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How spiders see the world

How spiders see the world
Photo Information
Copyright: Carmem Busko (carmem_busko) Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 76 W: 32 N: 91] (431)
Genre: Animals
Medium: Color
Date Taken: 2008-11-30
Categories: Spiders
Camera: Canon 40D, Canon 55-200mm EF f/4.5-5.6 II USM
Photo Version: Original Version
Date Submitted: 2009-01-11 13:57
Viewed: 4979
Points: 6
[Note Guidelines] Photographer's Note
Spiders usually have eight eyes (some have 6 or fewer), but few have good eyesight. Most are able to detect little more than light-dark intensity changes and rapid movement - enough to stimulate nocturnal web building, hunting or wandering activities, as well as to allow rapid reactions against daytime predators (e.g., by dropping from webs). Some spiders have median eyes that can detect polarised light and they use this ability to navigate while hunting. For most night-active spiders sight is unimportant compared with touch, vibration and taste stimuli.

For a few spiders good vision is vital for hunting and capturing prey and for recognising mates and rivals. They include the day active jumping spiders and flower spiders, and the wolf spiders and net-casting spiders, more often seen by twilight or later at night.

Types of eyes
Eight eyes are typically placed in two rows, on the front of the carapace. The AME or direct eyes, differ markedly in structure from the other indirect eyes (ALE, PLE, PME). The direct eyes appear dark, whereas the indirect eyes usually have a layer of light reflecting crystals, the tapetum, behind the light sensitive retina, giving these eyes a silvery appearance. The tapetum increases visual sensitivity because light entering the light sensitive retinal cells is immediately reflected back through them, so intensifying the image. These indirect eyes are adapted for seeing at low light intensities and their lenses are often enlarged in spiders with good vision. Spider eye lenses are better than photographic lenses in terms of their image brightness (very low F-numbers). However, because most spider eye retinas have relatively coarse-grained mosaics of receptor cells, their resolution of these images is much poorer than in the human eye.

Morigann, JoseMiguel, oscarromulus has marked this note useful
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Critiques [Translate]

Hello carmem,
this is a great capture with fine details and good DOF.
Vrey well done.

Hi Carmen,
Very interesting image of this spider.
I like the way it is surrounded by the web and the reflections on it.
So good the eye's details and the hairs on the legs.
Good work and thanks for share.
Best regards,

Hi Carmen,
Such detail!!!
Excellent work.
Loved your notes too.
Aires Mario saying thanks for sharing.

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