Cockroaches as vectors of Sarcocystis muris and of other coccidia in the laboratory.

To assess the roles of the German cockroach (Blatella germanica) and the American cockroach (Periplaneta americana) in the transmission of Sarcocystis muris and of 3 other coccidia of cats-Toxoplasma gondii, Isospora felis, and Isospora rivolta, cockroaches exposed to feces containing these coccidia were periodically fed to mice, as was a portion of the fecal matter. Sarcocystis muris sporocysts, which in feces remained infectious for at least 20 days, were also transmitted to mice by P. americana for at least 20 days and by B. germanica for 5 days after exposure to infectious feces. Toxoplasma gondii oocysts were transmitted by P. americana intermittently up to 10 days, but by B. germanica only immediately after exposure to feces. Oocysts of 2 species of Isospora, when associated with fecal matter, remained infectious for 20 days. Those of I. rivolta were transmitted by both cockroach species for 10 days, but I. felis was transmitted only by by B. germanica, and for only 2 days.     

Role of cockroaches Blatella germanica in the development of atopic bronchial asthma

The results of the development of manufacturing technology for the preparation of allergen from the bodies of cockroaches and the physico-chemical characteristics of this allergen are presented. The complex allergological examination of patients with atopic bronchial asthma revealed that 69.3% of such patients were sensitized to house dust, and in 68.4% of them IgE antibodies to cockroach allergens were detected. Patients with atopic bronchial asthma, not sensitized to house dust, were found to have sensitization to Blatella germanica in 12.2% of cases.     

Adjustability of the circadian clock in the cockroaches: a comparative study of two closely related species, Blattella germanica and Blattella bisignata.

A single 2h light pulse (250 lux) was given at various times to phase shift the locomotor circadian rhythm of two species of closely related cockroaches, Blattella bisignata and Blatella germanica. The phase-response curve (PRC) of both species showed a similar pattern. Phase delays and advances were induced by light pulse during the early and late subjective night, respectively, while no clear phase shifting was elicited during the subjective day. However, the magnitude of the phase delay (1.89h +/- 0.66h) and advance (0.69h +/- 0.36h) of B. bisignata was significantly larger than that of B. germanica (0.78h +/- 0.38h and 0.35h +/- 0.18h, respectively). This result indicates the superior adjustability of the circadian clock in B. bisignata. The period-response curve (PdRC) was also constructed for both species. Although both species did not show great flexibility in circadian period changes, the phase shifts were significantly correlated with the period changes in the advance zone of B. bisignata (r = 0.72, P < .1). This allowed the circadian clock of B. bisignata to display better entrainability since the phase advance adjustment was significantly more difficult than that of phase delay. The results indicate the overall adjustability of the circadian clock of B. germanica is inferior to that of B. bisignata. The significance of this finding is discussed from an ecological perspective.     

Experimental aspergillosis in the German cockroach Blattella germanica: a histopathological study

Inoculation of a spore suspension of Aspergillus flavus in the haemocoel of the German cockroach (Blatella germanica) resulted in large-scale invasion of various internal organs as seen in tissue sections stained with a fungal stain. The organs affected were the alimentary canal, fat bodies, muscle fibres, malpighian tubules and the cerebral neurosecretory cells. No invasion of the trachea and tracheoles was noted. This revised version was published online in June 2006 with corrections to the Cover Date.     

Field trial on the control effect of fipronil bait against German cockroaches

A field trial on the control effect of fipronil poison bait against German cockroaches (Blatella germanica) was carried out at different restaurant types in Sinchon, Seoul, Republic of Korea. Monitoring was performed applying food baited traps for 2 days per week. Reduction rates of German cockroaches by applying fipronil baits were 90.9% at Korean restaurants, 96.4% at Chinese restaurants, and 89.4% in beer hall kitchens after 4 weeks of the treatment. Overall average of the reduction rate was 93.9%. As the natural reduction rate at untreated restaurants was 11.5% after 4 weeks, a correction of the average reduction rate by applying the Abbot formula was 93.1%.     

Acquisition, persistence, and species susceptibility of the Hz-2V virus

Hz-2V, formerly called gonad-specific virus, is known to infect the reproductive organs of both males and females of the corn earworm Helicoverpa zea, rendering them agonadal or sterile. The primary mode of transmission is through mating by asymptomatic carrier moths. In this report we show that Hz-2V can be acquired by first instar larvae, through feeding on virus laced diet, although the incidence of agonadal condition was significantly lower. In a laboratory study, the virus appeared to persist for no more than three generations, with the incidence of agonadal progeny decreasing with each generation. Although, Hz-2V has been reported only from H. zea, in our tests when nine species of insects were artificially infected, four of the Noctuid species showed some signs of agonadal condition. Out of the remaining five species, the diamondback moth Plutella xylostella and the German cockroach Blatella germanica, showed no evidence of the virus in progeny of adults that were injected with Hz-2V, even after using the very sensitive PCR based assay.     

Insecticidal effectiveness ofMammea Americana (Guttiferae) extracts on larvae ofDlabrotica Virgifera Virgifera (Coleoptera:Chrysomelidae) andTrichoplusia Ni (Lepidoptera:Noctuidae)

Seed and leaf extracts ofMammea americana (mamey apple) have a historical use as a biopesticide with the active components previously characterized. We reexamined the utility of this natural bioinsecticide in light of existing sources of material as a by-product of the fruit processing industry. Our results addDiabrotica virgifera virgifera andTrichoplusia ni to the list of insects which are susceptible to the insecticidal ingredients ofM. americana and confirms earlier reports of activity againstBlatella germanica, Periplaneta americana, andPlutella xylostella. We report LD5Os for crude hexane extracts ofM. americana leaves and seeds againstT. ni. These materials represent renewable sources of bioinsecticides for agriculture, and should regenerate interest in coumarin-type compounds for novel pesticidal action.     

Virulence, horizontal transmission, and sublethal reproductive effects of Metarhizium anisopliae (Anamorphic fungi) on the German cockroach (Blattodea: Blattellidae)

Virulence of Metarhizium anisopliae (Metschnikoff) Sorokin strain EAMa 01/121-Su against the German Cockroach, Blatella germanica (L.), was determined using four concentrations ranging from 4.2 x 10(6) to 4.2 x 10(9) spores per milliliter. The LD50 value was 1.4 x 10(7) spores per milliliter (56,000 spores per cockroach) and LT50 values were 14.8 days and 5.3 days for 4.2 x 10(8) and 4.2 x 10(9) spores per milliliter, respectively. An experiment was conducted to evaluate whether a fungal transmission could exist among infected and healthy cockroaches. Percentage mortality at a ratio of 1:10 of infected to unexposed cockroaches was 87.5% and LT50 was 12.2 days, which indicated the potential of this strain to be horizontally transmitted and to rapidly spread the infection in the insect population. The effect of a sublethal dose (ca. LD60) of M. anisopliae EAMa 01/121-Su strain, applied topically on German cockroaches, was studied by reciprocal crossing. Othecal production, oothecal hatchability, and nymphal production declined upon exposure to M. anisopliae EAMa 01/121-Su strain. The mean number of oothecae laid by female was progressively and significantly reduced by fungal treatment from second oviposition period onwards. Oothecal hatch of fungally challenged females was reduced by 46-49%, oothecal viability by 48-85%, and nymphal production by 22-35%. Only treated females showed an effect on oothecal production, oothecal hatch, and nymphal production, although oothecal hatch was also governed by treated males at a higher significance level. Our results on virulence and horizontal transmission of fungal conidia of M. anisopliae EAMa 01/121-Su strain and its sublethal reproductive effects on German cockroach females are discussed in terms of its potential to decrease the pest status of B. germanica in the short and long terms.     

Fatty acyl-CoA elongation in Blatella germanica integumental microsomes

Insect cuticular hydrocarbons are synthesized de novo in integumental tissue through the concerted action of fatty acid synthases (FASs), fatty acyl-CoA elongases, a reductase, and a decarboxylase to produce hydrocarbons and CO2. Elongation of fatty acyl-CoAs to very long chain fatty acids was studied in the integumental microsomes of the German cockroach, Blatella germanica. Incubation of [1-14C]palmitoyl-CoA, malonyl-CoA, and NADPH resulted in the production of 18-CoA with minor amounts of C20, C22, C24, C30, and C32 labeled acyl-CoA moieties. Similar experiments with [1-14C]stearoyl-CoA rendered C20-CoA as the major product, and lesser amounts of C22 and C24-CoAs were also detected. After solubilization of the microsomal FAS, kinetic parameters were determined radiochemically or by measuring NADPH consumption. The reaction velocity was linear for up to 3 min incubation time, and with a protein concentration up to 0.025 microg/microl. The effect of the chain length on the reaction velocity was compared for palmitoyl-CoA, stearoyl-CoA, and eicosanoyl-CoA. The optimal substrate concentration was 10 microM for C16-CoA, between 8 and 12 microM for C18-CoA, and close to 3 microM for C20-CoA. In vivo hydrocarbon biosynthesis was inhibited from 55.5 to 72.5% in the presence of 1 mM trichloroacetic acid, a known inhibitor of elongation reactions.     

Local enhancement promotes cockroach feeding aggregations

Communication and learning from each other are part of the success of animal societies. Social insects invest considerable effort into signalling to their nestmates the locations of the most profitable resources in their environment. Growing evidence also indicates that insects glean such information through cues inadvertently provided by their conspecifics. Here, we investigate social information use in the foraging decisions by gregarious cockroaches (Blattella germanica L.). Individual cockroaches given a simultaneous choice in a Y-olfactometer between the odour of feeding conspecifics and the mixed odour of food plus non-feeding conspecifics showed a preference for the arm scented with the odour of feeding conspecifics. Social information (the presence of feeding conspecifics) was produced by cockroaches of all age classes and perceived at short distance in the olfactometer arms, suggesting the use of inadvertently provided cues rather than signals. We discuss the nature of these cues and the role of local enhancement (the selection of a location based on cues associated with the presence of conspecifics) in the formation of feeding aggregations in B. germanica. Similar cue-mediated recruitments could underpin a wide range of collective behaviours in group-living insects.     

Reproductive biology of the German cockroach,Blattella germanica: Juvenile hormone as a pleiotropic master regulator

Juvenile hormone (JH) exerts major pleiotropic effects on cockroach development and reproduction. The production of JH by the corpora allata (CA) in the adult female German cockroach, Blattella germanica, is dependent upon and modulated by both internal and environmental stimuli. Mating, intake of high-quality food, social interactions, and the presence of vitellogenic ovaries facilitate JH synthesis. Conversely, starvation, deficient diets, enforced virginity, isolation, and a pre- or post-vitellogenic ovary cause the CA to produce less JH. Sensory stimulation of the genital vestibulum by the ootheca also inhibits the CA via signals that ascend the ventral nerve cord. All these stimulatory and inhibitory signals are integrated by the brain, and a preponderance of favorable signals results in a graded lifting of brain inhibition, permitting the synthesis and release of JH. The effects of inhibitory signals on JH biosynthesis can be lifted experimentally by severing nervous connections between the brain and the CA. Such an operation accelerates activation of the CA. Besides controlling gonadal maturation in females, JH concurrently regulates the production of sexual signals, including both attractant- and courtship-eliciting pheromones, and the behavioral expression of calling (pheromone release) and sexual receptivity. Although JH is required for the expression of copulatory readiness in female B. germanica, it appears that signals associated with copulation (spermatophore, sperm, accessory secretions) can inhibit this behavioral state even when titers of JH are permissive for receptivity. These observations suggest that JH might regulate sexual receptivity in females indirectly through other directives. In males, JH accelerates not only the onset of sexual readiness but also synthesis of accessory reproductive products. Lastly, we present a novel cockroach control strategy that is based on the intimate association between food intake and rising JH titers in B. germanica females. JH analogs cause abortion of fertile oothecae in gravid females. In turn, rising JH titers and vitellogenic oocytes induce feeding in females. With strategic placement of insecticidal baits and JH analogs, gravid females, which normally feed little and are difficult to control, can thus be effectively targeted for elimination. Arch. Insect Biochem. Physiol. 35:405–426, 1997. © 1997 Wiley-Liss, Inc.     

Identification of leucomyosuppressin in the German cockroach, Blattella germanica, as an inhibitor of food intake

The feeding pattern of the adult female of Blattella germanica peaks in the middle of the vitellogenic cycle. Following the hypothesis that a factor inhibiting gut peristalsis also inhibits food intake and is involved in the regulation of feeding, we searched for the most powerful myoinhibitory peptide in brain extracts from B. germanica females collected after the peak within the feeding cycle. Through HPLC purification and sequence analysis, we obtained the peptide leucomyosuppressin (LMS): pQDVDHVFLRFamide. LMS elicited a powerful myoinhibitory effect on B. germanica foregut and hindgut, with ED(50) values around 10(-10) M. In addition, it inhibited food intake in vivo in a dose-dependent manner at doses between 5 and 50 microg. The study of the distribution of ingested food in the foregut, midgut and hindgut of B. germanica females treated with LMS showed that food accumulates in the foregut, which may be due to the myoinhibitory effects of the peptide. We propose that this accumulation inhibits food intake because of the persistence of the signals from gut stretch receptors.     

A densovirus of German cockroach Blatella germanica: detection,nucleotide sequence and genome organization

A new Blattella germanica densovirus (BgDNV, Parvoviridae: Densovirinae, Densovirus) was found. Virus DNA and cockroach tissues infected with BgDNV were examined by electron microscopy. Virus particles about 20 nm in diameter were observed both in the nucleus and in the cytoplasm of infected cells. Virus DNA proved to be a linear molecule sized about 1.2 microns. The complete BgDNV genome was sequenced and analyzed. Five ORF were detected: two coded for structural capsid proteins and were on one DNA strand, and three coded for regulatory proteins and were on the other strand. Potential promoters and polyadenylation signals were identified. Structural analysis was performed for terminal inverted repeats containing extended palindromes. The genome structure of BgDNV was compared with that of other Parvoviridae.     

Temporal separation of whale vocalizations from background oceanic noise using a power calculation

The process of analyzing audio signals in search of cetacean vocalizations is in many cases a very arduous task, requiring many complex computations, a plethora of digital processing techniques and the scrutinization of an audio signal with a fine comb to determine where the vocalizations are located. To ease this process, a computationally efficient and noise-resistant method for determining whether an audio segment contains a potential cetacean call is developed here with the help of a robust power calculation for stationary Gaussian noise signals and a recursive method for determining the mean and variance of a given sample frame. The resulting detector is tested on audio recordings containing southern right whale sounds and its performance is compared to a contemporary energy detector and a popular deep learning method. The detector exhibits good performance at moderate-to-high signal-to-noise ratio values. The detector succeeds in being easy to implement, computationally efficient to use and robust enough to accurately detect whale vocalizations in a noisy underwater environment.     

Detection and correction of erroneous eye movements by the brain error detector while tracking moving object

The models for research of function of the brain error detector of eye movements are described. The quantitative estimation of temporary parameters of erroneous eye saccades detection and correction of the healthy people is given. The data on distinctions in duration of the latency, speed and other parameters of erroneous and correctional saccades, are used for discussion on types of sensory signals used by the brain detector for revealing and correction of erroneous eye movements.     

The decomposition of the EPR spectra of multicomponent systems irradiated at 77 K into paramagnetic center signals of different natures]

Main principles of the way to decompose an EPR spectrum of a multicomponent system, irradiated at 77 K, into separate radiation-induced paramagnetic centre signals are given. The decomposition is possible due to the computer assistant spectra processing, and is based on different properties of different paramagnetic centres, namely, on different thermostability of the centres, on different rate of relaxation, and on different photosensitivity. Concrete examples of the EPR spectrum decomposition into different free radical signals are given for cases of murine liver and spleen irradiated at 77 K. Radiochemical yields of different free radicals, induced by gamma radiation at 77 K in whole biological tissues, were defined. The data on nature and properties of the paramagnetic centres induced by radiation in biological tissues are shortly reviewed.     

Screening of antifeedant activity in brain extracts led to the identification of sulfakinin as a satiety promoter in the German cockroach. Are arthropod sulfakinins homologous to vertebrate gastrins-cholecystokinins?

The feeding cycle of the adult female cockroach Blattella germanica parallels vitellogenesis. The study of the mechanisms that regulate this cycle led us to look for food-intake inhibitors in brain extracts. The antifeedant activity of brain extracts was tested in vivo by injecting the extract and measuring the carotenoids contained in the gut from carrot ingested after the treatment. By HPLC fractionation and tracking the biological activity with the carrot test, we isolated the sulfakinin EQFDDY(SO3H) GHMRFamide (Pea-SK). A synthetic version of the peptide inhibited food intake when injected at doses of 1 microg (50% inhibition) and 10 microg (60% inhibition). The sulfate group was required for food-intake inhibition. These biological and structural features are similar to those of the gastrin-cholecystokinin (gastrin-CCK) family of vertebrate peptides. However, heterologous feeding assays (human CCK-8 tested on B. germanica, and Pea-SK tested on the goldfish Carassius auratus) were negative. In spite of this, alignment and cluster analysis of these and other structurally similar peptide families suggest that sulfakinins and gastrin-CCKs are homologous, and that mechanisms of feeding regulation involving these regulatory peptides may have been conserved during evolution between insects and vertebrates.     

Hierarchical genetic structure of the introduced wasp Vespula germanica in Australia

The wasp Vespula germanica is a highly successful invasive pest. This study examined the population genetic structure of V. germanica in its introduced range in Australia. We sampled 1320 workers and 376 males from 141 nests obtained from three widely separated geographical areas on the Australian mainland and one on the island of Tasmania. The genotypes of all wasps were assayed at three polymorphic DNA microsatellite markers. Our analyses uncovered significant allelic differentiation among all four V. germanica populations. Pairwise estimates of genetic divergence between populations agreed with the results of a model-based clustering algorithm which indicated that the Tasmanian population was particularly distinct from the other populations. Within-population analyses revealed that genetic similarity declined with spatial distance, indicating that wasps from nests separated by more than approximately 25 km belonged to separate mating pools. We suggest that the observed genetic patterns resulted from frequent bottlenecks experienced by the V. germanica populations during their colonization of Australia.