Arthropod Structure & Development最新文献

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.

The onion thrips, Thrips tabaci Lindeman, is a cryptic species complex of three distinct lineages: L1, L2, and T, which exhibit considerable variation in their biological and ecological traits. The most accurate method for their identification is based on molecular techniques. This study aimed to investigate the morphometric variation of T. tabaci cryptic species complex and to distinguish characters that may be useful in discriminating the lineages. For this purpose, morphometric measurements were performed on the eggs, newly hatched first instar larvae, and newly emerged adults. Our results revealed significant differences in egg size between the three lineages. Moreover, the PCA analysis conducted on morphometric measurements of the first instar larvae and adults showed that females of the T lineage are very well separated from the females of the L lineages in the adult stage but not in the first instar larval stage. The distinction between the females is partially congruent with the results of genetic studies. Moreover, our results indicate that adult sexual dimorphism with regard to size in L1 and T lineages is not mediated by the size of eggs and first instar larvae, and this may be due to the different growth rates of males and females.

Compound eyes are the prominent visual organs of insects and can provide valuable information for the reconstruction of insect phylogeny. Although the largest butterfly family (Nymphalidae) has been well defined, the infrafamilial phylogenetic relationships remain controversial hitherto. In the present study the ultrastructure of the compound eyes of three nymphalids Neptis beroe, Childrena zenobia, and Palaeonympha opalina was investigated using light and transmission electron microscopy in an attempt to seek potentially important phylogenetic characters. The compound eyes of the nymphalids share a tracheal system in a “1–4−8” branching pattern. The eight tracheal subbranches exhibit distinct distribution patterns along the basal retinula cell as follows: the tracheal subbranches of Palaeonympha opaline are close to the rhabdom in the distance from the distalmost part of the basal retinula cell to the rhabdom end, while those of N. beroe and C. zenobia are on the periphery of the retinula along almost the whole basal retinula cell and become close to the rhabdom just at the proximal end of the basal retinula cell. The tracheal structure of the three nymphalids is discussed for their potential phylogenetic implications.

The complete larval development of Parasacculina pilosella (Van Kampen et Boschma, 1925) and Sacculina pugettiae Shiino, 1943 including five naupliar stages and one cypris stage is described and illustrated using SEM. P. pilosella and S. pugettiae have a sacculinid type of development. Nauplii possess a naupliar eye, short frontolateral horns with terminal processes, and a ventral process between the furcal rami. Larvae lack a flotation collar, seta 6 on the antennule and a seta on the antennal basis. Cyprids have a nearly straight LO2. Breakage zone and a spinous process are present only in male larvae. Nauplii of the two species differ by the morphology of the furca: in P. pilosella, the furcal rami are longer and not drowned into cuticular sockets. Naupliar antenna of S. pugettiae has a lateral seta on the endopod which is lacking in P. pilosella. Dorsal head shield setae 1 and 2a are present in S. pugettiae nauplii and not found in P. pilosella larvae. In P. pilosella, all dorsal setae have subterminal pores, whereas in S. pugettiae, pores of the setae 2 are shifted proximally. It is possible that the presence/absence of setae 1 and 2a is the distinctive feature of nauplii of the families Sacculinidae and Polyascidae.

Relatively few studies have focused on evolutionary losses of sexually selected male traits. We use light and electron microscopy to study the male and female reproductive anatomy of Apotomus ground beetles (Coleoptera, Carabidae), a lineage that we reconstruct as likely having lost sperm conjugation, a putative sexually selected trait. We pay particular attention to the structure of the testes and spermatheca. Both of these organs share a strikingly similar shape–consisting of long blind canals arranged into several concentric overlapping rings measuring approximately 18 mm and 19.5 mm in total length, respectively. The similarity of these structures suggests a positive evolutionary correlation between female and male genital organs. Males are characterized by unifollicular testes with numerous germ cysts, which contain 64 sperm cells each, and we record a novel occurrence of sperm cyst “looping”, a spermatogenic innovation previously only known from some fruit fly and Tenebrionid beetle sperm. The sperm are very long (about 2.7 mm) and include an extraordinarily long helicoidal acrosome, a short nucleus, and a long flagellum. These findings confirm the structural peculiarity of sperm, testis, and female reproductive tract (FRT) of Apotomus species relative to other ground beetles, which could possibly be the result of shifts in sexual selection.