Arthropod Structure & Development最新文献

The Bittacidae are unique in holometabolous insects in that their larvae bear a dorsal ocellus on the frons. The fine structure of the dorsal ocellus, however, has not been investigated to date. Here, the ultrastructure of the larval dorsal ocellus was studied in the hangingfly Bittacus planus Cheng, 1949 using light, scanning, and transmission electron microscopy. The dorsal ocellus of the larvae comprises a cornea, corneagenous cells, and retinula cells. The cornea is a laminated structure. A layer of corneagenous cells is located below the cornea. Numerous retinula cells are arranged tightly beneath the corneagenous cells. The retinula cells modify their adjacent membranes into numerous linear microvilli, which form an analogue of the rhabdom among adjacent retinula cells. The results show that the dorsal ocellus of larval Bittacidae is a highly vestigial organ and appears to be degenerating during the postembryonic development. The presence of the vestigial dorsal ocellus is likely to represent an ancestral plesiomorphy of holometabolous insects, providing new evidence for exploring the evolutionary origin of holometabolous larvae.

Interommatidial sensilla have been explored for their taxonomic value and other aspects in Diptera and Lepidoptera. In Heteroptera, Eurystethus is the only genus where these structures were examined in delimiting subgenera and species. This study investigates the presence, distribution, and morphology of interommatidial sensilla in Discocephalinae species and discusses the sensilla's value for cladistic and taxonomic appraisals. Twenty species of 18 genera were analyzed: 16 Discocephalini genera, one genus in Ochlerini, and one genus in Edessinae. Species' heads were observed from photographs taken with light microscopy (LM) and scanning electron microscopy (SEM). From these images, we identified eleven types of sensilla, classified into chaetica, trichoidea and coeloconica. In LM, only sensilla chaetica with a length of 40–100 μm were visible, present in six species. Under the SEM at least one type of sensillum was visible in 19 of the 20 species analyzed. No difference between the various kinds of sensilla were apparent between males and females or adults and nymphs of a given species. Both subgenera of Eurysthetus have the same type of sensillum (chaeticum type I), which suggests this is not a delimiting feature. We conclude that sensilla chaetica can be a valuable character to delimit groups of genera within Discocephalini.

Many long-legged Medetera flies are natural enemies of bark beetle pests, which they detect using olfactory cues, likely through olfactory sensilla on the antennae and maxillary palps. Morphological characterisation of olfactory sensilla among insects can provide a basis for future taxonomic, phylogenetic or electrophysiological studies. Scanning electron microscopy was used to describe the morphology of olfactory organs and sensillar equipment of Medetera signaticornis and M. infumata. Three different olfactory sensillum types were found in both fly species, sensilla trichodea, s. basiconica and grooved pegs. Based on size and wall structure, s. trichodea and s. basiconica were categorised into different subtypes. Sharp-tipped curved s. trichodea, and small, large and thin s. basiconica were found on the antennal postpedicel of M. signaticornis adults, while grooved s. basiconica were found in M. infumata. The density of sharp-tipped long s. trichodea was significantly higher in males compared to females, and in M. signaticornis compared to M. infumata. Long-grooved s. basiconica were found grouped in a small pit on the maxillary palps of both species. Comparison of our results with the limited available ecological data suggests that differences in numbers of specific sensillum types may reflect adaptations related to olfactory-driven behaviours such as host seeking.

The labial gland is a major exocrine gland in the thoracic cavity of ants, which is connected to the mouth area and opens at the base of the labium. The labial gland in the various castes and males of Camponotus japonicus were examined using dissection, light microscopy, scanning and transmission electron microscopy. Our findings reveal clear caste differences in the appearance of the labial gland, and suggest a relationship between gland structure and its behavioral role in queens, males and workers: queens possess the largest reservoir sac; males have the smallest; workers have abundant secretion droplets in the gland cells of the tubules; epithelial thickness of gland cells varies considerably between workers and reproductive ants. The apical cell region has a high density of microvilli and polymorphic mitochondria, whereas the central cell region is rich in rough endoplasmic reticulum (RER) which means its main secretions are proteinaceous compounds. We believe that the labial gland has a different function in the castes of C. japonicus: the gland of workers and queens may be used to feed the larvae; workers participate in trophallaxis in the nest, while the males are not involved in these activities. Calculations of the relative size of the labial gland for each caste and males indicated that minor workers have the relative highest developed labial gland, supporting a role in trophallaxis. In addition, we found a phenomenon of enlarged labial gland in minor workers, which accounted for almost 22%, but the reason for this is unknown.

Aradidae are known for their remarkably long stylets, coiled at rest in the anterior part of the head. However, previous reports indicated that at least some species lacked stylets during the first nymphal instar. A more detailed examination of Aradus betulae 1st-instar nymphs showed that their mandibular and maxillary stylets are abnormally short, not coiled, improperly interlocked, and clearly non-functional. The anteclypeus is relatively small and its internal diverticulum, which accommodates the stylet coil in the older stages, is vestigial. In contrast, the labium, labrum, food canal, and associated structures and muscles, including protractors and retractors of the stylets, are all normally developed. First-instar nymphs of Aradidae are the first known Heteroptera with non-functional mouthparts. To explain this phenomenon, a hypothesis is proposed which links previously unexplained records of non-feeding (but endowed with regular, functional mouthparts) 1st-instar nymphs of various pentatomomorphan families with the special role of that stage in acquiring microbial gut symbionts. A presumed loss of symbionts in the ancestors of Aradidae may have led to reduction of the now useless stylets in the first instar, which retained aphagy, despite a spectacular elongation of stylets in the older, feeding instars.

Miniaturization is one of the important trends in the evolution of terrestrial arthropods. In order to study adaptations to microscopic sizes, the anatomy of the smallest insects was previously studied, but not the anatomy of the smallest mites. Some of the smallest mites are Eriophyidae. In this study we describe for the first time the anatomy of the mite Achaetocoptes quercifolii, which is about 115 μm long. For this purpose, we used light, scanning, and transmission electron microscopy and performed 3D reconstructions. The anatomy of A. quercifolii is compared with the anatomy of larger representatives of Eriophyoidea. Despite the small size of the studied species, there is no considerable simplification of its anatomy compared to larger four-legged mites. A. quercifolii has a number of miniaturization effects similar to those found in microinsects: a strong increase in the relative volume of the reproductive system, an increase in the relative volume of the brain, reduction in the number and size of cells of the nervous system. As in some larger four-legged mites, A. quercifolii undergoes midgut lysis at the stage of egg production. On the other hand, in A. quercifolii a greater number of opisthosomal muscles are preserved than in larger gall-forming four-legged mites.

Micro air vehicles (MAVs) have wide application prospects in environmental monitoring, disaster rescue and other civil fields because of their flexibility and maneuverability. Compared with fixed wing and rotary wing aircraft, flapping wing micro air vehicles (FWMAVs) have higher energy utilization efficiency and lower cost and have attracted extensive attention from scientists. Insects have become excellent bionic objects for the study of FWMAVs due to their characteristics of low Reynolds number, low noise, hoverability, small size and light weight. By mimicking flying insects, it may be possible to create highly efficient biomimetic FWMAVs. In this paper, insect flight aerodynamics are reviewed, and the mechanism designs of insect-inspired FWMAVs and their aerodynamics are summarized, including the wing type effect, vibration characteristics and aerodynamic characteristics of the flapping wing.

The effect of chronic oxygen exposure on growth and development of insects is an active field of research. It seeks to unravel the triggers and limitations to molting and growth across many insect groups, although even now there are gaps in our knowledge and inconsistencies that need to be addressed. The oxygen dependent induction of molting (ODIM) hypothesis states that the impetus for molting is triggered by the development of hypoxic tissue due to the rapid increase in mass coupled with the fixed nature of tracheal systems between molts. In this study, we raised Manduca sexta in three chronic oxygen treatments (10, 21, & 30% O₂). We measured the mass of these insects throughout their larval development and as adults. We found that both hyperoxia and hypoxia had marked effects on size and developmental times. Hyperoxia exposure resulted in increased mass throughout development and into adulthood while increasing developmental times. Hypoxia also increased developmental time and decreased mass of adult moths. We show that pupation is a critical window for exposure to altered oxygen levels. This suggests that oxygen may play a role in affecting the timing of eclosion at the end of pupation.