Crabs: A Global Natural History by Peter J. F. Davie

Author:Peter J. F. Davie
Language: eng
Format: mobi, epub, azw3
Tags: Non-Fiction, Biology, Ecology, Animals, Reference, Science, Marine Life, Anatomy & Physiology, Illustrated, Natural History, Fauna
ISBN: 9780691230139
Publisher: Princeton University Press
Published: 2021-12-07T00:00:00+00:00

SEEING IN THE DARK

The eyes of hydrothermal vent crabs such as Austinograea are unique within the Brachyura. In the pitch darkness, normal vision is impossible, and like crabs that live in caves, their eyes are substantially atrophied, with the eyestalk fixed rigidly in the orbital socket. Research shows that the crab’s planktonic zoeae larvae – which develop in the mesopelagic (or twilight) zone, closer to the surface – have essentially normal crab eyes, with visual pigment sensitive to the blue light spectrum of the water depth in which they occur. By the time the crabs have become adult and settled around the vents, however, they have lost all image-forming capability, and instead have developed unique, highly sensitive ‘naked-retina’ eyes, better able to detect light produced by hydrothermal vent chemistry in the near-infrared portions of the spectrum.

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