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Palpal urticating hairs in the tarantula Ephebopus

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  • Palpal urticating hairs in the tarantula Ephebopus


    Foelix, R., Rast, B. & B. Erb. 2009. Palpal urticating hairs in the tarantula Ephebopus: fine structure and mechanism of release.
    Journal of Arachnology. 37(3): 292-298.

    Abstract:
    The tarantula genus Ephebopus is exceptional with respect to its urticating hairs: they are located on the palps
    rather than on the abdomen, as is the rule for other Neotropical tarantulas. These urticating hairs occupy a small field of 1–
    2 mm2 on the medial side of the palpal femora. Each urticating hair measures 500–600 mm in length and 5–6 mm in
    diameter. Almost the entire hair shaft is studded with little barbs that point toward the hair tip. Urticating hairs arise from
    a slipper-shaped socket in the cuticle, at an angle of 25–30u. When the spider is threatened, it shows a brief palpal flick as a
    defensive reaction, whereby many urticating hairs are brushed off and fly through the air. These hairs do not have a
    preformed breaking point but become detached at the very base and are then pulled out from their sockets, like an arrow
    from a quiver. The actual release behavior occurs too quickly (0.1 s) to be followed by the naked eye. Video film analyses
    reveal that a single upward movement of the palps rubbing against the lateral surfaces of the spread chelicerae causes the
    dispersal of urticating hairs into the air.

    Take care,
    Eric

    PS. Martin Huber brought it to my attention that this was first published in German in the ARACHNE journal. Now we have an English version.
    Foelix, R., Rast, B & B. Erb. 2009. Über die Brennhaare von Ephebopus cyanognathus WEST & MARSHALL, 2000. ARACHNE 14(2): 4-13.
    Last edited by Eric Reynolds; 30-11-09, 08:08 PM. Reason: Edited to include abstract and correct error in the citation
    MY FLICKR

  • #2
    Hi,

    same aticle as this one?
    • FOELIX, R. F., B. RAST & B. ERB (2009): Über die Brennhaare von Ephebopus cyanognathus West & Marshall, 2000. ARACHNE 14(2): 4-13.

      Summary:
      Ephebopus species are exceptional with respect to their urticating hairs: they are the only tarantulas that have their urticating hairs on the palps rather than on the abdomen. This was discovered by Marshall & Uetz (1990) but detailed descriptions on the morphology of the urticating hairs and on the mechanism of the »palp flicking« response were lacking so far.
      We have used light and scanning electronmicroscopy to provide a fine structural analysis of these urticating hairs. Video films taken of the defense reaction of provoked spiders revealed the interactions between the pedipalps and the chelicerae. Apparently a single rapid upward stroke (0.1s) of the pedipalps against the chelicerae is sufficient to release a puff of airborne urticating hairs.


    all the best,
    Martin
    »ARACHNE« – The Journal of the German Arachnology Society

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