T.S. Adams

Relationship of age, ovarian development, and the corpus allatum to mating in the house-fly, Musca domestica

Abstract Mating in the housefly, Musca domestica (L.), was correlated with the stage of ovarian development. Females with stage 3 and 4 ovaries rarely mated, but mating increased from 29·0 per cent in females with stage 5 ovaries to 97·0 per cent in females with stage 10 ovaries. When they were given a choice, males preferred females with ovaries in stages 6 to 10 for mating. Females that were allatectomized when they were 48 hr old or younger demonstrated both an inhibition of ovarian development and mating. The corpus allatum was activated in 100 per cent of the female population held at 21·7 ± 1°C after 60 hr. Ovariectomized females mated normally but tended to remate more frequently than the controls. Since topical application of 2·5 μg of the synthetic juvenile hormone stimulated mating and ovarian development, it was concluded that juvenile hormone stimulated both ovarian maturation and mating in the housefly and that the correlation between mating and ovarian development was caused by a response to the titre of this hormone.

Biosynthesis and Endocrine Regulation of Sex Pheromone Production in Diptera

Publisher Summary This chapter discusses the biosynthesis and endocrine regulation of sex pheromone production in Diptera. In Diptera, as in other insects, gamete fertilization is the end result of a complex series of behaviors that are released by taste, touch, sound, smell, and sight. Sex pheromones have been demonstrated in 43 species of Diptera, both male and female, and have been chemically identified in 17 species. These pheromones may be active at a distance, at close range, or only on contact. The female-produced sex attractant in Dacus oleae has an effective range of several meters. Other dipteran pheromones have an effective range of only several centimeters and release courtship behavior, as in Hippelates collusor, Lucilla cuprina, and Drosophila melanogaster, or increase mating strike activity as in Musca domestica, Haematobia irritans, and Cochliomyia hominovorax. Diptera vary considerably as to the sites of pheromone production. Pheromone is synthesized in the rectal glands of tephritids, in the intra-anal lobes in Drosophila grimshawi, and in epidermal tissue in the housefly and tsetse fly. The pheromone biosynthetic sites have not been identified for the remaining Diptera, although the oenocytes have been suggested as a synthetic site for pheromones in Culicoides nubeculosus.

Oöstatic hormone production in houseflies, Musca domestica, with developing ovaries

Abstract An oostatic hormone is produced by houseflies with eggs in stages 4 to 10. This hormone suppresses the development rate of stages 2 to 4 eggs. Complete inhibition of the second gonotropic cycle at stage 4 occurs when mature eggs from the first cycle are retained. Extracts from mature female flies inhibited ovarian development when injected into 24-hr-old flies with eggs in stage 2 of development. The oostatic hormone is soluble in 95% ethanol, chloroform-methanol (2 : 1), 20% glycerol, and water. The oostatic hormone maintains the cycle of egg production in the housefly.

The rôle of juvenile hormone in housefly ovarian follicle morphogenesis

Abstract Oogenesis in the housefly, Musca domestica , was divided into a series of 10 stages where stage 1 was the germarium, stage 4 was the beginning of yolk deposition, stage 7 was characterized by maximal nurse cell development, stage 9 by the degeneration of the nurse cells and chorion formation, and stage 10 was the mature egg. It required 69 hr from eclosion at 27°C to develop mature eggs. This represented an oocyte volume increase of 3700-fold, a seventeenfold increase in follicle length, and a sevenfold increase in weight. The application of 2 μg of isopropyl (E,E)-11-methoxy-3,7,11-trimethyldodeca-2,4-dienoate (ZR-515) to allatectomized (-CA) flies stimulated egg development, which progressed at the same rate as the controls. The -CA flies did not develop eggs past stage 4, which represented a cessation of development at a volume of 1·4 per cent that of a mature egg and an ovarian dry weight of 11 per cent that of a mature ovary. The follicle cells from -CA flies did not differentiate into the squamous condition over the nurse chamber, did not become columnar over the oocyte, did not produce the chorion or vitelline membrane, and did not decrease in number as they did on the stage 10 follicles. Endomitosis in the nurse cell nuclei of -CA flies stopped development at 290 c, but maximum development of 2400 c occurred in stage 7 follicles from controls, and then the nurse cells began to disintegrate.

The role of 20-hydroxyecdysone in housefly sex pheromone biosynthesis

Abstract 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.

Effect of pheromone components when applied to different models on male sexual behaviour in the housefly, Musca domestica

Abstract Male mating behaviour was studied by treating a pseudofly, newly emerged female or male fly, with all possible combinations of ( Z )-9-tricosene, the non-hydrocarbon fraction and the methylalkane fraction. All dosages were at physiological levels. Striking behaviour, both mating and homosexual, were increased by tricosene. When the non-hydrocarbon fraction was added to the tricosene, homosexual strikes decreased while mating strikes increased. This indicates that the non-hydrocarbon fraction contains sex recognition factors. Increased copulatory attempts were observed with the non-hydrocarbon fraction and the methylalkane fraction but not with the tricosene. The amount of time spent with the model, an arrestant effect, was determined by the methylalkane fraction.

Haemolymph ecdysteroid in the housefly, Musca domestica, during oögenesis and its relationship with vitellogenin levels

Abstract Ecdysteroid titre in the haemolymph of the housefly, Musca domestica , cycled during oogenesis and peaked at ∼50 pg/μl during stages 5, 6 and 7. Levels of 10–20 pg/μl were found in houseflies with pre- and post-vitellogenic ovaries. Removal of the corpus allatum and corpus cardiacum complex resulted in low ecdysteroid levels (10 pg/μl). Ovariectomized flies also had lower ecdysteroid levels than the controls at 2 days (5 pg/μl) after emergence but not at 6 days (22 pg/μl). It is possible that the ecdysteroid peak that occurred during stages 5, 6 and 7 was produced by the ovaries because ovaries secreted and synthesized ecdysteroid in vitro . Endogenous haemolymph ecdysteroid levels had a linear correlation with the amount of vitellogenin that held for hormone concentrations of 5–43 pg/μl. Furthermore, the injection of 20-hydroxyecdysone at doses of 10 ng−1.0 μg/fly increased the amount of vitellogenin from 6 h to 12 h after injection; by 24 h, the vitellogenin returned to control levels. When 20-hydroxyecdysone was injected into ovariectomized flies, it was rapidly degraded and 96% was cleared from the haemolymph within 1 h.

Ovarian regulation of the corpus allatum in the housefly, Musca domestica

Abstract Corpus allatum area in the housefly, Musca domestica L., decreased before vitellogenesis occurred in the ovaries and then increased in area by stage 5 or 6 of ovarian development. Both ovariectomy and oviposition resulted in a drop in corpus allatum area. It was concluded that a small corpus allatum released juvenile hormone, whereas a large gland stored hormone. Injection of extract containing oostatic hormone into ovariectomized flies increased the area of the corpus allatum; 26 μg of extract maintained a large corpus allatum for 32 hr. A humorally mediated inhibitory feedback mechanism exists between the ovaries and the corpus allatum.

Vitellin and vitellogenin concentrations during oögenesis in the first gonotrophic cycle of the house fly, Musca domestica

Abstract The house fly, Musca domestica , contains at least two native vitellin and two vitellogenin proteins. Both vitellins appear to have an identical vitellogenin partner. The major native vitellin has a mol. wt of 281 K Daltons, and the major native vitellogenin has a mol. wt of 283 K Daltons. These proteins are composed of three subunits with mol. wt of 48, 45 and 40 K Daltons. The relationship of the subunits to the native proteins is not known. Haemolymph vitellogenin levels are cyclical during oogenesis with no detectable amounts in previtellogenic flies and low levels in postvitellogenic flies. The highest level of vitellogenin, 10.5 μg/μl, occurred in flies with stage-7 ovaries. The vitellogenin levels during oogenesis fit a parabolic curve and the fat body vitellogenin content during oogenesis showed this same pattern. Uptake of vitellogenin into the ovary during each stage of oogenesis also fit a parabolic curve and produced a high linear correlation with haemolymph vitellogenin levels. The greatest uptake was 37 μg/stage and occurred during stage 6.

Induction of female sex pheromone production in male houseflies by ovary implants or 20-hydroxyecdysone☆

Abstract Implanting ovaries or injecting 20-hydroxyecdysone into male houseflies induced sex pheromone production, including (Z)-9-tricosene (muscalure), 9,10-epoxytricosane and (Z)-14-tricosen-10-one, which normally occurs only in vitellogenic females. Control males did not produce detectable amounts of these compounds. Injection of 20-hydroxyecdysone (5 μg/insect per day) for 3 days resulted in the accumulation of 1.81 μg/insect of (Z)-9-tricosene, 0.97 μg/insect of 9,10-epoxytricosane and 0.12 μg/insect (Z)-14-tricosen-10-one. Multiple injections of 20-hydroxyecdysone at doses as low as 50 ng resulted in the accumulation of 23:1, C23 epoxide and C23 ketone; shifted the distribution of label within the alkenes from 27:1 to 23:1 and decreased the amount of label in the hydrocarbon fractions as alkenes. Structures of the C23 alkene and epoxide produced by the males were verified by gas chromatography-mass spectrometry. Radioactivity from [1-14C] acetate was incorporated into the C23 alkene, epoxide and ketone in male insects after ovaries were implanted or they were injected with 20-hydroxyecdysone. Synthesis of the C23 pheromone components decreased rapidly within several days after the administration of 20-hydroxyecdysone ceased, indicating that the enzymes involved in sex pheromone production were not permanently induced by hormone treatment. Ecdysone was also effective in initianing pheromone production in males, whereas inokosterone and cholesterol were not effective. Data presented demonstrate that male houseflies possess the metabolic capability to produce the sex pheromone components, and this suggests that 20-hydroxyecdysone alters the production of cuticular hydrocarbons such that the C23 sex pheromone components become major products.