The source of chilopod sensory information: External structure and distribution of antennal sensilla in Scutigera coleoptrata (chilopoda, Scutigeromorpha)

Abstract

The investigation of the antennae of Scutigera coleoptrata (Linnaeus, 1758) by scanning electron microscopy (SEM) revealed the presence of five types of sensilla: sensilla trichodea, beak-like sensilla, cone-shaped sensilla brachyconica on the terminal article, sensory cones at the antennal nodes, and the shaft organ. Alongside the presence and absence of antennal sensillar types, three unique characters were found in the Scutigeromorpha: the presence of long antennae with nodes bearing sensory cones, the presence of a bipartite shaft including the shaft organ, and the presence of beak-like sensilla. Neuroanatomical data showed that the animals' brains are equipped with well-developed primary olfactory and mechanosensory centers, suggesting that the antennae must be equipped with specialized sensilla to perceive chemosensory and mechanosensory cues. With the evidence provided in this article for the Scutigeromorpha, SEM data are available at last on the antennal sensilla for all five chilopod taxa, allowing a comparative discussion of antennal morphology in Chilopoda.

The ultimate legs of Chilopoda (Myriapoda): a review on their morphological disparity and functional variability

“…Also, the differentiation of the two tarsi in up to 500 annuli (i.e., tarsomeres; Figs. 3B , 3C ) in Scutigera coleoptrata is well within the range of the number of antennomeres ( Latzel, 1880 ; Verhoeff, 1902 ; Sombke et al, 2011 ; note that Verhoeff only counted 200). In other species like Pilbarascutigera incola (Verhoeff, 1925) 359 tarsomeres have been counted ( Edgecombe & Barrow, 2007 ) while in Ballonema gracilipes Verhoeff, 1904 the tarsi are composed of 144 annuli ( Verhoeff, 1902 ).…”

“…For SEM images, specimens of Lithobius forficatus and Cryptops hortensis were collected in Greifswald (Germany), processed after the protocol by Sombke et al (2011) , and examined with a Zeiss EVO LS10 at the Imaging center of the University of Greifswald. For macro-images, specimen were fixed in 70% ethanol and analyzed using the BK PLUS Lab system (Dun Inc., http://www.duninc.com/bk-plus-lab-system.html ) with a customized Canon MPE 65 mm 1–5× micro-photography lens mounted on a Canon 6D camera.…”

“…The ultimate legs are always held in parallel or oblique to the substrate, similar to the posture of the antennae ( Fig. 2 ; Sombke et al, 2011 ), solely touching the ground in a “probing” manner. Occasionally, the animals can be observed making fast twitching up and downward movements with their ultimate legs which, at least in its appearance, bears a strong resemblance to the antennal flicking of crustaceans (e.g., Koehl, 2011 ; Waldrop & Koehl, 2016 , and own observations).…”

“…Usually tarsus 2, but also tarsus 1 (in Scutigeromorpha), is subdivided into a multitude of annuli, literally transforming the leg into an antenniform appendage that bears an as yet unspecified array of sensilla and trichomes. In various species of Scutigeromorpha, the ultimate legs are about twice as long as the walking legs and may reach or even surpass the length of their antennae ( Snodgrass, 1952 ; Lewis, 1981 ; Sombke et al, 2011 ) ( Fig. 1A ).…”

New avatars for Myriapods: Complete 3D morphology of type specimens transcends conventional species description (Myriapoda, Chilopoda)

“…A close examination of these prefemoral setae (Fig 5B in [ 9 ]) inspired us to compare them with the sensilla trichodea described on the antenna of various centipede species, i.e. Lithobius forficatus (Linnaeus, 1758), Scutigera coleoptrata (Linnaeus, 1758) and Cryptops hortensis (Donovan, 1810) ([ 18 ], [ 19 ], [ 20 ], respectively). These sensilla are generally assumed to have a mechano- and chemoreceptive function (and are named as such), a role very plausibly also played by the prefemoral ones.…”