Sensilla Patterns Research Articles

A century later: a new species of Mastigoceras Handschin, 1924 (Collembola, Orchesellidae), with morphological and systematic updates on the genus.

Mastigocerascamponoti Handschin, the sole member of its genus and the Mastigocerini tribe, exhibits unusual dorsal chaetotaxy compared to other Orchesellidae. This includes a reduction in dorsal macrochaetotaxy and a secondary covering of fusiform scales intermixed with ciliate microchaetae. Despite three redescriptions, Mastigoceras chaetotaxy remains poorly understood, with no data on tergal sensilla patterns or dorsal macrochaetae homology. Here, the genus is revisited by describing a new Brazilian species a century after the original description of M.camponoti, based on morphological depiction combined with the use of DNA barcoding, Mastigocerashandschini Rodrigues, Souza & Bellini, sp. nov. The two species are differentiated by a few and unusual aspects of the dorsal chaetotaxy, especially scales distribution, and may be considered as pseudocryptic taxa. Our study of tergal sensilla formula, scales morphology, and distribution in Mastigoceras reveals no clear morphological support for placing Mastigocerini within Heteromurinae.

Comparative SEM Study of Sensilla and Tyloid Structures in the Antennae of Vespinae (Hymenoptera: Vespidae).

This study investigates the distribution, morphology, and potential functions of antennal sensilla in various wasp species, including Dolichovespula flora, D. intermedia, Vespula structor, Vl. vulgaris, Provespa barthelemyi, Vespa bicolor, V. ducalis, V. mocsaryana, and V. velutina var. nigothorax. The study thoroughly analyzes the antennal structure of these species, representing all four genera of the yellow-jacket and hornet subfamily Vespinae. Using scanning electron microscopy (SEM), the study identifies a total of nineteen types of sensilla, including sensilla trichodea (ST-I, ST-II, ST-III), sensilla campaniform (SCF-I, SCF-II, SCF-III), pit organs (SCO-I, SCO-II, and SA), sensilla placodea (SP-I, SP-II), sensilla chaetica (SCH-I, SCH-II), sensilla basiconica (SB-I, SB-II), sensilla agmon (SAG-I, SAG-II), and sensilla coelocapitular (SCA). Additionally, tyloids were observed in the males of seven species, except for Vl. structor and Vl. vulgaris. The study provides insights into these sensilla types' morphology, abundance, and distribution. It discusses the variations in sensilla morphology among different species and the presence of gender-specific sensilla. This study provides new data about the morphology and distribution patterns of sensilla and tyloid.

Does Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida: Trypanosomatidae) modify the antennal phenotype of Triatoma dimidiata (Latreille, 1811) (Hemiptera: Triatominae)?

BackgroundTriatoma dimidiata is a vector of the protozoan parasite Trypanosoma cruzi, the etiologic agent of Chagas disease. Phenotypic plasticity allows an organism to adjust its phenotype in response to stimuli or environmental conditions. Understanding the effect of T. cruzi on the phenotypic plasticity of its vectors, known as triatomines, has attracted great interest because of the implications of the parasite–triatomine interactions in the eco-epidemiology and transmission of the etiologic agent of Chagas disease. We investigated if the infection of the vector with T. cruzi may be associated with a change in the antennal phenotype of sylvatic, domestic, and laboratory-reared populations of T. dimidiata.MethodsThe abundance of each type of sensillum (bristles, basiconic, thick- and thin-walled trichoid) on the antennae of T.cruzi-infected and non-infected T.dimidiata reared in the laboratory or collected in sylvatic and domestic ecotopes were measured under light microscopy and compared using Kruskal–Wallis non-parametric tests and permutational multivariate analysis of variance.ResultsWe found significant differences between sensilla patterns of infected and non-infected insects within sylvatic and domestic populations. Conversely, we found no significant differences between sensilla patterns of infected and non-infected insects within the laboratory-reared population. Besides, for sylvatic and domestic populations, sexual dimorphism tended to be increased in infected insects.ConclusionThe differences observed in infected insects could be linked to higher efficiency in the perception of odor molecules related to the search for distant mates and hosts and the flight dispersal in search of new habitats. In addition, these insects could have a positive effect on population dynamics and the transmission of T.cruzi.Graphical

A new genus and species of the family Microlaimidae (Nematoda: Chromadorea) from intertidal sand of the Jeju Island, South Korea

As a part of the study of marine nematofauna of a sandy intertidal zone of Jeju Island (South Korea), a number of species have been proven as new for science. Here a new species representing a new genus of the family Microlaimidae (Chromadorea), Jejulaimus sinyangensis gen. n., sp. n. is described. The new monotypic genus is characterized by head set off abruptly from the body; anterior sensilla pattern 6+10, where six outer labial setiform sensilla together with four longer cephalic setiform sensilla are integrated in a common crown; pharyngostoma armed with a dorsal tooth and surrounded by convex muscular pharyngeal tissue, forming an anterior pharyngeal bulb which is distinctly set off from the rest of the pharynx; terminal pharyngeal bulb oval; ventral pore and ampulla of the excretory-secretory gland situated just posterior to the nerve ring; an only anterior testis present. The new genus bears some resemblance to the genera Bolbolaimus, Pseudomicrolaimus and Spirobolbolaimus in having an anterior pharyngeal bulb and in the position of the ventral pore of the excretory/secretory gland, but differs from them by anterior sensilla pattern 6+10, absence of subventral teeth in buccal cavity, and monorchic condition of male reproductive system.

First neuronal projection from Haller’s organ to the synganglion and three-dimensional reconstruction of Amblyomma sculptum olfactory lobe

Because information regarding neural and sensory functions of ticks is scarce, the aim of the present study was to ascertain the neuronal projection patterns of olfactory sensilla from Haller’s organ to the olfactory lobes of the synganglion in Amblyomma sculptum adults. Additionally, the aim was to perform three-dimensional (3D) reconstruction of the glomeruli in the olfactory lobes. Unfed female and male adults of this tick species were immobilized, Haller’s organ was sectioned, and the olfactory nerves were labelled with a neuronal tracer (1% dextran tetramethylrhodamine). The labelled olfactory lobes were observed under a confocal laser scanning microscope and the images were analyzed using the Reconstruct software. The neuronal projection originating from the olfactory sensilla of Haller’s organ was found to be strictly confined to the olfactory lobes of the synganglion, which were organized into glomeruli. Males and females presented corresponding round-shaped glomeruli in the olfactory lobes. The number of glomeruli ranged from 26 to 30 in the males and 24–29 in the females. Positive correlations regarding the glomeruli volumes (μm3) intrasexually (females: r = 0.85, P < 0.05) and intersexually (r = 0.81, P < 0.05) were observed. This is the first report on 3D reconstruction of the olfactory lobes of a tick species.

A new species of Unixenus Jones, 1944 (Diplopoda, Polyxenidae) found in far north Queensland, Australia

Unixenus Jones, 1944 (Polyxenidae) is the dominant genus of penicillate millipedes found throughout mainland Australia. Herein, a new species, Unixenus mossmanus sp. nov., is described from coastal forest near Mossman. The new species is similar to U. karajinensis, sharing the same sensilla pattern on antennal article VI and the same arrangement of leg setae. Unixenus mossmanus sp. nov. differs by having only 3 ornamental trichomes c per side (v. 5-9), 2 pairs coxal glands in the male (v. 6 pairs), and a slender claw (v. robust). These characteristics differ from those of U. karajinensis, which has 5–9 ornamental trichomes c; 6 pairs coxal glands in male; and a robust claw structure. 18S sequence of Unixenus mossmanus sp. nov. is included.

Comparative Study of Antennal Sensilla of Corixidae and Micronectidae (Hemiptera: Heteroptera: Nepomorpha: Corixoidea).

Simple SummaryInsects’ antennae are an important location for the structures responsible for sensorial perception. These structures have different morphologies and respond to different mechanical and chemical stimuli. Corixidae and Micronectidae are groups of insects living in water. Because of that, their antennae are much smaller than the antennae of terrestrial insects. Apart from that, their position on the evolutionary tree has been changed over the years. We analyzed the antennae of different species of Corixidae and Micronectidae and found five different types of sensillar structures. Moreover, by comparing the two groups together and with other water insects, we established similarities and differences when it comes to the types and distributions of these structures. These findings allowed us to support the current systematic position of the studied insects.The goal of this study was to analyze the types and distributional patterns of sensilla in Corixoidea, which is part of the approach to the phylogeny study of Nepomorpha, based on the morphological characters of sensilla. This paper presents the results of the study, with the use of a scanning electron microscope (SEM), on the antennae of species from the families Corixidae and Micronectidae. The antennal sensilla of eleven species from Corixidae and two species from Micronectidae were studied. Five main types of sensilla with several subtypes of sensilla trichodea were found and described. The study has shown that the family Corixidae has a strong uniformity when it comes to antennal sensilla (similar patterns of sensilla trichodea and basiconica), and a similarity to the types and distributions of sensilla in two species of the family Micronectidae. However, significant differences between the families were also discovered (differences in sensilla presence on the first and second antennomeres, lack of sensilla coeloconica on the third antennomere in Micronectidae), which leads to a supportive conclusion of the systematic position of Micronectidae as a family.

Comparative morphology of antennal surface structures in pleurostict scarab beetles (Coleoptera)

The diverse pleurostict (phytophagous) scarab beetles with characteristically clubbed antennae exhibit striking morphological variation and a variety of different antennal sensilla. Here we compare the morphology of the antennal surface between major pleurostict lineages, including Cetoniinae, Dynastinae, Melolonthinae, Rutelinae, and a few outgroups, including Scarabaeinae and Hybosoridae. We identified various types of antennal sensilla morphologically and searched for phylogenetic patterns of sensilla within the Scarabaeidae. Sensilla were examined using SEM micrographs of 36 species and the occurrence of the different types of antennal sensilla was studied for each species. We observed a high diversity of sensilla, including multiple transitional forms. There were also a number of other interesting structures on the antennal surface with adaptive value, such as elongate elevations, serial bags, and fields of setae. Our results confirm earlier findings that within pleurostict scarabs there has occurred a clear differentiation of sensilla composition and patterns.

Ultrastructural Analysis of Mouthparts of Adult Horn Fly (Diptera: Muscidae) From the Brazilian Midwest Region.

The ultrastructure of the mouthparts of Haematobia irritans (L.) was investigated by scanning electron microscopy. The morphological characteristics of the maxillary palps, labium (prementum and postmentum), labrum, hypopharynx, haustellum, and labellar lobes are described, as well as of the sensilla evidenced on all the surface of the mouthparts, and the set of different positions assumed by the mouth apparatus of this fly. Based on their morphology, 12 well-differentiated sensilla were identified, among three types of cuticular sensilla: trichoidea, coeloconica, and campaniformia. A slight sexual dimorphism in the sensilla patterns found in the mouthparts of H. irritans was evidenced. These observations are discussed with reference to the current literature on the functional morphology of sense organs of Insecta. These results could facilitate the recognition of the chemosensory sensilla by electrophysiological techniques, and foment future taxonomic and phylogenetic studies to better elucidate the evolution of Diptera, Muscomorpha.

Does antennal sensilla pattern of different populations of Triatoma maculata (Hemiptera: Reduviidae) reveal phenotypic variability?

BackgroundIn Brazil, Triatoma maculata is only found in the State of Roraima and is a vector of Trypanosoma cruzi, the etiological agent of Chagas disease. It occurs in wild, peridomestic and domestic habitats, with an urban infestation in Boa Vista, the capital of this Brazilian state. The aim of this study was to assess the morphological variability of the T. maculata antennal phenotype in three populations of Roraima State, using the antennal sensilla pattern analyzed under optical microscopy.MethodsThe number and distribution of four antennal sensilla types (bristles, thin and thick walled trichoidea, and basiconic) of three Brazilian populations of T. maculata from Roraima State were compared. Univariate and multivariate analyses were performed.ResultsThe antenna of T. maculata presented the four types of sensilla. According to the density and distribution of the antennal sensilla characteristics, the multivariate analyses showed that the laboratory population is morphologically structured. Urban specimens showed a pronounced phenotypic variability. The main differences were observed in the pedicel segment, and between males and females.ConclusionsWe determined the antennal phenotype in three Roraima populations of T. maculata. These results support the idea that the patterns of antennal sensilla are sensitive markers for distinct populations in the Triatominae. The infestations of T. maculata in different habitats reinforces the ability of this vector to become adapted to a variety of environments, which, could have eco-epidemiological implications for the T. cruzi transmission that are still not well understood.

Antennal sensilla of cleptoparasitic and non-parasitic bees in two subfamilies of Apidae

In bees, most of the comparative studies linking the sensory system and behavior were performed in social species. Here, we describe the morphology of antennal sensilla in solitary and cleptoparasitic bees of Apinae and Nomadinae. The external and internal structure of sensilla and setae as well as their distribution in flagella were studied in detail in two different host-cleptoparasitic associations. In addition, taking into account the presence of pores, the distribution of sensilla was compared in females and males of 39 species of these subfamilies. It was found that males of non-parasitic bees showed a higher number of multiporous sensilla. Females had more uniporous and nonporous sensilla than males. Cleptoparasitic bees showed a low diversity in types of sensilla and no sexual dimorphism in number. The pattern of sensilla in males and their cleptoparasitic females was discussed in the context of their ecological roles.

The Distribution of Campaniform Sensilla on the Appendages ofMindarusSpecies (Hemiptera: Aphididae)

The proprioceptive function of a campaniform sensillum is to perceive stresses and changing forces on the cuticle, facilitating insect locomotion including walking and flight. In the aphid genus Mindarus (Hemiptera: Aphididae), campaniform sensilla are often clustered in groups and are found at specific locations on the insect's appendages. Ring-shaped, approximately 5µm in diameter, these sensilla are found in predictable numbers on the pedicel (1), the trochanter (4), the femur (2–4), and the distitarsus (1). Those situated on the wings are variable in number and size. The wing sensilla form five identifiable groups: four on the forewing and one on the hindwing, with an average of 4 or 6 sensilla per group. Light and electron scanning microscopy was conducted to reveal their external anatomical detail. The pattern and distribution of campaniform sensilla does not appear to inform Mindarus taxonomy.

“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.

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.

Antennal Sensilla ofCryptorhynchus lapathiL. (Coleoptera: Curculionidae)

ABSTRACT: The typology, number, and distribution pattern of antennal sensilla of Cryptorhynchus lapathi L. (Coleoptera: Curculionidae) were studied using scanning electron microscopy. The antennae of adult females and males were geniculate, consisting of scape, pedicel and a seven-segmented flagellum. Five types of sensilla including 10 subtypes were recorded: Bohm bristles, sensilla basiconica (Sb I-II), sensilla chaetica (Sch I-II), trichoid sensilla (Str I-II) and rod-like sensilla (Sr I-III). Sr III as unique sensilla on adult males were observed on the scape, pedicel and flagellum 1 and 2. There were more Sch I than any other type. No significant sexual differences in the types, numbers, size and distribution of the antennal sensilla were found except for Sr III. The putative functions of sensilla types are also discussed with reference to their morphology and distribution.

Ultramorphology of antennal sensilla of open-nesting honey bees Apis florea F. and Apis dorsata F. (Hymenoptera: Apidae)

Antenna of honey bees is geniculate and has been known to possess a wide variety of sensilla. The sensilla are sensitive to odor, temperature, humidity, air pressure and gustatory stimuli. In the present investigation, ultrastructural study on the antenna of the two open-nesting worker honey bees- Apis florea F. - the dwarf honey bee and A. dorsata F. - the giant honey showed considerable amount of variation in the types and distribution pattern of sensilla in the two species. The antennal form as well as the sensilla arrangement has been suggested to be adapted to the pheromone perception need of regarding a particular species.

Nymphal antennae and antennal sensilla in Aleurodicus dispersus (Hemiptera: Aleyrodidae).

Whiteflies have distinct nymphal stages: their first stage is mobile, whereas the later immature stages are sessile. The developmental and structural changes of antennae and antennal sensilla in whiteflies during these stages have rarely been investigated. This paper describes the morphology of antennae and antennal sensilla in four nymphal stages of Aleurodicus dispersus based on scanning electron microscopy. There were significant differences found in shape and length of the antennae, and differences in type, number, morphological structure and distributional pattern of antennal sensilla in the four nymphal stages of A. dispersus. We found two types of sensilla on the antennae of first-instar nymph, three types on the third-instar nymphal antennae, four types on the second-instar and seven types on the fourth-instar nymphal antennae. Sensilla trichoidea (ST) and elevated sensilla placodea were found on the antennae of each nymphal stage, sensilla chaetica only occurred on the antennae of fourth-instar nymph. Sensilla furcatea occurred on the antennae of second- and third-instar nymphs, and sensilla basiconica were found on the antennae of second- and fourth-instar nymphs. In addition, there were sensilla campaniform and sensilla coeloconica found only on the antennae of fourth-instar nymph, whereas the ST of fourth-instar nymphs included sensilla trichoidea 1 and sensilla trichoidea 2. The possible functions of antennal sensilla are discussed. Our results contribute to a better understanding of the development of the olfactory system of whitefly nymphal stages, and provide a basis for further exploration of chemical communication mechanisms between whiteflies and host plants.

Phase-Related Developmental Characteristics of Antennal Sensilla of Nymphal Laodelphax striatellus (Hemiptera: Delphacidae), a Serious Virus-Transmitting Insect Vector of Graminaceous Crops

Abstract The immature development of the antennal sensilla borne by the first—fifth instar nymphal Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) were studied using scanning electron microscopy. Sensillar types of nymphs did not vary, but the distribution pattern of sensilla gradually changed during the postembryonic development. Seven types of antennal sensilla were found on the antennae of each of the first—fifth instars. One Böhm bristle and one sensillum campaniformium I on the scape, one Böhm bristle and one sensillum campaniformium II on the pedicel, and one sensillum coeloconicum and three sensilla basiconica on the swollen flagellar base (main body) remain constant during development. The numbers of sensilla chaetica on the scape and pedicel and the numbers of sensilla trichodea, sensilla placodea, and sensilla basiconica on the pedicel gradually increased from the youngest to the oldest instars. In contrast, sensilla trichodea, which occurred on the swollen flagellar base of the first instar nymph, disappeared after the first molt, and one sensillum placodeum on the swollen flagellar base of the first instar nymph gradually degraded during development and finally disappeared after the third molt. The length and width of antennae increased during the development, except for the flagellar main body, which presented negative growth in its width after the first molt. The development of antennae seems according with the need for bearing sensilla.

Morphology and Distribution of Sensilla on Tarsi and Ovipositors of Six Fruit Flies (Diptera: Tephritidae)

Abstract Fruit flies (Diptera: Tephritidae) are among the most important pests of fruits and vegetables. In this study, the typology, number, size, and distribution pattern of sensilla on tarsi and ovipositors of six fruit fly species, including Bactrocera Cucurbitae Coquillett, Bactrocera diaphora (Hendel), Bactrocera dorsalis Hendel, Bactrocera minax (Enderlein), Bactrocera scutellata (Hendel), and Bactrocera tau (Walker), were analyzed by scanning electron microscopy techniques. The tarsi of these six fruit fly species are equipped with three types of trichoid sensilla (1, 2, and 3), chaetica sensilla, and basiconic sensilla. Two types of sensilla, trichoid sensilla (4 and 5) and campaniform sensilla, are identified on the ovipositors of the female fruit files. In addition, the possible functions of these sensilla are discussed in light of previously published literature, and the trichoid sensilla (1, 2, and 3) on the tarsi, and trichoid sensilla (4 and 5), as well as campaniform sensilla on the ovipositors are considered as mechanoreceptor. The basiconic sensilla might have an olfactory function, and the chaetica sensilla were suggested as a mechano- or olfactory / gustatory neurons. Future functional tarsi and ovipositors morphology and electrophysiological of tarsi and ovipositors studies are needed to confirm these proposed functions.

A Drosophila Protein Family Implicated in Pheromone Perception Is Related to Tay-Sachs GM2-Activator Protein

Low volatility, lipid-like cuticular hydrocarbon pheromones produced by Drosophila melanogaster females play an essential role in triggering and modulating mating behavior, but the chemosensory mechanisms involved remain poorly understood. Recently, we showed that the CheB42a protein, which is expressed in only 10 pheromone-sensing taste hairs on the front legs of males, modulates progression to late stages of male courtship behavior in response to female-specific cuticular hydrocarbons. Here we report that expression of all 12 genes in the CheB gene family is predominantly or exclusively gustatory-specific, and occurs in many different, often non-overlapping patterns. Only the Gr family of gustatory receptor genes displays a comparable variety of gustatory-specific expression patterns. Unlike Grs, however, expression of all but one CheB gene is sexually dimorphic. Like CheB42a, other CheBs may therefore function specifically in gustatory perception of pheromones. We also show that CheBs belong to the ML superfamily of lipid-binding proteins, and are most similar to human GM2-activator protein (GM2-AP). In particular, GM2-AP residues involved in ligand binding are conserved in CheBs but not in other ML proteins. Finally, CheB42a is specifically secreted into the inner lumen of pheromone-sensing taste hairs, where pheromones interact with membrane-bound receptors. We propose that CheB proteins interact directly with lipid-like Drosophila pheromones and modulate their detection by the gustatory signal transduction machinery. Furthermore, as loss of GM2-AP in Tay-Sachs disease prevents degradation of GM2 gangliosides and results in neurodegeneration, the function of CheBs in pheromone response may involve biochemical mechanisms critical for lipid metabolism in human neurons.