Structure and localization of sensilla on antennas of caddisflies (insecta: trichoptera)

The structures of antennal segments and ultrastructures of antennal sensilla were studied in representatives of 28 families of caddisflies from both extant suborders by the methods of light and scanning electron microscopy. Sixteen types of the sensilla have been found to occur on the antenna in Trichoptera; some of them were found for the first time. Morphological characters of the cuticular structures on the antennal surface demonstrate the significant structural differences both in various families and in the lower taxonomy levels. Specialized sensory fields differing structurally from the rest of the flagellomer surface have been found on the antennas in the suborder Phryganeina. A modified classification of sensilla based on the cuticular structures is proposed.     

Antennal sensilla of grasshoppers (Orthoptera: Acrididae) in relation to food preferences and habits

The external structure, i.e. number and distribution of sensillae on male and female antennae of 12 species of grasshoppers belonging to Pamphaginae, Catantopinae, Oedipodinae and Gomphocerinae in the grasslands of Inner Mongolia was investigated using scanning electron microscopy. Five major types of antennal sensillae were detected - trichoid, long basiconic, short basiconic, slender and short basiconic, and coeloconic sensillae. Total number of antennal sensillae varied among different sexes, subfamilies, feeding groups, life forms and eco-forms. Males showed significantly more sensillae than females, due to presence of more short basiconic and coeloconic sensillae. Species under Catantopinae showed more long basiconic sensillae than the others. The Oedipodinae had the highest number of slender and short basiconic sensillae and coeloconic sensillae, followed by Catantopinae and Gomphocerinae; while Pamphaginae had the fewest. The total number of sensillae showed the same trend for these two types amongst the subfamilies as well, species which prefer habits on the ground possessed fewer antennal sensillae than species which prefer to stay on plants. The maximal number of antennal sensillae were observed in hygrophytous species,Chorthippus albomarginatus, in the 12 grasshopper species investigated, although the data is not statistically significant. The general trend which emerged was that species feeding on grass possessed more antennal sensillae, particularly coeloconic sensillae, compared to other feeding group species.     

松突圆蚧雄成虫触角感器的扫描电镜观察

松突圆蚧(Hemiberlesia pitysophila Takagi)是我国南方重要的外来林业害虫。本研究利用扫描电镜对该蚧雄成虫的触角形态和感器进行了观察。结果表明:松突圆蚧雄成虫触角呈线状,由柄节、梗节和鞭节组成,共10节。触角感器共有5种,分别为Bhm氏鬃毛、毛形感器、乳头形感器、锥形感器、火柴形感器,其中,火柴形感器为首次在松突圆蚧雄成虫触角上发现并描述。不同感器在触角各节的数量和分布各不相同,其中,毛形感器数量最多,分布最广,乳头形感器次之,火柴形感器最少。此外,根据感器的分布、形态特征,结合已有的文献描述,推测了感器可能的功能。     

The labrum of Schedorhinotermes minor soldier (Isoptera,Rhinotermitidae)

The labrum of Schedorhiontermes minor soldier was examined to determine the distribution, types and structures of sense organs present with both light microscopy and scanning and transmission electron microscopy. Three types of sensilla were recognized: companiform sensillae and two types of sensillae trichodea, the short bristles and the long bristles. The companiform sensillae are singly-innervated receptors distributed in large numbers on the anterolateral margins of the labrum. The short and long bristles are multi-innervated; the former are found all over the surface, the latter are much more scarce and are found only at the front of the labrum. Both are at the same time chemo- and mechanoreceptors. The labrum is strewn with many glandular pits and exhibits at its apex a brush of cuticular not innervated spines. On the basis of ultrastructural evidence and of what we know of the defense mechanisms of the soldier, a functional interpretation is attempted.     

桉小卷蛾触角感器的超微结构

[目的] 桉小卷蛾是桉树、番石榴等林木和果树的一种重要害虫。为确定桉小卷蛾成虫触角上的感器对寻找生存环境及对外界环境的各种刺激所起的作用,研究了桉小卷蛾触角感器的种类、形态和分布。[方法] 利用扫描电镜对桉小卷蛾成虫触角感器进行了详细观察和研究。[结果] 桉小卷蛾雌、雄蛾触角由柄节、梗节和鞭节组成,触角的外侧面覆盖有鳞片;雄性触角略短于雌虫,且鞭节近1/4处有一凹陷。共发现7种感器,即鳞形感器、毛形感器、锥形感器、腔锥形感器、耳形感器、刺形感器和Böhm氏鬃毛,其中以毛形感器数量最多。[结论] 桉小卷蛾雌雄成虫触角的感器种类、分布、数量有一定的规律但又有差异。建议应用气相-触角电位联用技术GC-EAD和触角电位EGA等技术进一步解析触角感器的功能。     

草地贪夜蛾成虫触角感器超微结构观察

[目的]草地贪夜蛾是一种严重危害农业生产的迁飞性害虫,本研究旨在了解草地贪夜蛾成虫触角感器的类型、超微结构和分布.[方法]采用扫描电镜对其雌雄成虫触角感器类型及分布进行观察.[结果]草地贪夜蛾雌雄成虫触角由柄节、梗节及鞭节3部分组成,雄蛾触角稍长于雌蛾,且触角表面覆有大量鳞片.共观察到7种类型的感受器,分别为B?hm氏...     

Three-dimensional fine structural reconstruction of the nose sensory structures of Acrobeles complexus compared to Caenorhabditis elegans (Nematoda: Rhabditida)

Nematode sensory structures can be divided into two classes; cuticular sensillae, with dendrites ending outside the epidermis, and internal receptors, that typically are single dendrites terminating within the body cavity. Fine structure of the former has been described completely in more than a dozen nematode taxa, while the latter were previously only well understood in the microbial feeder Caenorhabditis elegans. The distantly related nematode Acrobeles complexus has a similar ecology and together the two span a clade representing a large proportion of nematode biodiversity. The cuticular sensillae and internal receptors of A. complexus are here shown to be remarkably similar in number, arrangement, and morphology to those of C. elegans. Several key differences are reported that likely relate to function, and suggest that this nematode has a cuticular sensillum morphology that is closer to that of the common ancestor of the two taxa. Internal sensory receptors have more elaborate termini than those of C. elegans. The existence of a novel form of mechanoreceptor in A. complexus and spatial relationships between sensillum dendrites suggest differences between two classes of sensillae in how a touch-response behavior may be mediated.     

Discrimination of conspecific individuals via cuticular pheromones by males of the cricket Gryllus bimaculatus

Cuticular substances on the body surface of crickets serve as pheromones that elicit a variety of different behaviors in male crickets. Antennal contact between males and females resulted in courtship behavior, and that between two males resulted in aggressive displays. As a first step in elucidating how crickets recognize and discriminate individuals, behavioral responses of male individuals to cuticular substances of conspecific males or females were investigated. The behavioral responses of males to antennal or palpal stimulation with an isolated antenna from a male or a female were recorded. To both antennal and palpal stimulation with female antennae, the majority of males responded with courtship behavior; to stimulation with male antennae, males responded with aggressive displays. To gain insight into the chemical nature of the behaviorally relevant components, isolated antennae were washed in either n-hexane, acetone or ethanol before behavior assays. Washed antennae no longer elicited courtship or aggressive responses in males. Next, polypropylene fibers were smeared with substances from the body surface of females and used for antennal stimulation. This experiment showed that the quality and quantity of cuticular substances appear to be highly age-dependent. Significantly more males responded with courtship behavior to cuticular substances from younger females. Isolated males generally showed higher levels of aggression than males reared in groups. Grouped males also were more likely to display courtship behavior towards antennae from younger females, and aggressive behavior towards antennae from older females. These results suggest that male discrimination of mating partners depends on the nature of female cuticular substances.     

Spike amplitude of single-unit responses in antennal sensillae is controlled by the Drosophila circadian clock

Circadian changes in membrane potential and spontaneous firing frequency have been observed in microbial systems, invertebrates, and mammals. Oscillators in olfactory sensory neurons (OSNs) from Drosophila are both necessary and sufficient to sustain rhythms in electroanntenogram (EAG) responses, suggesting that odorant receptors (ORs) and/or OR-dependent processes are under clock control. We measured single-unit responses in different antennal sensillae from wild-type, clock mutant, odorant-receptor mutant, and G protein-coupled receptor kinase 2 (Gprk2) mutant flies to examine the cellular and molecular mechanisms that drive rhythms in olfaction. Spontaneous spike amplitude, but not spontaneous or odor-induced firing frequency, is under clock control in ab1 and ab3 basiconic sensillae and T2 trichoid sensillae. Mutants lacking odorant receptors in dendrites display constant low spike amplitudes, and the reduction or increase of levels of GPRK2 in OSNs results in constant low or constant high spontaneous spike amplitudes, respectively. We conclude that spike amplitude is controlled by circadian clocks in basiconic and trichoid sensillae and requires GPRK2 expression and the presence of functional ORs in dendrites. These results argue that rhythms in GPRK2 levels control OR localization and OR-dependent ion channel activity and/or composition to mediate rhythms in spontaneous spike amplitude.     

Morphology of the antennal sensory cone in insect larvae from various orders

This article describes the morphology of antennae in larvae of three species of beetles from the families Cerambycidae and Chrysomelidae; one species of the caddis fly from the family Limnephilidae; and four species of dipterans from the families Culicidae, Chironomidae, and Muscidae. In all investigated species, the antenna has a sensory cone on it. Larvae of the caddis fly, longhorn beetles, and leaf beetles have on their antenna solitary sensillae and the sensory cone. This proves the advanced evolution of these species. Despite reduction of the head capsule, the antennal sensory cone in ±9/58 larvae of higher dipterans has become the dominant sensory structure.     

Structure and distribution of antennal sensilla in Oranmorpha guerinii (Gervais, 1837) (Diplopoda,Polydesmida)

Detailed information on sensory organs of Diplopoda especially on antennal sensilla are still sparse and fragmentary. The present study on the antennae of Oranmorpha guerinii (Polydesmida, Paradoxosomatidae) utilizing scanning electron microscopy revealed the presence of six sensillar types: (1) apical cones, (2) sensilla trichodea, (3) sensilla microtrichodea, (4) sensilla chaetica, (5) sensilla basiconica bacilliformia, and (6) sensilla basiconica spiniformia. External structure and distribution of cuticular antennal sensilla are compared with data from other diplopod species. We moreover discuss possible functions of antennal sensilla in millipedes.     

黄胸蓟马触角感器的形态和分布

[目的]本研究旨在明确黄胸蓟马Thrips hawaiiensis各个发育阶段触角感器类型、形态和分布.[方法]运用扫描电镜技术观察黄胸蓟马雌雄成虫、若虫、预蛹、蛹触角的形态结构以及触角上感器类型、形态和分布.[结果]黄胸蓟马成虫触角由柄节、梗节和鞭节3个部分组成,其中长的鞭节分为5个鞭小节(Ⅰ-Ⅴ).雌成虫触角平均长...     

Fine structure of the antennal glands of the ant nest beetle Paussus favieri (Coleoptera,Carabidae, Paussini)

The antennae of the ant nest beetle Paussus favieri are studied by using both SEM and TEM. In the myrmecophilous genus Paussus, these structures are composed of three joints: scape, pedicel and a wide third joint, the “antennal club”, resulting from the fusion of antennomeres A3–A11 (flagellum). The antennal club shows an exceptional glandular activity, with the presence of pores mostly crowded in special hairless cuticular areas, surrounding the base of single setae, grouped at the base of tufts of setae, or positioned inside deep pockets that store the secretions, with filiform material arising from them. The surface of A1 and A3 are covered by mechanoreceptors, modified to spread the glandular exudates, while the chemoreceptors are restricted to the apex of the club. The fine structural analysis shows a great number of antennal glands, that can be referred to three main typologies: type A (GhA) bi-cellular, composed of a large secretory cell and a small duct cell, positioned close to the antennal surface; type B (GhB), tri-cellular, composed of two secretory cells and one duct cell, less frequent and positioned deep inside the antennal club; type C (GhC), rare, located deeply within the antennal lumen, in the vicinity of the trophocytes. This complexity indicates that more than one substance could be released from the antennae. Possible functional aspects of the secretions dealing with symbiotic interaction with the host ants are discussed.     

Fine structure of antennal mechanosensilla of adult Rhodnius prolixus stål (Hemiptera: Reduviidae)

Each antenna of both sexes of adult Rhodnius prolixus has approximately 570 mechanosensitive neurons that innervate five morphologic types of cuticular mechanosensilla: campaniform sensilla, tapered hairs, trichobothria, and type I and type II bristle sensilla. Each campaniform sensillum and tapered hair is presumably innervated by one mechanosensitive bipolar neuron and probably functions in proprioception. The campaniform sensilla being located at the base of the scape could monitor the position of the antenna. Tapered hairs are found at the distal margin of flagellar segment I and projecting laterally from the bases of the pedicel and scape. They probably provide information about the relative positions of the antennal segments. Seven trichobothrium are located on the pedicel and three on flagellar segment I. Each trichobothrium has a long filamentous hair inserted into the base of a socket that extends inwardly as a cuticular tube and is innervated by one bipolar neuron with a tublar body, a parallel arrangement of microtubules associated with electron-dense material. The trichobothria may respond to small variations in air currents. Type I bristles occur at the base of the antenna and are the most numerous type of mechanosensillum; an average of 452 occur on each antenna of females and 440 on males. The bristle is curved toward the antennal shaft and is serrated distally. Type II bristles are located distally and are the second most numerous type of mechanosensillum; an average of 88 were counted on each antenna of females and 94 on males. The type II bristle is straight with small, longitudinal, external grooves and projects laterally from the antennal shaft. Each type I and II bristle sensillum is innervated by a bipolar neuron whose dendrite is divided into an inner and outer segment. The outer segment is encased by a dendritic sheath which may be highly convoluted and distally contains a tubular body. Two sheath cells are associated with each sensillum. Both types of bristle sensilla have a tactile function. The tubular bodies of both types of bristle sensilla have a complex structure indicating that they are very sensitive. Variations in the amount and arrangement of the electron-dense material at the tip of the tubular bodies may reflect differences in viscoelastic properties that underlie functional characteristics.     

Ultrastructure and development of single-walled sensilla placodea and basiconica on the antennae of the Sphecoidea (Hymenoptera : aculeata)

While the pore plates of some species of the Sphecoidea (Hymenoptera) rise above the antennal surface, those of other species are flush with it. Not all species possess pore plates. On the antennae of those species, which lack pore plates, small sensilla basiconica are found. The pore plates of Psenulus concolor were studied in detail. The cuticular apparatus rises above the antennal surface. Cuticular features are the encircling ledge and delicate cuticular ledges reinforcing the perforated plate, as well as a joint-like membrane that anchors the plate into the antennal cuticle. Each pore plate is associated with 9–23 sense cells and 4 envelope cells, the second of which is doubled. In very early developmental stages, however, supernumerary envelope cells are observed; they degenerate before the cuticulin layer is secreted. Envelope cell 1 secretes a temporary dendrite sheath, while the envelope cells 2–4 are responsible for the secretion of the cuticular apparatus.The morphology and the development of the small sensilla basiconica are described in Trypoxylon attenuatum. The curved sensillum pointing to the tip of the antenna is anchored by a joint-like membrane. About 15 sense cells innervate the sensillum. The number and the arrangement of the envelope cells resemble that of the sensilla placodea. During very early developmental stages, supernumerary envelope cells are also observed. They degenerate before the cuticle of the cone is secreted by the surviving envelope cells 2–4.     

The Role of Antennae in Mate Recognition in <Emphasis Type="Italic">Phoracantha semipunctata</Emphasis> (<Emphasis Type="Italic">Coleoptera: Cerambycidae</Emphasis>)

The mating behavior of the eucalyptus longhorned borer Phoracantha semipunctata was studied to understand its mate recognition system. Bioassays were conducted to determine the existence of a cuticular chemical on its body surface and how individuals perceived it. Males walked oriented to and attempted copulation with live conspecifics only upon antennal contact with their bodies. They showed similar responses to intact dead females and males, but failed to respond to washed bodies. Dummies carrying male extracts were more likely to elicit copulation attempts than control dummies. This constitutes behavioral evidence that unidentified chemical(s) on the body surface play a major role in mate recognition, and can only be perceived after antennal contact. Sensilla trichodea on the antennal flagellum are candidates for this contact chemoreception. They are distributed throughout the entire flagellum, especially along its margins and at the tip of the distal flagellomere, and share structural features with contact chemosensory sensilla of other insects.     

Wing receptors of the American cockroach Periplaneta americana]

Wing receptors of the cockroach have been studied using staining technique with methylene blue in living animals. Five types of the receptors were found: trychoid hairs, bristles, complaniform sensillae, chordotonal organs and multiterminal neurons. The majority of the receptors is located at the lower surface of the wing, especially along its ribs. Together with primitive features in the structure (polyneuronal origin of hairs and bristles, poor content of chordotonal organs, absence of distinct groups of companiform sensillae), some specialization of wing receptors with respect to flight function is noted (concentration of proprioceptors along the main mechanical axis of the wing and formation of distinct rows by the companiform sensillae).     

Gall midge olfaction: Pheromone sensitive olfactory neurons in Contarinia nasturtii and Mayetiola destructor

This study describes the morphology and function of the antennal sensilla in two gall midge species, Contarinia nasturtii and Mayetiola destructor, where multi-component sex pheromones have been identified. Both species possess sensilla trichodea, s. coeloconica, s. chaetica and s. circumfila. Sensilla circumfila, which consist of several sensilla that bifurcate and fuse into one structure, are unique for the gall midges. In C. nasturtii s. circumfila are sexually dimorphic. In males, they form elongated loops suspended on cuticular spines, whereas in females they run like worm-like structures directly on the antennal surface. Single sensillum recordings demonstrated that olfactory sensory neurons housed in male s. circumfila in C. nasturtii responded to the female sex pheromone. In M. destructor, s. circumfila were attached to the antennal surface in both sexes, and displayed no response to sex pheromone components.A sexual dimorphism was also found in the number of s. trichodea per antennal segment in both C. nasturtii (male 1 vs. female 7) and M. destructor (male 13 vs. female 10). OSNs located in male M. destructor s. trichodea responded to the sex pheromone. This is the first gall midge single sensillum study, and the first demonstration of the functional significance of s. circumfila.     

Coming apart at the seams: morphological evidence for pregnathal head capsule borders in adult <Emphasis Type="Italic">Tribolium castaneum</Emphasis>

Cephalization and seamless fusion of the anterior body segments during development obscure the segmental boundaries of the insect head. Most of the visible seams are thought to reflect cuticular infolding for structural reinforcement rather than a merger of cuticular plate borders. Incomplete fusions and other modifications of the adult head found in eight Tribolium mutations indicate that the frontal and gular sutures likely are true sutures that mark borders between adjacent cuticular plates, and suggest that the anterior facial shelf is a composite of three independent cuticular surfaces: ocular, antennal, and clypeo-labral. Additionally, midline splits of the clypeo-labrum and gula, and membranous lesions on the lateral head capsule reveal probable borders of adjacent cuticular plates where visible sutures are normally absent. The anterior lateral lesions seen in the Lucifer mutation mark a border between ocular and antennal plates and appear to identify part of the postfrontal sutures. While revealing or clarifying possible intersegmental borders between ocular, antennal, and clypeo-labral plates, the various modified or unfused surfaces of the head neither reveal an additional acronal plate nor support the view that the clypeo-labrum is segmentally associated with ocular cuticle.     

Central projections of olfactory receptor neurons from single antennal and palpal sensilla in mosquitoes

In insects, olfactory receptor neurons (ORNs) are located in cuticular sensilla, that are present on the antennae and on the maxillary palps. Their axons project into spherical neuropil, the glomeruli, which are characteristic structures in the primary olfactory center throughout the animal kingdom. ORNs in insects often respond specifically to single odor compounds. The projection patterns of these neurons within the primary olfactory center, the antennal lobe, are, however, largely unknown.We developed a method to stain central projections of intact receptor neurons known to respond to host odor compounds in the malaria mosquito, Anopheles gambiae. Terminal arborizations from ORNs from antennal sensilla had only a few branches apparently restricted to a single glomerulus. Axonal arborizations of the different neurons originating from the same sensillum did not overlap.ORNs originating from maxillary palp sensilla all projected into a dorso-medial area in both the ipsi- and contralateral antennal lobe, which received in no case axon terminals from antennal receptor neurons. Staining of maxillary palp receptor neurons in a second mosquito species (Aedes aegypti) revealed unilateral arborizations in an area at a similar position as in An. gambiae.