Biological characteristics of Evania appendigaster (L.) (Hymenoptera: Evaniidae) in different densities of Periplaneta americana (L.) oothecae (Blattodea: Blattidae)

Evania appendigaster (L.) is a solitary endoparasitoid of oothecae of the American cockroach, Periplaneta americana (L.). In this work we report our studies on the parasitism of P. americana oothecae by E. appendigaster and the biological characteristics of this egg parasite, as it is affected by host density and mating. Cockroach oothecae were presented for individual females at different densities (one, two, three, four, five and six oothecae) during 2 days of exposition time. Reproduction was determined to be biparental and arrhenotokous. Host density did not influence sex ratio and longevity. The greatest reproductive efficiency of the females occurred in the first 14 days of their lifetime. At higher densities low parasitism rates were accompanied by a high percentage of dead oothecae. The percentage of parasitism decreases with increase in host density.     

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.     

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.     

Suitability of heat- and freeze-killed oothecae of the American cockroach (Dictyoptera: Blattidae) as hosts for an oothecal parasitoid, Aprostocetus hagenowii (Hymenoptera: Eulophidae)

The objective of this study was to evaluate the suitability of heat- and freeze-killed oothecae of Periplaneta americana (L.) (Dictyoptera: Blattidae) as hosts for parasitoid Aprostocetus hagenowii (Ratzeburg) (Hymenoptera: Eulophidae). The oothecae were subjected to -20, 45, 48, 50, and 55 degrees C at different exposure times (15, 30, 45, and 60 min). The effects of heat- and freeze-killed oothecae on several biological parameters (e.g., parasitism and emergence rates, developmental times, progeny number, and sex ratio) ofA. hagenowii were determined. Embryonic development of 2-d-old oothecae was terminated by either freezing at -20 degrees C or heating at > or = 48 degrees C for > or =30 min. A. hagenowii parasitized live oothecae as well as both heat- and freeze-killed oothecae. Percentage parasitism, emergence rates, and developmental times ofA. hagenowii in both heat- and freeze-killed oothecae were not significantly different from those of the live oothecae. Both heating and freezing did not influence progeny number (male and female) and sex ratio of A. hagenowii emerged from killed oothecae.     

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.     

The complete mitochondrial genome of Evania appendigaster (Hymenoptera: Evaniidae) has low A+T content and a long intergenic spacer between atp8 and atp6

The apocritan Hymenoptera show extraordinary features in mitochondrial genomes, but no complete sequence has been reported for the basal lineage, Evanioidea. Here, we sequenced the complete mitochondrial genome of Evania appendigaster. This genome is 17,817 bp long; with low A+T content, 77.8%, compared with other hymenopteran species. Four tRNA genes were rearranged, among which remote inversion is the dominant gene rearrangement event. Gene shuffling is caused by tandem duplication-random loss while remote inversion is best explained by recombination. The start codon of nad1 was found as TTG, which might be common across Hymenoptera. trnS2 and trnK use abnormal anticodons TCT and TTT, respectively, and the D-stem pairings in trnS2 are absent. The secondary structure of two rRNA genes are predicted and compared with those in other insects. Five long intergenic spacers were present, including a long intergenic spacer between atp8 and atp6, where these two genes overlap in the previously reported animal genomes. A conserved motif was found between trnS1 and nad1, which is proposed to be associated with mtTERM. The A+T-rich region is 2,325 bp long, among the longest in insects, and contains a tandem repeat region.     

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.     

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.     

Fate of a bacteriophage in Aedes aegypti, Anopheles quadrimaculatus (Diptera: Culicidae), and Periplaneta americana (Orthoptera: Blattidae)

The viability of a bacteriophage of Escherichia coli was unaffected by injection into the hemocoel of the mosquitoes, Aedes aegypti and Anopheles quadrimaculatus, but was reduced by injection into the cockroach, Periplaneta americana. Treatment of the cockroach with India ink, known to be phagocytized in the cockroach hemocoel, did not block the reduction of phage viability. Phage viability was unaffected by incubation with gut homogenates of A. aegypti but was possibly affected by homogenates of P. americana.     

Tubular bodies in dendritic outer segments projecting to second embryonic cuticle from anlagen of contact chemoreceptors in Locusta migratoria L. (Orthoptera : Acrididae) and Periplaneta americana (L.) (Dictyoptera : Blattidae)

Bundles of dendritic outer segments project to the 2nd embryonic cuticle from anlagen of contact chemoreceptors in the antennae of 9-day embryos (80–85% stage) of Locusta migratoria L. (Orthopteroidea) and in the maxillary palps of 24-day embryos (80% stage) of Periplaneta americana (L.) (Blattodea). The dendrite sheaths fuse with irregular nodular thickenings in the 2nd embryonic cuticle in Locusta; in Periplaneta the sheaths are joined to it by filaments. In both species one of the dendritic outer segments shows a dilation within which a tubular body is contained. This tubular body is located in Locusta at the nodular thickening where the dendrite sheath is connected to the 2nd embryonic cuticle. In Periplaneta, the tubular body was observed near the junction between the dendrite sheath and the cuticle in most cases, but at some distance to the cuticle in others. The occurrence of a tubular body is discussed with reference to mechanoreceptive capacities of the sensory cells and to the phylogeny of the 2nd embryonic cuticle.     

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.     

Structure and function of the thecogen cell in contact chemosensitive sensilla of Periplaneta americana L. (Blattodea: Blattidae)

The functional morphology of the thecogen cell of the contact chemosensitive sensilla of the ventral sensory field on the maxillary palps of Periplaneta americana (Blattodea : Blattidae) was studied. There were electron-dense granules, which were examined using light and electron microscopy. Ultrastructural findings and acid phosphatase cytochemistry showed that these granules are lysosomes. The plasma membrane of the thecogen cell bordering the inner sensillum lymph also showed numerous coated pits. Intense fluid-phase endocytosis from the inner sensillum lymph into the thecogen cell was observed using Lucifer yellow as a fluorescent dye for infiltration. The endocytosed material is transported proximally and seems to be digested via the endosome-lysosome pathway. Lysosomes and endocytosis may serve the following functions: (1) the cleaning of the sensillum lymph from impurities entering via the tip porus; (2) the catabolic turnover during late embryonic development and before molting; (3) the continuous removal of stimulus molecules from the inner sensillum lymph after stimulation.     

Effects of GNA transgenic sugarcane on life history parameters of Parallorhogas pyralophagus (Marsh) (Hymenoptera: Braconidae), a parasitoid of Mexican rice borer

Parallorhogas pyralophagus (Marsh) is the principal parasitoid of the Mexican rice borer [Eoreuma loftini (Dyar)], the primary pest of sugarcane in south Texas. Insect resistant transgenic sugarcane producing Galanthus nivalis agglutinin (GNA) was developed to improve control of E. loftini. The present laboratory study addressed whether over two consecutive generations transgenic sugarcane delivered via artificial diet has adverse host-mediated effects on P. pyralophagus life history parameters. The results of this study showed that a number of life history parameters were affected by transgenic sugarcane, whereas others were not affected, and that effects varied between generations. In the first generation, adult longevity was increased by approximately 2 d, and cocoon to adult and egg to adult developmental times were prolonged by approximately 1 d in parasitoids exposed to transgenic sugarcane, whereas effects were not evident on adult size; egg load; egg to cocoon developmental time; rates of gain of longevity and egg load with adult size; and egg, larval, and pupal mortality. However, in the second generation, adult longevity was reduced by approximately 3 d, adult size by approximately 5%, egg load by approximately 24%, and rate of gain of longevity with adult size by approximately 21%, whereas effects were not evident on the rate of gain of egg load with adult size. It was concluded that although GNA transgenic sugarcane, ingested via E. loftini tissues, was not acutely toxic to P. pyralophagus, the sublethal effects on life history parameters measured in this study must be considered in a broader context to determine their possible ecological significance.     

The overwintering stages of Ectobius lapponicus (L.) (Dictyoptera: Blattidae)

An account is given of the overwintering stages of Ectobius lapponicus, involving the determination of a diapause in the egg and one of the nymphal instars. The significance of these periods in the life cycle is discussed.     

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.