Arthropod Structure & Development最新文献

Systematic issues regarding Plecoptera are still debated, and the molecular data seem to be unable to definitively clarify the relationships within the order. Spermatozoa are under constant evolutionary pressure, and comparative spermatology can be useful in carrying systematic and phylogenetic information. In the present paper we describe the sperm structure, using light, scanning and transmission electron and immunofluorescence microscopy, of six Euholognatha species belonging to genera not analyzed in our previous studies, i.e. Capnopsis, Amphinemura, Rhabdiopteryx, Tyrrhenoleuctra, Zwicknia and Protonemura. The spermatozoa of all the species examined are fîliform and have a flagellum characterized by an axoneme with 9 + 9+2 pattern and two mitochondrial derivatives. Their ultrastructure shows a degree of heterogeneity within the order. On the contrary, morphological features of sperm are well conserved inside a single Euholognathan family, and the species share a general family sperm model, even if different interspecific or intergeneric characters can be identified and used for systematic inferences. Among Nemouroidea, Taeniopterygidae, showing a peculiar sperm model, seems to have an isolated phylogenetic position. Nemouridae, with a mono-layered acrosome, are isolated among the remaining families, while we can hypothesize a sister taxa relationship between Leuctridae and Capniidae. As regards Perloidea, the sperm characters suggest a closer relationship between Chloroperlidae and Perlodidae, rather than between Perlidae and Perlodidae, as commonly hypothesized.

Psacothea hilaris is an important wood boring beetle that causes significant ecological and economic damage. The mouthparts of P. hilaris contain feeding and sensory structures that play important roles in many behaviors. The study of their functional morphologies provides insight into feeding and sensory mechanisms. The fine structures of the mouthparts and the sensilla of both sexes were observed by scanning electron microscopy, with special attention to quantitative comparisons. The general structures of the mouthparts are similar in males and females. However, the maxillary and labial palps of females are more well-developed than those of males. Six types of sensilla were found in both sexes: sensilla basiconca, sensilla trichodea, sensilla chaetica, sensilla digitiformia, sensilla coeloconica, and sensilla palmata. This was the first attempt to describe the sensilla on the epipharynx and ligula of Cerambycidae. There were differences in the number of sensilla of males and females, especially on the mandibles, maxillary and labial palps. However, not all types of sensilla have a greater number in females compared to males. The results provide basic information on the gustatory sensation mechanism of Cerambycidae.

The trilobite hypostome is a biomineralized ventral plate that covers the mouth, but its evolutionary origin remains controversial. The labrum is a lobe-like structure that can take on variety of shapes in front of the mouth in arthropods, while the anterior sclerite refers to a cuticular plate articulated to the anterior margin of the head in some Cambrian arthropods. Here I present a perspective that views the trilobite hypostome as a fusion of the anterior sclerite and the labrum based on anatomical, topological, and developmental evidence. According to this perspective, the anterior lobe of the hypostome originated from the anterior sclerite, while the posterior lobe reflects a remnant of the sclerotized cover of the labrum. The convex anterior lobe housed the root of the eye stalks, represented by the palpebral ridges and the hypostomal wing, and the posterior lobe occasionally developed a pair of posterolateral extensions, as do the labra. The position of the antennal insertion was located in front of the posterior lobe, displaying a similar topology to the Cambrian arthropods with the labrum. The hypostome was present in many artiopodans except for the Conciliterga, in which the anterior sclerite was separate from the labrum.

Hemocytes are cells present in the hemolymph of insects that play a role in combating invasive pathogens, ensuring defense by the immune system in these organisms. While the types of hemocytes are well known in some insect representatives, data on these cells in Hymenoptera are limited to certain bees and wasps, with little information available for ants. Among ants, the genus Atta has environmental and economic importance, forming highly organized colonies consisting of the queen and workers, with the latter subdivided into subcastes: gardeners, waste removers, foragers, and soldiers, which are exposed to different pathogens. This study describes the morphology of hemocytes in the worker subcastes of Atta sexdens rubropilosa. Hemolymph samples from the ant were submitted to light, confocal, and scanning electron microscopy analyses. Five types of hemocytes were identified in the hemolymph of all ant subcastes, including prohemocytes, oenocytoids, spherulocytes, plasmatocytes, and granulocytes. They exhibited nuclei with a predominance of decondensed chromatin. The granulocytes were the most abundant cell type in the subcastes, followed by prohemocytes, plasmatocytes, oenocytoids, and spherulocytes. Phagocytosis assays reveal that plasmatocytes and granulocytes are the main phagocytic cells in all castes evaluated. This study fills an important gap in understanding the immune response in this ant species.

Phoxichilidium femoratum is a common species of sea spiders – a small and unique group of chelicerates with unusual adult anatomy. In particular, substantial parts of the reproductive system in pycnogonids (unlike euchelicerates) are located in the appendages. Existing studies of pycnogonid gonads are often limited to light-microscopic level, cover a small range of species, and focus on the contents of the gonad diverticula. Ultrastructural data are rare and contradictory, and the organisation of the gonad wall and the gonoducts is unknown. Here we present a detailed light and transmission electron microscopy-based examination of the pedal portion of the adult female reproductive system in Phoxichilidium femoratum Rathke, 1799. We describe its gross anatomy and the ultrastructure of the gonad diverticulum, oviduct and gonopore, as well as development of the oocytes. Each gonad diverticulum is enclosed in the extracellular matrix of the horizontal septum and bears some internal cellular lining. However, neither the gonad lining, nor the septum sheath cells, ever form a continuous epithelial layer. Oocytes, which undergo maturation in the diverticulum, remain, until very late in the process, attached to the gonad wall though specialised stalk cells. Interestingly, stalk cells do not participate in egg envelope or yolk formation: both are synthesized endogenously in the oocytes. The oviduct is supplied with musculature, which assists in egg transport to the gonopore, whereas the gonopore itself is surrounded by specialised glands.

The advancements in microscopic techniques have stimulated great interest in the muscular and neural architectures of invertebrates, specifically using muscle and neural structures to infer phylogenetic relationships. Here, we provide the data on the development of the muscular and nervous systems during the larval development of stalked barnacle, Octolasmis angulata using the phalloidin F-actin and immunohistochemical labelling (e.g. acetylated α-tubulin and serotonin) and confocal laser scanning microscopy analysis. All naupliar stages shared the same muscle and neural architectures with only the discrepancy in size. The nauplii have a complex muscle arrangement in their feeding apparatus and naupliar appendages. Most naupliar muscles undergo histolyse during the cyprid metamorphosis. The cyprid muscles form beneath the head shield at the end of nauplius VI. The naupliar and cyprid central nervous systems exhibit the typical tripartite brain comprising the protocerebrum, deutocerebrum and tritocerebrum. The serotonin-like immunoreactivity is mainly found in the naupliar brain, mandibular ganglia, cyprid brain and posterior ganglia. Our study revealed that numerous muscle and neural architectures in the naupliar and cyprids have phylogenetic significance, but future studies on the myoanatomy and neuroanatomy of other barnacle species are necessary to determine the homology of these structures.

Methods of three-dimensional electron microscopy have been actively developed recently and open up great opportunities for morphological work. This approach is especially useful for studying microinsects, since it is possible to obtain complete series of high-resolution sections of a whole insect. Studies on the genus Megaphragma are especially important, since the unique phenomenon of lysis of most of the neuron nuclei was discovered in species of this genus. In this study we reveal the anatomical structure of the head of Megaphragma viggianii at all levels from organs to subcellular structures. Despite the miniature size of the body, most of the organ systems of M. viggianii retain the structural plan and complexity of organization at all levels. The set of muscles and the well-developed stomatogastric nervous system of this species correspond to those of larger insects, and there is also a well-developed tracheal system in the head of this species. Reconstructions of the head of M. viggianii at the cellular and subcellular levels were obtained, and of volumetric data were analyzed. A total of 689 nucleated cells of the head were reconstructed. The ultrastructure of M. viggianii is surprisingly complex, and the evolutionary benefits of such complexity are probably among the factors limiting the further miniaturization of parasitoid wasps.

Adult hangingflies are very sensitive to humidity, thereby frequently being used as ecological indicators to assess the degradation of the environment, especially forest ecosystems. Studies on the sense organs associated with hygro- and thermo-sensitivity, however, have been scant. Here, the ultramorphology and distribution of the flagellar sensilla were investigated in the adult hangingflies Bittacus planus Cheng, 1949 and Bittacus sinicus Issiki, 1931 using scanning electron microscopy. Four types of sensilla are identified in B. planus, including sensilla campaniformia, sensilla chaetica (SC1, SC2), sensilla basiconica (SB1, SB2), and sensilla coeloconica. In B. sinicus, sensilla chaetica III are present additionally from 7th to 14th flagellomeres. Abundant sensilla coeloconica are present on the flagella of Bittacus. Sensilla basiconica I are situated at the joints of flagellomeres. Sensilla campaniformia are densely distributed on the basal half of the first flagellomere, but scarcely on other flagellomeres. Sensilla chaetica II are present on the distal three flagellomeres. The size, abundance, and distribution of flagellar sensilla differ considerably between B. planus and B. sinicus. We infer that the abundance of sensilla coeloconica is likely associated with the hygro- and thermo-sensitivity in Bittacidae. Studies of flagellar sensilla can provide valuable information for subsequent electrophysiological, behavioral, biogeographical, and phylogenetic analyses of Bittacidae.

Mosquitoes rely mainly on the olfactory system to track hosts. Sensilla contain olfactory neuron receptors that perceive different kinds of odorants and transfer crucial information regarding the surrounding environment. Anopheles maculatus and An. sawadwongporni, members of the Maculatus Group, are regarded as vectors of malaria in Thailand. The fine structure of their sensilla has yet to be identified. Herein, scanning electron microscopy is used to examine the sensilla located on the antennae of adults An. maculatus and An. sawadwongporni, collected from the Thai-Myanmar border. Four major types of antennal sensilla are discovered in both species: chaetica, coeloconica, basiconica (grooved pegs) and trichodea. The antennae of female An. maculatus have longer lengths (μm, mean ± SE) in the long sharp-tipped trichodea (40.62 ± 0.35 > 38.20 ± 0.36), blunt-tipped trichodea (20.39 ± 0.62 > 18.62 ± 0.35), and basiconica (7.84 ± 0.15 > 7.41 ± 0.12) than those of An. sawadwongporni. Using light microscopy, it is found that the mean numbers of large sensilla coeloconica (lco) on both flagella in An. maculatus (left: 32.97 ± 0.48; right: 33.27 ± 0.65) are also greater when compared to An. sawadwongporni (left: 30.40 ± 0.62; right: 29.97 ± 0.49). The mean counts of lco located on flagellomeres 1–3, 6, and 9 in An. maculatus are significantly higher than those of An. sawadwongporni. The data in this study indicate that two closely related Anopheles species exhibit similar morphology of sensilla types, but show variations in length, and likewise in the number of large sensilla coeloconica between them, suggesting they might be causative factors that affect their behaviors driven by the sense of smell.

Among species of the spear-winged flies (Lonchopteridae) there is remarkable variation in sperm size, with some species producing giant spermatozoa. With a length of 7500 μm and a width of 1.3 μm the spermatozoon of Lonchoptera fallax ranks among the largest known to date. In the present study body size, testis size, sperm size, and spermatid number per bundle and per testis were examined across 11 Lonchoptera species. Results are discussed in terms of how these characters are related with each other and how their evolution affects the resource allocation amongst spermatozoa. Based on some discrete morphological characters and a molecular tree derived from DNA barcodes a phylogenetic hypothesis of the genus Lonchoptera is proposed. The occurrence of giant spermatozoa in Lonchopteridae is compared to convergent occurrences reported in other taxa.