Family Platytroctidae
Taxonomy: Moderately large family of rare deepwater fishes with 37 species in 13 genera; 4 genera and at least 6 species in Australian waters.
Distribution, ecology and habitat: Worldwide over continental slopes, submarine rises, seamounts; bentho-, bathy- or mesopelagic in slope and abyssal depths, most in 1000-3000 m; some juveniles and smaller species often in the open ocean, usually in 800-2000 m.
Characteristics:
Body soft, elongate, usually laterally compressed, head naked in most, eye moderate to large, aphakic aperture well-developed; jaw teeth small, in single series, gill openings wide; shoulder area between lateral line and pectoral fin-base with a modified scale supporting a conspicuous, short, black tube producing luminous fluid; single dorsal fin well posterior over similar anal fin, pectoral fins low on body, pelvic fins abdominal, caudal fin forked, no adipose fin; body scales cycloid, lateral line system subcutaneus, visible as a series of tiny pores; some species with serial photophores on head and ventral profile.
Size: Reach 35 cm, usually between 10 and 25 cm.
Food and feeding: Little known.
Reproduction and early life history: Eggs large, larval development direct. Larvae, long, slender, rare, distinguished from similar alepocephalid larvae in having black luminous sac and shoulder tube opening clearly visible in ery small larvae. Photophores if present appear in yolk-sac stage (13-15 mm SL); postflexion stage persists until pectoral fins are almost fully formed (up to 30 mm SL).
Fisheries: Rare fishes of no commercial importance occasionally taken by deepwater trawls; one species, Persparsia kopua, moderately abundant.
Remarks: Tubeshoulders are externally very similar in appearance to many of the common and abundant slickheads (family Alepocephalidae); differ from slickheads in having a tube supported by a modified lateral-line scale at the shoulder, leading to a sac containing luminous fluid. This blue-green luminous fluid is produced from the black shoulder sac apparatus under the shoulder girdle. Unlike slickheads, tube-shoulders do not form groups or schools.
Australian species:
- Holtbyrnia laticauda Sazanov, 1976 Tusked Tubeshoulder CAAB 37115002
- Maulisia acuticeps Sazonov, 1976 Sharpsnout Tubeshoulder CAAB 37115005
- Maulisia mauli Parr, 1960 Maul's Tubeshoulder CAAB 37115003
- Maulisia microlepis Sazonov & Golovan, 1976 Smallscale Tubeshoulder CAAB 37115006
- Persparsia kopua (Phillipps, 1942) Spangled Tubeshoulder CAAB 37115001
- Platytroctes apus Günther, 1878 Legless Tubeshoulder CAAB 37115004
References:
Matsui, T. & R.H. Rosenblatt. 1987. Review of the deep-sea fish family Platytroctidae (Pisces: Salmoniformes). Bull. Scripps Inst. Oceanogr. Univ. Calif. 26: i-iv + 1-159.
Sazonov, Yu. I. 1999. Family Platytroctidae. In Carpenter, K.E. & V.H. Niem. Species identification guide for fisheries purposes. The living marine resources of the western central Pacific. Batoid fishes, chimeras and bony fishes part 1 (Elopidae to Linophrynidae). FAO, Rome.
Sazonov, Yu. I., A.A. Balanov & V.V. Fedorov. 1993.Alepocephaloid fishes (Alepocephaloidei) from the western North Pacific Ocean. Trudy Inst. Okeanol. Akad. Nauk SSSR 128: 40-68. [In Russian, brief English summ.]