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Malacosteus niger

Malacosteus is a genus of deep-sea fish from the family of baleen dragon fish ( Stomiidae ) Unterfam. Malacosteinae.

Species

Of the four species originally described are still two valid: Malacosteus niger, which occurs with the exception of the Mediterranean world in all oceans between 66 ° N and 30 ° S latitude at depths of 500-3900 meters, and Malacosteus australis, of between 25 ° and 45 ° south latitude at depths of 500 to 2000 meters lives. The types differ from one another in the number of their light organs. In the Atlantic and the Pacific M. australis replaced south of 30 ° S, its sister species. In the Indian Ocean, both species live sympatrically.

Features

Body

Malacosteus species have a black, elongated, tapering to the rear body which can reach a length of up to 25 centimeters. Your skin is thin and without scales. Dorsal and anal fins located far back, just before the small tail fin. The dorsal fin is supported by 18 to 20, the anal fin 19 to 22 fin rays. Breast and pelvic fins are medium in size and are supported by three or four or six fin rays.

Head

The head is small ( 7.8 to 12.3 % of standard length ), the eyes large ( 4.3 to 6.9 % of standard length ). The muzzle is short and blunt, the mouth large column - it extends far beyond the eyes and can reach a quarter of the body length. Depending on a single round outer nostril is before the eyes. The palatine bone is not ossified and toothless. The teeth in the upper jaw are tiny, the lower jaw of different sizes. In front in the lower jaw are some razor-sharp, enlarged and curved backwards fangs that can reach a length of 2.1 to 7.5 per cent of standard length. All teeth are immobile and can not be " collapsed ". Lower jaw Malacosteus species bear no Bartel unlike other baleen dragon fish. There is no floor of the mouth skin between the mandibular branches. The number of Branchiostegalstrahlen is seven to ten. For the function of the jaw apparatus see Malacosteinae.

Light organs

Below the eye is a large teardrop- shaped light organ that emits red light is ( generating unclear ). Behind it there is a blue light radiating oval light organ, which is greater in male fish than in female. A tiny, white light emitting light organ located between the eye and the red light organ. Two rows of small, white light organs extend along the sides of the body.

The red light-emitting, teardrop-shaped light organ is unusual for deep-sea organisms and a unique feature of the three Malacosteinae genera. All three genera can also see light in the red spectral range, in contrast to all other deep sea organisms. In Malacosteus niger two special visual pigments were found to perceive the wavelengths of 520-540 nm, and another visual pigment, which has an absorption maximum at 670 nm. Thus, there is an exclusive light spectrum for intraspecific communication for the three genera. May facilitate the red light organ also foraging by potential prey, especially copepods in Malacosteus is ( Copepoda ), illuminated and perceived without the prey noticing.