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. 2022 Sep 1;13(9):799.
doi: 10.3390/insects13090799.

Ultra-Morphology and Mechanical Function of the Trichoideum Sensillum in Nabis rugosus (Linnaeus, 1758) (Insecta: Heteroptera: Cimicomorpha)

Shashikanth Chakilam  1 , Jolanta Brożek  2 , Łukasz Chajec  2 , Izabela Poprawa  2 , Rimvydas Gaidys  1
Affiliations

Ultra-Morphology and Mechanical Function of the Trichoideum Sensillum in Nabis rugosus (Linnaeus, 1758) (Insecta: Heteroptera: Cimicomorpha)

Shashikanth Chakilam et al. Insects. .

Abstract

The present study aims to investigate the morphological features of the antennal sensilla by using SEM and TEM. The construction of a 3D model of trichoideum sensillum using Amira software is presented in this paper. Five sensillum types, namely trichoideum, chaeticum, campaniformium, coeloconicum, and basiconicum, were recorded. This model exhibits the mechanosensillum components, including the embedded hair in a socket attached by the joint membrane and the dendrite connected to the hair base passing through the cuticle layers. TEM images present the dendrite way, micro-tubules inside the dendritic sheath, and terminal structure of the tubular dendrite body and so-called companion cells included in the receptor, e.g., tormogen and trichogen. The parameters noted for the external structure and ultrastructure of the mechano-receptor indicate that they are specific to a particular type of sensillum and would be useful in developing the model for a biosensor. Results show that bio-inspired sensors can be developed based on morphological and ultrastructural studies and to conduct mechanical studies on their components.

Keywords: 3D model; N. rugosus; mechanoreceptor; morphology; scanning electron microscopy; transmission electron microscopy; trichoideum sensillum.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Photograph of N. rugosus antennae: (a) different antennal segments (scapus (s), pedicel (p), first flagellum (f1), second flagellum (f2)); (b) magnification of sensillum types of the scape; chaetic sensillum (ChS) and basiconic sensilla aporous (BSa). (c) Magnification of sensillum types of the pedicel (p); chaetic sensillum (ChS) and campaniform sensillum (CS). (d) Magnification of the first flagellum (f1). (e) Magnification of sensillum types of the second flagellum (f2); chaetic sensillum (ChS). (f) Magnification of sensillum types of the proximal part of the pedicel; trichoid sensilla (TSa). Scale bar members of the antenna (b–e) show the same magnification.
Figure 2
Figure 2
Photograph of N. rugosus antennae: (a) magnification of the scapus with trichoid sensilla (TSa); (b) magnification of the pedicel with trichoid sensilla (TSa) in the distal part; (c) magnification of the trichoid sensilla (TSa) and trichoid sensilla (TSp1, TSp2) on the first flagellum; (d) magnification of the trichoid sensilla (BSp, TSp1) on the second flagellum; (e) magnification of the porous surface of the trichoid sensilla and groove surface of the trichoid a porous sensilla (TSa) with the flexible socket (fs); (f) inflexible socket of sensillum (ifs); (g) coeloconic sensillum (CoS) observed on two flagellomeres.
Figure 3
Figure 3
Different length of Sensilla (TSa) and shape of the flexible socket (fs) and (a) arrangement of the trichoid sensilla in the proximal and medium part of the pedicel; (b) arrangement of the trichoid sensilla in the distal part of the pedicel; (c) position of the sensilla embedded in the socket on the surface of the pedicel; (d) base part of sensillum with the membrane after removing it from the socket, when suspension fibre (sf) is visible; (e) size of the lumen after removing of the sensillum; (f) broken sensillum and diameter of the stem of the sensillum near its base.
Figure 4
Figure 4
Microscopic photograph of the ultra-section of the flexible socket and termination of the tubular body of trichoideum sensillum in N. rugosus, longitudinal section by part of the pedicel: (a,b) trichoideum sensillum visible from the cuticular side; (c,d) further longitudinal section, with the shape of the socket and membrane visible in the deeper layer of the cuticle; (e,f) inner side of the socket and lymph cavity (lm) and part of the dendrite of the mechanoreceptor; (g,h) dendritic way (Ds) and tubular body terminated at the base of the trichoideum sensillum; (i) magnification of the other trichoid sensilla and the base of the sensillum in the socket. Cl, cuticular layer; f, flexible socket (fs) in trichoideum sensillum (TSa); el, epidermal layer; mb, socket membrane; ss, socket septum.
Figure 5
Figure 5
TEM photograph explores the ultrastructure of a longitudinal/oblique section of the flexible socket and section of the tubular body of trichoideum sensillum of N. rugosus antennae: (a) section by flexible socket, where the shape of the membrane and suspension fibre is visible; (b,c) deeper section of the mechanoreceptor, where the dendrite coupling to the base of the socket is clearly visible; (d) tubular body in the oblique section. ss, socket septum; Ds, dendrite sheath; sf, suspension fibre; Mt, microtubules; To, tormogen cell; black stars, lymph cavity; mb, socket membrane or joint membrane; Tb, Tubular body; TSa, trichoideum sensillum.
Figure 6
Figure 6
TEM photograph explores the ultrastructures of the trichoid mechanoreceptor: (a) cross-section at the base of trichoid mechanosensillum, where tubular body (Tb) is visible; socket membrane or joint membrane (mb) (b) magnification microtubules (Mt) of the tubular body; (c) profound location of the mechanoreceptor, where tubular body is wider in this section of trichoid mechanosensillum; (d) enlargement and the shape of the tubular body; (e) tormogen cell (To) with the sensillum lymph cavity (marked star) and trichogen cell (Tr), dendrite sheath (Ds), line of granules (G), suspension fibre (sf), and membrane (M).
Figure 7
Figure 7
Model of the tubular body of trichoideum mechanosensillum in cross-section in N. rugosus: (a) original TEM photo of cross-section; (b) compilation of numerous thin slides to analyse particular components. Ds, dendrite sheath; G, line of granules; sf, suspension fibre; Mt, microtubules; M, membrane.
Figure 8
Figure 8
Three-dimensional model of trichoideum sensillum’s internal organizational structure, developed by Amira software. Individual components are (DI) hair; (DII) joint membrane; (DIII) socket; (DIV) dendrite; (DV) socket septum. (DVI) Sectional view model of the sensillum.
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