Neurosecretory system of Heteroptera (Hemiptera) and role of the aorta as a neurohemal organ.
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Two different inherited bacterial symbionts from ovary tissue of the bedbug Cimex lectularius were characterized by gene amplification and sequencing analysis of their 16S rDNA gene. The first bacterium belongs to the Wolbachia subgroup of the alpha-Proteobacteria, the second is a member of the gamma-subdivision, and is closely related to the bacterial parasite of the leafhopper Euscelidius variegatus (BEV) which was shown to be capable of transovarial transmission. The high similarity (> 97%) between the C. lectularius symbiont and BEV indicates that these two microorganisms belong to the same lineage and share the ability to invade distant insect hosts to fulfill their symbiotic functions and to establish transovarial transmission to future generations.
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Insect odorant binding proteins (OBPs) are thought to deliver odors to olfactory receptors, and thus may be the first biochemical step in odor reception capable of some level of odor discrimination. OBPs have been identified from numerous species of several insect orders, including Lepidoptera, Diptera, Coleoptera and Hymenoptera; all are holometabolous insects belonging to the monophyletic division of insects known as the Endopterygota. Recently, an antennal protein with OBP-like properties was identified from Lygus lineolaris, a hemipteran insect representing the Hemipteroid Assemblage, a sister division to the Endopterygota. The full length sequence of Lygus antennal protein (LAP) is presented in this report. In situ hybridization analysis revealed LAP expression in cell clusters associating with olfactory sensilla; expression was adult-specific, initiating in developing adult tissue during the transitional period that precedes the actual adult molt. Sequence analysis confirmed that LAP is homologous with the OBP-related protein family, and most similar to the OS-E and OS-F proteins of Drosophila, the ABPX proteins of Lepidoptera and the OBPRP proteins of the Coleoptera. Assuming that the OBP-related proteins represent one homologous family, the identification of LAP significantly expands the phylogenetic depth of that family and its underlying role in odor detection to encompass all members of the Endopterygota and Hemipteroid Assemblage, which comprise >90% of all insect species.
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Preferred temperature and activity patterns of Triatoma infestans Klug and Triatoma spinolai Porter were studied, both are vectors of Chagas' disease in Chile. In the laboratory, 24 T. spinolai and 18 T. infestans were exposed to a temperature gradient between 50 and 15 degrees C and a photoperiod of 14:10 (L:D) h. Temperature and hourly position of bugs in an experimental chamber were recorded for 24 h. Both species showed a cycle of preferred temperature, and both selected higher temperatures beginning at 1600 hours, although T. infestans maintains this preference over a longer period. For both species, activity patterns were synchronized with the light-dark cycle, although these activity rhythms were significantly different. T. spinolai had higher activity during the photophase, and T. infestans showed a lower activity in the photophase and a higher one during the scotophase. The similar pattern of preferred temperatures may facilitate the selection of similar environments in the event of colonization of houses by T. spinolai. Diurnal activity of this species might be a disadvantage (in terms of more exposure to defensive responses of the vertebrate hosts) but may allow T. spinolai to share the same habitat with T. infestans without competitive interference.
One hundred and fifty-seven specimens of Bolivian Triatoma infestans (Klug 1834), including 44 from the silvatic focus at Cochabamba (Bolivia), were compared using morphometric characters of the head capsule. From these specimens, 10 silvatic and 28 domestic adults were also compared using additional morphometric characters of the membranous part of the hemelytra. Nonparametric univariate comparisons between specimens from silvatic and domestic ecotopes indicated the importance of the postocular region as a possible diagnostic character for nymphs and adults from the different ecotopes, and they detected wing differences in males. Populations became more distinct entities when head or wing characters were considered jointly in canonical variate analysis. Regardless of whether size variation was considered, canonical variate analysis generally showed greater significance for wing than for head features. These morphological differences between silvatic and domestic bugs, particularly unrelated to size differences, are interpreted to indicate incipient separation between silvatic and domestic populations that had not been detected by previous isoenzyme analyses, and suggest a reinterpretation of the epidemiological significance of silvatic populations of T. infestans in Bolivia.
Salivary gland homogenates from 4 genera of triatomine bugs were assayed for anticlotting, apyrase, and vasodilatory activities, and these activities were correlated with the efficiency of each bug species to initiate a blood meal. Antihemostatic activities spanned a large range of values. Apyrase activity in members of the genus Rhodnius was markedly different from that in other genera with respect to their sensitivity to divalent cation activators. Apyrase and vasodilatory activities, but not anticlotting activity, correlated with feeding efficiency of bugs taking a blood meal on a rat. Results are discussed within the context of the evolution of blood-feeding by insects.
Population parameters of Triatoma spinolai Porter were studied using specimens collected in the north and central region of Chile. Two cohorts of 17 and 44 first instars were maintained at a constant temperature of 28 degrees C and 70% RH. Two similar cohorts of bugs were exposed to 16-24 degrees C and 55-75% RH and maintained under a photoperiod of 14:10 (L:D) h for 16 mo. The preimaginal period ranged between 285 and 372 d under constant conditions. The lower-density cohort required 9.5 mo to reach the adult stage compared with 12.4 mo for the high-density cohort. Bugs placed under variable temperature and relative humidity conditions did not survive long. Cohorts with higher densities had similar mortality rates with greater mortality occurring in cohorts that had lower numbers of bugs. Cohorts under constant temperature and relative humidity reproduced and basic reproduction rates (Ro, intrinsic growth rate [r], and generation time [G]) were estimated. Cohorts with higher numbers of bugs had higher Ro and r, whereas values of G were similar for both groups. Apparently, 25 degrees C was a critical temperature threshold for T. spinolai and there appeared to be a minimal population density that allowed reproduction.
Saliva of Triatoma infestans (Klug) produced a progressive reduction in the amplitude of the compound action potential recorded from rat sciatic nerve. The saliva also inhibited the Na+ current on GH3 cells. The data demonstrate that the saliva of T. infestans has an inhibitory effect on Na+ channels. We conclude that this effect may decrease the generation and conduction of nerve action potential, thereby decreasing the sensitivity of the region in which the insect probes, in a manner similar to that of local anesthetics. This study demonstrates such activity in the saliva of hematophagous insects. The adaptive value of this activity is clear, because the quantity of blood obtained by triatomines is limited by the irritation caused during the feeding process.