Sensilla Coeloconica Research Articles

Association between host species choice and morphological characters of main sensory structures of Culicoides in the Palaeartic region.

Culicoides (Diptera: Ceratopogonidae) serve as vectors of several mammalian and avian diseases, including bluetongue, Schmallenberg, African horse sickness, avian malaria and Oropouche. Host preference investigations are necessary to assess the transmission routes of vector-borne diseases and to inform mitigation strategies. A recent study examining the main sensory structures (palps and antennae) of Culicoides species suggests that they be classified as ornithophilic or mammalophilic according to their feeding habits. We analyzed Culicoides host preferences according to the literature and carried out a multiple correspondence analysis linking these preferences with morphological data. Seven out of 12 variables were found to be reliable predictors of host preference in Culicoides species: Antenna Flagellomer-Sensilla Coeloconica-Number: (7–10) and (11–13); Antenna Flagellomer-Sensilla Coeloconica IV–X: presence; Palpus-size: wide and/or narrow opening and shallow pit; Palpus-Shape: strongly swollen; Antenna-Short sensilla trichodea-distal part segment IV to X-Number: 2 seta each. Our results demonstrate that the presence of sensilla coeloconica and the maxillary palpus can be used to separate ornithophilic and mammalophilic or ornithophilic/mammalophilic species.

A New Type of Mythimna Separata (Lepidoptera: Noctuidae) Antennal Sensilla

ABSTRACT: The Oriental armyworm, Mythimna separata Walker (Lepidoptera: Noctuidae), is a major polyphagous pest with a wide range of hosts in Asia and Oceania. Scanning electron microscopy was used to further elucidate the function of the antennal sensilla and their type, number, and distribution in M. separata. The antenna of M. separata is filamentous. On each three-segmented antenna, from the basal scape, there is a pedicel and a flagellum composed of 70–80 subsegments. Eight morphologically distinct types of sensilla were found on the antennae, including sensilla trichodea, two types of sensilla chaetica, sensilla basiconica, sensilla styloconica, sensilla coeloconica, sensilla squamiformia, sensilla auricillica and Bohm bristles. Sensilla auricillica were found on the antennae of both sexes of M. separata for the first time. The sensilla auricillica in females were located on flagella F23–F44, while they were located on flagella F5–F80 in males.

Morphological study of the antennal sensilla in Gerromorpha (Insecta: Hemiptera: Heteroptera)

The external morphology and distribution of the antennal sensilla of 21 species from five families of semiaquatic bugs (Gerromorpha) were examined using scanning electron microscopy. Nine main types were distinguished based on their morphological structure: sensilla trichoidea, sensilla chaetica, sensilla leaflike, sensilla campaniformia, sensilla coeloconica, sensilla ampullacea, sensilla basiconica, sensilla placoidea and sensilla bell-mouthed. The specific morphological structure of one type of sensilla (bell-mouthed sensilla) was observed only in Aquarius paludum. Several subtypes of sensilla are described, differentiated by number, location and type of sensillum characteristic for each examined taxon. The present study provides new data about the morphology and distribution of the antennal sensilla in Gerromorpha.

An effective method for the identification and separation of Anopheles minimus, the primary malaria vector in Thailand, and its sister species Anopheles harrisoni, with a comparison of their mating behaviors

BackgroundSpecies of the Anopheles minimus complex are considered to be the primary vectors of malaria in South and Southeast Asia. Two species of the complex, Anopheles minimus and Anopheles harrisoni, occur in Thailand. They are sympatric and difficult to accurately distinguish based on morphological characters. The aim of this study was to investigate the potential of antennal sensory organs to distinguish these two species. Additionally, we investigated their ability to mate in cages of different sizes, as well as the possible mechanism(s) that evokes stenogamous behavior.MethodsLarge sensilla coeloconica present on the antennae of females of An. minimus and An. harrisoni were counted under a conventional light microscope and various types of antennal sensilla were examined under a scanning electron microscope (SEM). Determinations of mating ability were carried out in 20 and 30 cm3 cages with a density resting surface (DRS) of 7.2. The insemination rate, frequency of clasper (gonocoxopodite) movement of the male genitalia during induced copulation and duration of mating of the two species were compared.ResultsThe mean numbers of large sensilla coeloconica on antennal flagellomeres 1–8 and the mean number of large sensilla coeloconica on each flagellum in An. minimus (26.25) and An. harrisoni (31.98) were significantly different. Females of both species bear five types of antennal sensilla: chaetica, trichodea, basiconica, coeloconica and ampullacea. Marked differences in the structure of the large sensilla coeloconica were observed between the two species. Furthermore, only An. minimus could copulate naturally in the small cages. The frequency of clasper movement in the stenogamous An. minimus was significantly higher than in An. harrisoni, but there was no difference in the duration of mating.ConclusionsTo our knowledge, this study is the first to examine and discover the usefulness of large sensilla coeloconica on the antennae of females and the frequency of clasper movement in males for distinguishing the sibling species An. minimus and An. harrisoni. The discovery provides an effective and relatively inexpensive method for their identification. Additionally, the greater frequency of clasper movement of An. minimus might influence its ability to mate in small spaces.

Structure and distribution of the sensilla on the antennae of Tuta absoluta (Lepidoptera: Gelechiidae)

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is a widespread devastating pest that develops on tomato and other economically important solanaceous crops. Current semiochemically-based management strategies still fail to significantly reduce damages and need to be improved. Here we describe under scanning and transmission electron microscopy the structure and distribution of the sensilla that are displayed on adult antennae. These were similar in size between males (3424.4±135.3μm) and females (3292.1±111.5μm), being segmented into a scape, a pedicel, and a distal filiform flagellum. Eight morphological sensilla types were observed on both sexes: Böhm’s bristles, sensilla squamiformia, sensilla trichodea, sensilla basiconica (two subtypes), sensilla chaetica, sensilla coeloconica, sensilla auricillica, and sensilla styloconica. The main sexual dimorphism was related to the higher abundance of sensilla trichodea in males, twice as abundant as in females. The putative functional significance of the different sensilla types regarding the insect ecology is discussed based on the available literature. This work provides descriptions of the antennae and related sensory structures. We expect these results to help develop further electrophysiological investigations aiming to a better understanding of T. absoluta olfaction.

Ultrastructure of sensilla of antennae and ovipositor of Sitotroga cerealella (Lepidoptera: Gelechiidae), and location of female sex pheromone gland

The Angoumois grain moth, Sitotroga cerealella, is a serious pest of stored grains worldwide. Presently, the best effective control against the moth is to disrupt the sexual communication between sexes. Sexual communication in moths includes two processes in which females produce and release pheromones from the sex pheromone gland and males detect and respond to them with a relatively sophisticated olfactory system in their antennae. To better understand these processes, we studied the ultrastructure of antennal and ovipositor sensilla of S. cerealella and determined the location of the female sex pheromone gland. Seven types of antennal sensilla were identified on both sexes: sensilla trichodea, sensilla chaetica, sensilla coeloconica, sensilla styloconica, sensilla auricillica, sensilla squamiformia and Bӧhm bristles. Of these sensilla, the sensilla trichodea were significantly more abundant on male antennae than on those of females, suggesting that these sensilla may detect the sex pheromones. On the ovipositor, only sensilla chaetica of various lengths were found. The sexual gland was an eversible sac of glandular epithelium that was situated dorsally in the intersegmental membrane between the 8th and 9th abdominal segments. These results will lead to a better understanding of mate finding with sex pheromones for this worldwide pest species.

A comparison between the adult antennal sensilla of the cavernicolous stonefly Protonemura gevi and other epigean Protonemura species (Plecoptera: Nemouridae) in a biological context

SummaryIn the present paper we study the antennal sensilla of the unusual hypogean stonefly Protonemura gevi Tierno de Figueroa & López-Rodríguez, 2010 (Plecoptera: Nemouridae), comparing them with those of two epigean species of the genus Protonemura, P. alcazaba (Aubert, 1954) and P. meyeri (Pictet, 1842), with the aim to describe possible peculiarities. No differences exist in the types and morphology of antennal sensilla among the studied species and neither between sexes. The types of sensilla identified are long aporous trichoid sensilla with a tactile function, uniporous gustatory sensilla chaetica, multiporous sensilla basiconica (porous pegs) and sensilla coeloconica (digitated pegs), with a supposed olfactory function, and domes probably hosting aporous thermohygroreceptive pegs. These sensilla are very similar to those observed in other Plecoptera families and described in detail in Dinocras cephalotes (Curtis, 1827), thus suggesting a quite conserved sensory function for the antenna in the whole order, as it happens in other aquatic insects, such as Ephemeroptera and Odonata.

Scanning Electron Microscopy Study of the Antennal Sensilla of Monema flavescens Walker (Lepidoptera: Limacodidae).

Monema flavescens Walker (Lepidoptera: Limacodidae) is a serious polyphagous defoliator. Using scanning electron microscopy, the external morphology of the antennal sensilla of this pest was examined for a better understanding of the mechanisms of insect-insect and insect-plant chemical communications. The antennae of M. flavescens were filiform in shape, and 11 morphological types of sensilla were found in both sexes. Six types of likely chemosensory sensilla were identified: uniporous sensilla chaetica, multiporous sensilla trichodea, and four types of multiporous sensilla basiconica. The sensilla identified as likely mechanoreceptors included two subtypes of aporous sensilla chaetica, aporous sensilla coeloconica, aporous sensilla styloconica, and Böhm's bristles, whereas the position of the antennae was monitored by Böhm's bristles.

Antennal and mouthpart sensilla of Acanthoscelides obtectus say (Coleoptera: Bruchidae).

Acanthoscelides obtectus, a serious pest with a worldwide distribution, damages stored seeds of Phaseolus sp. To acquire a better understanding of the sensory orientation of bean weevils, their antennal and palpal sensilla were investigated. The antennae and palps possess several types of sensory hairs: blunt-tipped sensilla chaetica and trichoidea and also sharp-tipped sensilla trichoidea, these last being the most numerous. Sensilla basiconica are present only on the flagellomeres, but Böhm bristles occur on the basal sclerite and scape of the antennae. The terminal segments of the maxillary and labial palps bear a group of sensilla styloconica with single apical pores. Sensilla coeloconica are located only on the terminal palpal segments. They were unable to detect any distinct morphological differences between males and females. The possible chemosensory, mechanosensory, and thermo-/hygroreceptive functions of the sensilla are discussed.

A SEM study of the antenna and mouthparts of Omosita colon (Linnaeus) (Coleoptera: Nitidulidae).

There are direct relationships between the behavioral mechanisms and sensilla. To obtain a better understanding of the behavioral mechanisms in Omosita colon (Linnaeus) (Coleoptera: Nitidulidae), we investigated the types, quantities, and distribution of sensilla on the antenna and mouthparts of O. colon by scanning electron microscopy. The clavate antenna comprised the scape, pedicel, and nine segment flagellomeres and had six types of sensilla, including two subtypes of sensilla chaetica (SC), three subtypes of sensilla basiconica (SB) and sensilla trichodea (ST), and one type of sensilla cavity, sensilla styloconica, and Böhm bristles (BB). The chewing mouthparts of O. colon consist of the labrum, mandible, maxillae, labium, and hypopharynx and had seven types sensilla, including two subtypes of SC and sensilla placodea, seven subtypes of SB, and one type of BB, ST, sensilla coeloconica, and sensilla campaniformia. In this research, we also deduced the relationships between the sensilla on the antenna and mouthparts and their functions.

“Sensory structures on the antennal flagella of two katydid species of the genus Mecopoda (Orthoptera, Tettigonidae)”

The typology, number and distribution pattern of antennal sensilla in two species of the genus Mecopoda were studied using scanning electron microscopy. The antennae of both sexes of both species attain a length of 10cm. The antenna is made up of three basic segments: the scape, pedicel and flagellum, which is composed of more than 200 flagellomeres. We distinguished two types of sensilla chaetica, one type of sensilla trichodea, five types of sensilla basiconica and one type of sensilla coeloconica. The possible function of the sensilla was discussed. Six types of sensilla were considered as olfactory, one of which could also have a thermo- and hygrosensitive function. The remaining types of sensilla identified had a purely mechanosensory function, a dual gustatory- and mechanosensory function and a thermo- and/or hygrosensory function, respectively. Consistent sex specific differences in the types, numbers and distribution of antennal sensilla were not found. Interspecific differences were identified especially in terms of the numbers of sensilla chaetica.

Antennal Sensillum Morphology and Electrophysiological Responses of Olfactory Receptor Neurons in Trichoid Sensilla of the Diamondback Moth (Lepidoptera: Plutellidae)

Abstract Plant chemical signals are important olfactory cues for the survival and reproduction of phytophagous insects. The diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) is a Brassica spp. (Brassicales: Brassicaceae) specialist pest, with most of its life events occurring on Brassica spp. hosts. We conducted a scanning electron microscopy study on the morphology and distribution of antennal sensilla of male and female P. xylostella. Seven morphological types of sensilla were identified in the antennae of P. xylostella: 3 types of sensilla trichodea (Tr I, Tr II and Tr III), sensilla chaetica, sensilla coeloconica, sensilla auricillica and sensilla styloconica. One particular type of trichoid sensillum (Tr III) was present only in the males. The presence of numerous pores or deep longitudinal grooves on the surfaces of 5 morphological types of sensilla indicated that their major function is olfactory. Single sensillum recordings were also carried out on the trichoid sensilla of the fe...

Morphological comparison of proboscis sensilla between Plusiinae and Noctuinae (Lepidoptera: Noctuidae)

In higher Lepidoptera the proboscis and its sensilla vary from species to species in different feeding guilds. However, whether such morphological differences have a phylogenetic significance remains unclear. Here we compared the morphology of proboscis sensilla in 19 representative species of Plusiinae and four of Noctuinae using scanning electron microscopy. In Plusiinae four types of sensilla (sensilla chaetica, sensilla basiconica, sensilla styloconica, and sensilla coeloconica) were present on the proboscis, with cuticular processes only in the proximal region. In Noctuinae three types of sensilla (sensilla chaetica, sensilla basiconica, and sensilla styloconica) were found on the proboscis, with cuticular processes on its whole length. Morphological differences of proboscis sensilla between Plusiinae and Noctuinae mainly involve the shape, number, and length of sensilla styloconica and sensilla chaetica. The sensilla styloconica of Plusiinae are significantly shorter and fewer than those of Noctuinae. The styli of sensilla styloconica are glabrous in Plusiinae and are longitudinally ribbed in Noctuinae. These significant morphological differences are useful in distinguishing the two subfamilies, suggesting that proboscis sensilla may provide useful characters in the systematic and phylogenetic analyses at the subfamily level within Noctuidae.

Ultrastructure of Chemosensilla on Antennae and Tarsi ofEctropis obliqua(Lepidoptera: Geometridae)

Tea geometrid Ectropis obliqua Prout (Lepidoptera: Geometridae) is a devastating defoliator throughout the tea plantations in China. To explore the putative functions of chemosensilla involved in host selection, the morphology and ultrastructure of antennal and tarsal sensilla in E. obliqua moths were visualized by scanning and transmission electron microscopy. Eight types (including 15 subtypes) of sensilla were identified. On antennae, sensilla trichodea (STR I and STR II) were the most abundant sensillum type characterized by porous cuticle and dendrites in the sensillum lymph. Sensilla chaetica (SCH I–SCH III) possessed a terminal pore and thick nonporous wall, with dendrites in the inner lymph cavity. Three subtypes of sensilla basiconica (SBA I–SBA III) and one type of sensilla auricillica were equipped with thin porous cuticular walls and multiple dendrites in the lymph. Sensilla styloconica were equipped with two or three dendrites that lacked cuticular pores. Sensilla coeloconica possessed four to seven dendrites and were double walled with spoke channels. Böhm bristles and sensilla squamiformia were also observed on the antennae. On tarsi, two subtypes of sensilla chaetica (SCH IV and SCH V) comprised the majority of chemosensilla, and are believed to function in gustatory perception. We summarize the validated functions of related sensilla, and propose potential functions of the corresponding sensilla in E. obliqua . These findings provide a working basis for investigating sensillum function and sensory mechanisms in this pest species.

Morphology and ultrastructure of the antennal sensilla of Sitophilus granarius (Coleoptera: Curculionidae).

Sensilla are sense organs in insects, typically consisting of a group of cuticle or epidermal cells that appear as hairs or rod-shaped structures. Sensilla serve as the functional elements of sensory systems. The goal of this study was to determine the type and distribution of sensilla in the antennae of Sitophilus granarius (L.) using light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This is one of the first studies in which the morphology and distribution patterns of sensilla on antennal segments of male and female S. granarius have been investigated using SEM, followed by TEM. Different morphological sensilla types, including two sensilla basiconica (SB) types, with two subtypes, four sensilla coeloconica (SC) types and five sensilla chaetica (SCH) types, with one subtype, have been identified on S. granarius antennae, whose external structure and shape are peculiar. TEM micrographs of SB on the antennae of S. granarius are characterized by strongly corrugated pores around the cuticle, while micrographs of SC longitudinal sections showed flat-tipped and smooth-surfaced pegs bearing an apical pore that is suggestive of a gustatory function. TEM micrographs of SCH longitudinal sections showed dendrite branches and cuticular pore arrow heads that may be involved in the perception of humidity, temperature, heat and CO2. Because SCH of different sizes were distributed around the head and rostrum, these may function as contact-chemoreceptors .These results are discussed in relation to the possible roles of the sensilla types in the host location behavior of S. granarius.

Comparative Studies on the Stenogamous and Eurygamous Behavior of Eight Anopheles Species of the Hyrcanus Group (Diptera: Culicidae) in Thailand

Establishment of laboratory colony is essential for mosquito-borne-disease research. Mating behavior of stenogamous Anopheles peditaeniatus and seven eurygamous species (Anopheles argyropus, Anopheles crawfordi, Anopheles nigerrimus, Anopheles nitidus, Anopheles paraliae (=An. lesteri), Anopheles pursati and Anopheles sinensis), were investigated and compared in this study. The self-mating success of adult mosquitoes in different size cages at two density resting surface (DRS) values, 3.6 and 7.2, was statistically significant between stenogamous and eurygamous species. The results obtained from comparative measurements of specific characters in adult females (maxillary palpomere and antennal sensilla characters) and males (wing and genitalia) indicate those characters might influence the mating success of An. peditaeniatus in a small cage. The gonostylus of An. peditaeniatus was shorter than the eurygamous species. Additionally, the lower frequency of clasper movement and shorter mating time could be important mechanisms that control the stenogamous behavior of An. peditaeniatus. Interestingly, for the first time, a cluster of large sensilla coeloconica was recorded on the antenna of An. argyropus and An. peditaeniatus females. There was no statistically significant difference in the mean number per female of those large antennal sensilla coeloconica among six of the eurygamous species.

Reinvestigation of the antennal morphology of the white-backed planthopper Sogatella furcifera (Horváth) (Hemiptera: Delphacidae)

Reinvestigation of the antennal morphology of the white-backed planthopper Sogatella furcifera (Horváth), a major pest of rice in Asia, revealed the presence of sensilla and other structures not reported in previous studies of this species. Scanning electron microscopic examination of antennae of males and females confirmed that the antennae of S. furcifera are similar to those of other recently studied species, consisting of scape, pedicel, and flagellum composed of a basal bulb and an apical segmented arista. In contrast to previous studies that only described four types of sensilla, twelve types of sensilla were observed. The scape and pedicel have dispersed sensilla which contain a Böhm bristle, single dome-shaped campaniform sensilla, several sensilla trichodea I and papillae-like sensilla I. A sensilla basoconicum II, several sensilla basiconica I, single sensillum campaniformium II, sensilla trichodea I, sensilla trichodea II, plaque organs, and papillae-like sensilla II occurred on the pedicel. A single sensillum coeloconicum and three sensilla basiconica III are located apically on the posterior surface of the bulb. Sensilla trichodea I were the most abundant and plaque organs were the most conspicuous sensilla, distributed on the pedicel. No differences were observed in antenna shape and basic structure in the males and females. The possible functions of the sensilla are discussed in relation to their morphology and compared to those found in other Fulgoroidea, especially Delphacidae. The external morphology, distribution, and abundance of sensilla located on the antennae of S. furcifera are illustrated, with a brief discussion of their taxonomic, phylogenetic, and putative functional significance.

Antennal sensilla of phytophagous and predatory pentatomids (Hemiptera: Pentatomidae): a comparative study of four genera

Antennal sensilla of four genera of Pentatomidae (Hemiptera: Heteroptera) belonging to two subfamilies viz., Pentatominae and Asopinae were examined using scanning electron microscopy. The representatives selected from the subfamily Pentatominae (phytophagous)—Dolycoris indicus (Stål) and Plautia crossota (Dallas), and from the subfamily Asopinae (predatory)—Perillus bioculatus (Fabricius) and Eocanthecona furcellata (Wolff). They were studied in order to morphologically differentiate the sensilla present on the antennae. This study indicated the presence of six types of sensilla, most of which were found on the flagellar segments rather than on the scape or pedicel. Sensilla campaniformia were recorded on the flagellar segments as well as the scape and pedicel. Phytophagous species (D. indicus and P. crossota) showed a higher number of sensilla trichodea, basiconica and chaetica whereas sensilla coeloconica were restricted to the predatory species studied (E. furcellata and P. bioculatus). These differences may be related to their evolutionary history. The presence of multiporous chemo-sensilla as basiconic sensilla type and sensilla placoidea reflect the ability of the antennae to perceive chemical stimuli. A relatively higher abundance of mechanoreceptors could be considered as potential detectors for various mechanical functions and these appeared to be correlated with the genus and type of feeding but not with the sex of the studied species.

Antennal fine morphology of the threatened beetle Osmoderma eremita (Coleoptera: Scarabaeidae), revealed by scanning electron microscopy

The aim of this study was to characterize the antennal morphology of Osmoderma eremita, a threatened scarab beetle inhabiting tree hollows. O. eremita males produce a sex pheromone, (R)-(+)-γ-decalactone, responsible mainly for the attraction of females but also other males. Gross and fine morphology of microstructures including sensilla, microsculpture and pores were analyzed using Scanning Electron Microscopy. The antenna of O. eremita showed the typical lamellicorn shape of scarab beetles, with a basal scape, a pedicel, a funicle composed of five antennomeres and a club composed of three lamellae. Six different subtypes of sensilla chaetica (Ch.1 - 6), Böhm sensilla (Bo), one subtype of sensilla basiconica (Ba.1), two subtypes of sensilla coeloconica (Co.1 - 2), two subtypes of sensilla placodea (Pl.1 - 2), pores and peculiar folds were described. The two sexes did not show any significant differences in the occurrence and number of the sensilla placodea, known to be responsible for the pheromone reception. Instead, some sexual differences were found on the occurrence and topology of three different microstructures: (1) one subtype of sensillum chaeticum (Ch.2) occurring on the pedicel only in males; (2) a characteristic pore occurring on the funicle only in males; (3) a peculiar fold occurring on different antennomeres of the funicle in the two sexes, on the fourth in males and on the fifth in females. A comparison between sensilla of O. eremita and those of other Scarabaeoidea is provided.

Flagellar Sensillar Equipment of Two Morphologically Closely Related Aphid Hyperparasitoids (Hymenoptera: Figitidae: Alloxysta).

The antennal sensillar equipment in the parasitic wasp family Figitidae was analyzed to date only in few species, despite some are associated with crop pests and can have an economic importance. It is the case of the genus Alloxysta, which includes hyperparasitoids of aphids which can potentially reduce effectiveness of primary pest parasitoids. Here we analyzed, through scanning electron microscopy, the diversity, morphology, and distribution of the antennal sensilla in males and females of Alloxysta consobrina (Zetterstedt) and Alloxysta victrix (Westwood), two species with overall very similar morphology. In both species, antennae are filiform and cylindrical, and flagellum was longer in A. victrix. Eight sensillar types have been recognized: four types of sensilla trichoidea (ST-A, ST-B, ST-C, ST-D), sensilla coeloconica, sensilla placoidea, sensilla campaniformia, and sensilla basiconica. ST-A, ST-B, ST-C, and sensilla placoidea were the most abundant types on the antennae and often increased in number and decreased in size toward the tip of antenna. The two species seem to have several differences in their sensillar equipment, possibly in accordance with the different degree of host range. On the other hand, sexual dimorphism is probably due to the different stimuli that have to be correctly processed. The comparison with the other species of Figitidae studied by far showed, at subfamily-level, that variability in sensillar equipment and phylogeny do not agree. This suggests a complex series of morphological changes during evolution of this group. The taxonomic sample should be thus substantially enlarged to disclose possible trends in sensillar equipment evolution in the family.