前人針對蜘蛛身上鮮艷色彩功能的研究顯示結網型蜘蛛其鮮豔色彩對於其獵物捕食扮演著重要的角色，然而針對徘徊型蜘蛛體色功能的探討則非常少。越來越多的報導顯示夜行性動物像是鳥類與青蛙似乎會在晚上利用視覺訊號來溝通。而夜行性溪狡蛛 （Dolomedes raptor） 其成熟個體有明顯的雌雄二型性，成熟雌性在第一、二對步足的前端具有白色色斑；成熟的雄性則是在頭胸部上形成白色的環狀色斑。為探討此顏色訊號之功能，我首先利用視覺生理方法量化其體表光訊號；並利用與溪狡蛛體色相仿之色紙做成有白環(n = 35) 及無白環的蜘蛛模型(n = 46) 並利用夜視攝影機進行監控，探討體色視覺訊號所扮演之角色。而色斑操控的結果顯示在不同模型處理中，具白環者有較高之獵物靠近率，但此訊號在求偶中扮演何種角色仍不清楚。為回答此問題，我首先在野外採集成熟雄性個體攜回實驗室進行體型大小、重量、色斑面積及色斑光譜特性等各式型值的測量，來探討是否野外之族群在體色訊號上具變異性且與體型具特定關係。我接著在野外採集未成熟的雌性與雄性個體於實驗室固定條件下單獨飼養至成熟，在拍照後利用GIMP 2進行型值測量與色斑面積的量化，並同時利用光譜儀量化色斑的光譜性質，然後進行操縱色斑的求偶實驗。實驗組利用與體色相似的棕色顏料去除色斑訊號，而控制組則會把顏料塗在背甲的棕色部位上以避免氣味的影響，並利用夜視攝影機記錄。野外的調查結果顯示雄性色斑在環境中具有變異，從色班操縱實驗結果顯示出雄蛛色班的有無會顯著影響雌蛛交配的接受程度；而雄蛛營養操控實驗的結果顯示，在不同營養處理下雄蛛在第二性徵上的訊號會根據營養好壞而有所差異，並會影響雄蛛蛻皮時間的快慢。綜合以上結果，雄蛛鮮明的體色在其求偶時似乎可做為物種識別之訊號及品質高低之指標，顯示視覺訊號在夜行性節肢動物的求偶過程中亦扮演重要角色。 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.
