Tiny spiders have different mechanisms for recognizing colors

Jurgen Otto | Wayne P. Maddison/Wikimedia Commons Two species of the Australian spider Maratus (above and right) and one of the Habronattus species from North America (below): retina cells to see blue and redJurgen Otto | Wayne P. Maddison/Wikimedia Commons

Different species of jumping spiders, smaller than a thumbnail, have distinct mechanisms for seeing colors, according to a study by the University of Cincinnati (UC) in the United States. “It’s very rare to see bright colors on most spiders, as they don’t usually have the visual sensitivity to perceive color beyond drab blues, greens and browns,” says Nate Morehouse, a biologist at UC, in a statement to the National Science Foundation, the federal agency that funded the study. “But certain groups of jumping spiders deviate from this pattern. They recognize reds, yellows and oranges, and the males display their bodies with bright colors that they use during courtship dances.” The males also exhibit abdomen appendices that move like airplane flaps. Researchers identified various selection mechanisms and combinations of colors in the eyes of the spiders of the two genera studied – the Habronattus of North America and the Maratus of Australia, both of the Saticidae family, with 5,000 species. The visual systems evolved independently. Habronattus have a filter that is sensitive to red, which produces a new type of retina cell that sees red. Maratus have no filters, but they have two additional types of photoreceptors, one-blue sensitive and one red-sensitive. The UC team characterized the sensitivity of spiders to colors using microspectrophotometry by measuring photoreceptor cells in the retina directly and by mathematically modeling the visual system.