Electron microscopic studies on the palpi of Cybister fimbriolatus fimbriolatus (Say)

Abstract

The maxillary palpi of the predaceous diving beetle Cybister /imbriolatus /imbriolatus Say were observed by transmission and scanning electron microscopy.Scanning electron microscopy shows at least two types of sensilla at the tip of palp, which are referred to as "circumvallate and naked sensilla". The former are innervated with outer segments of distal processes of sensory cells, but the latter are provided only with chitin and cuticular substances.Key.Words: Maxillary palpi --Circumvallate sensilla --Naked sensilla --Sensory cells --Cybister/imbriolatus (beetle).A large number of studies necessary for understanding insect sense organs have been made by electron microscopy (e.g.

Morphology and distribution of sensilla on head appendages in the water beetle Hygrobia hermanni (Coleoptera: Adephaga: Hygrobiidae)

“…This remarkable architecture of palp apical sensory fields, with strict segregation of sensilla coeloconica versus basiconica and circumvallate in three distinct clusters, is unprecedented (Figure 8, character 4). In Dytiscidae, each palp apical sensory field is subdivided in two clusters, comprised of circumvallate sensilla of several subtypes, arranged in about the same way for both clusters (Baker, 2001; Yasuzumi et al, 1971; our SEM observations on Rhantus suturalis (W.S. Macleay, 1825), subfamily Colymbetinae).…”

“…At the resolution scale of this study, data available for comparisons have been published for adult Dytiscidae by Ivanov (1966, 1969) (species: Acilius sulcatus (Linnaeus, 1758), subfamily Dytiscinae; antenna only), Yasuzumi et al (1971) (species: Cybister fimbriolatus (Say, 1823), subfamily Cybistrinae; palps only), Guse and Honomichl (1980) (species: Agabus bipustulatus (Linnaeus, 1767), subfamily Agabinae; digitiform sensilla of the maxillary palp only), Jensen and Zacharuk (1991, 1992) (species: Graphoderus occidentalis Horn, 1883, subfamily Dytiscinae; antenna only), Baker (2001) (species: Ilybius gagates (Aubé, 1838), subfamily Agabinae) and Song et al (2017 (species: Cybister chinensis Motschulsky, 1854), subfamily Cybistrinae; antenna only). For other families of aquatic Adephaga and for larvae, data in the literature are scarcer.…”

Ultrastructure of sensilla on the maxillary and labial palps of three species (Coleoptera: Staphylinidae: Staphylininae)

“…The SCo are identified on the last segment of maxillary and labial palps in the three species. They were reported on the surfaces of maxillary palps of Cybister fimbriolatus where they present a similiar peg, surrounded by a deep ditch and located near the tip of palps (Yasuzumi et al ). SCo1 is found on the last distal segment of maxillary and labial palps of Carabus lefebvrei (Giglio et al ).…”

Ultrastructure and morphology of antennal sensilla of the adult diving beetle Cybister japonicus Sharp

“…These types of sensilla were also reported on the surfaces of maxillary palpi of diving beetle C . fimbriolatus Say , where they present a similiar peg, surrounded by a deep and thick circular furrow, coupled with a wall around, and located near the tip of palpi [ 33 ]. The peg of types I and II s. coeloconica are innervated by two neurons, packaged tightly within the thick cuticle, a typical feature of mechano-sensitive receptors [ 34 , 35 ], indicating the possible role associates with touch-reception that these types of sensilla may play.…”

“…Morphologically similar sensilla were also found on the surfaces of maxillary palpi of the same species ( S2 Fig ) and of C . fimbriolatus Say [ 33 ]. The fine structure of the Type III s. coeloconica shows that four dendrites are located in two separated cavities, and one of them ends beneath the basement of the peg, while the other three reach the tip of the peg ( Fig 8 ).…”