Postembryonic development of the complex tibial organ in the foreleg of the bushcricket Ephippiger ephippiger (Orthoptera,Tettigoniidae)

Summary The postembryonic development of the morphology and anatomy of the complex tibial organ in the foreleg of the bushcricket Ephippiger ephippiger is described. All the receptor cells are present in the subgenual organ, the intermediate organ and the crista acustica in the 1st larval instar. Generally, even in the 1st instar, the arrangement of the scolopidia in the three organs resembles the adult structure. The acoustic trachea, the tympana, the tympanal covers and the acoustic spiracle develop step by step in subsequent instars. The acoustic trachea resembles the adult structure for the first time in the 4th instar, although its volume is still small. The auditory threshold curves recorded from the tympanal nerve in instars 4, 5 and 6 show the same frequency maxima as those in the adult. The overall sensitivity significantly increases after the final moult. The dimensions of structures that lie within the crista acustica and that are probably involved in stimulus transduction and in frequency tuning have been analysed. The dorsal wall of the anterior trachea, the tectorial membrane and the cap cells have similar dimensions, especially in the last three instars and in adults.     

Morphology of the first instar of Calliphora vicina, Phormia regina and Lucilia illustris (Diptera, Calliphoridae)

Scanning electron microscopy documentation of first instar Calliphora vicina Robineau-Desvoidy, Phormia regina (Meigen) and Lucilia illustris (Meigen) (Diptera: Calliphoridae) is presented for the first time, and the following morphological structures are documented: pseudocephalon; antenna; maxillary palpus; facial mask; labial lobe; thoracic and abdominal spinulation; spiracular field; posterior spiracles, and anal pad. Light microscopy documentation and illustrations are provided for the cephaloskeleton in lateral and ventral views. New diagnostic features are revealed in the configuration of the facial mask, cephaloskeleton and posterior spiracles. The first instar morphology of C. vicina, Ph. regina and L. illustris is discussed in the light of existing knowledge about early instars of blowflies.     

External morphology of the two cypridiform ascothoracid-larva instars of Dendrogaster: The evolutionary significance of the two-step metamorphosis and comparison of lattice organs between larvae and adult males (Crustacea, Thecostraca, Ascothoracida)

We describe the external morphology of the two cypridiform larval instars (first and second ascothoracid-larvae, or “a-cyprids”) of the ascothoracidan genus Dendrogaster. Ascothoracid-larvae of five species were studied with light and scanning electron microscopy, including both ascothoracid-larval instars in Dendrogaster orientalis Wagin. The first and second instars of the ascothoracid-larvae differ in almost all external features. The carapace of instar 1 has a smooth surface and lacks pores, setae, and lattice organs, while instar 2 has all these structures. The antennules of the first instar have only a rudimentary armament, the labrum does not encircle the maxillae, thoracopods 2-3 are not armed with a plumose coxal seta, and the abdomen is four-segmented (versus five-segmented in instar 2). Thus, the first ascothoracid-larva of Dendrogaster represents a transitional, generally brooded stage between the naupliar stages and the dispersive and fully functional second ascothoracid-larva that accomplishes settlement. The presence of two instars of ascothoracid-larvae (a-cyprids) in members of the order Dendrogastrida differs from the single cypridiform instar found in the Cirripedia (cyprid) and Facetotecta (y-cyprid), and we discuss the evolutionary significance of these ontogenies. We found lattice organs in both the second ascothoracid-larvae and in adult males of Dendrogaster. We could not observe both ascothoracid-larvae and males in any single species, but our data suggests that the lattice organs change significantly at the molt between these two instars. The lattice organs of second ascothoracid-larvae have no distinct keel and are situated in wide, shallow pits, whereas they have the ground pattern “crest-in-a-trough” morphology in adult males of two additional species examined for comparison. The positions of the terminal pores of lattice organs 1 and 2 also seem to change during maturation. These findings show that comparative data on lattice organ morphology for phylogenetic purposes must derive from strictly homologous instars, viz., the second ascothoracid-larva (a-cyprid) of the Ascothoracida, the y-cyprid of the Facetotecta, and the cyprid of Cirripedia. The ascothoracid-larvae of Dendrogaster and those of the family Ascothoracidae have four pairs of lattice organs, which suggests that this genus and family form a monophylum, to the exclusion of Ulophysema, which then brings into question the monophyly of the Dendrogastridae. Ulophysema is currently placed in the Dendrogastridae, but its second ascothoracid-larva has lattice organs of different and more plesiomorphic number and morphology. We briefly review lattice organ morphology across the Thecostraca. These organs are normally considered structures of the cypridiform larva and their presence in adult (males) Ascothoracida is unique in the Thecostraca. The continued morphological modification of these sensory structures in males compared to ascothoracid-larvae may suggest that they originated in adult thecostracans, but have come to be functional in the cypridiform larvae as well.     

肥须亚麻蝇幼虫不同发育阶段气门形态学变化

为了满足实际工作中利用蝇类幼虫日龄推断尸体死后间隔时间的需求,本文采用显微镜观察不同龄期肥须亚麻蝇 Parasarcophaga crassipalpis (Macquart)幼虫气门的形态学变化,通过计算机图像分析系统对幼虫的前、后气门等可用于判断幼虫生长发育的形态学指标进行测量。结果表明：肥须亚麻蝇幼虫前、后气门随时间而发生规律性的变化,幼虫前气门色素管部的平均光密度及其长宽比,以及后气门的平均光密度这 3 项指标是推算幼虫日龄较理想的指标,对法医学中尸体死亡时间的推测具有重要的指示意义。此外,叠龄期作为幼虫发育的必经阶段,可为特殊时间点的推测提供可靠依据。     

Hox-controlled reorganisation of intrasegmental patterning cues underlies Drosophila posterior spiracle organogenesis

Hox proteins provide axial positional information and control segment morphology in development and evolution. Yet how they specify morphological traits that confer segment identity and how axial positional information interferes with intrasegmental patterning cues during organogenesis remain poorly understood. We have investigated the control of Drosophila posterior spiracle morphogenesis, a segment-specific structure that forms under Abdominal-B (AbdB) Hox control in the eighth abdominal segment (A8). We show that the Hedgehog (Hh), Wingless (Wg) and Epidermal Growth Factor Receptor (Egfr) pathways provide specific inputs for posterior spiracle morphogenesis and act in a genetic network made of multiple and rapidly evolving Hox/signalling interplays. A major function of AbdB during posterior spiracle organogenesis is to reset A8 intrasegmental patterning cues, first by reshaping wg and rhomboid expression patterns, then by reallocating the Hh signal and later by initiating de novo expression of the posterior compartment gene engrailed in anterior compartment cells. These changes in expression patterns confer axial specificity to otherwise reiteratively used segmental patterning cues, linking intrasegmental polarity and acquisition of segment identity.     

Biosteres longicaudatus: Developmental dependence on host (Anastrepha suspensa) physiology

Larvae of Anastrepha suspensa that were in the first day of the third instar were parasitized by females of the solitary endoparasitoid, Biosteres longicaudatus. At the end of the 6-hr oviposition period, larvae were ligated posterior to the ring gland so that some larvae had parasitoids anterior to the ligature while in others, the parasitoids were in the abdomen, posterior to the ligature. Ninety-two percent of the parasitoids anterior to the ligature hatched to the first through third instars. Parasitoids posterior to the ligature had a 75% egg hatch to the first instar only. No larval molts to the second or subsequent instars occurred in these parasitoids. Upon parabiosis to 3-day-old, unparasitized host pupae, the ligated larvae pupated and 97% of the first-instar parasitoids in these parabiosed larval abdomens molted to the second instar. Newly laid parasitoid eggs transplanted to 3-day-old pupal hosts had less than one-third of the egg hatch of those transplanted to first-day third-instar hosts. The data implicate the physiological state of the host (vis-a-vis pupation and associated events) as being an important factor in the development of the endoparasitoid.     

三种蚤生殖系统的细微结构:雄性外生殖器的发育

本文研究了缓慢细蚤Leptopsylla segnis(Schonherr),不等单蚤Monopsyllus anisus(Rothschild)和猫栉首蚤指名亚种Ctenocephalides felis felis(Bouche)雄性外生殖器的结构,观察了从幼虫、前蛹、蛹至成虫各发育时期的雄性外生殖器的内部结构变化.对有争议的雄蚤上抱器的起源,雄蚤生殖孔的位置,雄性外生殖器芽内陷的腹节以及射精管横切面的细胞数目和阳茎背、腹杆的结构等问题进行了详细的观察和探讨.     

DNA synthesis and endomitoses in the giant nuclei of the silkgland of Bombyx mori.

At the first symptoms of organisation of the silkgland in the embryo, mitoses stop and nuclei start to grow. Through autoradiographic studies, performed after sequenced labeling with [3H] and [14C] thymidine, the durations of the different phases of DNA synthesis cycles (T = 42 to 48 h, S = 22 to 25 h, G = 20 to 23 h) are established. These durations are in fact identical during the second and the third instar, and the same, whatever region is concerned : posterior, middle or anterior parts. A model has been established to account for the distribution of the S phases during the second and third instars. The DNA synthesis in all nuclei of a given region has been followed during the first four instars by labelling with [3H]thymidine. The activity goes through maxima and minima, depending on the percent of nuclei synthesizing DNA and their synchronism, both being characteristic of each region; long resting periods are observed during the molting stages of the first three instars in the middle and the anterior parts. The coincidence is obvious between the maxima and minima and respectively the S and G phases of the model. DNA assays agree with the distribution of cycles established by autoradiography if one admits that each cycle does lead to a doubling of the amount of DNA. The overall DNA synthesis from the diploid value is estimated to correspond to 18-19 endomitoic cycles in the nucleic of the posterior part, 19-20 cycles of those of the middle part and 13 in those of the anterior part. The analysis of chromosome structures, by squashing the nuclear content, shows that existence of a complete endomitotic cycle: the doubling of chromosomes is associated with condensed structures, alternating with a decondensed state of chromatin, responsible for the DNA synthesis. The female heterochromatin undergoes a restricted morphological cycle delayed with respect to bulk chromatin. It is characterized by a late DNA duplication and by non dispersed daughter chromosomes. Some of these aspects are, to a lesser extent, reproduced in groups of autosomic chromosomes.     

Comparative morphology of the first instar of three species of Metopia Meigen (Diptera: Sarcophagidae, Miltogramminae)

The first instar larva is described for three species of the kleptoparasitic miltogrammine genus Metopia Meigen: M. campestris (Fallén), M. argentata Macquart and M. argyrocephala (Meigen). Using a combination of light microscopy and scanning electron microscopy, the morphology of the cephaloskeleton as well as the general external morphology are extensively documented, and the phylogenetic implications are discussed. Like other species of Miltogramminae, the first instar of species of Metopia possesses a strong labrum and well‐developed mouth‐hooks. Some other features found in Metopia spp. are rare in the Miltogramminae, such as a serrated ventral surface of the tip of the mouth‐hook and the lack of a posterior spiracular cavity. A few larval features apparently unique for species of Metopia have so far been documented: base of mouth‐hook with a lateral arm‐like extension and abdominal segments with transverse furrow ventrally. The body is equipped with longitudinal cuticular ridges on all segments, which may be a subfamily ground‐plan autapomorphy. Marked morphological and behavioural differences are documented between the first instar of M. argentata and that of M. argyrocephala, the adult females of which are otherwise difficult to separate.     

The ontogeny of the spinning apparatus of Tengella perfuga (Araneae: Zoropsidae)

Silk is the most recognizable trait of spiders, and silk use has changed throughout spider evolutionary history. While morphology of the adult silk spigot has been a useful character for systematics, few studies have examined the ontogeny of the spinning apparatus, and none of these included cribellate spiders. Here, we report the first published full ontogeny of the spinning apparatus of a cribellate spider, Tengella perfuga. We found the presence of expected spigots: major ampullate gland and piriform gland spigots on the anterior lateral spinneret, minor ampullate gland and aciniform gland spigots on the posterior median spinneret, and aciniform gland spigots on the posterior lateral spinneret. Females, but not males, possessed cylindrical gland spigots on both the posterior median and lateral spinnerets. Spiderlings did not possess a functioning cribellum until the third instar. The cribellum grew with increasing numbers of spigots, but functionality was lost in adult males. Most intriguingly, second instars possessed a distinct triad of pre‐spigots on the posterior lateral spinneret. From the third instar onward, these structures formed the modified spigot along with two flanking spigots (in females) or formed nubbins (in males). We suggest that the modified spigot serves as the source of axial lines in the cribellate silk produced in T. perfuga. We also compare spigot ontogeny from previous studies of ecribellate spiders. These comparisons warrant further exploration using the recent spider tree of life in a phylogenetic comparative analysis of spigot ontogeny datasets, which could yield evidence for homologous spigots across the Araneomorphae, notably the Araneoidea and the Retrolateral Tibial Apophysis (RTA) clades.     

Light and electron microscopy studies of the midgut and salivary glands of second and third instars of the horse stomach bot,Gasterophilus intestinalis

A morphological study of the midgut and salivary glands of second and third instars of Gasterophilus intestinalis (De Geer) (Diptera: Oestridae) was conducted by light, scanning and transmission electron microscopy. The midgut is anteriorly delimited by a proventriculus, without caeca, and is composed of posterior foregut and anterior midgut tissue from which a double‐layered peritrophic matrix is produced. The midgut can be divided into anterior, median and posterior regions on the basis of the structural and physiological variations of the columnar cells which occur along its length. Two other types of cell were identified: regenerative cells scattered throughout the columnar cells, and, more rarely, endocrine cells of two structural types (closed and open). Different secretion mechanisms (merocrine, apocrine and microapocrine) occur along the midgut epithelium. Abundant microorganisms are observed in the endoperitrophic space of the anterior midgut. The origin and nature of these microorganisms remain unknown. No structural differences are observed between the second and third instar midguts. The salivary glands of G. intestinalis second and third instars consist of a pair of elongated tubular structures connected to efferent ducts which unite to form a single deferent duct linked dorsally to the pharynx. Several intermediate cells, without cuticle, make the junction with the salivary gland epithelium layer. Cytological characteristics of the gland epithelial cells demonstrate high cellular activity and some structural variations are noticed between the two larval stages.     

DNA-RNA bodies in midgut cells of the stick insect, Bacillus rossius.

In the anterior part of the midgut and in the Malpighian tubules of the stick insect Bacillus rossius, about 10% of the epithelial cells develop endonuclear bodies which appear as DNA-RNA masses; in these cells the usual nucleoli are no longer evident. The DNA-RNA bodies are first formed in third instar larvae, become numerous in the fourth instar and persist in adults. In all larval instars and adults a different kind of DNA-body has been noticed in the epithelial cells of the posterior midgut. The DNA-RNA bodies of the anterior midgut and of the Malpighian tubules have been interpreted as the result of somatic gene amplification, whereas the DNA masses of the posterior midgut are likely due to a virus infection.     

Developmental changes in the embryo, pronymph, and first molt of the scorpion Centruroides vittatus (scorpiones: buthidae)

For the first time the scanning electron microscope was used to compare developmental changes in scorpion embryos and the first and second stadia. In the buthid species of this study, Centruroides vittatus, and all other scorpions, the newborn climb up on their mother's back and remain there without feeding for several days. At this location, they undergo their first molt and in a few days they disperse, fully capable of foraging in the terrestrial environment. The results here support earlier suggestions that the first stadium (pronymph) is a continuation and extension of embryological development. The first molt results in a nymph with exoskeletal features much like those in the adult. In the first molt the metasoma becomes relatively longer, and the sting (aculeus) becomes sharp and functional. The metasomal segments are modified for dorsal flexion and sting use. The embryos and the pronymphs have spiracles that open into an invagination near the posterior margin of flap-like abdominal plates in segments 4-7 of the ventral mesosoma. The second instars have spiracles that lead to book lungs farther anterior in sternites. Tubular legs with cylindrical segments in embryos and pronymphs become more sculptured and oval in the transverse plane. Each leg in the pronymph has a blunt, cup-shaped tip while distal claws (ungues, dactyl) are present in the second instar and subsequent stages. There are some sharp bristles and primordial sensilla in the pronymphs, but the second stadium has adult-like surface features: rows of knobs or granulations (carinae), serrations on the inner surfaces of cheliceral and pedipalpal claws, filtering hairs at the mouthparts, peg sensilla on the pectines, and mechano- and chemoreceptor sensilla on the body and appendages. Scorpion embryos and pronymphs have some structures like fossil scorpions thought to have been aquatic. There is a gradual development of features that appear to be terrestrial adaptations. Evidence is provided for the formation of the sternum from third and fourth leg coxal primordia and possibly from the first abdominal segment. This study is the first to provide evidence for a forward shift of the gonopore along with other structures in the anterior abdomen.     

External structures of all larval instars of five common Culex species in Taiwan

The external structures of all larval instars of 5 different species of Culex were studied for the first time in Taiwan. Pictorial keys are provided for use to distinguish each species at any instar; one key is to larval instars of 5 common Culex species in Taiwan and the second, key to species of 5 common Culex species in Taiwan.     

A combinatorial enhancer recognized by Mad, TCF and Brinker first activates then represses dpp expression in the posterior spiracles of Drosophila

A previous genetic analysis of a reporter gene carrying a 375-bp region from a dpp intron (dppMX-lacZ) revealed that the Wingless and Dpp pathways are required to activate dpp expression in posterior spiracle formation. Here we report that within the dppMX region there is an enhancer with binding sites for TCF and Mad that are essential for activating dppMX expression in posterior spiracles. There is also a binding site for Brinker likely employed to repress dppMX expression. This combinatorial enhancer may be the first identified with the ability to integrate temporally distinct positive (TCF and Mad) and negative (Brinker) inputs in the same cells. Cuticle studies on a unique dpp mutant lacking this enhancer showed that it is required for viability and that the Filzkorper are U-shaped rather than straight. Together with gene expression data from these mutants and from brk mutants, our results suggest that there are two rounds of Dpp signaling in posterior spiracle development. The first round is associated with dorsal-ventral patterning and is necessary for designating the posterior spiracle field. The second is governed by the combinatorial enhancer and begins during germ band retraction. The second round appears necessary for proper spiracle internal morphology and fusion with the remainder of the tracheal system. Intriguingly, several aspects of dpp posterior spiracle expression and function are similar to demonstrated roles for Wnt and BMP signaling in proximal-distal outgrowth of the mammalian embryonic lung.     

Surface ultrastructure of third-instar Megaselia scalaris (Diptera: Phoridae)

We describe some ultrastructure of the third-instar Megaselia scalaris (Diptera: Phoridae) using scanning electron microscopy, with the cephalic segment, anterior spiracle and posterior spiracle being emphasized. This study provides the taxonomic information of this larval species, which may be useful to differentiate from other closely-related species.