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

The morphology and distribution of the antennal sensilla of adult diving beetle Cybister japonicus Sharp (Dytiscidae, Coleoptera), have been examined. Five types of sensilla on the antennae were identified by scanning electron microscope (SEM) and transmission electron microscope (TEM). Sensilla placodea and elongated s. placodea are the most abundant types of sensilla, distributing only on the flagellum. Both these types of sensilla carry multiple pore systems with a typical function as chemoreceptors. Three types of s. coeloconica (Type I-III) were also identified, with the characterization of the pit-in-pit style, and carrying pegs externally different from each other. Our data indicated that both type I and type II of s. coleconica contain two bipolar neurons, while the type III of s. coleconica contains three dendrites in the peg. Two sensory dendrites in the former two sensilla are tightly embedded inside the dendrite sheath, with no space left for sensilla lymph. There are no specific morphological differences in the antennal sensilla observed between males and females, except that the males have longer antennae and more sensilla than the females.

Ultrastructure of antennal sensilla of the peach aphid Myzus persicae Sulzer, 1776.

The antennal sensilla of alate Myzus persicae were mapped using transmission electron microscopy and the ultrastructure of sensilla trichoidea, coeloconica, and placoidea are described. Trichoid sensilla, located on the tip of the antennae, are innervated by 2-4 neurons, with some outer dendrites reaching the distal end of the hair. Coeloconic sensilla in primary rhinaria are of two morphological types, both equipped with two dendrites. Dendrites of Type II coeloconic sensilla are enveloped in the dendrite sheath, containing the sensillum lymph. In sensilla coeloconica of Type I, instead, dendrites are enclosed by an electron opaque solid cuticle, with no space left for the sensillum lymph. The ultrastructure of big placoid sensillum reveals the presence of three groups of neurons, with 2-3 dendrites in each neuron group, while both small placoid sensilla are equipped with a single group of neurons, consisting of three dendrites. Both large and small placoid sensilla bear multiple pores on the outer cuticle. The function of these sensilla is also discussed.

Immunolocalization of odorant-binding proteins on antennal chemosensilla of the peach aphid Myzus persicae (Sulzer).

The antennal sensilla of Myzus persicae were mapped using scanning and transmission electron microscopy. Placoid sensilla and coeloconic sensilla were found on the 6th segments, whereas 2 types of trichoid sensilla were present all through the length of the antenna. A single sensillum placoideum was located on the 5th segment, whereas alate aphids also presented placoid sensilla on the 3rd antennal segment. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of antennal chemosensilla. The antiserum against OBP7 intensively labeled all placoid sensilla from both primary and secondary rhinaria, with gold granules concentrated in the lymph surrounding the dendrite. OBP6 and OBP3 could also be detected in placoid sensilla, but less strongly than OBP7. Barely significant reaction or no reaction was observed with antibodies against OBP8.

The chemosensilla on tarsi of Locusta migratoria (Orthoptera: Acrididae): distribution, ultrastructure, expression of chemosensory proteins.

The chemosensilla on the tarsi of Locusta migratoria were mapped using light microscopy, as well as scanning and transmission electron microscopy. Only chemosensilla chaetica were found on the tarsi. On the basis of their ultrastructure, these can be grouped into three main subtypes: short, long, and sunken sensilla chaetica. Short sensilla chaetica can be further divided into two groups containing 6 or 7 neurons. Long sensilla chaetica are mainly located on the lateral surface of the tarsi. Short sensilla chaetica were mainly found on the dorsal surface of the tarsi. Sunken sensilla chaetica were only found on the ventral surface, such as the pulvilli and arolium. Immunocytochemical localization of chemosensory protein (CSP) was performed on ultrathin sections of chemosensilla on tarsi. The antiserum against LmigCSP-II intensively labeled all three types of sensilla chaetica. Gold granules were concentrated in the outer sensillum lymph surrounding the dendrite sheath, while the inner sensillum lymph containing dendrite branches was never labeled. Massive labeling with the anti-LmigCSP-II was also found in cuticle of the pulvilli on the ventral surface of tarsi.

Expression of odorant-binding and chemosensory proteins and spatial map of chemosensilla on labial palps of Locusta migratoria (Orthoptera: Acrididae).

The sensilla on labial palps in Locusta migratoria were observed and mapped using light microscopy, scanning and transmission electron microscopy. A dome region on the tip of the fourth segment (distal segment) of labial palps is mainly covered with sensilla chaetica (about 98%), and few sensilla basiconica (2%). The total number of both types of sensilla is significantly higher in females than in males. Sensilla chaetica can be further subdivided into three groups containing 6, 7 or 10 neurons. Immunocytochemical localization of odorant-binding protein (OBP) and chemosensory proteins (CSPs) was performed on ultrathin sections of sensilla on labial palps. The antiserum against odorant-binding protein from Locusta migratoria (LmigOBP) only labelled sensilla basiconica, with gold granules only found in the sensillum lymph. Chemosensory protein instead was specifically present in the outer sensillum lymph of all three subgroups of sensilla chaetica with antiserum against CSP-I from Schistocerca gregaria (SgreCSP-I). In contrast these three subgroups were never labelled with antiserum against CSP-II from Locusta migratoria (LmigCSP-II). In addition, a few sensilla chaetica could not be stained with any of the antisera used.