Antennal sensory structures in water bugs of Nepoidea (Insecta: Hemiptera: Nepomorpha), their morphology and function

Abstract

The Nepoidea superfamily belongs to the water bugs' infraorder (Nepomorpha) and consists of two families-Belostomatidae and Nepidae. Species from those families are the largest of all nepomorphans and are considered to be top predators in aquatic ecosystems. A characteristic feature of the group is the existence of short antennae concealed in grooves behind the eyes, which is an adaptation to the water habitat. The antennae bear many types of sensillar structures, which receive signals from the environment. Among such structures, mechanosensilla were of the greatest diversity. The antennal sensilla of species from both families were examined under the scanning electron microscope. 11 essential morphological types of sensilla were distinguished, including 5 new mechanosensilla types (sensilla paddle-like, cone-like, squamiformia, brush-like and club-like). Basal types of mechanosensilla such as trichodea, chaetica, basiconica (subtype 1) and campaniformia occur in Nepoidea and other Heteroptera. In some representatives of both families, sensilla paddle-like and sensilla basiconica type 1 were observed. Moreover, sensilla chaetica and cone-like were found in some species of Belostomatidae, whereas in Nepidae sensilla squamiformia, brush-like and club-like were observed. Apart from mechanosensilla, one type of thermohygrosensilla (ampullacea) and two different shaped olfactory sensilla basiconica (subtypes 2, 3) and coeloconica (subtypes 1, 2, 3) were found. It could indicate sensilla use in the identification of the water reservoirs and locating prey.

Insect evolution toward aquatic habitats; reassessment of antennal sensilla in the water bug families Ochteridae, Gelastocoridae and Aphelocheiridae (Hemiptera: Heteroptera: Nepomorpha)

“…All specimens have been cleaned in an ultrasound cleaner, the antennae have been dissected, dried in ethanol, mounted, sputtered with gold or chromium and observed with the use of the scanning electron microscopes Phenom XL and Hitachi UHR FE-SEM SU 8010 in the scanning microscopy laboratory of the Faculty of Natural Science, Institute of Biology, Biotechnology and Environmental Protection of Silesian University in Katowice. We follow the terminology and classification reported in other papers on antennal sensilla of insects (Altner & Prillinger, 1980;Nowińska & Brożek, 2019).…”

“…Moreover, a small amount of data about the morphology and distribution of more visible sensilla (trichodea or basiconica) on the surface of antennae of Notonecta glauca, Plea leachi, Nepa cinerea, Ranatra linearis and Sigara striata has been presented by Chaika & Sinitsina (1999), although the possible functions of the sensilla have not been indicated. However, newer morphological studies of antennal sensilla from species of Nepoidea, performed by Nowińska & Brożek (2019), have shown some inconsistencies in comparison to data from Chaika & Sinitsina (1999).…”

“…6). Some of these types have been described in other insects (McIver, 1975;Zacharuk, 1980), as well as in some heteropteran insects (Brożek, 2013(Brożek, , 2014Nowińska & Brożek, 2019). Sensilla trichodea, club-like, campaniformia and basiconica (subtype 1), because of their flexible sockets, are believed to play a mechanoreceptive function.…”

“…Limited information on morphology and physiology is available, for a small number of species. The identification and description of antennal sensilla, through the use of scanning electron microscopy (SEM), for a comprehensive understanding of the sensory systems of the antennae, was performed only for a few Nepoidea species (Nowińska & Brożek, 2019).…”

Neuronal Innervation of the Subgenual Organ Complex and the Tibial Campaniform Sensilla in the Stick Insect Midleg

“…Insects have multiple types of mechanoreceptors and other sensilla on body appendages like legs or antenna [1][2][3][4][5][6][7]. The neuronal innervation pattern shows the organization of motor nerves and muscles [8,9] or sensory nerves and their relation to different sensory organs in insect legs [10][11][12][13].…”