Adult Blattella Germanica Research Articles

Egfr signaling promotes juvenile hormone biosynthesis in the German cockroach

BackgroundIn insects, an interplay between the activities of distinct hormones, such as juvenile hormone (JH) and 20-hydroxyecdysone (20E), regulates the progression through numerous life history hallmarks. As a crucial endocrine factor, JH is mainly synthesized in the corpora allata (CA) to regulate multiple physiological and developmental processes, including molting, metamorphosis, and reproduction. During the last century, significant progress has been achieved in elucidating the JH signal transduction pathway, while less progress has been made in dissecting the regulatory mechanism of JH biosynthesis. Previous work has shown that receptor tyrosine kinase (RTK) signaling regulates hormone biosynthesis in both insects and mammals. Here, we performed a systematic RNA interference (RNAi) screening to identify RTKs involved in regulating JH biosynthesis in the CA of adult Blattella germanica females.ResultsWe found that the epidermal growth factor receptor (Egfr) is required for promoting JH biosynthesis in the CA of adult females. The Egf ligands Vein and Spitz activate Egfr, followed by Ras/Raf/ERK signaling, and finally activation of the downstream transcription factor Pointed (Pnt). Importantly, Pnt induces the transcriptional expression of two key enzyme-encoding genes in the JH biosynthesis pathway: juvenile hormone acid methyltransferase (JHAMT) and methyl farnesoate epoxidase (CYP15A1). Dual-luciferase reporter assay shows that Pnt is able to activate a promoter region of Jhamt. In addition, electrophoretic mobility shift assay confirms that Pnt directly binds to the − 941~ − 886 nt region of the Jhamt promoter.ConclusionsThis study reveals the detailed molecular mechanism of Egfr signaling in promoting JH biosynthesis in the German cockroach, shedding light on the intricate regulation of JH biosynthesis during insect development.

Regulation of insulin-like peptide expression in adult Blattella germanica females

The insulin-IGF-signalling (IIS) pathway regulates key processes in metazoans. The pathway is activated through the binding of the ligands, which in insects are usually referred to as insulin-like peptides (ILPs), to a class of receptor tyrosine kinases, the insect insulin receptor. To study the pathway regulation, it is therefore essential to understand how ILPs are produced and released. In this study we analysed the factors that regulate the expression of the seven ILPs (BgILPs) expressed in adult females of the German cockroach, Blattella germanica. The results showed that the starvation-induced expression reduction of brain BgILP3, 5 and 6 and fat body BgILP7 is not due to reduced juvenile hormone (JH) or decreased TOR pathway activity. In addition, depletion of FoxO in starved females did not correct the low levels of these BgILPs, but even reduced further BgILP5 expression, indicating the need to maintain certain basal levels of BgILP5 even during starvation. Furthermore, JH promoted increased BgILP5 and decreased BgILP3 expression in the brain, an effect that required Methoprene-tolerant (Met), the JH receptor, but not Krüppel homolog 1 (Kr-h1), the main JH transducer. On the other hand, JH inhibited the expression of BgILP7 in the fat body, although in this case, the action required both Met and Kr-h1. In addition, JH reduction treatments produced a decrease in the expression of the insulin receptor in the fat body, which suggests an increase in IIS. The results show a peculiar regulation of ILP expression in adult B. germanica females, which is clearly different than that seen in other species. This is understandable given that gene duplications in recent clades have resulted in different sets of ILP genes, involving substantial changes in gene regulatory networks.

饵料蛋白水平对德国小蠊肠道细菌群落的影响

昆虫肠道微生物在宿主营养代谢、生长发育、免疫以及抵御病原菌等方面具有重要作用。研究不同蛋白水平饵料饲养对德国小蠊（Blattella germanica）雄成虫肠道细菌群落组成及其功能的作用，探究德国小蠊肠道细菌对宿主营养和健康的影响，以期为发展生物防治的诱食性饵料提供理论支持。分别取连续饲喂低蛋白（LP2组：5%）、高蛋白（HP3组：65%）以及正常蛋白水平饵料（CD1组：25%）21 d的德国小蠊雄成虫，饥饿24 h后无菌条件下分离并提取肠道总基因组DNA，采用特异引物扩增细菌16S rDNA的V4可变区并进行高通量测序，分析德国小蠊肠道细菌群落组成及其功能特征。结果表明德国小蠊肠道细菌主要由拟杆菌门（Bacteroidetes）、变形菌门（Proteobacteria）、梭杆菌门（Fusobacteria）和厚壁菌门（Firmicutes）等细菌群落组成。饲喂低蛋白饵料LP2组的德国小蠊肠道细菌中拟杆菌属（Bacteroides）细菌丰度（47.44%）显著高于HP3组（23.97%）和对照CD1（7.04%）。饲喂高蛋白饵料的HP3组梭杆菌门丰度显著高于其他两组。LEfSe物种差异分析也表明HP3组德国小蠊肠道细菌中梭杆菌属（Fusobacterium）细菌与低蛋白饵料LP2组和对照CD1组有显著差异。基于Tax4Fun功能预测显示，HP3高蛋白饵料组的德国小蠊肠道细菌中与能量代谢功能相关基因的相对丰度极显著高于对照组CD1组，外源性物质代谢与降解和其他氨基酸代谢功能基因的相对丰度显著高于低蛋白LP2组。本研究结果表明饵料中蛋白质水平的差异能够显著改变德国小蠊肠道中细菌群落结构组成，并影响其代谢功能。;Gut bacteria of insect play important roles in host food digestion, growth and development, immunity and resistance to pathogens. This study aims to reveal the effects of protein levels of dietary on bacterial communities and functional characteristics of intestinal microbiota in male adult Blattella Germanica. It will provide a basis for evaluating the role of the intestinal bacteria in the host nutritional metabolism and health, and developing the attractive biocontrol dietary for cockroach pests. The male B. germanica adults were separately fed with low protein (LP2 group:5%), high protein (HP3 group:65%) diets, or the normal protein level rat food (CD1 group:25%) for 21 days. Then the intestine of B. germanica was seperated under sterile condition and the total intestinal genomic DNA was extracted. The V4 variable region of bacterial 16S rDNA was amplified by high-through sequencing. The intestinal microbiota of B. germanica was mainly composed of Bacteroidetes, Proteobacteria, Fusobacteria, and Firmicutes. The abundance of Bacteroidetes in LP2 group with low protein bait was significantly higher than those in the control CD1 group and HP3 groups with 65% protein bait. LEfSe analysis demonstrated that the abundance of Fusobacterium in the intestinal microbiota of B. germanica (HP3 group) fed with high protein bait was significantly different with those in LP2 and CD1 groups. The function prediction results from Tax4Fun demonstrated that the relative abundance of genes related to energy metabolism in intestinal microbiome of male adults fed with 65% protein bait (HP3) was significantly higher than that in B. germanica fed with 25% protein bait (CD1). And the relative abundance of the gene associated with xenobiotics biodegradation and metabolism, and metabolism of other amino acid functions were also significantly higher than those of B. germanica fed with 5% protein bait (LP2). The results showed that protein levels of the feeding dietary could significantly change bacterial community composition and metabolism of intestinal microbiome in B. germanica.

Protozoan Cysts in Faecal Pellets of German Cockroaches (Blattella germanica), with Particular Emphasis on Lophomonas blattarum

PurposeThe aim of this study was to investigate protozoan cysts and oocyts in the faecal pellets of the German cockroach (Blattella germanica), with emphasis on the prevalence of Lophomonas blattarum.MethodsThirty adult Blattella germanica (12 males; 18 females) were trapped near Madrid, Spain. Expelled faecal pellets were collected in the laboratory over 5 days in two plastic containers. Protozoan cysts from one container were weighted and those in the other used for morphologically identification.ResultsProtozoan cysts/oocysts per gram of faecal pellet were: Nyctotherus sp. (0.0019/g), Entamoeba (0.0007/g), Balantidium coli (0.0001/g), Lophomonas blattarum (0.00038/g). Observation of 189 protozoan cysts/oocysts indicated the following prevalence: Nyctotherus sp. 65 (34.4%); Gregarina spp. 34 (18%); Entamoeba sp. 24 (12.7%); Cryptosporidium sp. 17 (9%); Coccidia 16 (8.4%); Lophomonas blattarum 13 (6.8%); Balantidium coli 4 (2.1%); and unclassified 16 (8.4%).ConclusionLophomonas blattarum has previously been demonstrated in the gut of cockroaches, but this is the first assessment of the prevalence in Blattella germanica in faecal pellets. The presence of protozoa in faecal pellets provides some evidence for one step in a hypothesised route of respiratory infection whereby protozoa from household insects enter the respiratory tract.

Juvenile hormone biosynthesis in adult Blattella germanica requires nuclear receptors Seven-up and FTZ-F1

In insects, the transition from juvenile development to the adult stage is controlled by juvenile hormone (JH) synthesized from the corpora allata (CA) glands. Whereas a JH-free period during the last juvenile instar triggers metamorphosis and the end of the growth period, the reappearance of this hormone after the imaginal molt marks the onset of reproductive adulthood. Despite the importance of such transition, the regulatory mechanism that controls it remains mostly unknown. Here, using the hemimetabolous insect Blattella germanica, we show that nuclear hormone receptors Seven-up-B (BgSvp-B) and Fushi tarazu-factor 1 (BgFTZ-F1) have essential roles in the tissue- and stage-specific activation of adult CA JH-biosynthetic activity. Both factors are highly expressed in adult CA cells. Moreover, RNAi-knockdown of either BgSvp-B or BgFTZ-F1 results in adult animals with a complete block in two critical JH-dependent reproductive processes, vitellogenesis and oogenesis. We show that this reproductive blockage is the result of a dramatic impairment of JH biosynthesis, due to the CA-specific reduction in the expression of two key JH biosynthetic enzymes, 3-hydroxy-3-methylglutaryl coenzyme A synthase-1 (BgHMG-S1) and HMG-reductase (BgHMG-R). Our findings provide insights into the regulatory mechanisms underlying the specific changes in the CA gland necessary for the proper transition to adulthood.

Evaluations on the Lethal, Choice and Secondary Effects of Four Insecticidal Baits against the German Cockroach (Blattaria, Blattellidae)

ABSTRACT The laboratory studies were carried out for evaluating control effects of four commercial insecticidal baits such as two different hydramethylnon [2.0%(AI)] products (DBK® and Combat‐Gold®), fipronil [0.05 %(AI)] (Combat‐Power®) and (0.6% chlorpyrifos [0.6%(AI)] (Raid‐Roachbait®) against German cockroaches (Blattella germanica). The control rates of four kinds of toxic baits were all 100.0% mortality of German cockroaches in 5 days after treatment. The results of chlorpyrifos and fipronil brought 100.0% mortalities in 2 to 3 days after treatment, respectively. After 3 day treatment, there was no significant difference of control effect among the four toxic baits. As a result of this study, fipnonil and chlorpyrifos showed faster killing action against German cockroaches than the two hydramethylnon formulation products. In the choice test, DBK® (hydramethylnon) (average 17.0 ind.) significantly attracted more German cockroaches than Combat‐Gold® (hydramethylnon) (avg. 7.0 ind.), Combat‐Power® (fipronil) (avg. 5.3 ind.) and Raid‐Roachbait® (chlorpyrifos) (avg. 3.3 ind.). The difference in attraction effects came 10 minutes after treatment. In order to evaluate the secondary killing effect of toxic baits by coprophagy against adult Blattella germanica, the comparative test was carried out. The adult mortality rates were significantly different among the four toxic baits showing 86.7% mortality for fipronil, 60.0% for hydramethylnon (DBK®), 30.0% for chlorpyrifos, and below 13.3% for hydramethylnon (Combat‐Gold®) in 6 days. During the first 12 days, fipronil showed the highest mortality rate (90.0%), followed by hydramethylnon (DBK®) (60.0%). The secondary killing effect of toxic baits by coprophagy appeared in all of the baits against adult Blattella germanica.

Ovarian 3-hydroxy-3-methylglutaryl-CoA reductase in Blattella germanica (L.): pattern of expression and critical role in embryogenesis

In the ovary of adult Blattella germanica, the enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) is highly expressed in mid-late vitellogenesis, suggesting a functional link of the mevalonate pathway with choriogenesis. The inhibitor of HMG-CoA reductase, fluvastatin, applied in females in late vitellogenesis, inhibits the activity of the enzyme in the ovary and in the developing embryos within the ootheca. This does not affect choriogenesis or ootheca formation but reduces the number of larvae per ootheca. Our results suggest that fluvastatin is incorporated into the oocytes and has delayed inhibitory effects on the oviposited eggs. HMG-CoA reductase is essential for embryogenesis, but not for chorion formation.

Effects of hypocholesterolaemic agents on the expression and activity of 3-hydroxy-3-methylglutaryl-CoA reductase in the fat body of the German cockroach.

In the fat body of adult Blattella germanica females, the expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) during the first reproductive cycle is parallel to that of vitellogenin, suggesting a functional link between the mevalonate pathway, and vitellogenesis and reproduction. We have studied the effects of compactin and fluvastatin, two inhibitors of HMG-CoA reductase, on the expression and activity of the enzyme in the fat body, and on the ootheca formation, ootheca viability, and number of larvae per viable ootheca. Short-term assays showed that both compounds reduce the protein levels and enzymatic activity of HMG-CoA reductase, and long-term experiments revealed that fluvastatin impairs embryo development.

Cyclic juvenile hormone biosynthesis in the cockroach, Blattella germanica: Effects of ovariectomy and corpus allatum denervation

The corpora allata (CA) of ovariectomized adult Blattella germanica females exhibited delayed but high rates of juvenile hormone biosynthesis in vitro. Using the onset of sexual receptivity as a probe of the degree of CA activation in females, we demonstrated at least one cycle of CA activity in the experimentally synchronized ovariectomized females. Following their activation, the CA exhibited a partial and transient decline in activity, but in contrast to the CA of intact females, this decline was not accompanied by a regression in CA volume. CA of intact and ovariectomized females that were denervated from the brain were activated, but the subsequent decline in CA activity at the end of the cycle was prevented in ovariectomized females. The presence of an egg-case suppressed the reactivation of the inactive CA in intact females but not in CA-denervated females. We conclude that activation of the CA in B. germanica is not dependent upon either the presence of the ovary or intact nervous connections between the CA and the brain. The brain exerts a partial inhibition on CA activity through intact nerves which is relieved (by disinhibition) in the presence of a young ovary but is enhanced and sustained in the presence of the egg-case. Inhibition of the CA also occurs independently of nervous connections with the brain through factors that originate in the mature ovary and affect both CA activity and morphology.

Developmental regulation of juvenile hormone synthesis: ovarian synchronization of volumetric changes of corpus allatum cells in cockroaches

The corpus allatum (CA) cells of adult Blattella germanica females undergo cyclic volumetric changes in relation to juvenile hormone (JH) synthesis. In intact females the size of CA cells changes synchronously during the gonotrophic cycle, resulting in cyclic JH synthesis. In ovariectomized females volumetric changes among CA cells become asynchronous, resulting in highly variable but high rates of JH synthesis. Injection of the steroid hormone 20-hydroxyecdysone into ovariectomized females with active CA resulted in a transient decline followed by an increase in both CA volume and JH biosynthesis. This response was due to a change in the size distribution of CA cells and not in the total number of CA cells. In ovariectomized females, CA cells can be re-synchronized into a uniform population of small inactive cells with injection of 20-hydroxyecdysone and implantation of an artificial egg-case, mimicking the successive events of ovulation, oviposition and pregnancy.

Cuticular strength and pigmentation of five strains of adult Blattella germanica (L.) during sclerotization: Correlations with catecholamines, β-alanine and food deprivation

Five German cockroach Blattella germanica strains, wild-type ( VPI), yellow ( y), orange ( or), black ( Bl), and pale body ( Pb) which differ in cuticular colouration, were used to investigate possible correlations of catecholamine and β-alanine concentrations with cuticular strength as measured by puncture resistance of adult pronotal cuticle. The cuticular strength of all strains was the same at ecdysis, but that of VPI, or and y increased more rapidly than Bl and Pb during sclerotization. Cuticle of VPI, y and or reached maximal levels of puncture resistance by day 4, whereas Bl and Pb cuticles failed to achieve this strength by day 14. Extractable N-β-alanyldopamine (NBAD) and N-β-alanylnorepinephrine (NBANE) accumulated rapidly in VPI, y and or cuticles during the first 12 h after ecdysis, but their accumulation was delayed in Bl cuticle until 24 h. Pb cuticle had the least strength and also the lowest NBAD and NBANE levels. β-Alanine concentrations were also lowest in Bl cuticle during melanization. Conversely, dopamine was highest in Bl and or cuticles during melanization but was very low in y and Pb cuticles, which lack black pigmentation. Therefore, N-β-alanyl catecholamine and β-alanine concentrations in cuticle are positively correlated with increasing cuticular strength during stabilization of the exoskeleton, whereas dopamine is correlated with melanization. When dopamine is apparently shunted into the melanization pathway in Bl cuticle or when lower concentrations of the N-β-alanyl catecholamines occur in Pb cuticle, cuticular strength is reduced. Cuticular strength and weight were substantially reduced in cockroaches deprived of food after ecdysis and even later after feeding was resumed. However, cuticular thickness and catecholamine content in starved insects did not differ from those in fed insects. Deficiencies in the protein and chitin content of the procuticle as indicated by reduced weight and density likely result from starvation. Therefore, fewer sites for macromolecular cross-linking or other sclerotization reactions would be available and consequently a weaker cuticle would result.

Adult German Cockroach (Orthoptera: Blattellidae) Feeding and Drinking Behavior as a Function of Density and Harborage-to-resource Distance

There was an effect of harborage-to-resource distance but no main effect of density on the frequency of feeding and drinking activity of adult Blattella germanica , videotaped continuously for 96 h. Feeding and drinking diel periodicity was more pronounced when the resource was placed further from the harborage with activity peaking ca. 2 h into scotophase and declining at the onset of photophase. Nongravid females and males fed and drank more often than gravid females, with a high percentage of females carrying oothecae never feeding or drinking during the recording period.

Movement of German Cockroaches (Orthoptera: Blattellidae) as Influenced by Structural Features of Low-Income Apartments

Movements of adult Blattella germanica (L.) populations were significantly influenced by structural features of low-income apartments. Plumbing connections between adjacent apartments enhanced movement. Mark-recapture studies showed that 75% of the immigrants into a given apartment were from adjacent apartments with common plumbing. Applications of chlorpyrifos + dichlorvos at the termination of the study indicated that not all insecticides. even though containing flushing agents, increase inter apartment movement. Results suggest structural modification as a means to deter movement. The degree and frequency of movement suggests that management programs be aimed at entire structures as opposed to localized areas within buildings.

Is β-Phenylnitroethane the Active Principle of Dennettia Oil?

β-Phenylnitroethane (1-nitro-2-phenylethane) was synthesized from l-bromo-2-phenylethane and sodium nitrite and evaluated for its toxicity against four species of insects. Acetone deposits containing up to 32 µg/cm2 of 1-nitro-2-phenylethane produced no mortality within 96 h in adult Blattella germanica (L.) males and nymphal Periplaneta americana (L.). No toxicity was observed up to 7 days after topical application of the nitro compound at a dosage of 40 µg/g insect to the pennultimate sternite of B. germanica . Nymphs of Incisitermes minor (Hagen), exposed to 0.5 mg/cm2 deposits of the compound in a closed system, were killed within 48 h; however, in an open system, the termite mortality was ca. 40% after 1 day with no additional mortality for 4 weeks. When the nitro compound was evaluated against 2nd- and 4th-instar Culex quinquefasciatus Say, no substantial mortality was observed at the 1 and 10 ppm concentrations. The treatment of adult C. quinquefasciatus with the nitro compound produced 0, 5, 2, and 12% mortalities at 1.6, 7.8, 16.0, and 78 µg/cm2 surface area, respectively.

German Cockroach Movement Within and Between Urban Apartments12

Adult Blattella germanica (L.) are more mobile within urban apartment structures than was previously recognized. Interapartment movement up to 30% per week occurred where construction design permitted. Adult males are more mobile than females. Pyrethrin insecticide applications Increased interapartment movement rates. These results stress the need for a more holistic, community-wide perspective for cockroach pest management programs than currently exists in pest control practices and demonstrate that construction should be designed (or altered whenever possible) to reduce cockroach movement.

Juvenile hormone and its assay in virgin adult Blattella germanica females

The physiological bases for the gonadotrophic assay as presented by Kunkel were confirmed, and the assay method was found to be reproducible. However, the assay method was not found to be as useful as presented, due to the departure from linearity of the ovarian growth response above a hormone level of 5 μg/μl. Juvenile hormone (JH) titre higher than this level results in a depression of terminal oöcyte growth. Therefore, a valid assay of activity cannot be based on a single concentration. By injection, JH and FMC 23509 (10,11-epoxy-N-ethyl-3,7,11-trimethyl-2,6-dodecadienamide) were approximately equal in gonadotrophic activity. Topical application of FMC 23509 resulted in terminal oöcyte length of 2.45 mm in comparison to a length of 1.28 mm after injection of the same amount. This agrees with previous observations that such compounds are more active topically than by injection.