Image: 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.
- Adrian Flynn
- © Adrian Flynn
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.