Subtypes Of Sensilla Research Articles

Ultrastructure and distribution of antennal sensilla of parasitic wasp, Cotesia gregalis (Hymenoptera: Braconidae).

Cotesia gregalis Yang et Wei (Hymenoptera: Braconidae) is a gregarious koinobiont endoparasitic wasp attacking the larvae of fall webworm, Hyphantria cunea, an important invasive insect pest in China. To better understand the parasitic wasps' mating and parasitic behaviors, we examined the morphology of the antennae of adult C. gregalis, as well as the type, number, and distribution of antennal sensilla, via scanning electron microscopy. The antennae of female and male C. gregalis are filiform and comprise a scape, pedicel, and 16 flagellomeres. The female antennae are significantly shorter than those of male. A total of nine morphological types of antennal sensilla (mechanoreceptor and chemoreceptor) are presented in both sexes, including four mechanoreceptors (sensilla chaetica [two subtypes], sensilla trichodea and Böhm bristles); five chemoreceptors (sensilla basiconica [two subtypes], sensilla placodea, sensilla styloconica, and sensilla coelocapitula). There is no difference in the type and distribution of antennal sensilla between males and females, but the number and length of some antennal sensilla show sexual dimorphism. The functional morphology of the sensilla of C. gregalis is discussed by comparison with other parasitic wasps. These findings provide foundation for further research on the chemical communication and host localization mechanisms of C. gregalis. RESEARCH HIGHLIGHTS: The first report of morphology and distribution pattern of the antennal sensilla in C. gregalis is discussed. A total of seven main types and nine antennal sensilla subtypes are observed in male and female C. gregalis. The type and distribution of antennal sensilla in males and females are identical; however, the number and length of certain antennal sensilla show sexual dimorphism.

Ultrastructure of the antennal sensilla of the praying mantis Creobroter nebulosa Zheng (Mantedea: Hymenopodidae).

The praying mantis Creobroter nebulosa Zheng (Mantedea: Hymenopodidae) is an insect that has medicinal and esthetical importance, and being a natural enemy for many insects, the species is used as a biological control agent. In this publication, we used scanning electron microscopy (SEM) to study the fine morphology of antennae of males and females of this species. The antennae of both sexes are filiform and consist of three parts: scape, pedicel, and flagellum (differing in the number of segments). Based on the external morphology and the sensilla distribution, the antennal flagellum is could be divided into five regions. Seven sensilla types and eleven subtypes of sensilla were observed: grooved peg sensillum (Sgp), Bohm bristles (Bb), basiconic sensillum (Sb), trichoid sensillum (StI, StII), campaniform sensillum (Sca), chaetic sensillum (ScI, ScII, ScIII), and coeloconic sensillum (ScoI, ScoII). In Mantodea, the ScoII is observed for the first time, and it is located on the tip of the flagellum. The external structure and distribution of these sensilla are compared to those of other insects and possible functions of the antennal sensilla are discussed. The males and females of the mantis could be distinguished by the length of antennae and number of Sgp. Males have antennae about 1.5 times longer and have significantly larger number of Sgp compared to females. The sexual difference in distribution of the Sgp suggests that this type of sensilla may play a role in sex-pheromones detection in mantis.

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

Sensilla on head appendages were studied in detail for the first time in a member of the relict family Hygrobiidae (squeak beetles), closely related to Dytiscidae (diving beetles). Adult and third instar larval stage specimens of Hygrobia hermanni (Fabricius, 1775) were examined using scanning electron microscopy, focusing on antennae, palps and larval mandibles. In total, 37 sensilla subtypes are described, including 22 observed in the adult (basiconica: 3; Böhm's bristles: 2; circumvallate sensilla: 2; coeloconica: 10; ovoid placodea: 3; digitiform placodea: 2) and 16 in the larva (basiconica: 4; campaniformia: 1; chaetica: 4; coeloconica: 5; trichodea: 1; unnamed: 1). Only one subtype (of sensilla coeloconica) was shared between the adult and the larva. Autapomorphies of Hygrobiidae and Dytiscidae, and putatively shared derived characters (synapomorphies) of Hygrobiidae + Dytiscidae are discussed. Among the latter, the most remarkable is the acquisition of a special sensory field, located on the apical segment of the adult maxillary palp, subapically and postero-dorsally. This sensory field is made up of ovoid multiporous sensilla placodea otherwise present on the anterior (internal) surface of antennal segments, suggesting that in a common ancestor of Hygrobiidae and Dytiscidae, maxillary palps might have taken over enhanced capacities of longe-range molecule detection.

Morphology and distribution of sensilla on antennae and mouthparts of the adult bruchid beetles, Bruchidius coreanus (Coleoptera: Bruchidae).

Bruchidius coreanus is a serious pest on Gleditsia sinensis Lam during seed storage, causing significant losses to their yield in southwest China. To gain insight into their behavioral mechanisms, the external morphology, ultrastructure, and distribution of sensilla on antennae, maxillary palps, and labial palps of both male and female B. coreanus were observed using a scanning electron microscope. The results revealed that both male and female adults had serrated antennae comprising a scape, a pedicel, and nine flagellomeres (F1-F9). There were eight types and seven subtypes of antenna sensilla observed in both sexes, including Böhm sensilla (BS), two subtypes of sensilla chaetica (SC1 and SC2), two subtypes of sensilla trichodea (ST1 and ST2), three subtypes of sensilla basiconica (SB1, SB2, and SB3), sensilla auricillica (SA), sensilla styloconicum (SS), capitate pegs (CP), and sensilla cavity (SCa). The average length of BS and ST (ST1 and ST2) showed significant differences between males and females. Furthermore, the number of SC (SC1 and SC2), ST1, and SCa differed significantly between the sexes. Four types of sensilla were found on the maxillary palps and labial palps, with the length of ST on these palps significantly differing between males and females. Additionally, SS on male labial palps was significantly longer than in females. The number of SC significantly differed between the male and female maxillary palps and labial palps, while ST and SS showed significant differences in the maxillary palps. These findings will contribute to further electrophysiological recording and behavioral research. RESEARCH HIGHLIGHTS: The external morphology and distribution of various sensilla on the antennae, maxillary palps, and labial palps of Bruchidius coreanus were described. Eight types and seven subtypes of antenna sensilla were observed on the antennae, while four types of sensilla were observed on the maxillary palps and labial palps. The capitate pegs were found exclusively on the antennae of female B. coreanus.

Microscopic morphology and distribution of the antennal sensilla in the double-spined bark beetle, Ips duplicatus (Coleoptera: Curculionidae).

The double-spined spruce bark beetle, Ips duplicatus, has become an infamous secondary pest of Norway spruce, causing extensive ecological and economic destruction in many Central European countries. Antennae are the primary olfactory organs that play a fundamental role in insect-host chemical communication; therefore, understanding morphology is crucial before conducting electrophysiological investigations. Here, we present our analysis of sensilla types on the antennal surface of I. duplicatus for the first time, using high-resolution-scanning electron microscopy. We studied the external morphological characteristics of antennae and the types, numbers, and distribution of the antennal sensilla in males and females. Our results revealed the presence of five different types of morphologically distinct sensilla: sensilla chaetica, sensilla basiconica, sensilla trichodea, sensilla coeloconica, and Böhm's sensilla. We observed two subtypes of sensilla chaetica (SChI and SChII), four subtypes of sensilla basiconica (SBI, SBII, SBIII, and SBIV), three subtypes of sensilla trichodea (STrII, STrIII, and STrIV) and two subtypes of sensilla coeloconica (SCoI and SCoII), respectively in I. duplicatus males and females. Minor differences in length and numbers between the sexes for some sensilla types were found. Distribution maps for different sensillar types were constructed, and specific areas for the respective sensilla were found. Possible functions of observed sensilla types are discussed. The present study provides a basis for future electrophysiological studies to understand how I. duplicatus detects ecologically important olfactory cues. RESEARCH HIGHLIGHTS: • The first report of morphology and distribution pattern of the antennal sensilla in Ips duplicatus is discussed. • A total of 6 main types and 11 antennal sensilla subtypes were observed in male and female Ips duplicatus. • Minor sex-specific differences were seen in the length and numbers in several sensilla types.

Morphological Characterstics of the Sensilla in a Monophagous Insect: Agasicles hygrophila Selman and Vogt (Coleoptera: Chrysomelidae, Halticinae).

Agasicles hygrophila Selman and Vogt (Coleoptera: Chrysomelidae) is the key natural enemy of Alternanthera philoxeroides (Mart.) Griseb, an invasive weed worldwide. To understand the morphology of A. hygrophila and further explore the specific host localization mechanism, scanning electron microscopy was used to observe and study the morphological characteristics of sensilla on the head appendages, tarsi, and external genital segments of A. hygrophila. Twelve types and forty-six subtypes of sensilla were observed. These contain various types of head appendices, including sensilla chaetica, sensilla trichodea, sensilla basiconca, sensilla coeloconica, sensilla styloconica, Böhm bristles, sensilla campaniform, sensilla terminal, sensilla dome, sensilla digit-like, sensilla aperture, and many subtypes. A new type of sensor was reported for the first time, which may be related to host plant recognition. This sensor was located on the distal segment of the maxillary palps of A. hygrophila and was named as sensilla petal-shaped based on its morphological characteristics. Sensilla chaetica, sensilla trichodea, and sensilla basiconca are also found on the tarsi and external genital segments. In addition, sensilla basiconica 4, sensilla coeloconica 1 and 2, sensilla styloconica 2, Böhm bristles 2, and sensilla campaniform 1 were only found in females. On the contrary, sensilla styloconica 3, sensilla coeloconica 3, and sensilla dome were only found in males. Numbers and sizes of the sensilla were also different between males and females. The potential functions related to structure were discussed in comparison with previous investigations on beetles and other monophagous insects. Our results provide a microscopic morphological basis for further research on the localization and recognition mechanism of A. hygrophila and its obligate host.

Secondary Rhinaria Contribute to Major Sexual Dimorphism of Antennae in the Aphid Semiaphis heraclei (Takahashi)

Sexual generation is an important generation in the life cycle of host-alternating aphids, and its population size determines the intensity of the peak in the next spring. Although male trapping techniques based on olfactory stimuli have been successfully established in the field, the biological basis of olfactory perception in males is unclear. In this study, we compared the morphology of antennae and the types, sizes, numbers, and distribution of sensilla between males and sexual females in the host-alternating aphid Semiaphis heraclei (Hemiptera: Aphididae). We found that flagellum length differentiation contributed to the majority of the sexual dimorphism of antennae. Most sensillum types or subtypes, including trichoid sensilla subtype I, campaniform sensilla, and primary rhinaria subtypes I and II, were enlarged in males. In addition, males bore more trichoid sensilla subtype I than sexual females. In particular, secondary rhinaria were present in males only and could not be detected in sexual females. These results revealed the structural basis of male olfactory perception. Our findings provide insight into the mechanism underlying chemical communication between sexual aphids and could thus be useful for pest control.

Morphology of the Antennal Sensilla of the Nymphal Instars and Adults in Notobitus meleagris (Hemiptera: Heteroptera: Coreidae)

The bamboo bug Notobitus meleagris (Fabricius, 1787) is a serious pest of bamboo shoots in China, India, Myanmar, Vietnam, and Singapore. The antennae of the nymphal instars and adults of N.meleagris are involved in communication among individuals and finding the host plants. In order to understand the morphology of antennal sensilla, their types, and the distribution of sensilla on the antennae of nymphal instars and adults in N. meleagris, we studied the morphology of antennal sensilla with a scanning electron microscope. The antennae of the nymphs and adults comprised the scape, pedicel, and two flagellomeres. Four types and eight subtypes of sensilla were identified in the nymphal instars (sensilla trichodea [St].1, St.2, St.3, sensilla basiconica [Sb].1, Sb.2, sensilla chaetica [Sc].1, Sc.2, sensilla coeloconica [Sco].1), whereas those of the adults had five types and eleven subtypes of sensilla (St.1, St.2, St.3, Sb.1, Sb.2, Sb.3, Sc.1, Sc.2, Sco.1, Sco.2, and sensilla campaniformia [Sca]). There are significant differences in the number, type, and size of the sensilla in different nymphal instars, which increases with the increase in nymphal instars. There was no sexual dimorphism observed in the adult sensilla; however, the length and diameter of St.3, Sb.2, and Sb.3 were sexually dimorphic. The potential functions of each sensillum were discussed based on the morphology and distribution of the antennal sensilla and were compared with similar published studies. Our results provide primary data for further research on the behavioral mechanism, green prevention, and control of N. meleagris.

Evaluation of the Internal Morphology of Antennal Sensilla in Scirpophaga Incertulas for Male and Female by Scanning Electron Microscopy

The Scirpophaga incertulas (Walker), trivial name Yellow Stem Borer (YSB) is a serious pest contributing to significant yield loss to rice. YSB detects host/mate cues through olfactory receptors (sensilla) on antennae, which is critical for its survival, adaptability, and perpetuation. Though YSB is a destructive pest, its mechanism of olfaction is poorly understood. Using a scanning electron microscope, it is attempted to detect distinct sensilla, decode their characteristics, and compare the antennal sensilla of both males and females. Sensilla trichodea (S.T), Sensilla chaetica (S.Ch), Sensilla styloconica (S.St), Sensilla squamiformia (S.Sq), Sensilla coeloconica (S.Co), Sensilla cavity, and Bőhm bristles (BB) are the seven distinct kinds and subtypes of sensilla are recognized. Sexual dimorphism was observed in the arrangement of scales over the antenna in males and females. Interestingly, among the subtypes, the S.T-I was observed only in males. Furthermore, Sensilla coeloconica without a fence (type II) noticed in our studies was also reported earlier in other monophagous lepidopteran pests. The statistical analysis of the number and size of sensilla clearly indicates their involvement in sexual differentiation. This study may help in better understanding the processes of communication, identification of plant volatiles, oviposit site, and mate in YSB.

Ultrastructure of the Sensilla on the Antennae and Mouthparts of Bean Weevils, Megabruchidius dorsalis (Coleoptera: Bruchinae).

Simple SummaryIn this paper, we used scanning electron microscopy (SEM) to describe the morphological types, number of sensilla, and their distributions on the antennae and mouthparts of both sexes of the bean weevil, Megabruchidius dorsalis (Coleoptera: Bruchinae). The results showed twelve subtypes on antennal sensilla and five types of sensilla on maxillary and labial palps. No sexual dimorphism in sensilla type was observed, but there were variations between male and female in the numbers and distribution along with the antennae. In addition, we discussed potential function related to structure, through comparisons with previous studies of bruchids and other insects. This information will support further studies of semiochemicals as effective biological controls of this pest.Megabruchidius dorsalis (Fåhraeus, 1839) (Coleoptera: Bruchinae) is an important pest that damages the seeds of Gleditsia L. (Fabaceae: Caesalpinioideae). This beetle searches for host plants with its sensory system. To further explore the mechanisms of host location and to understand the ultrastructure of M. dorsalis, we examined the morphology and distribution of its sensilla on the antennae and mouthparts of male and female adults, using scanning electron microscopy (SEM). Both male and female antennae are serrated and can be divided into scape, pedicel, and flagellum. There were seven types and eight subtypes of antennal sensilla, including Bőhm bristles (BB), two subtypes of sensilla trichoid (ST1, ST2), two subtypes of sensilla chaetica (SC1, SC2), four subtypes of sensilla basiconic (SB1, SB2, SB3, SB4), sensilla cavity (SCa), sensilla auricillica (SA), and sensilla gemmiformium (SG). Five types of maxillary and labial palp sensilla in the mouthparts were observed: sensilla chaetica (SC), sensilla trichoidea (ST), sensilla styloconica (SSt), sensilla coeloconica (SCo), and sensilla digitiform (SD). No sexual dimorphism in sensilla type was observed, but there were variations between males and females in the numbers and distribution along the antennae. There were more SA in males than in females, while the number of ST sensilla in the maxillary palps were lower in males than in females. ST1 were most abundant in both sexes. We discussed potential function related to structure via comparisons with previous investigations of bruchids and other insects. Our results provide a theoretical basis for further studies on sensory physiological function, using semiochemicals as effective biological controls of M. dorsalis.

Scanning Electron Microscope Study of Antennae and Mouthparts in the Pollen-Beetle Meligethes (Odonthogethes) chinensis (Coleoptera: Nitidulidae: Meligethinae).

Simple SummaryThe present paper is aimed to further explore the structure of the antennae and mouthparts of specialized beetle species living on flowers, as well as the functions of their associated sensilla. In this study, we used scanning electron microscopy (SEM) to observe and describe for the first time the fine morphology of sensilla on the antennae and mouthparts of the pollen-beetle Meligethes (Odonthogethes) chinensis, a common Chinese species associated with flowers of Rosaceae. The results show that there are six types and twelve subtypes of sensilla on male antennae; seven types and fourteen subtypes on female antennae; seven types and seventeen subtypes on male mouthparts; seven types and sixteen subtypes on female mouthparts. The sensilla on the antennae and mouthparts of Meligethinae that feed on pollen were finally compared with similar sensilla known to occur in other insects, in order to obtain more insights on the evolution of these sensorial structures in specialized flower-inhabiting insects.Meligethes (Odonthogethes) chinensis is a common Chinese phytophagous species in the family Nitidulidae. Its main larval host plant is Rubus idaeus L. (Rosaceae), and adults feed on pollen and other floral parts. In this study, we used scanning electron microscopy (SEM) to observe and study the fine morphology of sensilla on the antennae and mouthparts of M. chinensis. The results show that there are six types and twelve subtypes of sensilla on male antennae; seven types and fourteen subtypes on female antennae; seven types and seventeen subtypes on male mouthparts; seven types and sixteen subtypes on female mouthparts. Sensilla coeloconica (SCo) are found on the female antennae of M. chinensis only, and they are also reported on the antennae of Nitidulidae for the first time. SCo2 on the labrum present sexual dimorphism, and one subtype of sensilla basiconica (SB6) is presented on the tip of maxillary and labial palps of the male only, while other types of sensilla are very similar on the mouthparts of male and female. Finally, by comparing similar sensilla in other insects, we also attempted to discuss the functions of all sensilla on the antennae and mouthparts of M. chinensis.

Sensilla on antennae and mouthparts of adult spruce bark beetle Ips typographus (Coleoptera: Curculionidae).

The spruce bark beetle, Ips typographus, is an invasive forest pest that occurs across Eurasia. To further understand the mechanism of insect-host chemical communication and the feeding choices of adult I. typographus, we examined the sensilla on the antennae and mouthparts of I. typographus using scanning electron microscopy. No sexual dimorphism in sensilla type or distribution was observed. Ten subtypes of antennal sensilla were identified: sensilla trichodea Types I-III (TR1 , TR2 , and TR3 ); sensilla chaetica Types I and II (CH1 and CH2 ); sensilla basiconica Types I-III (BA1 , BA2 , and BA3 ); sensilla coeloconica (CO); and Böhm sensilla (BS). BA2 were the most abundant among the antennal sensilla in both sexes. Thirteen mouthpart sensilla subtypes were observed: sensilla trichodea Types I-IV (TR1 , TR2 , TR3 , and TR4 ); sensilla chaetica Types I-III (CH1 , CH2 , and CH3 ); sensilla digitiformia (DI); sensilla basiconica Types I-II (BA1 and BA2 ); and sensilla styloconica Types I-III (ST1 , ST2 , and ST3 ). Among these, TR4 were the most abundant in both sexes. The apex of each maxillary and labial palp carried the same sensilla (BA2 , ST1 , ST2 , and ST3 ), although the apex of the maxillary palp contained more total sensilla. The functional roles of each sensilla type are discussed based on their external structure and distribution. The results provide a theoretical basis for further studies on the olfactory and feeding behaviors and electrophysiology of adult I. typographus.

SEM analysis of sensilla on the mouthparts and antennae of Asian larch bark beetle Ips subelongatus

The Asian larch bark beetle, Ips subelongatus, is a severe pest of larches in Northeastern China. The gustatory and olfactory systems of I. subelongatus play important roles in host location, mating, and feeding. In this study, we examined the types, distributions, and abundances of various sensilla associated with the mouthparts and antennae of I. subelongatus using scanning electron microscopy (SEM). On the mouthparts, five types of sensilla are present: sensilla trichodea (S.t.1–3), sensilla chaetica (S.c.1–3), sensilla basiconica (S.b.1–2), sensilla twig basiconica (S.tb.1–3), and sensilla placodea (S.p). S.t.3 are the most abundant sensilla subtype on the mouthparts in both sexes, while S.b.1 are the least abundant. Most sensilla on the mouthparts are located on the maxillae and labium, and the apex of each maxillary and labial palp carry the same sensilla subtypes (S.b.2 and S.tb.1–3). However, the total number of sensilla on the apex of each maxillary palp is higher than that on the labial palp. On the antennae, five types of sensilla are present: sensilla trichodea (S.t.1–3), sensilla chaetica (S.c.1–2), sensilla basiconica (S.b.1–3), Böhm bristles (B.b), and sensilla coeloconica (S.co). Antennal sensilla are mostly situated on the anterior surface of the antennal club, particularly on the two dense sensory bands. S.b.1 are the most abundant sensilla subtype on the antennae in both sexes, while S.t.1 are the least abundant. No sexual dimorphism in sensilla type or distribution on the mouthparts or antennae is observed between the sexes of I. subelongatus. However, S.t.3 (on mouthparts) and S.c.1 (on antennae) were significantly more abundant in males than in females, while more S.t.1 (on mouthparts) were observed in females than in males. Finally, the putative functions of each kind of sensilla with respect to their fine structures, distributions, and abundances on the mouthparts and antennae are discussed.

Ultrastructure of the Antennae and Sensilla of Nyssomyia intermedia (Diptera: Psychodidae), Vector of American Cutaneous Leishmaniasis.

The antennal sensilla and the antenna of females Nyssomyia intermedia, one of the main vectors of American cutaneous leishmaniasis, were studied by scanning electron microscopy. The main goal was to characterize the quantity, typology, and topography of the sensilla with particular attention to the olfactory types. The insects were captured in the city of Corte de Pedra, State of Bahia, Brazil, by CDC-type light traps and raised in a laboratory as a new colony. Fourteen well-differentiated sensilla were identified, among six cuticular types: trichoidea, campaniformia, squamiformia, basiconica, chaetica, and coeloconica. Of these, six sensilla were classified as olfactory sensilla due to their specific morphological features. Smaller noninnervated pilosities of microtrichiae type were also evidenced by covering all antennal segments. The antennal segments differ in shapes and sizes, and the amount and distribution of types and subtypes of sensilla. This study may foment future taxonomic and phylogenetic analysis for a better evolutionary understanding of the sand flies. Besides, it may assist the targeting of future electrophysiological studies by Single Sensillum Recording, and aim to develop alternative measures of monitoring and control of this vector.

Structure and Evolution of the Antennal Sensory Surface in Endemic Caddisfly Tribes Baicalinini and Thamastini (Trichoptera: Apataniidae) from Lake Baikal

A study of cuticular structures in 10 species from different phylogenetic lineages of Apataniidae enabled determination of the repertoire of antennal sensory surface which includes 8 types and subtypes of sensilla: long trichoid, curved trichoid, chaetoid, mushroom-like pseudoplacoid, spear-like pseudoplacoid, basiconic and coronary sensilla, as well as Bohm’s bristles. Major distribution patterns of sensilla in Apataniidae were established. Trends in the evolution of antennal structures within the endemic tribes Baicalinini and Thamastini of Lake Baikal were revealed.

Antennal Morphology and Ultrastructure of Holotrichia parallela (Coleoptera: Scarabaeidae)

Antennal morphology and type and distribution of antennal sensilla of Holotrichia parallela (Motschulsky) (Coleoptera: Scarabaeidae) were determined using scanning electron microscopy and transmission electron microscopy. Holotrichia parallela antennae were a typical lamellate type, including a basal scape, a pedicel, a flagellum, and a lamellar club composed of the three terminal flagellomeres. The antennae of males were slightly longer than those of females. Twenty-two subtypes of sensilla were identified on the outer and inner surfaces of the lamellae in both sexes: three sensilla trichodea (TRS), three sensilla chaetica (CHS), four sensilla placodea (PLAS), two sensilla coeloconica (COS), six sensilla auricilica (AUS), one Bohm's bristle (BB), and three sensilla basiconica (BAS). TRS, CHS, and BB were distributed primarily on the outer surfaces of the antennae as mechanoreceptor sensilla, while PLAS, COS, AUS, and BAS were concentrated on the inner surfaces of the lamellae as chemoreceptors. PLAS and BAS were more abundant in males than in females, but females had more COS and AUS. PLAS were distributed along the lamellar periphery, while COS, BAS, and AUS were distributed in the center of the lamellae.

Sensilla on the Antennal Funiculus of the Maize Weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae): A Morphological Investigation

Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae) has a great capacity to destroy stored grain worldwide. We report on the sensilla on the antennal funiculus of S. zeamais, using classical anatomical methods and scanning electron microscopy to obtain a detailed database of the antennal sensilla for each sex. The antenna is composed of eight antennomeres. Average antennal length is 781.58±20.64 µm for males and 808.91±11.80 µmfor females. Six types and subtypes of sensilla were identified on the funiculus: squamiform, basiconic (2 subtypes), chaetic (2 subtypes), and coeloconic. Sensilla squamiformia are distributed evenly but in few numbers on male and female antennomeres. Sensilla basiconica can be divided into subtypes, SB1 and SB2, according to the shape of the cone. Both subtypes occur on the last antennomere of the flagellum and there are fewer SB2 than SB1. Sensilla chaetica appear in the same position as sensilla basiconica and have two subtypes, SC1 and SC2. Significant differences were not found in the types of sensilla on the antennae of the two sexes, but a difference was found in the number of sensilla.

The molecular and cellular basis of olfactory response to tsetse fly attractants.

Dipteran or “true” flies occupy nearly every terrestrial habitat, and have evolved to feed upon a wide variety of sources including fruit, pollen, decomposing animal matter, and even vertebrate blood. Here we analyze the molecular, genetic and cellular basis of odor response in the tsetse fly Glossina morsitans, which feeds on the blood of humans and their livestock, and is a vector of deadly trypanosomes. The G. morsitans antenna contains specialized subtypes of sensilla, some of which line a sensory pit not found in the fruit fly Drosophila. We characterize distinct patterns of G. morsitans Odor receptor (GmmOr) gene expression in the antenna. We devise a new version of the “empty neuron” heterologous expression system, and use it to functionally express several GmmOrs in a mutant olfactory receptor neuron (ORN) of Drosophila. GmmOr35 responds to 1-hexen-3-ol, an odorant found in human emanations, and also alpha-pinene, a compound produced by malarial parasites. Another receptor, GmmOr9, which is expressed in the sensory pit, responds to acetone, 2-butanone and 2-propanol. We confirm by electrophysiological recording that neurons of the sensory pit respond to these odorants. Acetone and 2-butanone are strong attractants long used in the field to trap tsetse. We find that 2-propanol is also an attractant for both G. morsitans and the related species G. fuscipes, a major vector of African sleeping sickness. The results identify 2-propanol as a candidate for an environmentally friendly and practical tsetse attractant. Taken together, this work characterizes the olfactory system of a highly distinct kind of fly, and it provides an approach to identifying new agents for controlling the fly and the devastating diseases that it carries.

Antennal Morphology and Sexual Dimorphism of Antennal Sensilla in Callitettix versicolor (Fabricius) (Hemiptera: Cercopidae).

The rice spittlebug Callitettix versicolor (Fabricius) is an important pest of rice and maize in South Asia and causes severe economic damage. To provide background information for chemical ecology studies, the fine morphology of antennae and the types and distribution of the sensilla on the male and female antennae of Callitettix versicolor (Fabricius) are investigated by means of scanning electron microscopy (SEM). Results show that the antenna is filiform and composed of three segments: a scape, a pedicel, and a flagellum. The female antennae are slightly shorter than the male antennae. In both sexes, four types and nine subtypes of sensilla were observed: sensilla basiconica (SB1, SB2), sensilla campaniformia (SCa1, SCa2 and SCa3), sensilla coeloconica (SCo1, SCo2 and SCo3) and sensilla trichodea (ST). In addition, sensilla coeloconica (SCo1) are observed on the membrane of the top of the pedicel in Cercopidae for the first time. Sexual dimorphism mainly occurs in variation in the number of sensilla coeloconica (SCo2, SCo3) on the bulb-shaped portion of the flagellum and in the shape of sensilla basiconica (SB2). There are significantly more sensilla coeloconica in males than in females. The external structure and distribution of these sensilla are compared to those of other cercopids and possible functions of the antennal sensilla are discussed.

Ultrastructural Observations of Antennal Sensilla inPhauda flammansWalker (Lepidoptera: Zygaenidae)1

Abstract Ficus microcarpa L. and F. racemosa L. are often extensively damaged by the defoliating pest Phauda flammans Walker (Lepidoptera: Zygaenidae). The structure, morphology, abundance, and distribution of the antennal sensilla of P. flammans were studied using scanning electron microscopy. Six types and eight subtypes of sensilla were observed on the filiform antennae of both sexes, including trichodea (subtypes I and II), basiconica (subtypes I and II), coeloconica, styloconica, chaetica, and Bohm bristles. The most numerous sensilla were the trichodea on the antennae of both sexes. Sexual dimorphism was observed, with the male antennae having more sensilla trichodea than the female antennae. This information is essential for understanding the electrophysiological and behavioral aspects of chemical communication in P. flammans.