Neue Kantonsschule Aarau, Biology Department, Aarau, Switzerland.
J Exp Biol. 2012 Apr 1;215(Pt 7):1084-9. doi: 10.1242/jeb.066811.
Controversial views have been expressed about whether tarantula feet can secrete fine silk threads that could prevent them from falling off smooth vertical surfaces. Two studies have claimed that 'ribbed hairs' on the tarsi of tarantulas produce silk. We examined these ribbed hairs in several tarantula species using light and scanning electron microscopy, and compared them with the silk-producing spigots on the abdominal spinnerets. We found that, morphologically, these ribbed hairs correspond very closely to known chemosensitive hairs in spiders; they have a distinct socket, a bent hair shaft with fine cuticular ridges, an eccentric double lumen within the hair shaft, and a blunt tip with a subterminal pore. Spigots on the spinnerets have a large bulbous base instead of a socket, a long shaft with a scaly surface and a central terminal pore. We never observed any silk threads coming out of these ribbed hairs under the electron microscope. By contrast, silk threads exiting the spigots on the spinnerets were common. Interestingly, ribbed hairs also occur on the spinnerets, often side by side with the silk-producing spigots. Our conclusion is that the ribbed hairs are chemoreceptors, not spigots. Observations of live tarantulas clinging inverted to glass coverslips confirmed that some substance is produced by the ribbed hairs, but it remains unclear whether this secretion is actually silk. In any case, the thousands of adhesive setae on the tarsi of legs and pedipalps almost certainly far outweigh any potential contribution from the sparsely distributed trails secreted by the ribbed hairs.
关于狼蛛的腿是否能分泌出细小的丝线，从而使其不会从光滑的垂直表面掉落，人们对此存在争议。有两项研究声称，狼蛛跗节上的“脊状毛”能产生丝。我们使用光学显微镜和扫描电子显微镜检查了几种狼蛛物种的这些脊状毛，并将其与腹部纺器上产生丝的喷丝头进行了比较。我们发现，从形态上看，这些脊状毛与蜘蛛中已知的化学敏感毛非常相似；它们有一个明显的窝，毛发轴弯曲，有精细的角质脊，毛发轴内有偏心的双腔，尖端钝，有亚末端孔。纺器上的喷丝头有一个大的球茎状基部，而不是窝，有一个长的轴，表面有鳞片，中央有一个末端孔。在电子显微镜下，我们从未观察到这些脊状毛中有任何丝线出来。相比之下，从纺器上的喷丝头中出来的丝线则很常见。有趣的是，脊状毛也出现在纺器上，通常与产生丝的喷丝头并排出现。我们的结论是，这些脊状毛是化学感受器，而不是喷丝头。观察到活的狼蛛倒挂在玻璃盖玻片上，这证实了一些物质是由脊状毛产生的，但目前还不清楚这种分泌物是否真的是丝。无论如何，腿和触肢跗节上数以千计的粘性刚毛，几乎肯定比由脊状毛稀疏分泌的痕迹产生的任何潜在贡献都要大得多。
