Early postembryogenic development of the subgenual organ complex in the stick insect Sipyloidea sipylus.

Stick insects have elaborate mechanosensory organs in their subgenual organ complex in the proximal tibia, particularly the distal organ with scolopidial sensilla in linear arrangement. For early postembryonic developmental stages of Sipyloidea sipylus (Phasmatodea: Necrosciinae), the neuroanatomy of the scolopidial organs in the subgenual organ complex and the campaniform sensilla is documented by retrograde axonal tracing, and compared to the adult neuroanatomy. Already after hatching of the first larval instars are the sensory structures of subgenual organ and distal organ as well as tibial campaniform sensilla differentiated. In the distal organ, the full set of sensilla is shown in all larval stages examined. This finding indicates that the sensory organs differentiate during embryogenesis, and are already functional by the time of hatching. The constancy of distal organ sensilla over postembryonic stages allows investigation of the representative number of sensilla in adult animals as well as in larval instars. Some anatomical changes occur by postembryogenic length increase of the distal organ, and grouping of the anterior subgenual sensilla. The embryonic development of scolopidial sensilla is similar for auditory sensilla in hemimetabolous Orthoptera (locusts, bushcrickets, crickets) where tympanal membranes develop during postembryogenic stages, conferring a successive gain of sensitivity with larval moults.

Distribution and development of the external sense organ pattern on the appendages of postembryonic and adult stages of the spider Parasteatoda tepidariorum.

Spiders are equipped with a large number of innervated cuticular specializations, which respond to various sensory stimuli. The physiological function of mechanosensory organs has been analysed in great detail in some model spider species (e.g. Cupiennius salei); however, much less is known about the distribution and function of chemosensory organs. Furthermore, our knowledge on how the sense organ pattern develops on the spider appendages is limited. Here we analyse the development of the pattern and distribution of six different external mechano- and chemosensory organs in all postembryonic stages and in adult male and female spiders of the species Parasteatoda tepidariorum. We show that except for small mechanosensory setae, external sense organs appear in fixed positions on the pedipalps and first walking legs, arranged in longitudinal rows along the proximal-distal axis or in invariable positions relative to morphological landmarks (joints, distal tarsal tip). A comparison to other Entelegynae spiders shows that these features are conserved. We hope that this study lays the foundation for future molecular analysis to address the question how this conserved pattern is generated.

Two types of sensory proliferation patterns underlie the formation of spatially tuned olfactory receptive fields in the cockroach Periplaneta americana.

In the cockroach Periplaneta americana, to represent pheromone source in the receptive space, axon terminals of sex pheromone-receptive olfactory sensory neurons (pSNs) are topographically organized within the primary center, the macroglomerulus, according to the peripheral locations of sex pheromone-receptive single walled (sw)-B sensilla. In this study, we sought to determine when and where pSNs emerge in the nymphal antenna. We revealed two different pSN proliferation patterns that underlie the formation of topographic organization in the macroglomerulus. In nymphal antennae, which lack sw-B sensilla, pSNs are identified in the shorter sensilla, termed sw-A sensilla. Because new sw-A sensilla emerge on the proximal antenna at every molt, topographic organization in the macroglomerulus must be formed by adding axon terminals of newly emerged pSNs to the lateral region in the macroglomerulus at each molt. At the final molt, a huge number of new sw-B sensilla appeared throughout the whole antenna. Sw-B sensilla in the proximal part of the adult antenna were newly formed during the last instar stage, whereas those located in the distal antenna were transformed from sw-A sensilla. This transformation was accompanied by an increase in the number of pSNs. Axon terminals of newborn pSNs in new sw-B sensilla were recruited to the lateral part of the macroglomerulus, whereas those of newborn pSNs in transformed sw-B sensilla were recruited to the macroglomerulus according to the sensillar location. These mechanisms enable an increase in sensitivity to sex pheromone in adulthood while retaining the topographic map formed during the postembryonic development.

Characterization of antennal chemosensilla and associated odorant binding as well as chemosensory proteins in the parasitoid wasp Microplitis mediator (Hymenoptera: Braconidae).

Odorant binding proteins (OBPs) and chemosensory proteins (CSPs) expressed in antennal chemosensilla are believed to be important in insect chemoreception. In the current study, we fully described the morphological characteristics of the antennal sensilla in parasitoid wasp Microplitis mediator and analyzed the expression patterns of OBPs and CSPs within the antennae. In M. mediator, eight types of sensilla were observed on the antennae. Sensilla basiconica type 2 and s. placodea with wall pores may be involved in olfactory perception, whereas s. basiconica type 1 and type 3 with tip pores may play gustatory functions. Among the 18 OBPs and 3 CSPs in M. mediator, 10 OBPs and 2 CSPs were exclusively or primarily expressed in the antennae. In situ hybridization experiments indicated that the 12 antennae-enriched OBPs and CSPs were mapped to five morphological classes of antennal sensilla, including s. basiconica (type 1-3), s. placodea and s. coeloconica. Within the antennae, most of OBP and CSP genes were expressed only in one type of sensilla indicating their differentiated roles in detection of special type of chemical molecules. Our data will lay a foundation to further study the physiological roles of OBPs and CSPs in antennae of parasitoid wasps.

Regeneration of adhesive tail pad scales in the New Zealand gecko (Hoplodactylus maculatus)(Reptilia;Squamata;Lacertilia) can serve as an experimental model to analyze setal formation in lizards generally.

During the regeneration of the tail in the arboreal New Zealand gecko (Hoplodactylus maculatus) a new set of tail scales, modified into pads bearing setae 5-20 µm long, is also regenerated. Stages of the formation of these specialized scales from epidermal pegs that invaginate the dermis of the regenerating tail are described on the basis of light and electron microscopic images. Within the pegs a differentiating clear layer interfaces with the spinulae and setae of the Oberhäutchen according to a process similar to that described for the digital pads. A layer of clear cytoplasm surrounds the growing tiny setae and eventually cornifies around them and their spatular ends, later leaving the new setae freestanding on the epidermal surface. The fresh adhesive pads help the gecko to maintain the prehensile function of its regenerated tail as together with the axial skeleton (made of a cylinder of elastic cartilage) the pads allow the regenerated tail to curl around twigs and small branches just like the original tail. The regeneration of caudal adhesive pads represents an ideal system to study the cellular processes that determine setal formation under normal or experimental manipulation as the progressive phases of the formation of the setae can be sequentially analyzed.

A map of sensilla and neurons in the taste system of drosophila larvae.

In Drosophila melanogaster larvae, the prime site of external taste reception is the terminal organ (TO). Though investigation on the TO's implications in taste perception has been expanding rapidly, the sensilla of the TO have been essentially unexplored. In this study, we performed a systematic anatomical and molecular analysis of the TO. We precisely define morphological types of TO sensilla taking advantage of volume electron microscopy and 3D image analysis. We corroborate the presence of five external types of sensilla: papilla, pit, spot, knob, and modified papilla. Detailed 3D analysis of their structural organization allowed a finer discrimination into subtypes. We classify three subtypes of papilla and pit sensilla, respectively, and two subtypes of knob sensilla. Further, we determine the repertoire of receptor genes for each sensillum by analyzing GAL4 driver lines of Ir, Gr, Ppk, and Trp receptor genes. We construct a map of the TO, in which the receptor genes are mapped to neurons of individual sensilla. While modified papillum and spot sensilla are not labeled by any GAL4 driver, neurons of the pit, papilla, and knob type are labeled by partially overlapping but different subsets of GAL4 driver lines of the Ir, Gr, and Ppk gene family. The results suggest that pit, papilla and knob sensilla act in contact chemosensation. However, they likely do these employing different stimulus transduction mechanisms to sense the diverse chemicals of their environment.

Development of antennal sensilla of Tetragonisca angustula Latreille, 1811 (Hymenoptera: Meliponini) during pupation / Desenvolvimento das sensilas antenais de Tetragonisca angustula latreille, 1811 (Hymenoptera: Meliponini) durante a pupação

Abstract The antennal sensilla are sensory organs formed by a group of neurons and accessory cells, which allow perception of environmental cues, which play a role as mechanoreceptors and chemoreceptors. This study describes the post-embryonic development of the antennal sensilla of the stingless Tetragonisca angustula (Hymenoptera: Meliponini) workers. The development of the antennal sensilla begins in the transition stage of the pre-pupae to white-eyed pupae. The sensilla are completely developed at the black-eyed pupae stage, but they are covered by the old cuticle. The sensilla are exposed to the environment only in newly emerged workers of T. angustula, but it is possible that environmental stimuli can be recognized due to the pores in the old cuticle.

Resumo As sensilas antenais são órgãos sensoriais formados por um conjunto de neurônios que captam estímulos ambientais e células acessórias, desempenhando as funções de mecanorreceptores e quimiorrecepterores. Este trabalho descreve o desenvolvimento pós-embrionário das sensilas antenais de operárias das abelhas sem ferrão Tetragonisca angustula (Hymenoptera: Meliponini). O desenvolvimento das sensilas tem início na transição de pré-pupa para pupa de olho branco e estão completamente desenvolvidas no estágio de pupa de olho preto, mas ainda estão cobertas pela cutícula velha. As sensilas estão completamente expostas em operárias recém-emergidas de T. angustula, mas é possível que estímulos ambientais sejam percebidos em estágios anteriores devido aos poros presentes na cutícula velha.

Characterization of antennal sensilla, larvae morphology and olfactory genes of Melipona scutellaris stingless bee.

There is growing evidence in the literature suggesting that caste differentiation in the stingless bee, Melipona scutellaris, and other bees in the genus Melipona, is triggered by environmental signals, particularly a primer pheromone. With the proper amount of food and a chemical stimulus, 25% of females emerge as queens, in agreement with a long-standing "two loci/two alleles model" proposed in the 1950s. We surmised that these larvae must be equipped with an olfactory system for reception of these chemical signals. Here we describe for the first time the diversity of antennal sensilla in adults and the morphology of larvae of M. scutellaris. Having found evidence for putative olfactory sensilla in larvae, we next asked whether olfactory proteins were expressed in larvae. Since the molecular basis of M. scutellaris is still unknown, we cloned olfactory genes encoding chemosensory proteins (CSP) and odorant-binding proteins (OBPs) using M. scutellaris cDNA template and primers designed on the basis CSPs and OBPs previously reported from the European honeybee, Apis mellifera. We cloned two CSP and two OBP genes and then attempted to express the proteins encoded by these genes. With a recombinant OBP, MscuOBP8, and a combinatorial single-chain variable fragment antibody library, we generated anti-MscuOBP8 monoclonal antibody. By immunohistochemistry we demonstrated that the anti-MscuOBP8 binds specifically to the MscuOBP8. Next, we found evidence that MscuOBP8 is expressed in M. scutellaris larvae and it is located in the mandibular region, thus further supporting the hypothesis of olfactory function in immature stages. Lastly, molecular modeling suggests that MscuOBP8 may function as a carrier of primer pheromones or other ligands.

Development of antennal sensilla of Tetragonisca angustula Latreille, 1811 (Hymenoptera: Meliponini) during pupation.

The antennal sensilla are sensory organs formed by a group of neurons and accessory cells, which allow perception of environmental cues, which play a role as mechanoreceptors and chemoreceptors. This study describes the post-embryonic development of the antennal sensilla of the stingless Tetragonisca angustula (Hymenoptera: Meliponini) workers. The development of the antennal sensilla begins in the transition stage of the pre-pupae to white-eyed pupae. The sensilla are completely developed at the black-eyed pupae stage, but they are covered by the old cuticle. The sensilla are exposed to the environment only in newly emerged workers of T. angustula, but it is possible that environmental stimuli can be recognized due to the pores in the old cuticle.

Development of mouthparts in the cicada Meimuna mongolica (Distant): successive morphological patterning and sensilla differentiation from nymph to adult.

Development of the mouthparts in the cicada Meimuna mongolica (Distant) is investigated here for the first time using scanning electron microscopy in order to document changes occurring in different nymphal instars and from nymph to adult, during which a shift from subterranean root-feeding to feeding on aboveground parts of the host plant occurs. The structure and component of mouthparts is similar to those found in other hemipteran insects. Fourteen types of sensilla and five types of cuticular processes were found on the mouthparts of nymphs and adults. Significant general transformations during development include changes in: (a) the size and shape of the labrum from square to long and shovel-shaped; (b) increases in type and quantity of sensilla with the stage of development; (c) the ridges at the tips of the mandiblar stylets become more prominent in later stages of nymphal development, while odontoid protrusions more prominent in the female than in the male of the adult; and (d) the cross section of the stylets is subcircular in nymphal stages but oblong elliptical in the adult. The implications of these mouthpart transformations on the feeding ability of nymphs and adults and their possible relationship to the feeding niche are discussed.

Antennal sensory organs of Scathophaga stercoraria (Linnaeus, 1758) (Diptera: Scathophagidae): ultramorphology and phylogenetic implications.

Scathophaga stercoraria (Linnaeus, 1758) is a well-established insect model species involved in numerous investigations on behavior, biology, phylogeny, genetics and evolution. The antennal sensilla of S. stercoraria are examined via scanning electron microscopy in order to emphasize their importance on taxonomy and phylogeny. On antennal scape and pedicel, both microtrichiae and several sharp-tipped mechanoreceptors are observed, while another two structures, setiferous plaques and pedicellar button, are also detected on antennal pedicel. One type of sensory pit and four types of antennal sensilla, including trichoid sensilla, basiconic sensilla, coeloconic sensilla and clavate sensilla, are observed on antennal funiculus. Similarity and disparity of setiferous plaques among different calyptrate groups are analyzed in terms of phylogeny. The phylogenetic results supported by morphology of setiferous plaques strongly accord with the cladistic relations based on known molecular tree, implying the potential taxonomic and phylogenetic implications of the plaques in Calyptratae.

Thermoarcturidae, a new crustacean family of three genera (Isopoda: Valvifera).

A new family Thermoarcturidae of valviferan isopod is erected for three genera, Califarcturus n. gen., Spinarcturus Kensley, 1978 and Thermoarcturus Paul & Menzies, 1971, each represented by one species. All share strong stiff setae on distal articles of pereopods 2-4, uropods with two rami, and a tomentum of fine setae over the cuticle. The members are distinguished from Antarcturidae, Arcturididae, Rectarcturidae and Arcturidae, similar arcturoid families that differ in having rows of filter setae on pereopods 2-4 and usually lack one or more uropodal rami.

Morphological diversity of the labial sensilla of phytophagous and predatory Pentatomidae (Hemiptera: Heteroptera), with reference to their possible functions.

Sensory structure on the labial surface of five genera of Pentatomidae (Hemiptera: Heteroptera) belonging to two subfamilies i.e. Asopinae and Pentatominae have been studied using Scanning Electron Microscopy. Three representatives of the subfamily Pentatominae (phytophagous)-Dolycoris indicus (Stal), Plautia crossota (Dallas) and Piezodorus hybneri (Gmelin) and two of Asopinae (predatory)-Perillus bioculatus (Fabricius) and Eocanthecona furcellata (Wolff) were studied to morphologically characterize and compare the sensory structures present on the labium. Six types of labial sensilla were found on their labial tip and surface. The labial sensilla identified were sensilla peg (SP), basiconica (SB), campaniformia (SCa), chaetica (SCh), styloconica (SStc) and trichodea (ST). Their possible functions were discussed relating to morphology and location. A new form of sensilla basiconica was also observed in D. indicus. Sensilla styloconica were restricted only to the predatory pentatomid bugs. Cuticular projections (Cpr) on the sensorial region of the studied pentatomids were also observed along with labial cuticular pores.

Metamorphic changes in abdominal spines of Forcipomyia nigra pupae (Diptera: Ceratopogonidae).

Pupae of Forcipomyia nigra biting midges bear double rows of dorsal and lateral spines. Their arrangement corresponds to the distribution of larval mechanosensory setae. They are serrated simple cuticular structures with tubercles but, in contrast to larval secretory mechanoreceptors, they are not innervated and do not exhibit any pores. The ultrastructure of abdominal spines varies among different pupal stages. They are produced by epidermal cells which fill the interior of the spine. In the youngest pupae epidermal cells are tightly packed and adhere to the cuticle. Then, the cells withdraw from the spinal cavity and the beginning of autophagy is observed. The last stage represents abdominal spines without any cellular material and then apoptosis probably proceeds in the withdrawn epidermal cells. Since the pupal spines occupied the same region of the segment as the larval setae, we consider that the same genes are responsible for their formation as for the formation of epidermal cells but that their mechanosensory and secretory function is no longer needed.

A re-examination of the selection of the sensory organ precursor of the bristle sensilla of Drosophila melanogaster.

The bristle sensillum of the imago of Drosophila is made of four cells that arise from a sensory organ precursor cell (SOP). This SOP is selected within proneural clusters (PNC) through a mechanism that involves Notch signalling. PNCs are defined through the expression domains of the proneural genes, whose activities enables cells to become SOPs. They encode tissue specific bHLH proteins that form functional heterodimers with the bHLH protein Daughterless (Da). In the prevailing lateral inhibition model for SOP selection, a transcriptional feedback loop that involves the Notch pathway amplifies small differences of proneural activity between cells of the PNC. As a result only one or two cells accumulate sufficient proneural activity to adopt the SOP fate. Most of the experiments that sustained the prevailing lateral inhibition model were performed a decade ago. We here re-examined the selection process using recently available reagents. Our data suggest a different picture of SOP selection. They indicate that a band-like region of proneural activity exists. In this proneural band the activity of the Notch pathway is required in combination with Emc to define the PNCs. We found a sub-group in the PNCs from which a pre-selected SOP arises. Our data indicate that most imaginal disc cells are able to adopt a proneural state from which they can progress to become SOPs. They further show that bristle formation can occur in the absence of the proneural genes if the function of emc is abolished. These results suggest that the tissue specific proneural proteins of Drosophila have a similar function as in the vertebrates, which is to determine the time of emergence and position of the SOP and to stabilise the proneural state.

Gasteruption youngi sp. nov. (Hymenoptera: Evanioidea: Gasteruptiidae) from South Australia; an unusual species with trichoid sensilla on the ovipositor sheaths.

Gasteruption youngi, sp. nov. (Evanioidea: Gasteruptiidae) is described based on several female specimens from South Australia. The new species is unusual in that it has stout trichoid sensilla on the ovipositor sheaths and long, thin trichoid sensilla on metasomal tergites T3-T8. The likely host is the colletid bee Euryglossula microdonta (Rayment, 1934).

Antennal development in the praying mantis (Tenodera aridifolia) highlights multitudinous processes in hemimetabolous insect species.

Insects possess antennae equipped with a large number of segments (flagellomeres) on which sensory organs (sensilla) are located. Hemimetabolous insects grow by molting until they reach adulthood. In these species, the sensory structures develop and mature during each stage of development; new flagellomeres are generated at each molt elongating the antennae, and new sensilla appear. The praying mantis (Tenodera aridifolia) is a hemimetabolous insect with 7 different instars before it reaches adulthood. Because their antennae are provided with an atypical sensillar distribution, we previously suggested that their antennae develop with a different mechanism to other hemimetaboulous insect species. In the present study, we measured the number, length and width of flagellomeres along the antennae in nymph and adult mantis Tenodera aridifolia. For this study, we developed a new and innovative methodology to reconstruct the antennal development based on the length of flagellomeres. We observed and confirmed that the antennae of mantises develop with the addition of new segments at two distinct sites. In addition, we constructed a complete database of the features of the flagellum for each stage of development. From our data, we found that sexual dimorphism appears from the 6 instar (larger number and wider flagellomeres in males) in accordance with the appearance of their genital apparatus. The antennal sexual dimorphism completes at adulthood with longer flagellomeres and the emergence of a huge number of grooved peg sensilla in males during the last molting, which suggests once again their function as sex-pheromone receptive sensilla.

Observation of antennal sensilla in Xylotrechus grayii (Coleoptera: Cerambycidae) with scanning electron microscopy.

The longicorn beetle Xylotrechus grayii (White, 1855) has been spreading rapidly in China, causing mass mortality of honeysuckle which is economically and medicinally important. In order to elucidate the mechanisms of mate and host location and to advance efficient control methods, antennal sensilla features were investigated in both sexes of X. grayii using scanning electron microscopy (SEM). The filiform antennae of both sexes consist of scape, pedicel, and nine flagellomeres (f1-9). Five types of sensilla were observed: sensilla chaetica (5 subtypes, SC1-5), sensilla basiconica (4 subtypes, SB1-4), Böhm bristles (Bm), grooved peg sensilla (Gp), and sensilla campaniformia (Ca). SC were most common on the antennae, followed by SB and Bm. No significant sexual differences in the type, amounts, and distribution of antennal sensilla were found except for the distribution of SB clusters and Ca. SB clusters and Ca occurred on f1-8 of male antennae but were absent on those segments in females, suggesting a potential function as receptors for female sex pheromones. The putative functions of other sensilla are discussed based on their characteristics in related species. This study provides an important foundation for further research on sensory mechanisms and control measures of X. grayii.

Ontogeny of mouthpart sensilla of Muga silkworm: a scanning electron microscopic study.

Scanning electron microscopy on the postembryonic development of the mouthpart sensory structures of the Muga silk moth, Antheraea assamensis revealed the presence of a variety of sensilla. The types, distribution pattern of the sensilla remained almost the same in the different larval stages except for the number and dimension in some cases. The findings of the study assumes significance because the silk moth, Antheraea assamensis is a species endemic to the North Eastern part of India and very few reports are available on it. In fact, the present study provides the first report on the ontogeny of the mouth part sensilla of the silk moth species. Since mouth part sensilla and their surface micro structural characteristics are extremely important in understanding their roles in searching behavior during feeding, the present study will certainly help in developing strategies for proper rearing of this economically important insect species.

Scanning electron microscopy analysis of the cephalic sensilla of Chrysolina aeruginosa Fald. (Coleoptera, Chrysomelidae).

Chrysolina aeruginosa Fald. (Coleoptera, Chrysomelidae) is an important pest of Artemisia ordosica Krasch. In recent years, this phytophagous beetle has spread rapidly throughout northwest China, which has led to mass mortalities of the A. ordosica. This pest has caused great damage to the local ecology. To address this problem, this study compared the sensilla types and their densities on the antennae, maxillary palps, and labial palps of C. aeruginosa. Six different types of sensilla were observed on the antennae using scanning electron microscopy, i.e., sensilla chaetica, sensilla trichodea, sensilla basiconica, sensilla coeloconica, sensilla styloconica, and Böhm bristles. Sensilla chaetica were the main sensilla on the antennae. There was a significant difference in the distribution and density of sensilla trichodea between males and females. Sensilla basiconica were distributed from the fifth to the ninth flagellomeres. Sensilla coeloconica and sensilla styloconica were usually found from the fifth to the eighth flagellomeres. Böhm bristles were found only on the terminal region of the scape and pedicel. Sensilla chaetica and sensilla twig basiconica were observed on the maxillary and labial palps. Sensilla chaetica were distributed all over the maxillary and labial palps. Sensilla twig basiconica were located in the distal areas of these two types of palps. In this study, we also discussed the responses of C. aeruginosa to the volatile semiochemicals produced by their host plants and the behaviours exhibited during host and habitat selection.