Ultrastructure and distribution of sensory receptors on the nonolfactory organs of the soldier caste in subterranean termite (Coptotermes spp.)

• Published in: Arthropod structure & development 2022-09, Vol.70, p.101201-101201, Article 101201
• Main Authors: Wikantyoso, Bramantyo, Imai, Tomoya, Himmi, S. Khoirul, Yusuf, Sulaeman, Hata, Toshimitsu, Yoshimura, Tsuyoshi
• Format: Article
• Language: English
• Subjects: Chemoreceptor; Cuticular structures; Dendrite; Functional morphology; Mechanoreceptor; Sensory cells
• ISSN: 1467-8039; 1873-5495
• DOI: 10.1016/j.asd.2022.101201

The soldier caste of termites uses sensilla to sense pheromonal, tactile, and vibrational cues to communicate inside and outside their nest. Although sensilla with many modalities on the antennae of subterranean termites have been well explored, there remains a lack of information regarding sensillum characteristics and distribution of the nonolfactory organs of the soldier caste in the Coptotermes genus. In this study, the ultrastructure of sensilla from the soldier caste of three Coptotermes spp. (Coptotermes formosanus, Coptotermes curvignathus, and Coptotermes gestroi) was observed by scanning and transmission electron microscopy, and the putative function of each type was deduced. Six total sensillum types were observed, with two mechanoreceptive sensillum types (hair and plate). The long flexible-peg mechanoreceptive sensilla may work as contact-chemoreceptive sensilla due to their elongated dendritic outer segments and uniporous characteristics. There was a significant depletion of mechano-chemoreceptive sensillum numbers in C. gestroi, which was compensated by a high density of short-peg mechanoreceptive sensilla on the pronotum. Finally, cuticular and innervation characteristics of thermo-/hygrosensitive sensilla were observed for the first time on the labrum of the soldier caste of Coptotermes. [Display omitted] •On the nonolfactory organs of Coptotermes, long flexible-peg sensilla can be mechanoreceptors or mechano-chemoreceptors.•Significant depletion of mechano-chemoreceptive sensilla on the nonolfactory organs of C. gestroi.•The short-peg mechanoreceptive sensilla compensated for the depletion of mechano-chemoreceptive sensilla in C. gestroi.•Sensilla with thermo-/hygroreceptor characteristics existed on the labrum tip of Coptotermes spp.