Master student (Department of Life Sciences, National Chung-Hsing University, Taiwan)
Interactive effects of conspicuous body color and web decoration of Cyclosa ginnaga
Some animals use body coloration to improve foraging success or to enhance survival. In general, a conspicuous appearance for attracting the intended receiver would inevitably get the attention of unintended receiver such as predators. In this study, how the conspicuous appearance of an animal can exhibit prey attraction and predator defense functions was examined simultaneously. Juvenile Cyclosa ginnaga has bright silver body coloration and it builds a discoid decorations made of white silk bands on orb web. Most previous studies supported the prey attraction function of conspicuous body color in spider, whereas silk decorations function to attract prey or defense against predator is still under debate. I manipulated the color signals of silver dorsum and silk decoration of C. ginnaga and responses of prey and predators to each treatment were monitored by video cameras. Altering the color signal of spider silver dorsum by black paint significantly reduced prey interception rate, indicating that conspicuous body color of C. ginnaga functioned to visually attract Homoptera prey. Altering the color signal of discoid decoration did not affect prey interception rate but probability of ichneumon fly predator attacks were significantly increased. Since the reflectance spectrum of decoration was similar to that of C. ginnaga silver dorsum, decoration seemed to function to conceal the outline of the conspicuous spider and to make the spider discoid decoration combination look like a bird dropping to mislead the Hymenoptera predators. By adding a discoid decoration chromatically similar to the conspicuous body color, C. ginnaga eliminate the cost of increased predation risk without reducing the attractiveness of sliver dorsum.
Updated: Mar-10-2014 01:22:51 (Taiwan, GMT+08:00).