無脊椎捕食者的學習可塑性：一種跳蛛能夠學習要不要吃紅色的獵物

標題：Flexible color learning in an invertebrate predator: Habronattus jumping spiders can learn to prefer or avoid red during foraging

摘要

Understanding the design of prey defenses, such as aposematic colors, involves considering perceptual and cognitive abilities of predators that drive their evolution. Research has focused on avian predators, with little attention to small invertebrate predators. Jumping spiders are abundant and voracious; here, we examined their ability to learn, remember, and generalize color from interactions with aposematic prey. First, we demonstrated that Habronattus pyrrithrix can learn to avoid red, aposematic milkweed bugs. Then, we asked whether exposure to either palatable or unpalatable red prey can drive generalized color biases. Spiders were assigned to one of 3 diets that included exposure to 1) distasteful red milkweed bugs (fed milkweed seeds), 2) palatable red milkweed bugs (fed sunflower seeds), or 3) white-eyed Drosophila only (control). After exposure, we tested spiders for red biases using artificially colored crickets. In our first color-learning experiment, field-collected adult spiders did not exhibit generalized color biases. However, in a second (similar) experiment with lab-raised juveniles, we found evidence of generalized color learning: Group 1 demonstrated red aversion, Group 2 demonstrated red preference, and Group 3 showed no bias. Finally, we examined persistence of memory and found that learned aversions to milkweed-fed bugs lasted less than 2 weeks if they were not continuously reinforced. We discuss our findings in the context of predator psychology and suggest that jumping spider color generalization may differ from that of avian predators. Such invertebrate predators should be considered more when thinking broadly about the evolution of prey color.

很多的研究與很多的例子告訴我們，警戒色與擬態的基本配色就是紅、黃、黑，捕食者似乎也自然而然的接受別去招惹這類的獵物，這個現象可能是因為捕食者天生就對某些顏色偏好或厭惡。若是前者，就需要捕食者的判斷以及學習，若是後者，則無關捕食者聰不聰明，反正天生就是討厭這類東西。討論這樣的問題的時候，一般說來會想到的是高等脊椎動物，因為視力好，行為容易觀察，並且確定有某種程度的心智力。但比起脊椎動物來說，數量更多的無脊椎動物反而討論的少，主要是因為對於其視覺系統難以想像，以及比起脊椎動物來說，更豐富的行為多樣性。

這篇文章以一種跳蛛(Habranattus pyrrithrix)為研究對象，跳蛛主要是以兩顆大大的前中眼做為判別周遭情況的受器，比起很多昆蟲與蛛型綱物種來說，視力算是極佳，但問題在於這樣的視力是不是能判別某些顏色，而喜歡或厭惡這些顏色又是來自天生內在的或是後天學習的。這個實驗設計三個不同的處理，分別是餵食馬利筋的椿象（代表有毒），餵食向日葵的椿象（代表無毒），以及白眼果蠅（控制組），分別給跳蛛取食這三種不同的獵物。結果顯示跳蛛對於有毒的獵物產生避忌，而對無毒的獵物有偏好，控制組則沒有明顯差異。也就是說，如果獵物外觀一樣，跳蛛是透過學習來判斷獵物是否能吃，而非透過天生的偏好，而且對於紅色也沒有特殊的偏好。

這樣的研究提醒我們，除了一直認為的脊椎動物可能推動警戒色與擬態的演化，無脊椎動物也可能有重要的生態角色

意思就是未來要考慮的事情越來越多，實驗越來越難做了（嘆）。