Laurie Tompkins

Conditioned courtship inDrosophila and its mediation by association of chemical cues

AlthoughDrosophila melanogaster males usually court virgin females vigorously, a male will perform very little courtship in response to a virgin female if he has previously been in the presence of a fertilized female. The normal courtship response is restored after approximately 3 h [Siegle, R. W., and Hall, J. C. (1979).Proc. Natl. Acad. Sci. USA76:3430–3434]. Experiments designed to account for this phenomenon exclude the possibilities that the visible “rejection” behaviors performed by the fertilized female in response, to the male are either a necessary or a sufficient basis for the transitory decrement in courtship. A role for other visual, cues is also ruled out. However, mutant males with olfactory defects do court virgins after experiences with fertilized females. Also, males exposed to extracts from fertilized females while in the presence of a male or virgin female fly thereafter perform very little courtship with virgin females. Finally, we describe a new mutant strain whose males court and mate with wild-type, virgin females normally; but after such a mating, the wild-type female is readily courted by a wild-type male, and that male subsequently exhibits vigorous courtship of other females. Since both virgin and fertilized females can stimulate males to court them, these observations fuggest the following hypothesis. After fertilization by a wild-type male, a female becomes a source of an aversive chemical cue which is sensed by a courting male [cf. Tompkins, L., and Hall, J. C. (1981).J. Insect Physiol.27:17–21]. The courting male associates that substance with the courtship-stimulating cues emanating from females which he subsequently encounters, and he therefore learns to avoid courting these females.

Male Esterase 6 Catalyzes the Synthesis of a Sex Pheromone in Drosophila melanogaster Females

Esterase 6, a component of the seminal fluid of Drosophila melanogaster males, hydrolyzes cis-vaccenyl acetate, a lipid made only by males, to cis-vaccenyl alcohol. This reaction occurs in the female reproductive tract and is virtually complete within 6 hours after copulation. Both the alcohol and the acetate decrease the number of matings among pairs of virgin flies in which the female is treated topically with these substances. Although females tested 10 minutes after copulation elicit less courtship than virgin females, females tested 6 hours after copulation stimulate even less courtship if they received active esterase 6 in the seminal fluid of their respective mates. Either the alcohol or a derivative appears to be an antiaphrodisiac that decreases courtship elicited by inseminated females and thus reduces the probability of further mating. Thus the activity of the pheromone depends on a final reaction which occurs in the female, using both substrate and enzyme provided by the male.

Courtship of young males is ubiquitous in Drosophila melanogaster

In eightDrosophila melanogaster stocks, males which are only a few hours old stimulate courtship which is qualitatively and, in many of the stocks, quantitatively indistinguishable from the courtship elicited by virgin females. Although the sex appeal of young males and the extent to which it declines as the males become sexually mature vary somewhat from stock to stock, homosexual courtship appears to be characteristic of the species.

Identification of stimuli that mediate experience-dependent modification of homosexual courtship inDrosophila melanogaster

A naive, sexually matureD. melanogaster male tested with a young, sexually immature male will perform vigorous courtship, but the mature male will perform much less courtship if he is subsequently tested with a second young male. This phenomenon is called experience-dependent courtship modification (EDCM). We have shown that exposure to either or both of the two courtship-stimulating pheromones that immature males synthesize is sufficient to induce EDCM.

Early visual experience affects mate choice of Drosophila melanogaster

Experience-dependent development of the nervous system is now recognized among insects, in which its functional significance can be studied readily. Depriving normal Drosophila melanogaster of visual stimulation during their first few days of adult life (‘dar-rearing’) had a dramatic effect on mate choice. Dark-reared males were at a disadvantage when they competed with males reared in alternating light-dark cycles (‘light-rearing’) for light-reared females. Dark-rearing also affected reproductive success when deprived males or females were paired with light-reared flies of the opposite sex; the pairs that had the same rearing histories had higher copulation frequencies and lower copulation latencies than those that did not. Dark-reared males tested with light-reared females under dim red light to reduce the use of visual cues were less successful at copulating than light-reared control males. The effects of dark-rearing thus may not be limited to the visual system.

The ontogeny of sex appeal in Drosophila melanogaster males

Drosophila melanogaster males are sexually attractive when they are young, but they elicit very little courtship when they are 2–3 days old. We have shown that males from a Canton-S stock start to lose their sex appeal between 3 and 4 h after they eclose from their pupal cases because they have begun to synthesizecis-vaccenyl acetate, an inhibitory pheromone, by that time. Later, when the young males are between 20 and 24 h old, mature males perform even less courtship because the young males have begun to produce less of a courtship-stimulating pheromone.

Drosophila Males Produce a Pheromone which Inhibits Courtship

Abstract Normal Drosophila males produce a volatile pheromone which inhibits courtship. This chemical cue is not identical to the pheromone made by mated female flies, which also inhibits male sexual behavior. Mutant olfC males, which fail to respond to several organic compounds, are not inhibited by the pheromone made by males; hence, unlike normal sexually mature males, olfC males court each other vigorously.

Identification of acoustic stimuli that mediate sexual behavior inDrosophila busckii (Diptera: Drosophilidae)

We have shown that D. busckiimales and females, unlike other drosophilids that have been analyzed in this regard, court and copulate as well in relatively dim red light as they do in bright white light. We have also shown that males and females of this species flutter their wings during courtship and that wing fluttering in both sexes is associated with acoustic stimuli. Wingless males perform vigorous courtship but are incapable of mating, suggesting that females must perceive male song to be receptive to copulation. When they are tested with normal males, wingless females stimulate vigorous courtship, but their copulation frequencies are significantly lower than winged females. This observation suggests that perception of the females song by either or both sexes facilitates mating.

Olfactory adaptation in Drosophila larvae.

To accommodate both high sensitivity as well as the ability to respond to a broad range of stimulus concentrations, an organism must possess some means of modulating the gain of its sensory systems. This phenomenon is known as adaptation. Here, we demonstrate that Drosophila larvae can adapt to three odorants in a behavioral paradigm. Larval olfactory adaptation is concentration- and dose-dependent. Olfactory and visual adaptation in Drosophila melanogaster adults is dependent on the transient receptor potential (trp) calcium channel. Recovery from olfactory adaptation, which is TRP-dependent in adults, is shown to be unaffected by a loss-of-function trp mutation in larvae. Moreover, the TRP gene product is not expressed in the larval olfactory organs. These observations suggest a role for trp in mediating sensory function that is conserved between sensory modalities in adults but is not conserved between developmental stages.

Behavioral and pheromonal phenotypes associated with expression of loss-of-function mutations in the sex-lethal gene of Drosophila melanogaster.

We have shown that female-specific functions of the sex determination gene Sex-lethal (Sxl) regulate sexual behavior and synthesis of the three major sex pheromones that have been identified in normal, sexually mature Drosophilia melanogaster males and virgin females. Diplo-X flies, heterozygous in trans for two partial loss-of-function Sxl mutations, elicit less courtship than normal females and produce large quantities of the inhibitory pheromones that normal males synthesize. In addition, the mutant flies fail to synthesize the female-predominant aphrodisiac pheromone or make very small quantities of this compound.