Built-in polarizers form part of a compass organ in spiders

Some insects and vertebrates use the pattern of polarized light in the sky as an optical compass. Only a small section of clear sky needs to be visible for bees and ants to obtain a compass bearing for accurate navigation. The receptors involved in the polarization compass are confined to a small pa...

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Bibliographic Details
Published in:Nature (London) 1999-09, Vol.401 (6752), p.470-473
Main Authors: Dacke, M, Nilsson, D.-E, Warrant, E. J, Blest, A. D, Land, M. F, O'Carroll, D. C
Format: Article
Language:English
Subjects:
Animal behavior
Arachnida
Arachnids
Araneae
Biological and medical sciences
Drassodes
Formicidae
Fundamental and applied biological sciences. Psychology
Humanities and Social Sciences
Invertebrates
letter
Morphology. Histology. Cytology
multidisciplinary
Science
Science (multidisciplinary)
Spiders
Zoology
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Summary:Some insects and vertebrates use the pattern of polarized light in the sky as an optical compass. Only a small section of clear sky needs to be visible for bees and ants to obtain a compass bearing for accurate navigation. The receptors involved in the polarization compass are confined to a small part of the retina, and the eyes are built predominantly for other visual tasks. Here we report the discovery of a unique compass organ in the spider Drassodes cupreus, where a pair of specialized secondary eyes cooperate to analyse skylight polarization. These eyes do not form images, but use a built-in polarization filter to determine precisely the direction of polarization. Measurements using a model eye indicate that the compass organ is best suited for navigation at dusk and dawn. Behavioural experiments show that the spiders are primarily active after sunset and that they use polarization cues to find their way back to the nest after foraging trips. A similar organization of the secondary eyes in several spider families indicates that such compass organs may not be an isolated phenomenon.
ISSN:0028-0836
1476-4687
DOI:10.1038/46773