Edina L. Burns

A new component of the female sex pheromone ofBlattella germanica (L.) (Dictyoptera: Blattellidae) and interaction with other pheromone components.

A fourth component, 3,11-dimethyi-2-heptacosanone, was identified as a cuticular contact sex pheromone of the female German cockroach,Blattella germanica. In behavioral assays, higher dosages of 3,11-dimethyl-2-heptacosanone were needed to elicit similar sexual responses in males to those elicited by the major pheromone component, 3,11-dimethyl-2-nonacosanone. A 15∶85 blend of the C27 and C29 methyl ketone homologs resulted in a dose-response curve intermediate between that of each of the components alone, indicating independence of activity of each component and lack of synergism. Moreover, the activity of 3,11-dimethyl-2-nonacosanone was not enhanced by female cuticular hydrocarbons. The relationship between sexual responses of males to females and to isolated female antennae, and the amount of cuticular pheromone on whole females was investigated. Cuticular sex pheromone found on females increased with the age of the female, as did the male response to whole females. However, a bimodal male response was elicited by isolated female antennae. Differences between behavioral and analytical assays of pheromone are discussed.

Structural correlation between cuticular hydrocarbons and female contact sex pheromone of German cockroachBlattella germanica (L.)

The structural relationships between the cuticular hydrocarbons and the contact sex pheromone of the female German cockroach,Blattella germanica, were investigated. Cuticular hexane extracts were separated into hydrocarbon and ketone fractions by TLC or silicic acid column chromatography. The ketone fraction (which contains the major contact sex pheromone component) was analyzed by GC-MS before and after reduction to ydrocarbon. In addition to 3,11-dimethyl-2-nonacosanone, 3,11-dimethyl-2-heptacosanone was also identified. Females have the 3,11- and 3,9-dimethyl C27 and C29 alkanes, but only the 3,11- isomer of the dimethylketones. Inddition to the hydrocarbon components previously reported, a number of new components were characterized. Although the ratios of cuticular hydrocarbons differ among nymphs, adult males, and adult females, they have qualitatively identical hydrocarbon profiles, suggesting that the production of the contact sex pheromone results from the sex-specific oxidation of 3,11-imethylalkanes to pheromone components by the female.

Role of the brain in juvenile hormone synthesis and Oöcyte development: effects of dietary protein in the cockroach Blattella germanica (L.)

Abstract We demonstrate links between the protein content of diets, food intake, the resultant body mass, juvenile hormone synthesis by the corpora allata, and oocyte maturation in Blattella germanica. Oocyte development and oviposition were suppressed in starved females as well as in females fed deficient artificial diets (low- or high-protein contents). On all diets, as well as in starved females, oocyte growth was significantly potentiated by hydroprene, indicating that the suppressed oocyte growth on deficient diets was largely due to juvenile hormone deficiency. Also, under all dietary treatments, including in starved females, transection of the nervi corporis cardiaci (NCC)-I and II significantly potentiated juvenile hormone biosynthesis, oocyte development and oviposition compared with the respective sham-operated females. These results clearly show that intact nerves are a major route of allatostatic signals from the brain which in turn are regulated by food quality. However, a partial suppression of juvenile hormone synthesis and smaller oocytes in females with denervated corpora allata that were fed protein-deficient diets (starved, 0%, 5%) or high-protein diets (78%) compared with females that were fed normal diets (25%, dog and rat foods) highlights the importance of humoral signals in allata activity. Oocyte size and juvenile hormone biosynthetic rates were also significantly lower in adult females that were fed a 7.5%-protein diet as nymphs compared with females fed a 25%-protein diet. Denervation of the corpora allata resulted in potentiation of their activity, but to significantly lower rates in females that were raised on the low-protein diet as nymphs, further supporting the importance of the nutritional milieu in corpus allatum activation. Both food intake and body mass varied directly with the protein content of the diet, confounding the conclusion that corpus allatum activity was affected by signals related to the dietary protein content. To dissociate food consumption and body mass from corpora allata activity and oocyte growth, 2% trypsin synthesis inhibitor was added to a 7.5%-protein diet. Neither body mass nor total food consumption were changed relative to control females, but oocytes were significantly small on this diet. Together with data showing that oocyte maturation can be induced with hydroprene in protein-deprived or even in starved females, these data argue that signals associated with the protein content of the diet partially lift brain inhibition of the corpora allata.

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.

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.

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.

Biochemistry and regulation of pheromone production in Blattella germanica (L.) (Dictyoptera, Blattellidae)

Abstract Females of the German cockroach, Blattella germanica , produce a contact sex pheromone consisting of the methyl ketones 3,11-dimethyl-2-heptacosanone, 3,11-dimethyl-2-nonacosanone, 29-hydroxy- and 29-oxo-3,11-dimethyl-2-nonacosanone. We review evidence in support of the hypothesis that in adult females the hydrocarbon 3,11-dimethylnonacosane is oxidized to the corresponding methyl ketone pheromone. Recent studies on the precursors and directionality of synthesis of the methyl-branched alkane indicate that it is formed by the insertion of methylmalonyl units derived from propionate, isoleucine, valine, methionine and succinate early in chain elongation. The hydrocarbon is then hydroxylated and oxidized at the 2-position to form the methyl ketone pheromone. The in vivo synthesis of pheromone and its accumulation on the cuticle are correlated to the synthesis of juvenile hormone (JH) by the corpora allata (CA) in vitro and to oocyte development, suggesting common regulation by JH of pheromone production as well as other reproductive events. The patterns of pheromone and hydrocarbon production in starved, allatectomized and head-ligated females, as well as in females rescued with hormone-replacement therapy, suggest two mechanisms of regulation of pheromone production: a JH-induced conversion of hydrocarbon to pheromone is related to the CA cycle and to oocyte development, while a JH-independent mechanism, which is probably related to feeding, supplies precursors for hydrocarbon biosynthesis.

Ovarian regulation of cyclic changes in size and activity of corpus allatum cells in Blattella germanica

The roles of the ovary and egg case in the regulation of the development and activity of the corpora allata were studied in Blattella germanica adult females. The corpora allata of ovariectomized females exhibit a delayed pattern of development and activity compared with intact females. Implantation of a young ovary into ovariectomized females resulted in a faster activation of the corpora allata to the same peak juvenile hormone biosynthetic rates exhibited by intact females. Injection of 20-hydroxyecdysone caused transient declines in both the activity and the size of corpus allatum cells. Insertion of a waxed egg case into the genital atrium of ovariectomized females, with or without injection of 20-hydroxyecdysone, mimicked the 21-day pregnancy in intact females and caused corpus allatum cells to become small and inactive. The size and activity of corpus allatum cells increased again when the inserted egg case was removed manually or had been carried by the ovariectomized female for more than 3 weeks. In both intact and ovariectomized females, the activity of the corpora allata, as measured by the spontaneous and farnesoic acid-stimulated rates of juvenile hormone biosynthesis, and corpus allatum development, as reflected by the size of cells, always exhibited the same patterns and responded concurrently to the various ovarian factors. These results indicate that ovarian factors, both stimulatory and inhibitory, regulate juvenile hormone production mainly by inducing changes in the cellular machinery rather than in rate-limiting enzymes.

Sexual differentiation of nymphal corpora allata and the effects of ovariectomy on adult gland morphometrics inBlattella germanica

Changes in the number of corpus allatum (CA) cells were investigated in nymphs and in intact and ovariectomized adult femaleBlattella germanica. The CA of intact adult females exhibit cyclic changes in volume in relation to juvenile hormone (JH) synthesis, while the CA of ovariectomized females become significantly hypertrophied as a result of a gradual and continuous increase in volume that is independent of JH biosynthesis. In both intact and ovariectomized females changes in JH synthesis and CA volume are not related to total cell number which remains relatively constant. However, adult females have twice as many CA cells as do adult males as a result of a female-specific increase in total cell number late in the last nymphal instar.

Juvenile hormone regulation of the left colleterial gland in intact and ovariectomized Blattella germanica (L.) (Dictyoptera: Blattellidae)

Abstract The left colleterial glands of intact and ovariectomized females were shown to accumulate protein in response to juvenile hormone III. Their distal tubule diameter was highly correlated with their protein content. While intact females excreted the oothecal proteins to produce an egg case, ovariectomized females retained these proteins without apparent loss from the gland. In overiectomized females the colleterial gland therefore became larger and contained more protein than in intact females. The size and protein content of the left colleterial gland of ovariectomized females were arrested after the insects were allatectomized, and both were induced by injections of synthetic juvenile hormone III. Thus, the left colleterial gland can be used as a cumulative record of circulating juvenile hormone within an individual ovariectomized female, much as the basal oocytes are used in intact females, and it can be used to distinguish betwen females that had increased juvenile hormone synthesis and those that had not.