Australian Super Spider Colours!
Doekele G. Stavenga, Jurgen C. Otto and Bodo D. Wilts of the Universities of Groningen and Fribourg (Netherlands and Switzerland respectively) have studied the Splendid coloration of the peacock spider , Maratus splendens, from Australia, very diligently. The vision of this beautiful species matches the brightness of the coloration in the male His scales have white, cream and red pigments while there are also blue scales which have special optical properties to produce their colour.
The specimens were taken from the vicinity of Sydney, NSW, and single scales from the body examined. Using an imaging scatterometer, the reflections were studied by focussing a white light beam onto a 13 mu m area of the scale. Light as well as scanning EM micrographs were also taken and a microspectrophotometer supplied measurements of transmittance spectra. The results indicated that the scales had spiny extensions that scatter light in a diffuse way. The blue-reflecting scales had a convex surface, but need further investigation as they are basically transparent, formed as flattened tubes with a significant air layer and producing the same effect as an anti-reflective coating. This subtle effect of colour in the iridescent blue scales is thought to be unique to this spider with the nanostructure producing amplified reflected light whose colour never fades. The specific pigments producing white, cream, and red colours were also found in the other scales.
The effect of the display is found in the sensitivity of the eye to ruby red colour and it acts as a functionally trichromatic system, with a rich set of photoreceptors.
The puzzle of the violet-blue scales remains to be solved, however, with the likely blue and red receptors within the spider eye able to distinguish their beauty as well as we do. We certainly look forward to reports of more progress on eyes such as these that can record as much as mammalian eyes, or probably much more! The squid and other molluscs have eyes and colours we need to study more, but the spider and the insect obviously have just as much to offer science. Here were some spiders trying out Spider Sociability, which may surprise some of us as much as these beautiful colours!
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