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Foelix et al. – "Tarantula feet silk": alleged spigots are probably chemoreceptors

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  • Foelix et al. – "Tarantula feet silk": alleged spigots are probably chemoreceptors

    Foelix, R. F., B. Rast & A. M. Peattie. 2012. Silk secretion from tarantula feet revisited: alleged spigots are probably chemoreceptors. Journal of Experimental Biology (April 1, 2012) 215, 1084–1089. doi: 10.1242/​jeb.066811

    Abstract. 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.

    Also, here is an article which basically summarises the above:​jeb.071597

    The DOIs apparently are not working so: and
    Spider Myths | Curious Taxonomy | The World Spider Catalog - Theraphosidae

    "We are all taxonomists." -Judith Winston
    "The laws of biology are written in the language of diversity." -Edward Osborne Wilson
    "Principle of Priority - the oldest fool is always right!" -H. Segers & Y. Samyn