Bathylychnops exilis

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Bathylychnops exilis
Bathylychnops exilis.gif

Bathylychnops exilis

Systematics
Overcohort : Clupeocephala
Cohort : Euteleosteomorpha
Order : Golden salmon (Argentiniformes)
Family : Ghostfish (Opisthoproctidae)
Genre : Bathylychnops
Type : Bathylychnops exilis
Scientific name
Bathylychnops exilis
Cohen , 1958

Bathylychnops exilis is a deep sea fish species from the ghost fishfamily(Opisthoproctidae). It lives in the Atlantic, north of the Azores and in the northern Pacific on the coasts of British Columbia and California , Japan and in the central northern Pacific. The fish live pelagically in the mesopelagial at depths of 100 to 1000 meters. Eggs and larvae are also pelagic.

features

With a maximum length of 50 cm, Bathylychnops exilis is the largest representative of the ghost fish. Its body is transparent and elongated like a pike, the dorsal and anal fins sit far back. These are supported by 13 to 16 soft dorsal rays and 10 to 14 soft anal rays. The number of vertebrae is 78 to 84, that of the Branchiostegal rays 2. The muscles of Bathylychnops exilis are well developed and suggest an active swimmer, while most other deep-sea fish are rather sluggish.

eyes

The closely spaced, large eyes of Bathylychnops exilis are remarkable. They reach a diameter of 3% of the body length and are equipped with a strange, spherical outgrowth in the lower half. Originally these outgrowths were held for luminous organs (where the name comes from: βαθύ "deep" (deep sea), λύχνος "lantern", ὄψ "eye"; exilis "lean") until a lens and a retina were found in them. The outgrowths form additional eyes pointing downwards and probably serve to detect predators coming from the depths that could pose a threat to the fish. The main eyes are upward and likely allow stereoscopic vision. The lenses of the additional eyes reach half the diameter of the main eye lenses. The retina of the additional eyes has grown on the lower edge of the main eye retina. There is only one optic nerve .

literature

  • WG Pearcy, SL Meyer, O. Munk: A 'four-eyed' fish from the deep-sea: Bathylychnops exilis Cohen, 1958. In: Nature. Volume 207, Number 5003, September 1965, pp. 1260-1262, PMID 5884641 .
  • IR Schwab, V. Ho, A. Roth, TN Blankenship, PG Fitzgerald: Evolutionary attempts at 4 eyes in vertebrates. In: Transactions of the American Ophthalmological Society. Volume 99, 2001, pp. 145-156, PMID 11797302 , PMC 1359005 (free full text).

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