Image: Head of a Glasshead Barreleye

Head of a Glasshead Barreleye

Side view of the head of a Glasshead Barreleye trawled from a depth of around 1000 m on the abyssal plain in the southern Tasman Sea, between Tasmania and New Zealand. The translucent round structure is the primary eye.  The fish also has ancillary mirror-organs that collect light from the side and below.  The opening through which light passes is clearly visible.  The mirror-organs have guanine crystals and a 'retina' of sorts that bounce the light they detect back into the main eye or it may be detected by the mirror organ itself.  The fish essentially has 4 'eyes'.  View an excellent diagram on Wikipedia of the workings of the eyes of Dolichopteryx longipes, another species of barreleye.

Photographer:
Adrian Flynn
Rights:
© Adrian Flynn

Notes

The barreleyes are an unusual family of deepsea fishes, most of which have upwardly-directed eyes. The eyes detect the silhouettes of prey swimming above.

In Australia, the Glasshead Barreleye has been collected from bathypelagic and mesopelagic depths off New South Wales.

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Tags fishes, ichthyology, Rhynchohyalus natalensis, Glasshead Barreleye, Opisthoproctidae,