Endocrine regulation of female contact sex pheromone production in the German cockroach, Blattella germanica

ABSTRACT The amount of the major component of the cuticular sex pheromone, 3, 11-dimethyl-2-nonacosanone, on individual female German cockroaches, Blattella germanica (L.), as a function of age was determined by gas-liquid-chromatographic analysis. Accumulation of phermone increased with age in both virgin and mated females. During the first gono-trophic cycle, the pheromone accumulated most rapidly when oocyte growth rates were maximal (days 5–10), and least rapidly while the female carried an ootheca (days 11–32). Pheromone accumulation was similar in virgin and mated females when the same physiological stages (determined by oocyte maturation) were considered. Inhibition of Juvenile Hormone release, through allatectomy, chemicals (precocene or fluoromevalonate), or through mechanical egg case implants, suppressed or delayed pheromone production and oocyte growth. The Juvenile Hormone analogue ZR512 induced allatectomized or head-ligated females and females with chemically or mechanically inhibited corpora allata to produce pheromone and enlarge their basal oocytes. Finally, ZR512 applied to intact females stimulated pheromone production in a dose-dependent manner.     

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.     

Ultrastructure and maturation of a sex pheromone gland in the female German cockroach, Blattella germanica

A volatile sex pheromone is produced in an adult female-specific gland located on the anterior of the last abdominal tergite of the female German cockroach, Blattella germanica (L.). In this area, the cuticle forms deep depressions in which a large number of cuticular orifices are located. The cuticular orifices are connected to secretory cells via cuticular ducts surrounded by duct cells. The pheromone gland exhibits a clear developmental maturation in relation to sexual maturation of the female. The secretory cells of a newly formed gland in the imaginal female are small and contain few secretory vesicles. The amount of extractable pheromone in the gland is low on day-0 but it increases with age and peaks on day-6. The secretory cells in a mature day-6 gland are characterized by a large number of electron-lucid secretory vesicles. abundant RER and SER, a large nucleus and a long, convoluted end apparatus which is lined with numerous microvilli. The contents of the secretory vesicles are exocytosed into extracellular reservoirs at the base of microvilli and then transported to the cuticular surface through the long ducts. The supportive function of the duct cell in the glandular organization and developmental regulation of the gland are discussed.     

Biosynthesis of contact sex pheromone in the female tsetse fly, Glossina morsitans morsitans Westwood

Injection of [2,3 ¹⁴C] sodium succinate into recently emerged, unfed females of Glossina morsitans morsitans resulted in incorporation of radiolabel mainly into surface cuticular alkanes. In vivo experiments with intact flies showed that the distribution of labelled alkanes depended on fly mobility, the legs of unrestrained flies possessing proportionately larger amounts of radioactive hydrocarbon material than those of flies whose legs were tied together with a silk suture. The heads of both restrained and unrestrained flies contained proportionately more material per unit surface area than did any other body part. However, ablation experiments and in vitro incubation showed that the most active incorporation of label into alkanes occurred in the abdomen and that all dorsal abdominal segments were equally active. The ventral abdomen also incorporated label into cuticular alkanes in vitro, but other body parts were apparently less able to do so. The sex pheromone of G. m. morsitans is a trimethyl-substituted alkane, the labelling of which appeared to be in proportion to the relative abundance of its methyl groups among those of the other alkanes of the cuticle following injection of either intact or legless flies. Hence it is proposed that sex pheromone is synthesized along with other cuticular alkanes mainly by cells closely associated with the abdominal cuticle of females and that it is spread over the external surface both by diffusion and by grooming which leads to accumulations of hydrocarbon material on the legs.     

Effect of the pheromone biosynthesis activating neuropeptide on sex pheromone biosynthesis in Spodoptera littoralis isolated glands

The control of Spodoptera littoralis sex pheromone biosynthesis has been investigated with synthetic pheromone biosynthesis activating neuropeptide (PBAN) and different labeled tracers using an in vitro isolated gland system. Responsiveness of the glands to PBAN stimulation was impaired by careless tissue manipulation. The fact that PBAN is active in the isolated gland system suggests that this might be a target organ for this peptide in S. littoralis. As reported previously with Br-SOG extracts and intact females, label incorporation into the pheromone increased in glands treated with PBAN from all the precursors tested. However, the formation of labeled intermediates from d₅E11–14:Acid also occurred in glands incubated in the absence of the peptide, but the amounts of d₅Z9, E11–14:Acid were lower in PBAN treated glands than in controls. These results indicate that PBAN controls pheromone biosynthesis in S. littoralis by regulating the reduction of acyl moieties. © 1994 Wiley-Liss, Inc.     

The role of 20-hydroxyecdysone in housefly sex pheromone biosynthesis

Houseflies ovariectomized within 12 h after emergence do not produce (Z)-9-tricosene nor demonstrate the shift from alkene to alkane synthesis that is typcal of flies with developing ovaries. A single injection of 20-hydroxyecdysone at doses of 0.1 to 10 μg will induce the pattern in ovariectomized insects that is characteristic of flies with ovaries. Furthermore, this pattern persists for 3 days, but by 6 days after hormone injection, the synthesis of (Z)-9-tricosene stops and more alkenes are produced than alkanes. A post-hormone treatment time of 16 h was required before detectable amounts of (Z)-9-tricosene appeared on ovariectomized flies. Multiple injections of 20-hydroxyecdysone at doses of 50 ng into ovariectomized flies induced (Z)-9-tricosene synthesis and a shift in alkene to alkane synthesis. Thus, 20-hydroxyecdysone was able to act as an ovarian substitute in ovariectomized flies by stimulating pheromone synthesis.     

Identification,accumulation, and biosynthesis of the cuticular hydrocarbons of the southern armyworm,Spodoptera eridania (cramer) (lepidoptera: Noctuidae)

The accumulation and biosynthesis of cuticular and internal hydrocarbons in the Southern armyworm, Spodoptera eridania, were examined at closely timed intervals during larval and pupal development. Gas chromatography-mass spectrometry (GC-MS) was used to identify n-alkanes, monomethylalkanes, and dimethylalkanes ranging in chain length from 23 to 35 carbons. The amount of cuticular hydrocarbon stayed relatively constant during each stadium, while the amount of internal hydrocarbon increased dramatically during the first half of each larval stadium, presumably to replace the cuticular hydrocarbon lost on the shed cast skin with each molt. The accumulation of internal hydrocarbon was mirrored by large increases in the rate of incorporation of labeled acetate into the hydrocarbon fraction. Hydrocarbon production fell to very low rates during the latter part of the fourth and fifth larval stadia. Relatively high rates of hydrocarbon production were observed during the first and last one-third of the pupal stage and essentially all of the hydrocarbons produced during this stage remained internal. These data document large changes in the rates of hydrocarbon production during development in S. eridania and suggest that most of the hydrocarbon produced during each stage was stored internally and then transported to the cuticle of the next stage.     

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.     

Temperature-mediated sex pheromone production and response of the American cockroach

Temperature affects the production of and response to sex pheromone by the American cockroach. Female sex-pheromone production is directly related to acclimation temperature and rapidly decreases 1 week after acclimation to lower temperatures. Production decreases slightly between weeks 1 and 2 and remains constant thereafter. Phermone-release rates are not affected by substrate temperature. Male response to a 1 ♀-equivalent hr pheromone dose is also temperature dependent. Maximal response was obtained at 26.7°C. Acclimated males were able to perceive pheromone (EAG technique) and capable of movement at lower temperatures (10°C), suggesting central nervous system inhibition.     

Arthropod immune system. III. Septate junctions in the hemocytic capsule of the german cockroach, Blattella germanica

Granulocytes (GRs) and/or plasmatocytes (PLs), the two major immunocytes in arthropods, participate in cellular encapsulation of foreign tissue. Although gap and desmosome junctions have been reported in insect capsules, smooth septate junctions are being reported for the first time by both thin section and freeze-fracture techniques in Blattella germanica. In 7-day-old capsules, the septa are 23 nm thick, faintly 'scalloped' and slightly curved in appearance; the interseptal space has a periodicity of about 5 nm. In freeze-fractured capsules, the septa are associated on both sides with the corresponding intramembranous structures, belonging to the plasma membranes of the two junction-forming GRs. The intercellular space is 27 nm wide. There are 36-40 septa/1 mum junctional length. The junctions show furrows on the extracellular fracture face (E) and the complementary regular rows of intramembranous particles on the cytoplasmic face (P). The septate junctions often occur in the region of the capsule that also shows the presence of gap junctions, but only rarely that of desmosomes. The septate junctions are in close proximity with mitochondria. It is suggested that the function of these junctions is to produce compact capsules.     

Patterns of ionic currents around the developing oocyte of the German cockroach, Blattella germanica

The development of patterns of current around vitellogenic oocytes of the cockroach, Blattella germanica, was examined by means of a two-dimensional vibrating probe. Previtellogenic oocytes exhibited small unstable currents. Shortly after vitellogenic uptake began (oocytes 0.6-0.8 mm anterior to posterior) currents were either all inward or all outward at the plane of measurement. A dorsoventral pattern of currents was first observed around oocytes a little larger than 0.8 mm. Current exited dorsally (source) and entered ventrally (sink). In these oocytes source and sink were small, less than half the anterior-posterior length. As oocytes grew, relative sizes of source and sink increased until they extended across the major part of dorsal and ventral surfaces. Many late vitellogenic oocytes had a pattern of dorsal outward current with a bimodal distribution. At the onset of chorionation measured currents were again small, unstable, and exhibited no well-defined pattern. Current density was greatest during midvitellogenesis.     

Synergism of chlorpyrifos against the German cockroach, Blattella germanica

Of fifteen compounds tested as synergists for chlorpyrifos against susceptible and resistant strains of Blattella germanica, the German cockroach, eleven were active against the resistant strain but only seven were synergistic against the susceptible strain. Overall, the most effective synergist was S,S,S-tributyl phosphorotrithioate (DEF) followed by phenyl saligenin cyclic phosphonate (PSCP) and two substituted N,N-dimethylcarbamates: SK-102 and SK-37. The most effective synergist for overcoming chlorpyrifos resistance was SK-37 which reduced the resistance ratio by 3.2-fold. Four other synergists which reduced chlorpyrifos resistance, in order of their effectiveness, were: SK-102 > PSCP > DEF > tridiphane. The potential usefulness of these synergists for German cockroach control is discussed.     

Properties of the Δ11-desaturase enzyme used in cabbage looper moth sex pheromone biosynthesis

The biosynthesis of a large number of sex pheromone components of various moth species can be explained by invoking a Δ 11-desaturation of common fatty acids. A Δ11-desaturase system from Trichoplusia ni, the cabbage looper moth, is identified and partially purified. Some of its properties are defined and compared with those of the ubiquitous Δ-9 desaturase enzyme. Similarities between the two systems include subcellular location (microsomal), substrate specificity (16- and 18-carbon acids), and lack of sensitivity to carbon monoxide, while differences include cofactor preference (NADH rather than NADPH), sensitivity to cyanide ion, pH optimum (7.4-7.8 vs 6.8-7.2), and location in the organism (in the pheromone gland compared to generally distributed). The effects of insect age were also investigated.     

Nutritional regulation in nymphs of the German cockroach,Blattella germanica

Synthetic foods varying in protein-carbohydrate ratio and total nutrient concentration were used in food selection experiments to investigate the ingestive and post-ingestive regulation of macronutrients by male and female nymphs of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae). For both nutrient imbalance and food dilution, food ingestion varied between treatments with the effect that nutrient ingestion was regulated. However, this mechanism was insufficient to compensate for some food dilution treatments. In those cases, the regulation of protein intake was prioritised over that of carbohydrate intake, and two additional regulatory responses were seen. Firstly, cellulose digestion supplemented shortfalls in dietary soluble carbohydrates, and secondly the feeding period within the stadium was prolonged. These ingestive, post-ingestive and developmental responses were orchestrated in such a way that, in all treatments, nutrient gain approached similar levels, despite the variation in food properties.     

Phospholipid composition and pheromonal activity of nuptial secretion of the male German cockroach, Blattella germanica

As a part of the sequential courtship behavior of the German cockroach, Blattella germanica, females feed on the nuptial secretion from the male tergal glands. The pheromonal secretion, consisting mainly of oligosaccharides and phospholipids, strongly elicits a feeding response in virgin females. The phospholipids were composed of phosphatidylethanolamine and phosphatidylcholine. Their fatty acid compositions were determined by chromatographic and enzymatic methods. Although an authentic blend of phospholipids (1,2-dioleoylphosphatidylethanolamine and 1,2-dioleoylphosphatidylcholine) showed a marginal phagostimulant activity, addition of the blend to an authentic blend of oligosaccharides (maltose and maltotriose) strongly enhanced the activity to nearly the level of the crude extract. These results indicate that the nuptial feeding behavior is elicited by a synergistic action between phospholipids and oligosaccharides.     

Catecholamines in the cuticles of four strains of the german cockroach Blattella germanica (L.) during sclerotization and melanization

Catecholamines were extracted from the cuticles of four strains of the cockroach Blattella germanica at different times 48 h after adult ecdysis and analyzed by reverse phase HPLC with electrochemical detection. The wild (VPl), black (Bl), orange (or), and yellow (y) phenotypes differ in cuticular pigmentation, particularly in the extent of melanization. N-β-Alanyldopamine (NBAD) and N-β-alanylnorepinephrine (NBANE) were major o-diphenolic compounds in extracts from cuticle of all strains during the main period of sclerotization. N-Acetyldopamine (NADA) and N-acetylnorepinephrine (NANE) were minor the first day after ecdysis, but accumulated to higher levels thereafter. Dopamine (DA) concentrations were higher in the darker pigmented cuticles of strains Bl and or than in the lighter-colored cuticles of strains VPl and y. Extractable DA rapidly increased in VPl, Bl, and or cuticles shortly after ecdysis, reached peak levels 6–24 h later, and then decreased after melanization. Only small amounts of DA were detected in strain y cuticle, whereas NBANE concentrations were very high. Therefore, high DA levels in cuticle are correlated with melanization that occurs during the first few hours after adult ecdysis, whereas sclerotization is correlated with high levels of the N-β-alanylcatecholamines. Sclerotization appears to be delayed in strain Bl, since only low concentrations of the N-acylated catecholamines accumulate until after melanization is completed.     

Comparisons of toxic baits for controlling the cockroach, Blattella germanica: attractiveness and feeding stimulation

Female German cockroaches, Blattella germanica (L.) (Dictyoptera: Blattellidae) and nymphs (stages 1, 3 and 6) were used to test the attractiveness and the feeding stimulation of several commercial gel formulations of insecticide food baits in laboratory binary choice tests. The four toxic gel baits tested were: 'Avert' (0.05% abamectin=avermectin B1), 'Drax' (33.3% boric acid), 'Goliath' (0.05% fipronil) and 'Maxforce' (2.15% hydramethylnon). The attractiveness of a bait was estimated by the number of cockroaches that chose it first, and by their tendency to change to it secondarily. Feeding stimulation was estimated by the mean duration of feeding bouts and total duration of food intake. Variability of these factors was assessed in relation to age of cockroaches and to age of baits. With a few exceptions, cockroach age did not affect performance in any of these tests. Attractiveness to B. germanica ranked 'Goliath' gel higher than 'Avert', 'Drax' and 'Maxforce' gels, whether or not the active ingredient fipronil was present in 'Goliath' gel. Feeding stimulation ranked 'Avert' and 'Maxforce' gels higher than 'Goliath' gel, and 'Drax' gel was inferior. With ageing up to 3 months, the feeding stimulation power of 'Goliath' and 'Maxforce' gels increased, whereas that of 'Avert' fluctuated. Assuming that all types of bait effectively kill cockroaches once ingested, these results illustrate the importance of behavioural observations on bait efficiency and show that ranking of these different food baits varies in relation to the parameter analysed.     

Correlation of housefly sex pheromone production with ovarian development

Pheromone production in the housefly was monitored during oögenesis and in ovariectomized insects by gas-liquid chromatography (GLC) and radio-GLC. The presence of vitellogenic ovaries was required for the initiation of (Z)-9-tricosene (muscalure), (Z)-9,10-epoxytricosane and (Z)-14-tricosen-10-one synthesis. Methylalkane synthesis was enhanced by developing ovaries. Insects ovariectomized within 12 hr after emergence produced no detectable amounts of (Z)-9-tricosene, C₂₃ epoxide nor C₂₃ ketone and synthesized less methylalkanes than the controls. This effect was reversed by ovary implants. When flies were ovariectomized after oviposition, synthesis of (Z)-9-tricosene, C₂₃ epoxide and C₂₃ ketone continued. Thus, initiation of the synthesis of these C₂₃ pheromone compounds required a vitellogenic ovary, but the ovary was not required to maintain synthesis.     

Correlation between glycerolipids and pheromone aldehydes in the sex pheromone gland of female tobacco hornworm moths,Manduca sexta (L.)

Analysis by TLC and HPLC revealed that the triacylglycerols comprise the most abundant lipid class in the sex pheromone glands of Manduca sexta females. Also, conjugated olefinic acyl analogs of the major pheromone aldehydes occur principally in the triacylglycerols. The amount of triacylglycerols with conjugated diene acyl moieties significantly decreased when the period of pheromone production was extended by 7 h beyond the normal period of pheromone production by 3 injections of pheromone biosynthesis activating neuropeptide (PBAN) at 3 h intervals. This decrease indicates that the triacylglycerols stored in the gland may serve as major sources of pheromone precursors in the biosynthesis of the sex pheromone aldehydes. Furthermore, analysis of pheromone aldehydes and triacylglycerols in the gland from moths treated with PBAN showed that the proportions of the triacylglycerols with conjugated diene moieties were closely correlated with the proportions of aldehydes found in the same gland. This correlation suggests that the proportions of fatty acids bound to certain triacylglycerols regulates the proportions of aldehydes in biosynthesis of the pheromone blend in M. sexta. © 1995 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

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.