Genetic studies of a behavioral mutant,glucose aversion,in the German cockroach (Dictyoptera: Blattellidae)

Glucose aversion(Glu) is a naturally occurring behavioral mutant of the German cockroach,Blattella germanica. Earlier work suggested thatGlu is a semidominant autosomal trait. Further study was undertaken to place the mutant gene in the linkage map of the species and expand the information on its genetic basis. Linkage was investigated in test crosses with morphologic markers for 7 of the 11 autosomal linkage groups. Assays for amounts of glucose ingested per individual confirmed the expected low consumption ofGlu heterozygotes(Glu/+) and that continuous selection pressure on the parental strain had resulted in near- and probably complete homozygosity forGlu. Glu genotypes were identified by means of a discriminating ingestion that separated heterozygotes from wild type(Glu+). Variations in expression indicate that genetic factors influence food consumption inB. germanica. Positive results were obtained in linkage tests ofGlu with ruby eye(ru), indicating that theGlu locus lies in linkage group VIII (chromosome 9), a group notable for mutants that apparently result in the expression of latent, highly primitive development pathways.     

Calling behavior of the female german cockroach,Blattella germanica (Dictyoptera: Blattellidae)

Virgin German cockroach females, Blattella germanica(L.), were observed, for the first time, to exhibit a characteristic calling behavior during which females emit a volatile sex pheromone. Under a photoperiod of 12L12D, the percentage of 7-day-old virgin females that exhibited this behavior peaked before the end of the scotophase in a similar pattern to the diel periodicity of mating. A clear relationship was evident between calling and stages of sexual receptivity during successive gonotrophic cycles. Females initiated calling 5–6 days after the imaginal molt, when their basal oocytes were 1.6 mm long. If not mated, females continued to exhibit bouts of calling during the next 3–4 days until 24 h before ovulation. Calling was completely suppressed by mating as well as the presence of an egg case in the genital atrium in both virgin and mated gravid females. We suggest that calling and the emission of a volatile sex pheromone serve to attract males from a distance as well as to potentiate responses to contact sex pheromone in aggregations.     

Water composition and loss by body color and form mutants of the German cockroach (Dictyoptera: Blattellidae)

Body water composition and rates of water loss were determined for adult males of five body color or form mutants of the German cockroach, Blattella germanica (L.). Body water content ranged from 68.4% for a yellow body strain to 74.7% for the balloon wing strain. Dark body strains (black and black×orange) contained less water than lighter color strains (orange and yellow). There were no differences in whole-body lipid content among the strains. Cuticular permeability at 30°C ranged from 18.44 to 24.8 μg cm^-2 h^-1 mmHg^-1 for black body and balloon wing strains, respectively; dark body strains had lower cuticular permeabilities than light body strains. Brief, whole-body extraction with hexane increased cuticular permeability from 5.6-fold for the balloon strain to 8.3-fold for the orange body strain. Cuticular permeabilities of hexane-extracted dark body strains again had lower cuticular permeabilities than those of light body strains, indicating that differences in permeability were due to the cuticle itself and not differences in the amount or composition of epicuticular lipids. Measurements of cuticle water content indicated that light body strains contained significantly more water than dark body strains. Rate of percent original mass and percentage of total body water lost increased linearly with time. Implications of cuticular water content to cuticular permeability are discussed.     

Discontinuous carbon dioxide release in the German cockroach, Blattella germanica (Dictyoptera: Blattellidae), and its effect on respiratory transpiration

The discontinuous gas exchange cycle (DGC) was described in the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae) for the first time. Also, the effect of the DGC on water loss was investigated. The CO(2) emission pattern in both insecticide resistant and susceptible B. germanica varied with temperature. At 10, 15, and 20 degrees C the pattern was discontinuous. Cycle frequency increased at 25 and 30 degrees C, and at 35 degrees C the pattern became cyclic. In most DGCs, there was no clear distinction between the closed and flutter phases in both strains thus data for these phases were combined and analyzed as the interburst phase. The probability that B. germanica would breath discontinuously varied with temperature. Most cockroaches (62.8%) displayed DGCs at 10 degrees C, therefore measurement of metabolic rate and water loss was carried out at this temperature. Using repeated measures of analysis of variance, the interburst and burst V(.)(CO(2))(ml h(-1)) were not significantly different between the two strains. The variability in CO(2) emission during the interburst and burst phases over time was not significantly different from cycle to cycle or between strains. Overall metabolic rate during the entire recording was not significantly different between both strains. There was a significant difference in the duration of the interburst and burst phases between the strains. The susceptible strain had significantly longer interburst and burst phase durations during a complete DGC than the resistant strain. The interburst and burst phase durations were 5.01+/-0.19 and 6.21+/-0.13 min, respectively, for the resistant strain, whereas the durations were 7.16+/-0.37 and 6.73+/-0.17 min, respectively, for the susceptible strain. This resulted in a DGC of significantly longer duration (13.89+/-0.44 min) in the susceptible strain compared with the resistant strain (11.23+/-0.26 min). The duration of the interburst phase was significantly different from the open phase duration in the resistant strain such that during a single DGC lasting approximately 11.23 min, 43.5% consisted of the interburst phase while the burst phase made up 56.5% of the cycle. The cuticular permeability at 10 degrees C and 0% RH was 2.26 microg cm(-2) h(-1) mmHg(-1) for the resistant strain and 3.42 microg cm(-2) h(-1) mmHg(-1) for the susceptible strain. In both strains, cuticular transpiration accounted for approximately 95% of total water loss. The significantly longer duration of the interburst phase of the susceptible strain was not important in reducing water loss.     

Spatial distribution of the cockroach, Blattella germanica, in a swimming-bath facility

A population of Blattella germanica L. was studied in a swimming-bath facility using a sampling method. A set of traps deposited weekly, over a period of 50 weeks, allowed us to follow the variations of the temporal and spatial distributions of the population inside the building. A Factorial Correspondance Analysis, performed on the data, led us to the conclusion that the population was stable in time. The spatial distribution of the insects was contiguous. Inside an aggregate, we were able to define a circular movement from the center towards the periphery and vice versa; this movement can be superimposed up on the biological development on the individuals. After birth in the middle of the aggregate, during development, larvae explore further a field as far as the border of the aggregate; this exploratory phase, related to foraging behavior or search for new shelters when these become limiting factors, could be considered as the spreading phase of the population. Then, with the imminence of the imaginal moult, old larvae tend to gather in high density areas in the middle of the aggregate. Newly molted adults look for a sexual partner. And finally females remain in the shelters during oothecae maturation.

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Résumé L'étude d'une population de Blattella germanica L. dans une piscine par des piégeages hebdomadaires pendant une période de 50 semaines, nous a permis de suivre l'évolution spatiale et temporelle de cette population. Les résultats des piégeages étudiés par Analyse Factorielle des Correspondances nous permettent de conclure à une certaine stabilité temporelle de la population. Elle se répartit en larges agrégats dans lesquels s'inscrit un mouvement circulaire, allant du centre vers la périphérie et retour, qui se superpose au cycle de développement des individus.

     

The occurrence of translocations in insecticide resistant and susceptible field-collected strains of the German cockroach

Insecticide resistant and susceptible field-collected strains of the German cockroach were surveyed for the occurrence of chromosome polymorphisms. Analyses were on meiotic cells of males that hatched from oothecae with unusual numbers (>5) of incompletely developed eggs (aberrant oothecae). Three males were reciprocal translocation heterozygotes. A spontaneous translocation was noted in one cell of a fourth male. The males were from insecticide resistant strains. Partially developed eggs in oothecae from outcrosses of two of the translocation herozygotes ceased development in early stages and were characterized by gross morphologic abnormalities. Chromosome abnormalities other than translocations occurred in a low percentage of males from aberrant oothecae in both resistant and susceptible strains. The only general differences between susceptible and resistant strains were that, in pooled data, the frequencies of unhatched oothecae and of aberrant oothecae were higher in the resistant than susceptible strains.     

Circadian calling behavior of the adult female brown-banded cockroach,Supella longipalpa (F.) (Dictyoptera: Blattellidae)

The diel pattern of pheromone-releasing behavior (calling) of the adult female brown-banded cockroach, Supella longipalpa (F.),was examined. Calling occurs discontinuously throughout most of the scotophase in a 12L: 12D photoperiodic regime. Females exhibited a free-running calling rhythm after transfer to continuous light or dark conditions. Shifts in the temporal pattern of calling following changes in the timing of the photoperiodic cues indicated that lights-off is the Zeitgeber. Studies of insects under long- and short-day conditions suggest that, although insects within a population may call synchronously or asynchronously, respectively, the duration of an individual's calling bout is innately limited.     

A Densovirus of German Cockroach Blattella 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 m. 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.     

Inter- and intra-instar food consumption in the German cockroach, Blattella germanica

Food consumption was measured in an insecticide-susceptible (Orlando) and-resistant (Village Green) strain of German cockroach, Blattella germanica (Dictyoptera: Blattellidae), throughout each stadium. All instars exhibited a similar pattern of consumption over the course of the instar; consumption was low to moderate at the beginning of each instar, climbed steadily to a maximum near the middle, declined progressively from the mid-instar maximum, and ceased or was minimal several days before the next molt. Consumption ceased or was minimal during the final two to four days of each instar. Cumulative consumption for the six instars was significantly greater in the Village Green strain as compared with the Orlando strain. Village Green nymphs consumed 79.6±0.7 mg of rat chow while Orlando nymphs consumed 63.7±3.4 mg. Total consumption by instar increased significantly with each successive instar in the Village Green strain. In addition, Village Green sixth instar females consumed significantly more food than sixth instar males. A similar trend was observed for the Orlando strain; consumption tended to increase in each successive instar. Relative consumption rate (food consumed/cockroach/instar divided by the mean weight of the instar) was highest in the first two instars and decreased in subsequent instars.     

Synergism between Metarhizium anisopliae (Deuteromycota: Hyphomycetes) and Boric Acid against the German Cockroach (Dictyoptera: Blattellidae)

Mortality of German cockroaches, Blattella germanica (L.), caused by Metarhizium anisopliae (Metschnikoff) Sorokin strain AC-1 alone and in combination with different formulations of boric acid, was evaluated in laboratory bioassays. Topical application of M. anisopliae alone (8.96 × 10⁹ conidia/m²) required 28 days to cause >92% cockroach mortality (LT₅₀ = 10 days). In contrast, in combination with boric acid (topically applied as a dust or in drinking water), M. anisopliae killed cockroaches significantly faster than without boric acid. M. anisopliae conidial dust (8.96 × 10⁸ conidia/m²) with either 12.5% (w/w) boric acid dust or 0.1% (w/v) boric acid in drinking water killed 100% of the cockroaches in only 8 days (LT₅₀ = 5 days) and 10 days (LT₅₀ = 6 days), respectively, without compromising the fungus emergence from cadavers. Replacement of M. anisopliae with flour dust or heat-killed M. anisopliae conidia eliminated this effect, demonstrating that it was not the consequence of greater boric acid ingestion due to more extensive cockroach grooming upon exposure to M. anisopliae conidia. Moreover, injections of a low dose of M. anisopliae, which caused only 30% mortality, together with sublethal concentrations of boric acid into the cockroach hemocoel resulted in a doubling of mortality. Statistical analysis demonstrated a synergistic interaction between these two insecticides.     

Feeding Behavior and Survival of Glucose-Averse Blattella germanica (Orthoptera: Blattoidea: Blattellidae) Provided Glucose as a Sole Food Source

Glucose-averse (Glu/Glu) male German cockroaches, Blattella germanica, rejected brief exposures to glucose solutions despite food deprivation so extreme as to cause high mortality. In the 24-h period following 5 days of food deprivation, both Glu/Glu and wild-type (+/+) were given a continuous source of 1 M glucose solution. Although Glu/Glu visited the solution as frequently as +/+, feeding bouts were significantly shorter. These truncated feeding bouts were sufficient to extend Glu/Glu longevity to ca. 80 days, regardless of glucose concentration. When provided continuously, the glucose was completely rejected by Glu/Glu for the first 3 days. However, by day 9, glucose intake levels were similar to those of wild-type cockroaches. The initial feeding lag probably accounted for the lower long-term survival of the Glu/Glu vs the +/+ strain. Under the stress of food deprivation, glucose-averse B. germanica modify their feeding behavior toward glucose like many phytophagous insects provided non-host plants in no-choice situations.     

Trail-following behavior in the German cockroach (Dictyoptera: Blattellidae)

The trail-following behavior of the German cockroach, Blattella germanica (L.), was evaluated by comparing the distance between cockroach movement paths and preapplied "trails" of fecal extract. For each cockroach group tested (adult males, females, gravid females, and late instars), the mean perpendicular distance of the cockroach from the trail was significantly less than the distance from a control trail. The results indicated that the German cockroaches did exhibit trail-following behavior. Trail- following accuracy varied among the cockroach groups. The mean distance from the fecal trail ranged from 18.45 to 110.05 cm with adult males < or = adult females < or = late instars < gravid females. Very dilute fecal extract could still induce trail-following behavior in adult male cockroaches. A 5.6% concentration of fecal extract in methanol was able to induce trail-following behavior in 50% of the cockroaches. Although German cockroaches have demonstrated trail-following behavior, fecal trails are still not thought to be actively deposited. Rather, the passive distribution of fecal material within the home range results in the accumulation of trails along frequently traveled routes (i.e., between resources and the cockroach harborage).     

Effects on German cockroach nymphs of contact exposure to IGRs, singly and in combination

Late instar German cockroach male and female nymphs were exposed continuously for two weeks to surfaces treated with fenoxycarb, diflubenzuron, and pyriproxyfen, singly and in combination. Concentrations were determined that eliminated or nearly eliminated reproduction in matings with untreated mates, either through mortality, effects on reproduction, or a combination of mortality and sterility (no hatch). The major effect of fenoxycarb, pyriproxyfen, and pyriproxyfen plus fenoxycarb was on reproduction. The major effect of diflubenzuron was mortality. No hatch occurred in matings of females that were exposed to low concentrations of pyriproxyfen and fenoxycarb (2 ng/cm² and 6 ng/cm², respectively); sterility was incomplete when females were exposed to 600 ng/cm² of diflubenzuron. Mortality and sterility acted together to eliminate productive matings (matings that produced nymphs) when relatively high concentrations of diflubenzuron were combined with one or both of the other insect growth regulators (IGRs). In the triple combination, very small amounts of fenoxycarb and pyriproxyfen (total 1.1 ng/cm²) combined with 200 ng/cm² of diflubenzuron eliminated productive matings of treated females, but similar results with treated males were found only at higher concentrations of each IGR.     

Response of German cockroaches to a dispersant emitted by adult females

A bioassay technique was used to compare the response of six age/sex classes of German cockroaches, Blattella germanica (L.), to a dispersant emitted by adult females when crowded. Differences occurred among the classes in the rate, intensity, and apparently thresholds of their response. Adults, especially males, responded more strongly than nymphs. A greater repellency was associated with filter papers conditioned by non-oothecae than by oothecae bearing females, suggesting a higher emission by the former.

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Résumé Des papiers filtres contaminés ont été utilisés pour comparer les réponses de six catégories (âge/sexe) de Blattella germanica à une substance antiagrégative émise par les femelles adultes groupées. Des différences apparaissent entre les catégories quant aux taux, intensité et seuils apparents des réponses. Les adultes, particulièrement les mâles, répondent plus vigoureusement que les larves. Le pouvoir répulsif des papiers filtres contitionnés par des femelles ne portant pas d'ootheque était supérieur à celui de femelles porteuses; ceci suggère une plus forte émission par les premières.

     

A microdialysis study of allatostatin degradation in Blattella germanica (L.) (Dictyoptera, Blattellidae)

Allatostatins with a typical C‐terminal sequence YXFGL‐NH₂ are insect neuropeptides with inhibitory properties upon Juvenile Hormone production in the corpora allata, vitellogenin release by the fat body, and gut and dorsal vessel motility. All these biological effects are rapidly reversible, suggesting the occurrence of effective mechanisms for inactivation of the peptides. We have studied the degradation of DRLYSFGL‐NH₂ (BLAST‐2), one of the allatostatins of Blattella germanica, in the internal milieu of adult females of this cockroach. The experimental approach combined the use of the radioiodinated derivative [¹²⁵I‐Tyr⁴]BLAST‐2, microdialysis techniques and HPLC analysis with a radioisotope detector. Under these experimental conditions, the half‐life of BLAST‐2 in the internal milieu of the adult female of B. germanica was between 3 and 6 min. Such a short half‐life explains the high doses of allatostatins required to obtain the expected biological effects when tested in vivo, and suggests that circulating allatostatins are subject to rapid rates of synthesis and degradation in order to be operative physiologically.     

Influence of carbon dioxide gas on German cockroach (Dictyoptera: Blattellidae) knockdown, recovery, movement and feeding

Abstract. Carbon dioxide anaesthesia differentially affects the knockdown and recovery of cockroaches, depending on the strain and the length of time that the colony has been subjected to a CO₂ regime. Adult males from two laboratory and two field-collected strains of German cockroaches, Blattella germanica, are knocked down within 7–45 s after exposure to CO₂. After 5 min of CO₂ exposure, presumptive recovery (i.e. the time for the cockroach to right itself after knockdown) for laboratory strains occurs significantly sooner than for field-collected strains. Control cockroaches, exposed to compressed air rather than CO₂, exit harbourage cups rapidly (≤3.20 min). However, although allowed a recovery period of 5 min, significant movement impairment occurs for all cockroach strains anaesthetized with CO₂. Carbon dioxide exposure significantly reduces consumption of 2.15% hydramethylnon bait and delays mortality even when 24 h is allowed for recovery before bait placement. Cockroaches allowed to recover for 48 h after 5 min of CO₂ exposure consume significantly more bait and die significantly faster than CO₂ exposed groups allowed 24 h of recovery, and mortality is not significantly different from nonanaesthetized bait-fed controls.     

Differential adaptation to water deprivation in first-instar nymphs of the German cockroach (Blattella germanica) and the brown-banded cockroach (Supella longipalpa)

This study compares the relative abilities of rist-instar nymphs of the german cockroach (Blattella germanica L.) and the brown-banded cockroach (Supella longipalpa F.) to survive prolonged periods of food and/or water deprivation.S. longipalpa nymphs survived significantly longer thanB. germanica nymphs when drinking water was absent, but the advantage ofS. longipalpa overB. germanica disappeared if food was also absent. These results are consistent with the hypothesis thatS. longipalpa is adapted to drier habitats than isB. germanica, and suggest thatS. longipalpa nymphs may be more capable of producing and utilizing extra metabolic water from food thanB. germanica nymphs. Evidence from the literature suggests that this species difference applies mainly to juveniles, since adults ofB. germanica andS. longipalpa do not differ in ability to withstand water deprivation, regardless of food availability.     

A Glandular Gift in the German Cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae): The Courtship Feeding of a Female on Secretions from Male Tergal Glands

In the courtship behavior of the German cockroach, the male presents tergal glands to the female and feeds her with glandular secretions to place her in the appropriate precopulatory position. The phagostimulant activity of the secretions was quantitatively examined using the polyethylene glycol film method. The methanol extract of the glands on the eighth tergite induced a potent feeding response in 6-day-old virgin females (EC ₅₀ = 0.0037 male equivalent/40 g PEG spot). However, there was no temporal relation between the feeding response and the sexual receptivity of the females. Moreover, besides virgin females, the extract induced a feeding response in gravid or mated females, males, and the last-instar nymphs. These results strongly suggest that the secretions function as a dietary feeding stimulant in principle but as a courtship pheromone in the context of courtship behavior where the stimulants are offered as a nuptial gift.     

Biochemical characterization and purification of esterases from three strains of German cockroach,Blattella germanica (Dictyoptera: Blattellidae)

Three strains of German cockroach, Blattella germanica (L.) showed varying levels of resistance to chlorpyrifos, methyl parathion, propoxur, bendiocarb, and cypermethrin. The general esterase activity was at least twofold higher than susceptible strain. The subcellular distribution studies revealed that the majority of the esterase activity is present in the 100,000g cytosolic fraction. Only a small portion of the activity was membrane bound. Using non-denaturing gel electrophoresis, ten isozymes were identified in German cockroaches. These isozymes were isolated individually from the gels and analyzed for differences in activity. The isozymes E5, E6, and E7 of resistant strains had significantly higher specific activities when compared with the susceptible strain. The purification process using various column chromatography and preparative gel electrophoresis resulted in 9–11% of total esterase recovery. About double the amount of E6 was recovered from the resistant strains when compared with the susceptible strain. Kinetic analyses of E6 did not indicate differences in K_m and V_max values between the resistant and susceptible strains. Also, inhibition of esterase activity by paraoxon, chlorpyrifos, and propoxur did not suggest any structural differences in esterase E6 between strains. The results suggest that the increased production of E6 esterase contributes to insecticide resistance in German cockroaches. The role of E6 may be sequestration of toxic molecules rather than hydrolysis. © 1996 Wiley-Liss, Inc.