紅衣新郎：人面蜘蛛雄蛛體色功能初探

Abstract

吸引獵物假說過去在很多結網性蜘蛛的研究上得到證實，這些結網性蜘蛛會利用身上鮮艷的體色吸引昆蟲靠近蛛網。不過相關研究都僅針對雌性蜘蛛，而對雄性蜘蛛體色的研究則相當缺乏。性成熟之後的結網性蜘蛛雄蛛，在行為上和雌蛛有很大的差異，這些差異可能導致即使同樣在吸引假說的預期下，雄蛛的體色功能會有有別於雌蛛體色功能的目的。大人面蜘蛛雄蛛性成熟後會變成鮮豔的橘紅色，並且一直待在雌蛛網上等待交配機會。根據吸引假說，我預測大人面蜘蛛雄蛛鮮豔的體色可以吸引昆蟲靠近雌蛛的網，增加雌蛛的捕食率，進而延長雌蛛在該結網地停留的時間，最終可以提升雄蛛自己的交配成功率。我利用黑色塗料改變大人面蜘蛛雄蛛的體色訊號，並用攝影機在白天和晚上記錄昆蟲與蜘蛛網和雄蛛體色的互動，藉以探討雄蛛體色是否具有吸引昆蟲的功能。而為了確認吸引的效果是來自體色，不是其他因子，我製作蜘蛛紙片模型模擬大人面蜘蛛雄蛛的體色，進行相似的實驗。除了攝影外，我也持續追蹤雌蛛在同一個結網地停留的天數，以探討雄蛛體色對雌蛛結網地停留時間的影響。實驗結果顯示，雄蛛的體色在白天確實可以吸引昆蟲，而模型實驗則證實吸引的效應是來自於顏色，但是吸引效應並沒有影響雌蛛結網地的停留時間。或許後續需要更多研究來探討是什麼選汰壓力促使大人面蜘蛛雄蛛演化出鮮豔的體色來吸引昆蟲。

Prey attraction hypothesis had been tested on many orb web spider species in recent years, and the results show that conspicuous coloration of spiders may attract insects to the webs. However, all of these studies focus on female spiders rather than males. After reaching maturity, male spiders behave differently from females, so the body coloration of male spiders probably functions in ways different from that of female spiders . Male Nephila pilipes is conspicuous orange-red color and it seldom build its own web after reaching maturity but lives on female’s web waiting for copulating with female. I hypothesize that the conspicuous coloration of male N. pilipes may attract insects to female’s web and then increase the web site tenacity of female to increase male’s opportunity of mating. I manipulated the coloration of male N. pilipes and monitored the webs with male spiders by video cameras day and night and I also recorded the number of days a female stayed in a particular web site. In order to confirm if the attraction effect was caused by coloration instead of other factors, I made spider dummies resembling male N. pilipes in appearance and color. Results showed that the conspicuous coloration of male N. pilipes attracted insects to female’s web during day time, and similar results was found in dummy experiment. However, the prey attraction effect did not increase the web site tenacity of female spiders. Results of my study demonstrate the attraction function of body coloration of male N. pilipes. More researches are needed to realize the factors facilitating the evolution of conspicuous body colors in male N. pilipes.