Sensilla Trichodea Research Articles

Moth pheromone receptors: gene sequences, function, and evolution

The detection of female-released species-specific sex pheromones in moths is mediated by the pheromone receptors that are expressed in the sensory neurons in the olfactory sensilla of conspecific male antennae. Since the pioneering studies on the tobacco budworm Heliothis virescens and the silkworm Bombyx mori a decade ago, genes encoding pheromone receptors have been identified from a number of moth species. Pheromone receptor genes constitute a specialized olfactory receptor subfamily that shares sequence homology. In most cases the pheromone receptor genes are more abundantly expressed in male antennae, and the expression is confined to the neurons in the long sensilla trichodea, which are responsible for pheromone sensing. Both highly specific and more broadly tuned pheromone receptors have been described in various moth species. We review the advances in moth pheromone receptor studies over the past decade, including the methods used in receptor gene isolation and functional characterization, the different ligand profiles of the identified receptors, and the evolution of this multigene family.

Specific olfactory neurons and glomeruli are associated to differences in behavioral responses to pheromone components between two Helicoverpa species.

Sex pheromone communication of moths helps to understand the mechanisms underlying reproductive isolation and speciation. Helicoverpa armigera and Helicoverpa assulta use (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-9-hexadecenal (Z9-16:Ald) as pheromone components in reversed ratios, 97:3 and 5:95, respectively. H. armigera also produces trace amount of (Z)-9-tetradecenal (Z9-14:Ald) in the sex pheromone gland, but H. assulta does not. Wind tunnel studies revealed that the addition of small amounts (0.3%) of Z9-14:Ald to the main pheromone blend of H. armigera increased the males' attraction, but at higher doses (1%, 10%) the same compound acted as an inhibitor. In H. assulta, Z9-14:Ald reduced male attraction when presented as 1% to the pheromone blend, but was ineffective at lower concentrations (0.3%). Three types (A–C) of sensilla trichodea in antennae were identified by single sensillum recording, responding to Z11-16:Ald, Z9-14:Ald, and both Z9-16:Ald and Z9-14:Ald, respectively. Calcium imaging in the antennal lobes (ALs) revealed that the input information of the three chemicals was transmitted to three units of the macroglomerular complex (MGC) in ALs in both species: a large glomerulus for the major pheromone components, a small one for the minor pheromone components, and a third one for the behavioral antagonists. The type A and C neurons tuned to Z11-16:Ald and Z9-16:Ald had a reversed target in the MGC between the two species. In H. armigera, low doses (1, 10 μg) of Z9-14:Ald dominantly activated the glomerulus which processes the minor pheromone component, while a higher dose (100 μg) also evoked an equal activity in the antagonistic glomerulus. In H. assulta, instead, Z9-14:Ald always strongly activated the antagonistic glomerulus. These results suggest that Z9-14:Ald plays different roles in the sexual communication of two Helicoverpa species through activation of functionally different olfactory pathways.

Interference of plant volatiles on pheromone receptor neurons of male Grapholita molesta (Lepidoptera: Tortricidae)

In moths, sex pheromone components are detected by pheromone-specific olfactory receptor neurons (ph-ORNs) housed in sensilla trichodea in the male antennae. In Grapholita molesta, ph-ORNs are highly sensitive and specific to the individual sex pheromone components, and thus help in the detection and discrimination of the unique conspecific pheromone blend. Plant odors interspersed with a sub-optimal pheromone dose are reported to increase male moth attraction. To determine if the behavioral synergism of pheromone and plant odors starts at the ph-ORN level, single sensillum recordings were performed on Z8-12:Ac and E8-12:Ac ph-ORNs (Z-ORNs and E-ORNs, respectively) stimulated with pheromone–plant volatile mixtures. First, biologically meaningful plant-volatile doses were determined by recording the response of plant-specific ORNs housed in sensilla auricillica and trichodea to several plant odorants. This exploration provided a first glance at plant ORNs in this species. Then, using these plant volatile doses, we found that the spontaneous activity of ph-ORNs was not affected by the stimulation with plant volatiles, but that a binary mixture of sex pheromone and plant odorants resulted in a small (about 15%), dose-independent, but statistically significant, reduction in the spike frequency of Z-ORNs with respect to stimulation with Z8-12:Ac alone. The response of E-ORNs to a combination of E8-12:Ac and plant volatiles was not different from E8-12:Ac alone. We argue that the small inhibition of Z-ORNs caused by physiologically realistic plant volatile doses is probably not fully responsible for the observed behavioral synergism of pheromone and plant odors.

Targeted disruption of a single sex pheromone receptor gene completely abolishes in vivo pheromone response in the silkmoth.

Male moths use species-specific sex pheromones to identify and orientate toward conspecific females. Odorant receptors (ORs) for sex pheromone substances have been identified as sex pheromone receptors in various moth species. However, direct in vivo evidence linking the functional role of these ORs with behavioural responses is lacking. In the silkmoth, Bombyx mori, female moths emit two sex pheromone components, bombykol and bombykal, but only bombykol elicits sexual behaviour in male moths. A sex pheromone receptor BmOR1 is specifically tuned to bombykol and is expressed in specialized olfactory receptor neurons (ORNs) in the pheromone sensitive long sensilla trichodea of male silkmoth antennae. Here, we show that disruption of the BmOR1 gene, mediated by transcription activator-like effector nucleases (TALENs), completely removes ORN sensitivity to bombykol and corresponding pheromone-source searching behaviour in male moths. Furthermore, transgenic rescue of BmOR1 restored normal behavioural responses to bombykol. Our results demonstrate that BmOR1 is required for the physiological and behavioural response to bombykol, demonstrating that it is the receptor that mediates sex pheromone responses in male silkmoths. This study provides the first direct evidence that a member of the sex pheromone receptor family in moth species mediates conspecific sex pheromone information for sexual behaviour.

Electron microscope study on workers antennae and sting lancets of three subspecies of honey bee Apis mellifera L. (Hymenoptera: Apidae) and its bearing on their phylogeny

Ultrastructure of antennae and sting of the honey bee workers in three subspecies of Apis mellifera; Egyptian A. m. lamarckii, Carniolan A. m. carnica and Italian A. m. ligustica was investigated. Twelve types of sensilla were recorded on the worker antennae; placodea, basiconica, trichodea types (A, B, C and D), ampullaceal, coeloconica, coelococapitular, non-innervated hair seta, campaniformia and sensilla chaetica. The latter is recorded for the first time on antennae of A. mellifera. The number and distribution of the various types of sensilla are recorded. Sensilla trichodea were found most frequently and were present on all the antennal segments. Sensilla placodea were present on the distal eight flagellomeres. Sensilla ampullaceal and sensilla coeloconica were present on the distal five while sensilla campaniformia were confined to the distal seven flagellomeres. The barbs carried on the lancets of sting differ in numbers among the workers of the three subspecies; 10, 9 and 7 in A. m. lamarckii, A. m. carnica and A. m. ligustica, respectively. Depending on morphometrical analysis, a dendrogram separated the Egyptian subspecies from the other two subspecies with a highly genetic distance of 0.25 between them. The Italian and the Carniolan subspecies were grouped into one main cluster with a genetic distance of 0.01 between them.

Types and Functions of Mole Cricket (Orthoptera: Gryllotalpidae) Antennal and Palpal Sensilla

Invasive mole crickets (Orthoptera: Gryllotalpidae: Scapteriscus spp.) are destructive subterranean pests that cause significant economic losses for the turfgrass, sod and pasture industries. Their behavior suggests that they may sense insecticides applied to the soil, so we sought to examine and describe the antennal and palpal structures of S. vicinis Scudder, S. borellii Giglio-Tos, S. abbreviatus Scudder, and the native mole cricket, Neocurtilla hexadactyla Perty, by scanning and transmission electron micrography. The most abundant sensilla were antennal sensilla chaetica with mechanoreceptory and contact chemoreceptory functions. Each segment had olfactory sensilla basioconica and sensilla trichodea, sensilla coeloconica (with olfactory and thermo-hydroreceptory functions), and sensilla campaniformia (proprioreceptor). Sensilla on the mole cricket palps were non-pore or tip-pore, which suggests mechanoreceptory and contact chemoreceptory functions. Similar to other hemimetaboulous insects, mole cricket nymphs and adults have the same sensilla types. However, the number and size of antennomeres increased with each molt, allowing the antennae to accommodate more sensory sensilla as insects matured.

The effect of different host plants on the antennal and mouthparts sensilla of the larvae of Spodoptera littoralis; (Lepidoptera; Noctuidae)

The distribution and mor phology of various sensory organs (sensilla) on the antenna and mouthparts of Spodoptera littoralis larvae were investigated using scanning electron microscopy. In this study we focused on the morphological alterations of the antennal and mouthparts sensilla of Spodoptera littoralis last instar larvae reared on different hos t plants; alfalfa, cotton, and soybean leaves. Based on our results, we found that sensillum chaeticum on the antenna was morphologically affected by shifting the host plan t since it became longer in those larvae reared on soybean and alfalfa leaves when compared with those reared on cotton leaves. Furthermore, several morphological variations were observed in sensilla trichodea on the labium, mandibles, and labrum by shifting the host plant. In addition, clear morphological changes were observed in sensillum digitiformium on the maxillary palps due to changing the host plant. On the other hand, no morphological changes in ante nnal basiconic, trichodium and styloconic galeal sensilla styloconica, maxillary campaniform and placodeum sensilla were observed. Taken together, these results showed that shifting host plants of Spodoptera littoralis larvae induced plasticity and morphological changes of th e antennal and mouthparts sensilla.

Ultrastructure of antennal and posterior abdominal sensilla in Chlorophorus caragana females

Chlorophorus caragana Xie & Wang is a destructive wood-boring beetle that damages Caragana spp. bushes and is distributed in desert areas in north-west China. Using scanning electron microscopy and transmission electron microscopy, we observed the morphology and ultrastructure of antennal and posterior abdominal sensilla in C. caragana females, to discuss the putative functions of these sensilla in host location and oviposition behaviors.In total, seven types (24 subtypes) of sensilla were located on the antenna and posterior abdomen. On the antenna, there were Böhm's bristles (BB.); four subtypes of sensilla chaetica (Ch.1–Ch.4) characterized by non-porous surfaces and sensillum-lymph cavities without dendrites; two subtypes of sensilla trichodea (Tr.1 and Tr.2) with a tip pore and dendrites surrounded by dendritic sheaths; dome-shaped sensilla (Dom.) emerging from a deep cavity with one tip pore; four subtypes of sensilla basiconica (Ba.1–Ba.4) and one type of sensilla auricillica (Au.) with a porous cuticular surface and dendrites in the sensillum-lymph cavity; and one type of sensilla styloconica (Sty.) with grooves on the cuticular wall. On the posterior abdomen, there were four subtypes of sensilla chaetica (Ch.5–Ch.8); three subtypes of sensilla trichodea (Tr.3–Tr.5); and three subtypes of sensilla basiconica (Ba.5–Ba.7; Ba.5 had no groove in the cuticular wall, Ba.6 had one tip pore, and Ba.7 was located in a cuticular cavity). The antennal sensilla were believed to be mechanosensitive, chemosensitive, and sensitive to humidity and temperature, and to play roles in mating, host location and oviposition. The abdominal sensilla are believed to be related to oviposition behaviors.

Expression Analysis and Binding Assays in the Chemosensory Protein Gene Family Indicate Multiple Roles in Helicoverpa armigera.

Chemosensory proteins (CSPs) have been proposed to capture and transport hydrophobic chemicals to receptors on sensory neurons. We identified and cloned 24 CSP genes to better understand the physiological function of CSPs in Helicoverpa armigera. Quantitative real-time polymerase chain reaction assays indicate that CSP genes are ubiquitously expressed in adult H. armigera tissues. Broad expression patterns in adult tissues suggest that CSPs are involved in a diverse range of cellular processes, including chemosensation as well as other functions not related to chemosensation. The H. armigera CSPs that were highly transcribed in sensory organs or pheromone glands (HarmCSPs 6, 9, 18, 19), were recombinantly expressed in bacteria to explore their function. Fluorescent competitive binding assays were used to measure the binding affinities of these CSPs against 85 plant volatiles and 4 pheromone components. HarmCSP6 displays high binding affinity for pheromone components, whereas the other three proteins do not show affinities for any of the compounds tested. HarmCSP6 is expressed in numerous cells located in or close to long sensilla trichodea on the antennae of both males and females. These results suggest that HarmCSP6 may be involved in transporting female sex pheromones in H. armigera.

Antennal sensilla in the parasitoid Sclerodermus sp. (Hymenoptera: Bethylidae).

Parasitoid wasps of the genus Sclerodermus (Hymenoptera: Bethylidae) are an important natural enemy of the Japanese pine sawyer beetle Monochamus alternatus Hope (Coleoptera: Cerambycidae). In this study, we used scanning electron microscopy to examine the external morphology of the antennal sensilla of Sclerodermus sp. Antennae of females and males comprised the scape, pedicel, and 11 flagellomere segments. Based on the morphology of the sensilla in each sex, seven types of sensillum were identified: sensilla trichodea (Tr.1, Tr.2 and Tr.3), sensilla basiconica (Ba.1, Ba.2, and Ba.3), sensilla styloconica (St.1 and St.2), sensilla placodea, sensilla coeloconica, sensilla squamiforma, and Bohm’s bristles. Tr.2, Ba.1, and St.1 were only found in females, whereas Ba.2, Ba.3, and St.2 were only observed in males. Sensilla placodea were the most common, given that they occur on the antennae of many parasitoid Hymenoptera, whereas sensilla Tr were the most abundant, being distributed over the entire antennal surface. These sensilla are likely to have roles in the host locating and habitat searching behavior of adult Sclerodermus wasps. Therefore, our findings provide a basis for further studies of the host location behavior of this and other species of parasitic wasp.

An antenna-biased carboxylesterase is specifically active to plant volatiles in Spodoptera exigua

Odorant-degrading enzymes (ODEs) in sensillar lymph are proposed to play important roles in the maintenance of the sensitivity of the olfactory sensilla, by timely degrading the odorants that have already fulfilled the activation of the odorant receptor (OR). Here we reported the cloning and characterization of an ODE gene (SexiCXE10) from the polyphagous insect pest Spodoptera exigua. SexiCXE10 is a carboxylesterase (CXE) gene, encoding a protein with 538 amino acid residues, and bearing typical characteristics of Carboxyl/cholinesterase (CCE, EC 3.1.1.1.) gene family. Tissue-temporal expression pattern by qPCR revealed that the SexiCXE10 mRNA was highly antenna biased, and maintained at high level throughout the adult stage. Further fluorescence in situ hybridization demonstrated that SexiCXE10 mRNA signal was detected under sensilla basiconica and short and long sensilla trichodea. Finally, enzymatic study using purified recombinant enzyme showed that SexiCXE10 had high activity specifically for ester plant volatiles with 7–10 carbon atoms, while no activity was found with S. exigua sex pheromone components and plant volatiles with more carbon atoms. In addition, SexiCXE10 displayed lower activity at acidic pH (pH 5.0), while higher activity was found at neutral and alkaline conditions (pH 6.5–9.0). Our results suggest that SexiCXE10 may play an important role in the degradation of the host plant volatiles, and thus contributes to the high sensitivity of the olfactory system in S. exigua. Meanwhile, the CXE would be a potential target for developing behavioral antagonists and pesticides against S. exigua.

Morphology of the Preimaginal Stages ofLasioptera donacisCoutin (Diptera: Cecidomyiidae), a Candidate Biocontrol Agent for Giant Arundo Cane

The larval stages ofLasioptera donacisCoutin consist of three instars which develop within the mesophyll of the leaf sheaths ofArundo donax(L.) (Poaceae). The larvae feed aggregatively on mycelia of an ambrosia fungus. The third instars are similar to other members of the genus except for a three-pronged spatula (typically two-pronged) and five lateral papillae (typically four) and with a nonbristled first instar. A related species,L. arundinis(Schiner) which breeds on fungus inPhragmites(Poaceae), also has a three-pronged spatula and five lateral papillae but has a bristled first instar. The third instar ofL. donacishas a feeding and a nonfeeding prepupal stage. Papillae associated with the spatula are sensory organs, sensilla chaetica, sensilla trichodea, and sensilla ampullacea, perhaps related to extraoral digestion of the fungal mycelia. Pupation occurs in the host plant within a silken cocoon. Egression of the adult is through an escape hatch excavated by the third instar.

Immunolocalization and role of an olfactory co-receptor in chemosensory organs of Aedes albopictus

An olfactory co-receptor gene AalbOrco was isolated and described from Aedes albopictus using the RACE technique. AalbOrco contained typical structures of seven transmembrane domains and Nin-Cout. Sequence analysis demonstrated that AalbOrco is very similar to Orco orthologs from other dipterans, especially in the C-terminus. AalbOrco was expressed at significantly higher levels in embryos compared with larvae, however, AalbOrco transcripts were found to greatly increase in number from the larval to the pupal stage and were at the highest level at the adult stage. Since AalbOrco is abundantly expressed in adults and is distributed in chemosensory organs such as the antenna, maxillary palps and proboscis suggests that AalbOrco may play an important role in locating hosts. In addition, AalbOrco is also highly expressed in male abdomens as compared to female abdomens, however, no expression was detected in the ovipositor and the copulatory organ. SEM (scanning electron microscopy) and immunolocalization showed that AalbOrco is located in the cell bodies of olfactory sensory neurons (OSNs) under antennal cuticula and the dendrites of neurons in sensilla trichodea. Moreover, fluorescence signals were detected in some neuronal cell bodies and sensilla T2 from the labellum but were scarcely detected in male maxillary palps. The transcription level of AalbOrco in female adults decreased by 55.7% after the larvae continued to ingest exogenous AalbOrco dsRNA expressed bacterially until eclosion. Blood-sucking behavior was impaired by 44.7% compared to the control groups, although pupation and emergence rate were not significantly different between the control and treatment groups. We conclude that AalbOrco has the general characteristics of Orco orthologs and plays an important role in host-locating behavior. AalbOrco performs the olfactory function in antennae as well as in female maxillary palps.

Insight Into the Ultrastructure of Antennal Sensilla of Mythimna separata (Lepidoptera: Noctuidae).

The oriental armyworm, Mythimna separata (Walk), is one of the most serious pests of cereals in Asia and Australasia. The structure and distribution of the antennal sensilla of M. separata were studied by scanning electron microscopy and transmission electron microscopy. The results showed that antennae of both female and male M. separata are filiform in shape. Three groups and seven morphological sensillum types were recorded in both sexes, including uniporous sensilla (sensilla chaetica), multiporous sensilla (sensilla trichodea, basiconica, coeloconica, and styloconica), and aporous sensilla (sensilla squamiformia and Böhm bristles). S. trichodea, which were the most abundant sensilla, was made of three subtypes (ST I, ST II, and ST III) according to external features and two subtypes of s. basiconica (SB I and SB II) and s. coeloconica (SCo I and SCo II) were identified, respectively. Sexual dimorphisms in sensilla of M. separata were mainly perceived as the variations in the numbers of several sensilla subtypes. Also, the possible functions of the antennal sensilla were discussed. These results contribute to our understanding of the function of antennae in the behavior of M. separata.

Morphology of the mouthparts of the spittlebug Philagra albinotata Uhler (Hemiptera: Cercopoidea: Aphrophoridae)

Mouthparts associated with feeding behavior and feeding habits are important sensory and feeding structures in insects. To obtain a better understanding of feeding in Cercopoidea, the morphology of mouthparts of the spittlebug, Philagra albinotata Uhler was examined using scanning electron microscopy. The mouthparts of P. albinotata are of the typical piercing–sucking type found in Hemiptera, comprising a cone-shaped labrum, a tube-like, three-segmented labium with a deep groove on the anterior side, and a stylet fascicle consisting of two mandibular and two maxillary stylets. The mandibles consist of a dorsal smooth region and a ventral serrate region near the apical half of the external convex region, and bear five nodules or teeth on the dorsal external convex region on the distal extremity; these are regarded as unique features that distinguish spittlebugs from other groups of Hemiptera. The externally smooth maxillary stylets, interlocked to form a larger food canal and a smaller salivary canal, are asymmetrical only in the internal position of longitudinal carinae and grooves. One dendritic canal is found in each maxilla and one in each mandible. Two types of sensilla trichodea, three types of sensilla basiconica and groups of multi-peg structures occur in different locations on the labium, specifically the labial tip with two lateral lobes divided into anterior sensory fields with ten small peg sensilla arranged in a 5 + 4 + 1 pattern and one big peg sensillum, and posterior sensory fields with four sensilla trichodea. Compared with those of previously studied Auchenorrhyncha, the mouthparts of P. albinotata may be distinguished by the shape of the mandibles, the multi-peg structures and a tooth between the salivary canal and the food canal on the extreme end of the stylets. The mouthpart morphology is illustrated using scanning electron micrographs, and the taxonomic and putative functional significance of the different structures is briefly discussed.

Influence of Different Statuses of Honey Bee Queens, Apis mellifera L. on the Ultrastructure of the Flagella on (3-Day Old) Workers

The effect of different statuses of honeybee queens, Apis mellifera (one-year-old mated queen; supersedure queen; three-day old virgin queen; queen cell; without queen; and without queen/without bee bread) on many aspects of 3- day old workers were studied with scanning electron microscopy (SEM). This study was carried out to describe the (types, distribution, numbers and measurements) of the different sensilla on the workers' flagellum. Electrone microscopic study of workers under different queen statuses showed the morphological structure of the antennae (Geniculate antennae). Each antenna composed of scape, a pedicel, and a flagellum of 10 segments. SEM revealed the presence of seven types and eleven subtypes of sensilla on the dorsal side of the different flagellomeres; they were Sensilla Ampullacea {Am}, Sen- silla Basiconica {Ba}, Sensilla Campaniformia {Cf}, Sensilla Chaetica I, II {Ch}, Sensilla Coelloconica I, II {Co}, Sen- silla Placodea I, II, III {PL}, Sensilla Trichodea I, II, III, IV {Tr}. This study revealed that, there is no significant differ- ence in the numbers of sensilla (Am), (Ba), (Co I) of the workers under all the queen statuses. The measurements of sen- silla Chaetica differ significantly according to the different queen statuses. The numbers and distributions of (Co II) were exhibited at extremely low percentages in the different statuses. There is significant difference in the percentages of each (PL I, II, III) between the different queen statuses. Also, the (Tr I, II, III, IV) are found in all statuses, There is significant difference in the percentages of each sensilla types between the different queen statuses.

Response profile of pheromone receptor neurons in male Grapholita molesta (Lepidoptera: Tortricidae)

The response profile of olfactory receptor neurons (ORNs) of male Grapholita molesta (Busck) to the three female sex pheromone components [(Z)-8-dodecenyl acetate (Z8-12:Ac), (E)-8-dodecenyl acetate (E8-12:Ac), and (Z)-8-dodecenyl alcohol (Z8-12:OH)] was tested with single sensillum electrophysiology. Sensilla trichodea housed normally one, but sometimes two or three ORNs with distinct action potential amplitudes. One third of the sensilla contacted contained ORNs that were unresponsive to any of the pheromone components tested. The remaining sensilla contained one ORN that responded either to the major pheromone component, Z8-12:Ac (“Z-cells”, 63.7% of sensilla), or to its isomer E8-12:Ac (“E-cells”, 7.4% of sensilla). 31% of Z- and E-sensilla had 1 or 2 additional cells, but these did not respond to pheromone. None of the 176 sensilla contacted hosted ORNs that responded to Z8-12:OH. The proportion of Z- and E-cells on the antennae (100:11.6, respectively) is similar to the proportion of these compounds in the blend (100:6, respectively). The response of Z-cells was very specific, whereas E-cells also responded to the Z isomer, albeit with lower sensitivity.

Scanning electron microscopy studies of antennal sensilla of Isoceras sibirica Alpheraky (Lepidoptera, Cossidae)

SummaryThe carpenterworm, Isoceras sibirica Alpheraky (Lepidoptera, Cossidae), is a destructive pest affecting Asparagus officinalis L. To provide background information for chemical ecology studies, we examined the external morphology of the antennal sensilla of this pest with scanning electron microscopy. Antennae of male and female I. sibirica are bipectinate in shape, and nine morphological sensilla types were recorded in both sexes. The uniporous sensilla chaetica are gustative sensilla. The multiporous sensilla trichodea, multiporous sensilla basiconica and multiporous sensillum coeloconica are presumably olfactive sensilla. The aporous sensilla styloconica are thermo-hygroreceptors while Böhm’s bristles monitor the position of the antennae.

Ultrastructure of antennal sensilla of an autoparasitoid Encarsia sophia (Hymenoptera: Aphelinidae)

Encarsia sophia (Hymenoptera: Aphelinidae) is a parasitoid utilized for biological control of Bemisia tabaci, with selection of prey aided by chemoreceptor organs. The morphology and distribution of the antennal sensilla (chemoreceptors) of E. sophia were examined using Transmission electron micrographs. The total antennal length for E. sophia was 429.28±0.95μm for females and 437.19±8.21 for males, and each antennae was found to consist of seven sensilla of different types. Both sexes possessed sensilla chaetica, sensilla trichodea, basiconic capitate peg sensilla, multiporous grooved-surface placoid sensilla (MG-PS), uniporous rod-like sensilla, nonporous finger-like sensilla, and sensilla coeloconica. Transmission electron micrographs of longitudinal sections of female antennae showed that they were composed of fat body, cuticle, mesoscutello-metanotal muscles, neurons, and glandular tissue, and cross-sections of the basal MG-PS showed sensillar lymph cavities and dendrites. The MG-PSs were imbedded in an electron-dense mass with cuticular invaginations which acted as pores that connected to a central lumen. The possible function of each type of sensilla is discussed.

The sensory neurone membrane protein SNMP1 contributes to the sensitivity of a pheromone detection system.

Male moths detect female-released sex pheromones with extraordinary sensitivity. The remarkable sensory ability is based on a cooperative interplay of pheromone binding proteins in the lymph of hair-like sensilla trichodea and pheromone receptors in the dendrites of sensory neurones. Here we examined whether in Heliothis virescens the so-called 'sensory neurone membrane protein 1' (SNMP1) may contribute to responsiveness to the pheromone component, (Z)-11-hexadecenal (Z11-16:Ald). By means of immunohistochemistry and in situ hybridization we demonstrated that SNMP1 is in fact present in cells expressing the Z11-16:Ald receptor HR13 and the dendrites of sensory neurones. To assess a possible function of SNMP1 we monitored the responsiveness of cell lines that expressed HR13 alone or the combination SNMP1/HR13 to stimulation with Z11-16:Ald by calcium imaging. It was found that SNMP1/HR13 cells were 1000-fold more sensitive to pheromone stimulation compared with HR13 cells. In contrast, cells that expressed HR13 and the non-neuronal SNMP2-type showed no change in pheromone sensitivity. Overall, our reconstitution experiments demonstrate that the presence of SNMP1 significantly increases the HR13-based responsiveness of cells to Z11-16:Ald, suggesting that SNMP1 also contributes to the response of the antennal neurones and thus to the remarkable sensitivity of the pheromone detection system.