How sharks see in the deep sea
Amy Newman from the University of Western Australia has discovered that the eyesight of deep sea sharks has evolved a variety of adaptations for finding food and avoiding getting eaten in the particular depths that they inhabit.
Presenting her work at the recent World Conference on Marine Biodiversity, Newman studied the light detecting cells, known as photoreceptors, in 7 species of deep water sharks all caught as incidentally as by-catch in trawling boats off the NW coast of New Zealand, from waters between 750 and 1100 m beneath the waves.
By examining the patterns of light receptors across the retina she found out a lot about how these sharks go about their daily lives, all that way down beneath the waves.
For example, she looked at the eyes of a very rare shark, the Beige catshark, which has only been found once before, which as well as another rare species, the McMillan's Catshark have a cluster of light detecting cells in a spot on their retina that allows them to catch sight of animals sneaking up on them from behind - and being fairly small sharks, around 50cm, it suggests that being able to spot a larger predatory shark approaching would be an excellent survival strategy.
Newman also found that all the species she looked at had a cluster of light detecting cells arranged to see clearly in the visual field right ahead of the shark - which would let them detect bioluminescent prey animals that they're prowling after.
The interesting thing about this research is how it's using detailed anatomical studies of dead specimens brought back up from the depths to understand more about the lives of animals that are otherwise extremely difficult to study in the wild as they roam around in the dark, deep seas.
Find out more:
World Conference on Marine Biodiversity