Adult Cockroaches Research Articles

Comparative nutrient analysis of four species of cockroaches used as food for insectivores by life stage, species, and sex.

A variety of insects are fed to insectivorous animals; however, nutritional analyses are often limited to adult life stages. Four species of nymph and adult female and male cockroaches (Blaberus giganteus, Blaptica dubia, Blatta lateralis, and Gromphadorhina portentosa) were analyzed for moisture, crude protein (CP), acid detergent fiber (ADF), fat, ash, and mineral content. The small sample size of this study precluded statistical analyses, however comparatively, CP in adult B. lateralis and B. dubia was greater than the CP in nymphs of the same species. Adult and nymph B. dubia had the greatest CP (96.6% and 65.3%, respectively) compared to the other three species. Inversely, fat content in adult B. lateralis and B. dubia was lower than that of nymphs of the same species. All adults contained similar levels of ADF, yet adult B. giganteus had greater ADF than nymphs; conversely, B. lateralis and B. dubia adults had less ADF than nymphs. There were differences noted in mineral parameters among the four species and life stages. Adult B. giganteus had less Ca than G. portentosa, and the lowest Ca content of the four species of nymphs and adults analyzed. This study underscores the differences in nutrient content with respect to life stage and species in previously understudied cockroaches to improve nutrient intake in captive insectivores.

Turkestan Cockroaches Avoid Entering a Static Electric Field upon Perceiving an Attractive Force Applied to Antennae Inserted into the Field.

Simple SummaryElectrostatic devices that generate a static electric field (S-EF) are used as barriers to repel insect pests because insects habitually avoid entering a S-EF. Understanding the avoidance mechanism would provide an experimental basis for developing electrostatic-based pest control methods. An apparatus generating a S-EF was constructed by placing a polyvinyl chloride-insulated iron plate (N-PIP) that was negatively charged using a voltage generator parallel to a grounded metal net (G-MN) that was positively polarised via electrostatic induction due to the negative charge of the N-PIP. The S-EF formed in the space between the N-PIP and G-MN, where the negative charge of the N-PIP generated a repulsive force to push electrons in the field toward the ground via the G-MN. A test insect (an adult Turkestan cockroach, Shelfordella lateralis Walker) released in the space surrounded by the apparatus inserted its antenna into the S-EF and reflexively moved backward. Free electrons were pushed out of the antenna tip toward the ground, and the antenna became positive. The positively polarised antenna was attracted to the N-PIP, and in response to this force, the insect pulled its antennae back reflexively and moved backward. This insect action was recognised as avoidance behaviour.This study analysed the mechanism of avoidance behaviour by adult Turkestan cockroaches (Shelfordella lateralis Walker) in response to a static electric field (S-EF) formed in the space between a negatively charged polyvinyl chloride-insulated iron plate (N-PIP) and a grounded metal net (G-MN). The negative surface charge supplied to the iron plate by a voltage generator caused the G-MN to polarise positively via electrostatic induction. In the S-EF, the negative charge of the N-PIP created a repulsive force that pushed free electrons in the field toward the ground via the G-MN. When insects released in the space surrounded by the S-EF inserted their antennae into the S-EF, they pulled them back reflexively and moved backward. The analysis indicated that an electric current flowed transiently toward the ground when an insect inserted its antennae into the S-EF. The insect became positively charged via this discharge and was attracted to the opposite pole (N-PIP). In response to this attractive force, the insect pulled its antennae back quickly. The positive electrification caused by the removal of free electrons from the antenna tip triggered the avoidance behaviour.

The effectiveness of commercial gel baits against German cockroach Blattella germanica (Linnaeus, 1767) in Indonesia

Gel baits product sold commercially to the public has long been used to control German cockroach populations in urban areas. The effectiveness and resistance level of gel bait products need to be known for the successful control of German cockroaches in the field. However, there have been no reports of resistance in Indonesia. This study used toxicity tests of six gel bait products (MF, CBG, SPB, OTG, BTX, and UBA) against two populations of adult male German cockroaches (VCRU-WHO and RKMN-BKT). Fipronil, boric acid and emamectin benzoate containing gel baits were effective to knock down and kill the German cockroaches. In contrast, gel bait with imidacloprid as an active ingredient was only useful to knock down the German cockroaches. Commercial gel bait product in Indonesia are still useful in controlling German cockroaches’ populations with a time of effectiveness to cause mortality between three to four weeks after being exposed in the field and the level of cockroach resistance to gel bait are susceptible until low resistance.

Optimizing the Loading Level of Boric Acid in a Particle Bait: A Preliminary Study with Periplaneta americana (Blattodea: Blattidae)

Optimizing the Loading Level of Boric Acid in a Particle Bait: A Preliminary Study with <i>Periplaneta americana</i> (Blattodea: Blattidae)

Принципы конструирования инсектицидных средств для медицинской дезинсекции с использованием диатомитов и маршалитов

Insecticidal properties of diatom and marshalite powders are known, but similar properties of siliceous marshalite and quartz-aleuropelite rocks have not been studied. We have studied the insecticide content of powders from certain breeds for adult red cockroaches Blattella germanica L. and bed bugs Cimex lectularius L. All the samples studied by us had different insecticidal activity. This is very important to take into account for specialists who want to develop and further produce an insecticide based on diatom powders. Before starting work, the insecticidal activity of samples from each deposit should be determined.

Repellency and insecticidal properties of seed oil of Jatropha curcas L. against American cockroach, Periplaneta americana L.

BackgroundThis study evaluated the effect of Jatropha curcas seed oil against adult American cockroach, Periplaneta americana, a mechanical disease vector, using three bioassay methods to determine the repellent activity, contact and fumigant toxicity. This involved the use of J. curcas oil solution (diluted with acetone (20%)) and J. curcas pure oil. For repellency test, concentrations 0.30, 0.60 and 0.90% v/v were used for the oil solution while 1.0 and 2.0 ml concentrations were used for the pure oil. All test groups were exposed for 15 min. Contact toxicity test involved the use of 0.30, 0.60, 0.90, 1.20 and 1.50% v/v concentrations for the oil solution while 1 and 2 ml concentrations were used for the pure oil. Exposure period for all test groups was 24–120 h. For the fumigant test, 0.15% v/v and 0.5 ml concentrations were used for the oil solution and pure oil groups respectively; exposure period for the test groups was 24–120 h. All test and the control groups had ten cockroaches (P. americana) per group with four replicates.ResultsRepellency was higher in test groups treated with pure J. curcas oil than in groups treated with the oil solution with repellency of 70–100% and 60–100% respectively after 15 min exposure period. For the contact test, a higher mortality rate was observed with the oil solution than the pure oil. Mortality was lower for 1 ml of pure oil with 20% at 24 h and 40% at 120 h than 2 ml of pure oil with 30% mortality at 24 h and 50% mortality at 120 h. A 100% mortality was recorded in the highest concentration (1.50% v/v) at 120 h. Fumigation test with 0.15% v/v of oil solution resulted in 20% mortality at 120 h while fumigation test with 0.5 ml of J. curcas pure oil resulted in 60% mortality at 120 h.ConclusionJ. curcas seed oil possesses repellent and insecticidal properties against P. americana . Thus, the menace caused by this mechanical disease vector could be reduced using J. curcas seed oil.

The effect of illumination with different light wavelengths on the orientation of Turkestan cockroach, Blatta lateralis (Walker,1868) (Blattodea: Blattidae)

Bu calismada, farkli dalga boylarina (kirmizi, yesil, sari, mavi, beyaz ve karanlik) sahip isinlarin Turkistan hamambocegi, Blatta lateralis (Walker,1868) (Blattodea: Blattidae)’in yonelimi uzerindeki etkisi arastirilmistir. Calisma, 2019 yilinda Bursa Uludag Universitesi’nde laboratuvar kosullarinda yurutulmustur. Yonelim denemelerinde, ergin hamambocekleri uc farkli isik siddetine (25, 250 ve 2500 luks) maruz birakilmistir. Denemeler 6-kollu ve 2-kollu secimli olarak yurutulmustur. Tum denemelerde 3 tekerrur ve her tekerrurde 100 birey kullanilmistir. Elde edilen veriler, isik siddetine bagli olarak farkli dalga boyuna sahip isinlara yonelim hassasiyetinin artabilecegini gostermektedir. Ozellikle, alti -kollu ve iki -kollu denemede, 2500 luks siddetinde mavi isik uygulandiginda, hamamboceginin yonelimi en dusuk seviyede olup, sirasiyla, %0.9 ve %1.8 oraninda olmustur. Genel olarak en yuksek yonelim, tum denemelerde karanlik (kontrol) odaciga olmustur. Ayrica tum luks degerleri altinda kirmizi isiga yonelim, yesil, sari, mavi ve beyaz isiga gore daha fazla olmustur. Bu calisma sonucunda, mavi isigin hamambocekleri uzerinde kacirici bir etki gosterebilecegi, kirmizi isigin ise diger dalga boylarina gore daha cekici olabilecegi tespit edilmistir. Yapilan bu calismalar, hamamboceklerine karsi kullanilan kimyasallarin yerini alabilecek insan sagligina ve cevreye zararsiz olan alternatif bir mucadele metodunun gelistirilmesinde faydali olabilir.

Comparative Microbiome Analysis of Three Species of Laboratory-Reared Periplaneta Cockroaches.

Cockroaches inhabit various habitats, which will influence their microbiome. Although the microbiome can be influenced by the diet and environmental factors, it can also differ between species. Therefore, we conducted 16S rDNA-targeted high-throughput sequencing to evaluate the overall bacterial composition of the microbiomes of 3 cockroach species, Periplaneta americana, P. japonica, and P. fuliginosa, raised in laboratory for several generations under the same conditions. The experiments were conducted using male adult cockroaches. The number of operational taxonomic units (OTUs) was not significantly different among the 3 species. With regard to the Shannon and Pielou indexes, higher microbiome values were noted in P. americana than in P. japonica and P. fuliginosa. Microbiome composition was also evaluated, with endosymbionts accounting for over half of all OTUs in P. japonica and P. fuliginosa. Beta diversity analysis further showed that P. japonica and P. fuliginosa had similar microbiome composition, which differed from that of P. americana. However, we also identified that P. japonica and P. fuliginosa host distinct OTUs. Thus, although microbiome compositions may vary based on multiple conditions, it is possible to identify distinct microbiome compositions among different Periplaneta cockroach species, even when the individuals are reared under the same conditions.

Uji Efektivitas Ekstrak Biji Lamtoro (Leucaena leucocephala) sebagai Insektisida terhadap Kecoa Amerika (Periplaneta americana)

Research on the effectiveness of lamtoro seeds (Leucaena leucocephala) extract has been carried out as an insecticide against American cockroaches (Periplaneta americana). The lamtoro seeds were extracted using maceration method with ethanol solvent, and obtained ethanol extract of lamtoro seeds. Lamtoro seeds extract was made in 5 concentrations of 0%, 2%, 6%, 10% and 14%. The effectiveness of the extract was tested using spray method with 10 adult cockroaches as a testing animal with 3 times repetition and observed for 72 hours. Observations have shown the decline in American cockroaches’ activity is causing death. Mortality data were analyzed using probit analysis to determine LC50. The result of phytochemical test of lamtoro seeds extract are flavonoids, tannins and saponins. Lamtoro seeds extract was effective to kill American cockroaches, which percentage of mortality were 0%, 33%, 66%, 86% and 96% respectively at concentration 0%, 2%, 6%, 10%, and 14% with LC50 3,35%.Â

Neitherper, nor tim1, nor cry2 alone are essential components of the molecular circadian clockwork in the Madeira cockroach.

Circadian clocks control rhythms in physiology and behavior entrained to 24 h light–dark cycles. Despite of conserved general schemes, molecular circadian clockworks differ between insect species. With RNA interference (RNAi) we examined an ancient circadian clockwork in a basic insect, the hemimetabolous Madeira cockroach Rhyparobia maderae. With injections of double-stranded RNA (dsRNA) of cockroach period (Rm´per), timeless 1 (Rm´tim1), or cryptochrome 2 (Rm´cry2) we searched for essential components of the clock´s core negative feedback loop. Single injections of dsRNA of each clock gene into adult cockroaches successfully and permanently knocked down respective mRNA levels within ~two weeks deleting daytime-dependent mRNA rhythms for Rm´per and Rm´cry2. Rm´perRNAi or Rm´cry2RNAi affected total mRNA levels of both genes, while Rm´tim1 transcription was independent of both, also keeping rhythmic expression. Unexpectedly, circadian locomotor activity of most cockroaches remained rhythmic for each clock gene knockdown employed. It expressed weakened rhythms and unchanged periods for Rm´perRNAi and shorter periods for Rm´tim1RNAi and Rm´cry2RNAi.As a hypothesis of the cockroach´s molecular clockwork, a basic network of switched differential equations was developed to model the oscillatory behavior of clock cells expressing respective clock genes. Data were consistent with two synchronized main groups of coupled oscillator cells, a leading (morning) oscillator, or a lagging (evening) oscillator that couple via mutual inhibition. The morning oscillators express shorter, the evening oscillators longer endogenous periods based on core feedback loops with either PER, TIM1, or CRY2/PER complexes as dominant negative feedback of the clockwork. We hypothesize that dominant morning oscillator cells with shorter periods express PER, but not CRY2, or TIM1 as suppressor of clock gene expression, while two groups of evening oscillator cells with longer periods either comprise TIM1 or CRY2/PER suppressing complexes. Modelling suggests that there is an additional negative feedback next to Rm´PER in cockroach morning oscillator cells.

Effect of developmental stage on the nutritional value of edible insects. A case study with Blaberus craniifer and Zophobas morio

As the demand for sustainable, cost-effective food production increases, edible insects are an important alternative to traditional livestock as a source of human food. Understanding the differences in the nutritional composition of edible insects is essential for the optimization of rearing process. This study investigated the effects of developmental stage on the quantity and quality of nutrients in “superworms” (Zophobas morio), and the death’s head cockroach (Blaberus craniifer). Superworms at 60, 90, and 120 days of age showed no significant variation in basic nutrient content, and no significant differences were found in protein quality (expressed as the essential amino acid index). In contrast, adult cockroaches contained significantly more digestible protein than either small or large nymphs, but of lower quality. Cockroach nymphs contained significantly higher amounts of fat than the adults, and the lipid quality (described by the atherogenicity and thrombogenicity indices) increased over time. Conversely, the lipid quality of superworm larvae decreased with age. The study provides a better understanding of the chemical composition of insects over their lifespan and may help to optimize rearing technology in order to harvest insects as high-quality nutritional biomass, facilitating their application as a potential food source for humans.

Türkistan Hamamböceği Blatta lateralis (Dictyoptera: Blattidae)’in Hidrofil Kumaş Kullanılarak Entomopatojen Nematod Heterorhabditis bacteriophora HBH (Rhabditida: Heterorhabditidae) ile Mücadelesi

Chemical insecticides used against cockroaches, which are an important urban pest and considered public health, are harmful to human health and cause insects to gain resistance. The entomopathogenic nematode (EPN), Heterorhabditis bacteriophora HBH, were used in place of chemical insecticides within the scope of biological control against the Turkestan cockroaches Blatta lateralis in this study. The hydrophilic fabric traps were set to provide the moist environment needed by the EPNs on aboveground. The fabrics inoculated with the nematodes at 50, 100 and 150 IJs/cm2 were used throughout the 37-day experiment. The first treatment was performed by adding 10 adult cockroaches immediately after the establishment of the traps. In the same way, the second treatment was applied after 15 days and the third treatment after 30 days. The mortality rates of cockroaches after 4 and 7 days of exposure to EPNs were determined for all treatments. Although Turkestan cockroaches were exposed to HBH 30 days after the setting of the traps, infection occurred. As a result of this study, the above-ground persistence and infectivity of HBH could be achieved more than 4 weeks by using hydrophilic fabric. In addition, the mortality rates of the Turkestan cockroaches were found to increase depending on exposure time and the nematode dosage.

Pathogenicity statistical analysis of Beauveria bassiana against German cockroach (Blattella germanica)

ABSTRACT The pathogenicity of fifteen isolates of Beauveria bassiana against German cockroach (Blattella germanica, Linnaeus, 1767) at three instars was tested and analysed in order to find the best fungal isolate available for the mortality of cockroaches. For the bioassay, three groups of instars were inoculated with a spore suspension, and the subsequent mortality recorded, the response variable was the number of dead cockroaches of a total of 10. For analysing proportion data, three models were analysed: binomial, quasi-binomial, and beta-binomial models. Due overdispersion, binomial model was not appropriate, quasi-binomial and beta-binomial statistical models were suitable for the analysed data. The quasi-binomial model provided a numerically greater standard error than the beta-binomial model although the difference was not significant. All tested isolates of B. bassiana were pathogenic to German cockroaches, although the average mortality percentages differed among isolates. The instar of German cockroach was a significant factor in the pathogenicity of fungal isolates, the pathogenicity of B. bassiana was greater in adult cockroaches and first instars compared with second instars. Four groups of isolates were detected, based on p-values of the hypothesis test of the difference between isolates; Each group of isolates showed statistically the same mortality percentage within the group but differences between groups. The group with the highest percentage of pathogenicity effectiveness against German cockroach (above 74%) only contained isolates derived from Metamasius spinolae at the instar of pupa and larvae, these isolates could be considered for biological control of German cockroach.

RNA interference supports a role for Nanchung-Inactive in mechanotransduction by the cockroach, Periplaneta americana, tactile spine.

Proteins encoded by nanchung, inactive, nompC and piezo genes have been shown to play crucial roles in the initial detection of mechanical force by various insect auditory neurons, nociceptors and touch receptors. Most of this previous research has been performed on the larval and adult fruit fly, Drosophila melanogaster. We identified and assembled all four homologous genes in transcriptomes from the cockroach, Periplaneta americana. Injection of long double-stranded RNA (dsRNA) into the adult cockroach abdomen successfully reduced the expression of each gene, as measured by quantitative PCR (RT-qPCR). A simple electrophysiological assay was used to record action potential firing in afferent nerves of cockroach femoral tactile spines in response to a standardized mechanical step displacement. Responses of nanchung knockdown animals were significantly reduced compared to matched sham-injected animals at 14 and 21days after injection, and inactive knockdowns similarly at 21days. In contrast, responses of nompC and piezo knockdowns were unchanged. Our results support a model in which Nanchung and Inactive proteins combine to form a part of the mechanotransduction mechanism in the cockroach tactile spine.

Development of New Boric Acid Gel Baits Against German Cockroaches, Blatella germanica L (Blattodea: Blattellidae)

The German cockroach, Blatella germanica, is a pest of human habitats distributed throughout the world. Boric acid (BA; H3BO3), in the form of powder, pellets, or blocks, has been used to control German cockroaches. Gel baits are also considered highly effective for controlling German cockroach populations. However, BA is not currently available as a gel bait. Thus, the present study was carried out to determine the best concentration of BA to formulate as a gel bait, and measure its direct effectiveness and the horizontal transfer of the active ingredient (AI) through cannibalism in adult German cockroaches (domino effect). Effectiveness of laboratory-prepared BA gel baits (lab baits) was analysed, and the efficacy and horizontal transfer of the most effective lab bait was compared to four commercial baits. Among three tested lab baits, the bait prepared with 40% BA (lab bait A) resulted in significantly greater cockroach mortality and a lower lethal time (LT50) value than other lab baits. When compared with commercial baits, there was no significant difference between lab bait A and BA baits in the amount of bait consumed and the detection time. Similarly, mortality of cockroaches caused by lab bait A was equal to mortality caused by the commercial BA bait. Percentage of bait unfed adult cockroaches killed by transferred BA from lab bait A fed and dead adult cockroaches (secondary mortality) was significantly greater than that caused by both commercial BA bait and fipronil bait.

Complex and Diverse Drivers of Parasite Loads in a Cosmopolitan Insect

The goal of parasite epidemiologists is to understand the factors that determine host infection levels. Potential infection determinants exist at many scales, including spatial and temporal environmental variation, among-host differences, and interactions between symbionts infecting the same host. All of these factors can impact levels of parasitism, but frequently only a subset is considered in any host-parasite system. We examined several potential determinants of pinworm infection in wild Australian cockroaches (Periplaneta australasiae) from multiple biological scales: (1) habitat; (2) season; (3) cockroach body size, developmental stage, and sex; and (4) interactions between 2 pinworm species (Leidynema appendiculata and Thelastoma sp.). Over 1 yr, we collected 239 cockroaches from 2 separate rooms in an Illinois greenhouse. We used generalized linear mixed-effects models (GLMMs) to evaluate simultaneously the influence of these factors on pinworm abundance, and nearly all had significant effects. Overall, the abundance of L. appendiculata was greater than Thelastoma sp., but the relative abundance of the 2 species was reversed in each room (i.e., a taxon × habitat effect). Abundance varied over 4 trapping seasons and increased with cockroach size. Adult cockroaches had more pinworms than nymphs, and there was also a significant taxon × stage effect: adult cockroaches had fewer pinworms than expected for their larger size, and this reduction was greater in Thelastoma sp. than in L. appendiculata. Cockroach sex had no effect on infection. Although females had more worms than males, this difference could be explained by the larger size of females. Finally, after controlling for all other potential determinants of infection, we found a strong negative association between Thelastoma sp. and L. appendiculata; cockroaches tended to be infected with either 1 pinworm species or the other. Our work underscores the importance of measuring potential determinants of infection from as many scales as possible. Such approaches are necessary to unravel the complexities of host-parasite interactions.

Antennal grooming facilitates courtship performance in a group-living insect, the German cockroach Blattella germanica

The antennae of adult male German cockroaches detect a contact sex pheromone embedded in the female’s cuticular lipids. The female pheromone stimulates courtship behavior in males, notably a wing-raising (WR) display. Within aggregations, however, cuticular lipids are disseminated by contact among group members, including nymphs and adults of both sexes, and “contamination” of cockroaches with the cuticular lipids of another stage or sex may interfere with sex discrimination and disrupt courtship. We used behavioral observations, bioassays and chemical analysis to determine how males maintain their sensitivity to sex pheromone in aggregations. Males contaminated with female pheromone displayed lower courtship, because residual female pheromone on their antennae adapted their peripheral sensilla and habituated the central nervous system. Female pheromone that contaminated the male’s antennae also elicited courtship from other non-contaminated males, disrupting their sex discrimination in the group. However, antennal grooming effectively removed female pheromone from males’ antennae and maintained their chemosensory acuity and sexual discrimination among group members. Thus, grooming of the antennae and other sensory appendages is an important strategy to enhance sensory acuity, especially in group-living insects like the German cockroach.

The sources of electrophysiological variability in the retina of Periplaneta americana.

Variability in the electrophysiological properties of homotypic photoreceptors is widespread and is thought to facilitate functioning under disparate illumination conditions. Compound eyes of insects have three sources of variability: inter-individual, intra-individual, and intra-ommatidial, the latter two overlapping. Here, I explored the causes of variability in Periplaneta americana, a nocturnal insect characterized by highly variable photoreceptor responses. By recording from photoreceptors in dissociated ommatidia, including consecutive recordings from photoreceptors in the same ommatidium (SO), I studied the variability of six properties: whole-cell membrane capacitance (Cm), phototransduction latency, maximal conductance (Gmax) and the slope factor of the sustained Kv current, absolute sensitivity in dim light, and sustained light-induced current (LIC) amplitude in bright light. Coefficient of variation (CV) metrics were used to compare variances in four experimental groups: SO, same animal (SA), all data combined "full sample" (FS), and full sample of all SO recordings (FSSO). For the normally distributed parameters Cm, Gmax, slope factor, and latency, the highest CV values were found in FS and FSSO, intermediate in SA, and the lowest in SO. On average, SO variance accounted for 47% of the full-sample variance in these four parameters. Absolute sensitivity and LIC values were not normally distributed, and the differences in variability between SO and FS/FSSO groups were smaller than for the other four parameters. These results indicate two main sources of variability, intra-ommatidial and inter-individual. Inter-individual variability was investigated by exposing adult cockroaches to constant light or dark for several months. In both groups, the majority of CV measures for the six parameters decreased compared to control, indicating substantial contribution of phenotypic plasticity to inter-individual differences. Analysis of variability of resting potential and elementary voltage responses revealed that resting potential is mainly determined by the sustained Kv conductance, whereas voltage bump amplitude is mainly determined by current bump amplitude and Cm.

A Review on the Insecticide Resistance of Three Species of Cockroaches (Blattodea: Blattidae) in Iran.

In Iran, there are four pest domestic species of cockroaches: Periplaneta americana (Linnaeus, Blattodea: Blattidae), Blatta orientalis (Linnaeus, Blattodea: Blattidae), Blattella germanica (Linnaeus, Blattodea: Blattidae), and Supella longipalpa (Fabricius, Blattodea: Blattellidae). The aim of this study was to compile and review studies conducted on insecticide resistance of domestic cockroaches in Iran to assess the current knowledge and gaps. Twenty insecticides were used in susceptibility testing of cockroaches. The bioassay methods varied, and included surface contact (exposure tests), topical applications and feeding studies on baits. Resistance ratio (RR) stated in the reviewed studies showed that B. germanica was resistant (RR > 10) to DDT, permethrin, and cypermethrin, while P. americana and S. longipalpa were categorized as low levels of resistance (RR = 1-2). S. longipalpa is newly reported from houses in some areas of Iran, including Tehran, and there are very few studies on its' biology, ecology and insecticidal resistance. Most studies used adult cockroaches, while the susceptibility status of nymphs was evaluated only in few studies. Use of different test methods and lack of a World Health Organization (WHO) updated procedure, including revised/updated insecticide diagnostic dosages and test kits. The lack of susceptible strains of cockroaches was a major challenge in the assessment of data. A comprehensive national program for monitoring susceptibility of household pests to insecticides in Iran is of great concern and is highly recommended.

Phenotypic plasticity in Periplaneta americana photoreceptors

Plasticity is a crucial aspect of neuronal physiology essential for proper development and continuous functional optimization of neurons and neural circuits. Despite extensive studies of different visual systems, little is known about plasticity in mature microvillar photoreceptors. Here we investigate changes in electrophysiological properties and gene expression in photoreceptors of the adult cockroach, Periplaneta americana, after exposure to constant light (CL) or constant dark (CD) for several months. After CL, we observed a decrease in mean whole-cell capacitance, a proxy for cell membrane area, from 362 ± 160 to 157 ± 58 pF, and a decrease in absolute sensitivity. However, after CD, we observed an increase in capacitance to 561 ± 155 pF and an increase in absolute sensitivity. Small changes in the expression of light-sensitive channels and signaling molecules were detected in CD retinas, together with a substantial increase in the expression of the primary green-sensitive opsin (GO1). Accordingly, light-induced currents became larger in CD photoreceptors. Even though normal levels of GO1 expression were retained in CL photoreceptors, light-induced currents became much smaller, suggesting that factors other than opsin are involved. Latency of phototransduction also decreased significantly in CL photoreceptors. Sustained voltage-activated K+ conductance was not significantly different between the experimental groups. The reduced capacitance of CL photoreceptors expanded their bandwidth, increasing the light-driven voltage signal at high frequencies. However, voltage noise was also amplified, probably because of unaltered expression of TRPL channels. Consequently, information transfer rates were lower in CL than in control or CD photoreceptors. These changes in whole-cell capacitance and electrophysiological parameters suggest that structural modifications can occur in the photoreceptors to adapt their function to altered environmental conditions. The opposing patterns of modifications in CL and CD photoreceptors differ profoundly from previous findings in Drosophila melanogaster photoreceptors.