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The Journal of Experimental Biology 204, 2481-2490 (2001)
© 2001 The Company of Biologists Limited

Review

Polarized light detection in spiders

Marie Dacke1,*, Thuy A. Doan2 and David C. O’Carroll2

1 Department of Zoology, University of Lund, Helgonavägen 3, S-223 54 Lund, Sweden and
2 Department of Zoology, University of Washington, Box 351800 Seattle, WA 98195, USA

*Author for correspondence (e-mail: marie.dacke{at}zool.lu.se)

Accepted April 19, 2001

We describe here the detection of polarized light by the simple eyes of spiders. Using behavioural, morphological, electrophysiological and optical studies, we show that spiders have evolved two different mechanisms to resolve the e-vector of light. Wolf spiders (Lycosidae), are able to turn in response to rotation of a polarized pattern at the zenith of their visual fields, and we also describe a strip in the ventral retina of the principal (anterio-median) eyes that views this location and has receptors tiered into two layers. This provides each pair of receptors with a similar optical solution to that provided by the ‘dorsal rim area’ of the insect compound eye. In contrast, gnaphosid spiders have evolved a pair of lensless secondary eyes for the detection of polarized light. These two eyes, each sensitive to orthogonal directions of polarization, are perfectly designed to integrate signals from the larger part of the sky and cooperate to analyse the polarization of light. Built-in polarizers help to improve signal purity. Similar organisation in the eyes of several other spider families suggests that these two mechanisms are not restricted to only a few families.

Key words: polarized light detection, simple eye, spider, vision, retinal tiering.






© The Company of Biologists Ltd 2001