Aubrey Manning

The control of sexual receptivity in female Drosophila

Abstract 1. 1. This paper describes various experiments on the integration of reproductive physiology and behaviour in female Drosophila melanogaster and D. simulans. 2. 2. The sexual behaviour of females is ascribed to two distinct processes. One determines the state of receptivity, i.e. whether a female is ‘accessible’ to stimulation from the courtship of a male, the other summates the various stimuli from courtship and eventually leads to the female accepting a male. 3. 3. Females are unreceptive to males on the day of eclosion (day 0) about 25 per cent are receptive on day 1, the rest by day 2. More precise tests place the transition period between 24 and 40 hr from eclosion. In any individual the change is a sudden one; females are either fully receptive or fully unreceptive. Accordingly this change is called ‘switch-on’. 4. 4. The corpus allatum and ovaries show a growth cycle parallel to that of receptivity. Evidence is presented that increase in juvenile hormone titre is responsible for the ‘switch-on’ of receptivity. 5. 5. Virgin females remain receptive for many days, but an increasing proportion become unreceptive after the first week of adult life. ‘Switch-off’ like ‘switch-on’ is a rapid, all-or-nothing process. Females also become unreceptive immediately after mating and this inhibition of receptivity has two components, (a) an effect of copulation itself, probably mechanical, which wears off after 48 hr, (b) an effect due to the presence of live sperm, which wears off once a female has exhausted the sperm by egg laying, after some 8 to 10 days. 6. 6. Old females which have mated and used up their sperm are more often receptive than virgins of the same age. It is suggested that this is so because their corpora allata are more active and the juvenile hormone concentration is kept up above the critical level for longer. 7. 7. The situation revealed in Drosophila is compared with that found in other insects, particularly with regard to the role of the endocrine system.

The effects of artificial selection for mating speed in Drosophila melanogaster

Abstract 1. 1. This paper describes an experiment in which lines of Drosophila melanogaster were selected for fast and slow mating speed over some 25 generations. 2. 2. After 7 generations selection had produced a divergence in mating speed such that the mean speed of a 50 pair population was about 80 minutes in the slow mating (S) lines but only 3 minutes in the fast (F) lines. Subsequently selection made little progress though there have been wide fluctuations in speed, probably environmentally determined. 3. 3. Hybridizing S- and F- lines produces an F1 with intermediate mating speed. Other tests show that the behaviour of both sexes has been altered in a complementary fashion. 4. 4. As measured in an open arena, the general activity of S- line flies is much greater than that of the F- lines and unselected controls resemble the S- lines in this respect. Measurements of the sexual behaviour of males show that the F-Lines and controls have a higher intensity courtship than the S- line males. 5. 5. The most conspicuous effects of selection are to raise the reaction thresholds of sexual behaviour in the S- lines and of general activity in the F- lines. To situations involving a mixture of both sexual and activity stimuli, the S- lines respond with prolonged activity but the F-lines show scarcely any and begin courtship immediately. Controls show a brief burst of activity but rapidly change over to courtship. 6. 6. Natural selection will normally lead to the levels of activity and sexual behaviour being positively correlated and at an optimum which does not result in over-responsiveness in either direction. Artificial selection has led to a separation of the two systems and no concept of a “vigour” which inevitably affects all behavioural levels is adequate. 7. 7. There are no signs of general metabolic changes to the selected lines and it is probably that the accumulated genes affect thresholds in the nervous system.

Antennae and Sexual Receptivity in Drosophila melanogaster Females

For the female to be normally responsive to the display of wing vibrations by males, the arista and funiculus of the females antenna must be intact and able to move freely. The arista probably acts as a sail, twisting the funiculus and thus stimulating units of Johnstons organ at its base.

The sexual isolation between Drosophila melanogaster and Drosophila simulans

1. 1. Some of the stimuli involved in the sexual isolation between D. melanogaster and D. simulans have been analysed. 2. 2. Females of both species show a slow rise in receptiveness to their own males which reaches a peak at 3 days of age and thereafter falls slowly. Foreign males are more successful with young (1-day-old) females than mature ones. 3. 3. Males court young foreign females better than mature ones, but removing their fore-tarsi prevents their discriminating against the latter to a marked extent. 4. 4. Antennaless melanogaster males also show some reduction in isolation, but this is not seen with simulans, whose males are more affected by sensory deprivation. 5. 5. The behaviour of hybrid flies is briefly discussed.

Selection for mating speed in Drosophila melanogaster based on the behaviour of one sex

1. 1. The experiment described was an attempt to change the mating speed of Drosophila by selection upon one sex only. Lines in which the males were selected for fast mating showed no response after 20 generations, nor did slow mating female selected lines. Both male lines selected for slow mating responded, the most extreme having a mean mating speed of some 40 minutes compared with 4 minutes for controls. 2. 2. In early stages of selection the mating speed of females from these lines was unaffected. Later they also showed some reduction in mating speed. 3. 3. Both sexes were less active in an ‘open field’ test than control flies, and males had reduced courtship intensity. 4. 4. The behavioural changes are discussed and compared with a previous pair-selection experiment. Genes which are sex-limited in their expression may be involved, but most of the changes can be ascribed to the differential effects of lowered activity upon the two sexes.

Some aspects of the efferent control of walking in three cockroach species

Abstract We have studied the efferent commands to muscles during walking in three widely different species of cockroach and find no significant differences between them in the patterns of motor output. Several different patterns can be employed by the same species to get the same stepping rate, particularly at low speeds. As stepping rate increases, the following general trends can be seen. (a) There is recruitment of additional units, first of slow axons and then of fast. (b) The reciprocal relationship between antagonist muscles becomes less obvious, particularly with respect to the slow axon system. (c) At extremely high stepping rates the number of fast potentials becomes greatly reduced.

Neonatal androgen and sexual behavior in female house mice

Abstract A series of experiments investigated masculine response potential in normal BDF1 female mice and in females who had been injected with 100 μg of testosterone propionate on the day of birth. Sixty-five percent of BDF1 females mounted females in estrus; ovariectomy lowered this response potential while injections of TP in adulthood raised masculine RP in both ovariectomized and intact females. Neonatally androgenized females with or without TP in adulthood exhibited the full range of masculine responses including the ejaculatory reflex. Comparisons of elements of sexual behavior are made between neonatally androgenized females and normal males.

Postcastration retention of sexual behaviour in the male bdf1 mouse. The role of experience.

Male BDF1 mice (the F1 progeny of a cross between C57BL/6 females with DBA/2 males) show a remarkable retention of sexual behaviour following castration. Two experiments were conducted to describe in detail the postcastration copulatory performance of the BDF1 male mouse and to determine to what extent such performance is influenced by experience prior to castration. Experiment I found that castration leads to significant increases in the number of mounts and intromissions needed to reach ejaculation, and to a significant increase in ejaculation latency. Experiment II found that although precastrational sexual experience is not essential for the performance of the ejaculatory reflex after castration, it does influence the frequency of its occurrence. Furthermore, type of post-weaning social experience influenced the display of ejaculatory behaviour by non-experienced castrates, as those with female social experience were superior to those with social experience with males or no social experience. The interactions of experience, hormones and genotype in the control of sexual behaviour in the BDF1 male are discussed.

Courtship song and mating speed in hybrids betweenDrosophila melanogaster andDrosophila simulans

Courtship song and mating speed of hybrids betweenDrosophila melanogaster andD. simulans were investigated. The courtship song of hybrid males is identical to that ofD. simulans, suggesting that X chromosome determination, known from the cross betweenD. pseudoobscura andD. persimilis, is also possible here. Wingbeat frequency of hybrids is intermediate between that of the two parents, demonstrating that courtship song and wingbeat frequency are inherited independently of each other. In mating tests, hybrid males court and are accepted byD. simulans females more than hybrid females (presumably because their song is more “acceptable” to the former).D. melanogaster females reject hybrid males. Hybrid females acceptD. melanogaster males readily, hybrids less readily, andD. simulans least.

The persistence of courtship stimulation in Drosophila melanogaster

Five minutes of pre-stimulation with simulated courting sound before mixing with males, leads to enhanced receptivity of female D. melanogaster. The effects of pre-stimulation fade and can no longer be detected after 5 min. One minute of sound was ineffective and so were sounds with pulse intervals one-half and twice the natural interval. It is concluded that the female not only can summate stimuli over time but that the effects of stimuli perseverate for some minutes in the absence of continuing stimulation.