The role of conspicuous markings in courtship of nocturnal fishing spiders Dolomedes raptor

• Main Authors: Lin, Tai-Shen, 林泰申
• Other Authors: Tso, I-Min
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/99702707256285122012

碩士 === 東海大學 === 生命科學系 === 100 === Previous studies investigating the function of conspicuous body coloration in spiders focus on orb-weaving spiders and the results show that such signal plays an important role in attracting prey. So far, few studies had examined the role of body coloration of nocturnal wandering spiders. More and more studies show that nocturnal terrestrial animals such as anurans and birds will use visual signal to communicate. The nocturnal fishing spider Dolomedes raptor exhibits sexual color dimorphism. Female has white hairs on metatarsus of first two pairs of legs and male has white stripes on both sides of cephalothorax. To realize the function of conspicuous coloration in male D. raptor, I first measured the spectra of this spider’s body coloration. I then manipulated the color signal of male spiders by using dummies constructed from papers with reflectance spectra similar to those of real spiders. The control dummies had white stripes while the experimental dummies did not and the responses of prey and female D. raptor to them were monitored by infrared video cameras. The results showed that in the field the control dummies attracted significantly more prey. However, the exact roles played by this conspicuous signal in the courtship of these nocturnal spiders are still unclear. To answer this question, I first collected mature male D. raptor from the field and measured their body size, weight, white stripe area and reflectance spectra to see whether individuals varied in these properties. Then I collected juvenile male and female D. raptor from the field and raised them individually under the same feeding conditions. When they matured I measured the body weight and took pictures of males and used GIMP 2 software to quantify the area and a spectrometer to measure reflectance spectra of white stripes. Males were divided into experimental (white stripes covered by brown paint) and control (brown paint on brown carapace) groups and females’ responses to them were determined by laboratory experiments. The results of field survey show that males in the field exhibited variations in their white stripes. In the laboratory experiment, whether males exhibited conspicuous white stripes or not significantly affected the acceptability of females. The results of nutrition manipulation experiments showed that males receiving high nutrition intake exhibited larger white stripes and matured faster. My results demonstrate that conspicuous body color of male D. raptor seems to serve as species recognition signal and male quality indicator. Therefore, visual signal also plays an important role in the courtship of nocturnal arthropods.