Field of Science

Leucicorus: FAKE EYES!

In an earlier post, I told you about the fishes known as brotulas. These are one of the most prominent groups of fish in the deep sea. They tend not to be attractive fish: their lack of outstanding dorsal and tail fins makes them look like something between an eel and a cod, and like many deep-sea fishes they look somewhat flabby and lumpish. There are numerous genera of brotulas out there; the individual in the photo below represents the genus Leucicorus.

Leucicorus atlanticus, from Okeanos Explorer.


Leucicorus belongs to the brotula family Ophidiidae, commonly known as the egg-laying brotulas though Leucicorus' own reproduction has (so far as I have found) not been directly observed. The feature that most immediately sets Leucicorus apart from other brotulas is the eyes: Leucicorus species have very large eyes but the actual lenses are rudimentary or absent (Cohen & Nielsen 1978). It almost looks like they grew bigger and bigger to cope with the low light of the deep sea before they just kind of gave up at some point.

Two species of Leucicorus are currently recognised, each known from separate parts of the world. Leucicorus lusciosus is found in the eastern Pacific, whereas L. atlanticus is known from around the Caribbean. The two species differ in meristic characters and proportions: for instance, L. lusciosus has more dorsal and anal fin rays, but fewer vertebrae and gill rakers, and has a deeper body (Nielsen & Møller 2007). Leucicorus has also been found in the vicinity of the Solomon Islands, but interestingly enough Nielsen & Møller (2007) identified the specimen found as L. atlanticus rather than L. lusciosus, despite the latter species' more proximate distribution. One wonders if perhaps a third species is involved, yet to be recognised.

REFERENCES

Cohen, D. M., & J. G. Nielsen. 1978. Guide to identification of genera of the fish order Ophidiiformes with a tentative classification of the order. NOAA Technical Report NMFS Circular 417.

Nielsen, J. G., & P. R. Møller. 2007. New and rare deep-sea ophidiiform fishes from the Solomon Sea caught by the Danish Galathea 3 Expedition. Steenstrupia 30 (1): 21–46.

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