoma regani Zugmayer, 1914...
    
    , 1911).
  • Sciadonus galatheae (Nielsen, 1969).
  • Sciadonus jonassoni (Nybelin, 1957).
  • Sciadonus pedicellaris Garman, 1899.