Alleged silk spigots on tarantula feet: Electron microscopy reveals sensory innervation, no silk

Foelix, Rainer F.; Erb, Bruno; Rast, Bastian

doi:10.1016/j.asd.2013.02.005

Cited by 8 publications

(4 citation statements)

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“…In some spider taxa, such as Mygalomorpha (see Table 1), Theridiidae, and Clubionidae, release of inner sensillum lymph from tip‐pore sensilla (“ribbed hair sensilla”) located on scopula (adhesive) pads was observed (e.g., Peattie, Dirks, Henriques, & Federle, 2011; Wolff & Gorb, 2016). Once released, receptor lymph may not only coagulate in and around the terminal pore but also extend from the pore forming “trails” (Foelix et al, 2013; Foelix, Rast, & Peattie, 2012; Peattie et al, 2011). These “trails” were erroneously considered to be silk threads, serving adhesion (e.g., see Gorb et al, 2006 and rejection by Foelix et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…Once released, receptor lymph may not only coagulate in and around the terminal pore but also extend from the pore forming “trails” (Foelix et al, 2013; Foelix, Rast, & Peattie, 2012; Peattie et al, 2011). These “trails” were erroneously considered to be silk threads, serving adhesion (e.g., see Gorb et al, 2006 and rejection by Foelix et al, 2013). Albeit, these findings indicate that small amounts of sensillum lymph are released through the terminal pore of the spider tip‐pore sensilla.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies showed that spiders possess tip‐pore sensilla only (e.g., Foelix, 1970, 2011, 2015; Foelix & Chu‐Wang, 1973a; Foelix, Erb, & Rast, 2013; Ganske & Uhl, 2018; Harris & Mill, 1973; Kronestedt, 1979; Pfreundt & Peters, 1981; Ross & Smith, 1979; Tichy, Gingl, Ehn, Papke, & Schulz, 2001), with one possible exception in a species‐poor and basally branching off taxon (Foelix et al, 1975). Consequently, based on the anatomical equipment alone, one might assume that spiders are not able to perceive volatile odours.…”

Section: Introductionmentioning

confidence: 99%

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Ultrastructure of chemosensory tarsal tip‐pore sensilla of Argiope spp. Audouin, 1826 (Chelicerata: Araneae: Araneidae)

Müller

Ganske

Uhl

2020

Journal of Morphology

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While chemical communication has been investigated intensively in vertebrates and insects, relatively little is known about the sensory world of spiders despite the fact that chemical cues play a key role in natural and sexual selection in this group. In insects, olfaction is performed with wall-pore and gustation with tip-pore sensilla. Since spiders possess tip-pore sensilla only, it is unclear how they accomplish olfaction. We scrutinized the ultrastructure of the trichoid tip-pore sensilla of the orb weaving spider Argiope bruennichi-a common Palearctic species the males of which are known to be attracted by female sex pheromone. We also investigated the congener Argiope blanda. We examined whether the tip-pore sensilla differ in ultrastructure depending on sex and their position on the tarsi of walking legs of which only the distal parts are in contact with the substrate. We hypothesized as yet undetected differences in ultrastructure that suggest gustatory versus olfactory functions. All tarsal tip-pore sensilla of both species exhibit characters typical of contact-chemoreceptors, such as (a) the presence of a pore at the tip of the sensillum shaft, (b) 2-22 uniciliated chemoreceptive cells with elongated and unbranched dendrites reaching up to the tip-pore, (c) two integrated mechanoreceptive cells with short dendrites and large tubular bodies attached to the sensillum shaft's base, and (d) a socket structure with suspension fibres that render the sensillum shaft flexible. The newly found third mechanoreceptive cell attached to the proximal end of the peridendritic shaft cylinder by a small tubular body was likely overlooked in previous studies. The organization of tarsal tip-pore sensilla did not differ depending on the position on the tarsus nor between the sexes. As no wall-pore sensilla were detected, we discuss the probability that a single type of sensillum performs both gustation and olfaction in spiders.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultrastructure of chemosensory tarsal tip‐pore sensilla of Argiope spp. Audouin, 1826 (Chelicerata: Araneae: Araneidae)

Müller

Ganske

Uhl

2020

Journal of Morphology

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“…The Theraphosidae family consists of hairy and often large spiders, which are capable of climbing on smooth surfaces, including perpendicular glass walls. This is enabled by their adhesive foot pads (scopulae) which can be found on both the metatarsal and tarsal leg segments in theraphosids (Foelix and Chu-Wang, 1975). An impor-tant structure of tarantula feet, similarly to many other wandering spiders (Wolff and Gorb, 2012), are claw tufts (also called pretarsal scopulae), which are defined as dense arrays of adhesive setae, located at the tip of the tarsus ventrally of the paired claws (Niederegger, 2013).…”

Section: Introductionmentioning

confidence: 99%

Claw tuft setae of tarantulas (Araneae, Mygalomorphae, Theraphosidae) and the production of fibrous materials. Do tarantulas eject silk from their feet?

Hajer

Řeháková

2019

BioComm

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The study focused on the specialised tarsal setae of tarantulas Avicularia metallica and Heteroscodra maculata, and the fibrous and non-fibrous material produced by them. When irritated spiders moved along smooth, perpendicularly-oriented glass walls not covered in silk, the claw tuft setae, located at the tips of the tarsal segments, left behind footprints containing two types of fibrous material. Using electron scanning microscopy, it was discovered that these represent fragments of parallelly oriented bundles of hollow fibres forming the shafts of the setae and their lateral branches (1), as well as clusters of contracted nanofibrils which aggregated at the ends of these fibres (2). During climbing, this fibrous material was detected both on the substratum on which the spiders were moving, and also on their claw tuft setae. The climbing activity of irritated tarantulas is also associated with the secretion of a fluid which dries on contact with air. This secretion acts as an adhesive and facilitates the movement of tarantulas on smooth surfaces, but while doing so it also glues together the distal, lamellar parts of the groups of setae which are in contact with the substratum during climbing. There are no such claw tuft setae morphological changes observed in undisturbed tarantulas, moving freely around their tube-like shelters and on the surfaces of objects covered with silk which they have produced. The sources of the air-drying secretion are probably the tubular fibres forming the shafts of pretarsal setae. The bundles of hollow fibres are an example of a system that produces secretions via a surficial pathway. The spinnerets and silk-producing glands associated with them, located in the opisthosoma, represent a system that produces silk via a systemic pathway. However, the results of observational studies have not confirmed the ability of tarantulas’ feet to produce silk fibres of the same, or at least similar ultrastructure to that of the silk fibres produced by the activity of spinnerets and spinneret-associated silk glands.

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Adhesive Features of the Theraphosid Tarantulas

Pérez‐Miles¹,

Perafán²,

Ortíz-Villatoro³

2020

New World Tarantulas

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Alleged silk spigots on tarantula feet: Electron microscopy reveals sensory innervation, no silk

Cited by 8 publications

References 20 publications

Ultrastructure of chemosensory tarsal tip‐pore sensilla of Argiope spp. Audouin, 1826 (Chelicerata: Araneae: Araneidae)

Ultrastructure of chemosensory tarsal tip‐pore sensilla of Argiope spp. Audouin, 1826 (Chelicerata: Araneae: Araneidae)

Claw tuft setae of tarantulas (Araneae, Mygalomorphae, Theraphosidae) and the production of fibrous materials. Do tarantulas eject silk from their feet?

Adhesive Features of the Theraphosid Tarantulas

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