Antennal sensilla in male gall-wasps (Hymenoptera: Cynipidae) and insights on the evolution of sexual dimorphism in cynipoid sensory equipment

Exploring the potential of cryo-FESEM for the taxonomic study of aquatic microcrustaceans: Bathynellacea (Crustacea, Malacostraca) as an example

The taxonomic study of microcrustaceans is a time consuming and challenging endeavor, which has slowed the rate of new discoveries, and in turn knowledge on, global aquatic biodiversity. To facilitate the study of these small organisms, new applications continually need to be explored. Here, we assess the potential use of environmental scanning electron microscopy (ESEM) techniques, specifically cryo-field emission SEM (cryo-FESEM), for taxonomic descriptions of microcrustaceans. Using a species of Parabathynellidae (Crustacea, Bathynellacea) from groundwater as a case study, we found sample preparation for cryo-FESEM to be relatively rapid and minimal compared with traditional preparation methods. The high-definition images obtained using this technique complement the drawings and digital photographs obtained using light microscopy (at 1000x). Moreover, the ability to obtain higher magnification images (up to 100,000x) allowed for a detailed observation of ultrastructures, revealing the presence of previously unreported structures in the family Parabathynellidae, including small denticles on the teeth of the dentate lobe of the male thoracopod VIII. Unfortunately, cryo-FESEM samples are too fragile to recover post-imaging and therefore cannot, at present, replace current taxonomic methods that allow for the preservation of samples, specifically holotypes and type series specimens, for future study. For cases in which many specimens are available for study, cryo-FESEM serves as a good method to supplement traditional methods to provide a more detailed description and understanding of the external morphology of a species.

Hymenoptera and biomimetic surfaces: insights and innovations

The extraordinary adaptations that Hymenoptera (sawflies, wasps, ants, and bees) exhibit on their body surfaces has long intrigued biologists. These adaptations, which enabled the immense success of these insects in a wide range of environments and habitats, include an amazing array of specialized structures facilitating attachment, penetration of substrates, production of sound, perception of volatiles, and delivery of venoms, among others. These morphological features offer valuable insights for biomimetic and bioinspired technological advancements. Here, we explore the biomimetic potential of hymenopteran body surfaces. We highlight recent advancements and outline potential strategic pathways, evaluating their current functions and applications while suggesting promising avenues for further investigations. By studying these fascinating and biologically diverse insects, researchers could develop innovative materials and devices that replicate the efficiency and functionality of insect body structures, driving progress in medical technology, robotics, environmental monitoring, and beyond.

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.

Functional Morphology of the Antennae and Sensilla of Coeloides qinlingensis Dang et Yang (Hymenoptera: Braconidae)

Coeloides qinlingensis Dang et Yang, 1989 (Hymenoptera: Braconidae) is a biocontrol agent of several scolytid pine pests in Southwest China. We examined the fine morphology of the antennae of adult C. qinlingensis, as well as the type, shape, and distribution of antennal sensilla, via scanning electron microscopy. The antennae of female and male C. qinlingensis are filiform and comprise a scape, pedicel, and 31-36 flagellomeres. We detected sexual dimorphism in antennal flagellar length but not in the length of other subsegments. A total of nine morphological types of antennal sensilla varying in cuticular pore structure are present in both sexes, including nonporous types (sensilla trichodea, sensilla chaetica (2 subtypes), and sensilla coeloconica); apical pore types (sensilla basiconica and sensilla auricillica); and multiporous types (dome-shaped sensilla and sensilla placodea (2 subtypes)). Dome-shaped sensilla and sensilla auricillica are reported for the first time for C. qinlingensis, and their shape differs from that of sensilla in other parasitic wasps. The functional morphology of the sensilla of C. qinlingensis was compared with that of the sensilla of other parasitic wasps, including those that parasitize concealed insects. This information provides a foundation for further research on the chemical communication and behavior of C. qinlingensis.

Antennal Sensilla in Vespidae: A Comparison Between a Diurnal and a Nocturnal Polistinae Wasp

Social wasps have a widespread Neotropical distribution and are important pollinators and biological control agents for pest insects. The foraging activity of wasps is influenced by biotic and abiotic factors that are detected by the antennal sensilla that vary according to species, sex, caste, and environmental conditions. This study compares the types and quantities of antennal sensilla with a scanning electron microscope between the nocturnal Apoica flavissima and the diurnal Polistes simillimus wasps. Six types of sensilla were found in the antennae of both species: placoid, coeloconic, basiconic-type 1, basiconic-type 2, trichoid-type 1, and trichoid-type 2. Sensilla chaetica were found only in the scape and pedicel of A. flavissima. In the nocturnal wasp, there are 19,132.27 ± 1,247.72 sensilla in the left and 17,746.46 ± 1,477.46 in the right antennae, whereas in the diurnal wasp 14,936.72 ± 1,271.69 in the left and 16,090.82 ± 1,345.3 in the right antennae. A. flavissima has a longer antennal length and number of sensilla than P. simillimus. The higher number of antennal sensilla in the nocturnal wasp is not linked with the antennal size. The association of antennal sensilla functions with ecological and behavioral factors of A. flavissima and P. simillimus are discussed.

Fine Morphology of Antennal and Ovipositor Sensory Structures of the Gall Chestnut Wasp, Dryocosmus kuriphilus

Dryocosmus kuriphilus is a gall-inducing insect, which can cause significant damage on plants of the genus Castanea Mill., 1754. Antennae and ovipositor are the main sensory organs involved in the location of suitable oviposition sites. Antennal sensilla are involved in the host plant location, while ovipositor sensilla assess the suitability of the ovipositional bud. On both organs, diverse sensillar organs are present. Here, the distribution and ultrastructural organization of the sensilla were investigated by scanning and transmission electron microscopy. The antennae of D. kuriphilus are filiform and composed of 14 antennomeres, with the distal flagellomere bearing the highest number of sensilla. On the antennae, 6 sensilla types were found; sensilla chaetica, campaniformia, coeloconica-I, coeloconica-II, trichoidea and placoidea. The sensilla placoidea and trichoidea were the most abundant types. On the external walls of the ovipositor, gustatory and mechanoreceptive sensilla were observed. Internally, the egg channel hosted two additional sensory structures. The putative functional role of each sensilla in the context of insect's ecology is discussed as well as the ovipositional mechanism used by this insect.