Differentiation of metacoxal muscles in Periplaneta americana (L.) (Dictyoptera : Blattidae)

Flight muscles of the cockroach, Periplaneta americana (Dictyoptera : Blattidae) in different development stages (10 mm and 30 mm nymphs, and adult) are investigated for histochemical activity and by electron microscope. The 177 C muscle of 10 mm nymph shows low succinic dehydrogenase (SDH) and myosin-ATPase activities (+). Each myofibril is surrounded by an extensive network of sarcoplasmic reticulum. Regarding myofilament array, one thick filament is surrounded by 10–12 thin filaments. At the stage of 30 mm nymph, SDH and myosin-ATPase activities increase (+ +). Except for an increase in the number of mitochondria, electron microscopic features are similar to those in the 10 mm nymph. In the adult stage, both SDH and myosin-ATPase activities are highest. The distribution of sarcoplasmic reticulum and T-tubules is fundamentally unchanged, whereas the myofilament array is drastically changed, so that 6 thin filaments surround a thick one.     

Contact chemoreceptors among wind-sensitive head hairs of Locusta migratoria L. (Orthoptera: Acrididae)

The peg sensillum, a type of sensillum intermingled with the long hair sensilla in the hair fields on the head of Locusta migratoria (Orthoptera: Acrididae), was studied by light, transmission and scanning electron microscopy. The peg sensilla have the features typical of contact chemoreceptors; each peg is innervated by 5 sense cells; and 4 of the dendrites, enclosed within a “dendritic canal”, pass through the central lumen of the peg to the distal part, below the apical pore. The 5th dendrite ends in a tubular body at the caudal side of the peg articulation. Each distal segment of the 5 dendrites has a ciliary structure (9 ×2+0) at the transition to the short proximal segment, which in each case turns to the side to merge with the soma of the bipolar sense cell. Four sheath cells are associated with the group of sense cells and they are surrounded by a 5th, special epidermis cell. The innermost (thecogen) sheath cell (No. 1) encloses the receptor-lymph space 1 and forms the cuticular sheath; sheath cells 2 and 4 form the boundary of the large volume of receptorlymph space 2. The number of sheath cells is discussed with reference to other insect sensilla and in a phylogenetic context.     

Chemosensory proteins of Locusta migratoria (Orthoptera: Acrididae)

We describe a family of proteins abundantly expressed in the chemoreception sensory organs, the antennae and legs, of the desert locust, Locusta migratoria (Orthoptera, Acrididae). Using polymerase chain reaction-based approaches and homology screenings, "OS-D"-like proteins were identified in L. migratoria. The different sub-types (LmigOS-Ds) are very similar to each other and share about 50-70% identity with OS-Ds from Drosophila melanogaster and Periplaneta americana. A similar degree of identity was also observed with moth OS-Ds. Northern blot analysis revealed a strong expression of the LmigOS-Ds in the antennae and legs, suggesting their involvement in chemosensory processes. Despite the lack of direct evidence for their role in chemosensation, LmigOS-Ds and their homologs seem to constitute a large protein family, characterized by a striking abundance and diversity among insect chemosensory organs.     

Muscles and nerves of the posterior abdomen and genitalia of male Periplaneta americana (L.) (Dictyoptera : Blattidae)

Segmental and intersegmental muscles of abdominal segments 7–10 are described for adult, male Periplaneta americana (L.) (Dictyoptera : Blattidae). Locations of extrinsic and intrinsic genitalic muscles are documented, and the actions of those associated with the right phallomere are hypothesized. Muscles of the 5 abdominal segments are innervated by branches from 5 pairs of segmental nerves and 3 pairs of transverse nerves. These stem from a terminal synganglion, formed during embryogenesis by fusion of neuromeres of abdominal segments 7–11. One pair of segmental nerves issues from each of the 5 neuromeres, and one pair of transverse nerves arises from neuromeres of abdominal segments 7–9. The nerves are traced to the muscles, integument, and reproductive glands, and their peripheral unions are characterized. Serial homologies of the nerves and muscles are proposed, and comparisons are made with neuromusculature of the female.     

Diversity of neurohormonal release sites in insects: Neurohemal areas associated with peripheral neurosecretory cells in Periplaneta americana L. (Dictyoptera: Blattidae) and Locusta migratoria R. & F. (Orthoptera : Locustidae)

Neurohemal areas are located on the distal region of the transverse nerve and on the link nerve of the cockroach, Periplaneta americana (Dictyoptera : Blattidae) and the locust, Locusta migratoria (Orthoptera : Locustidae). They constitute the sites at which the peripheral neurosecretory cells on these nerves discharge their products. Histological and ultrastructural studies suggest that, at least in Periplaneta, these areas also serve to release neurosecretory products different from those found in the perisympathetic organs (POs). These products come from the ganglion cells, some of them via the transverse nerve, and others, via the somatic nerves. The existence of these neurohemal areas broadens the problem of the release zones and shows that the POs are not the only neurohemal structures associated with ventral ganglion cells. An attempt is made to explain the reason for the existence of these different release sites, as well as the role of the peripheral cells.     

Serotonin-immunoreactive neurons in the retrocerebral neuroendocrine complex of the cricket Teleogryllus commodus (Walker) (Orthoptera : Gryllidae) and cockroach Periplaneta americana (L.) (Dictyoptera : Blattidae)

Retrocerebral glandular complexes of Teleogryllus commodus (Orthoptera : Gryllidae) and Periplaneta americana (Dictyoptera : Blattidae) were examined for 5-hydroxytryptamine (serotonin)-immunoreactive (5-HTi) neurons. In Teleogryllus, a prominent tract of 5-HTi axons crosses the ventral surface of the corpus allatum (CA) from nervus corporis allati 1 (NCA 1), and seems to end at varicosities in NCA 2. Serotoninergic axons within this tract pass cephalad to the corpus cardiacum (CC), which also contains numerous, fine 5-HTi branches. 5-HTi axons originate anteriorly, presumably from the pars intercerebralis (PI) and pars lateralis (PL) of the brain. This is suggested by absence of immunoreactivity at the NCA 2-subesophageal ganglion junction, by intense immunofluorescence of the nervi corporis cardiaci (NCC) 1 and 2, by the presence of 5-HTi perikarya in PI and PL, and by previous data obtained by backfilling NCA 1 and 2. In Periplaneta, 5-HTi varicosities are rare in the CA, but abound in the NCA 2, and in NCC 1, 2, and 3. A few 5-HTi fibers project anteriorly from NCA 2 into the cap-like junction of CA and CC, and some traverse the CA to enter the postallatal nerves. Large, 5-HTi axons of NCC 3 ramify within the CC, while others contribute to an anterior branch of NCA 2. As in Teleogryllus, it is unlikely that 5-HTi fibers in NCA 2 originate from somata in the subesophageal ganglion. When cobalt staining and serotonin immunocytochemistry were combined to stain subesophageal neurons of Periplaneta, 5-HTi somata could not be paired with those back-filled via NCA 2. Conspicuous 5-HTi tracts between NCA 2 and the CC of Teleogryllus have no counterpart in Periplaneta.     

Pattern of bacteriocyte formation in Periplaneta americana (L.) (Blattaria: Blattidae)

In the embryos of Periplaneta americana (L.) (Blattaria: Blattidae), bacterial symbionts, together with vitellophages, form a mycetomic structure inside the deutoplasm; this regresses between the 15th and 16th day after deposition of the ootheca. In this article we describe the migration of bacteria across the wall of the midgut from the mycetome, and the topographic distribution of pre-bacteriocyte cells. We also report that the pre-bacteriocytes are present only on the lateral surface of the internal abdominal fat bodies. We discuss the possible embryological origin and evolution of these cells, and put forward the hypothesis that pre-bacteriocytes are derived from oenocytes activated to perform phagocytosis.     

东亚飞蝗胚胎体节的形成过程

体节形成是昆虫胚胎发育过程中的关键问题.东亚飞蝗Locusta migratoria manilensis(Meyen)是一种重要的农业害虫,其体节形成的时序过程尚无详细报道.本研究采用免疫组化和品红染色方法研究了室内人工饲养东亚飞蝗的体节形成过程.结果表明:完成受精后,细胞核开始分裂并向卵表面迁移.细胞核到达卵表面的...     

Organisation of wing cuticle in Locusta migratoria linnaeus,Tropidacris cristata linnaeus and Romalea microptera beauvais (Orthoptera : Acrididae)

The composite fibrous architectures of the wing cuticles of Locusta migratoria, Tropidacris (= Eutropidacris) cristata and Romalea microptera (Orthoptera : Acrididae) have been established. The wing cuticle in all the 3 species consists of: (i) an exocuticle, which is either pigmented or birefringent, and which under an electron microscope shows constantly helicoidal architecture of chitin microfibrils; (ii) endocuticle, which shows alternately birefringent and isotropic layers when sectioned transversely across the wing veins; these layers show helicoidal and unidirectional architecture, respectively of chitin microfibrils under the electron microscope. In transverse section, the chitin microfibrils appear as clear rods (2.8 nm in diameter) in a darkly stained matrix. However, in the hinge called the “claval furrow”, these microfibrils are considerably larger, being 25 nm in diameter. This presumably gives sufficient hardness to the claval hinge, which is the most vulnerable area for wear and tear during flight. The pore canals follow the parabolic pattern of microfibrils in the helicoidal layer, but remain straight in the unidirectional layers. The thickness of wing cuticle increases up to about 10–12 days, the time at which the acridids most probably attain the optimum flight ability. It is suggested that changes in the wing cuticle are related to increased wing beat frequency and speed of flight with age, and may help in resisting the simultaneous increase in the bending and twisting forces on the wing.     

Contributions to Physiology of the Antenna-Heart in Periplaneta americana (L.) (Blattodea: Blattidae)

An accessory pulsatile organ of an open circulatory system in insects supplying the antennae with haemolymph was investigated. The rhythm of this so-called antenna-heart is generated by a myogenic automatism and can be neuronally influenced via the nervus cardioantennalis.The action potentials of the muscle fibres show typical pre-depolarization and mostly no overshoot. A specific membrane resistance (R(m)) of about 660Omegacm(-2) was calculated for the fibres. Some electrical coupling between the muscle fibres is presumed for synchronization of any myogenically triggered heart beat which could actually be proved experimentally by current injection in the antenna-heart. However, intercalated disks or gap junctions could not be found. Nevertheless, a good coupling factor (U(2)/U(1)) between all fibres was demonstrated by parallel recordings and can be well described by a conductance model according to fibre topology.     

Muscles and innervation of the genital and postgenital abdominal segments of the female american cockroach Periplaneta Americana (L.) (Dictyoptera : Blattidae)

The locations of skeletal muscles in abdominal segments 7–10 of female Periplaneta americana (Dictyoptera : Blattidae) are described, and the action of some of those attached to the gonapophyses is hypothesized. The muscles are innervated from a terminal synganglion, a composite formed by fusion of embryonic neuromeres of abdominal segments 7–11. Pathways of the 5 pairs of segmental nerves and 3 pairs of transverse nerves that issue from the synganglion are documented. In addition to supplying skeletal muscles, certain of the nerves can be traced to the oviducts, spermatheca, colleterial glands, ventral glands, hindgut, and apparently, to sensilla of the cerci, gonapophyses, paraprocts, tergum, pleura, and sternum. Homologous relationships of the nerves are proposed, and the observations are compared to those reported by others who have, for the most part, examined males only. Putative neurosecretory somata occur in abdominal segments 7 and 8, at the junction of the transverse and segmental nerves. The association may be comparable to the “link nerve” complex described by others.     

Mechanism for range fractionation in chordotonal organs of Locusta migratoria (L) and Valanga sp. (Orthoptera : Acrididae)

The femoral chordotonal organ (FCO) of Locusta migratoria and Valanga sp. (Orthoptera : Acrididae) is a leg stretch receptor containing scolopophorous sensory neurones embedded in a ligament, which emerges distally from the body of the organ and connects to a distal apodeme. The ligament is pulled when the tibia is flexed. Thus the FCO bridges the femur-tibia joint. The ligament is divided into separate strands, each of which is composed of several or more, long attachment cells. These cells link individual scolopidia to the apodeme. An additional unloading strand connects the body of the FCO to a static point on the femoral integument. Because the strands are inserted along the apodeme in a sequential array, and because the unloading strand holds all the tension on the FCO when the ligament is relaxed (tibia extended), a mechanism for gradual, sequential uptake of tension by the ligament strands exists when the ligament is pulled (tibia flexed). This leads to a range fractionation of stretch-sensitive neurone responses during tibial flexion, and of relaxation-sensitive neurone responses during tibial extension. Observations on the ultrastructural distribution of desmosomes suggest that groups of attachment cells may be functionally connected and may collectively transmit force to specific groups of neurones.     

Changes in distribution and abundance of antennal sensilla during growth of Locusta migratoria L. (Orthoptera : Acrididae)

The antenna of Locusta migratoria (Orthoptera : Acrididae) increases in length by the production of new annuli proximally and by elongation of existing annuli. The most distal annuli are fully differentiated at the time of hatching and no new olfactory sensilla are added to them at subsequent molts. More proximally, the differentiation of trichoid contact chemoreceptors precedes the development of olfactory sensilla. Sensillum differentiation proceeds from distal to proximal along the antenna and more distal annuli attain full development at each molt. The biggest increase in numbers of olfactory sensilla occurs at the final molt. On any one annulus, most olfactory sensilla are restricted to sensory fields on the anterior and posterior faces. Their spacing within these fields is consistent with the existence of separate but interacting chaetogens regulating the differentiation of basiconic and coeloconic sensilla.     

Expression of chemosensory proteins in hairs on wings of Locusta migratoria (Orthoptera: Acrididae)

The hairs on the wings of Locusta migratoria were observed and mapped using light microscopy, as well as by scanning and transmission electron microscopy. Based on their ultrastructure, we can distinguish four main types of hairs on the wings of adult L. migratoria , viz, short, medium and long hairs, and sensilla chaetica. The long hairs are located only on the ventral surface of the hindwing, whereas the other three types are present both on the dorsal and ventral surfaces of forewing and hindwing in both sexes. Medium hairs and sensilla chaetica are significantly more abundant on the dorsal surface of forewings in both females and males, than on the ventral surface, whereas the opposite was observed for short hairs (P < 0.01). No significant difference between males and females was observed in the density of any type of hairs (P > 0.1). Several dendritic branches, enveloped by a dendrite sheath, are situated in the lymph cavity of sensilla chaetica. Instead, no dendritic structure was observed in the cavity of the other three types of hairs. Immunocytochemical localization of chemosensory proteins (CSPs) was performed on ultrathin sections of hairs on wings. The antiserum against chemosensory proteins from L. migratoria (LmigCSP-II) strongly labelled sensilla chaetica, with gold granules only found in the outer sensillum lymph. In addition, the epidermal cell membrane of the wing was stained by the antiserum against LmigCSP-II. The other three types of hairs were never labelled. The results indicate that the wings might involve in contact chemoreception process.     

Perception of cuticular hydrocarbons by the olfactory organs in Periplaneta americana (L.) (Insecta: Dictyoptera)

Despite the importance of cuticular hydrocarbons (CHs) in insect chemical communication, direct proof that they are detected and recognized by insects by contact or by olfactory receptors are rare. In Periplaneta americana, CHs induce aggregation. The aim of our study was to investigate how CHs are detected by P. americana antennae. Using solid phase microextraction and gas chromatography, the three main CHs of the species profile were identified in the volatiles emitted by these insects. Gas chromatography coupled to electroantennography recordings demonstrated that the antennae responded to these three CHs. Furthermore, CHs had an attraction effect in Y-olfactometer bioassays when presented at high concentrations. As CHs can be perceived by P. americana, at least from a short distance, they could play a role in attracting conspecifics during aggregation processes, in addition to inducing aggregation when direct contact is possible.     

Evidence for widespread genomic methylation in the migratory locust, Locusta migratoria (Orthoptera: Acrididae)

The importance of DNA methylation in mammalian and plant systems is well established. In recent years there has been renewed interest in DNA methylation in insects. Accumulating evidence, both from mammals and insects, points towards an emerging role for DNA methylation in the regulation of phenotypic plasticity. The migratory locust (Locusta migratoria) is a model organism for the study of phenotypic plasticity. Despite this, there is little information available about the degree to which the genome is methylated in this species and genes encoding methylation machinery have not been previously identified. We therefore undertook an initial investigation to establish the presence of a functional DNA methylation system in L. migratoria. We found that the migratory locust possesses genes that putatively encode methylation machinery (DNA methyltransferases and a methyl-binding domain protein) and exhibits genomic methylation, some of which appears to be localised to repetitive regions of the genome. We have also identified a distinct group of genes within the L. migratoria genome that appear to have been historically methylated and show some possible functional differentiation. These results will facilitate more detailed research into the functional significance of DNA methylation in locusts.