Courtship suppression in Drosophila melanogaster: The role of mating failure

Abstract

Drosophila melanogaster is a popular model organism in the study of memory due to a wide arsenal of methods used to analyze neuronal activity. The most commonly used tests in research of behavioral plasticity are shock avoidance associated with chemosensory cues and courtship suppression after mating failure. Many authors emphasize the value of courtship suppression as a model of behavior most appropriate to natural conditions. However, researchers often investigate courtship suppression using immobilized and decapitated females as targets of courtship by males, which makes the data obtained from such flies less valuable. In our study, we evaluate courtship suppression towards immature mobile non-receptive females after training with mated or immature females combined with an aversive stimulus (quinine). We have shown that the previously described mechanisms of courtship suppression, as a result of the association of the courtship object with the repellent, as well as due to increased sensitivity to the anti-aphrodisiac cVA after mating failure, are not confirmed when immature mobile females are used. We discuss the reasons for the discrepancies between our results and literature data, define the conditions to be met in the courtship suppression test if the aim is to analyze the natural forms of behavioral plasticity, and present data on the test modifications to approximate conditions to natural ones.

Fig 1. Courtship indices (CI) of naive and trained males towards immature females.

(A) The CIs are shown within the first 5 minutes (5) and the last 5 minutes (60) of one-hour training, conducted in either a clean chamber or a quinine chamber (5Q and 60Q). (B) The CIs are shown in the courtship suppression test conducted in a clean chamber after training in either a clean (-/-) or quinine chamber (Q/-), as well as in the test where quinine was added to the chamber after training in a clean (-/Q) or quinine chamber (Q/Q). (C) Comparisons of the CIs are provided in clean chambers between the first 5 minutes of training (5) and the tests conducted after training in a clean (-/-) or quinine chamber (Q/-), as well as in quinine chambers between the first 5 minutes of training (Q5) and the test conducted after training without quinine (-/Q). Mean values and 95% confidence intervals are shown. The p-values (two-tailed randomization test) are indicated above the respective columns in the comparison, and the number of flies in each group is shown below.

Fig 2. Comparison of courtship suppression and courtship behaviors during training with immature and mated females.

(A) The CIs of males in tests with mated females are shown after training with immature and mated females. The comparison group consists of males placed in a chamber without a female during the training stage (sham). (B) Percentages of behaviors observed within the first 5 minutes during training with immature and mated females are displayed. See legend in Fig 1.

Fig 3. Courtship of males after being reared in a mixed group with females.

CIs in males kept alone or isolated from the mixed group are shown in immediate (A) and 24-hour delayed (B) courtship assays conducted with virgin and mated females. (C) CIs towards virgin females by males kept alone or isolated from the mixed group at different time intervals (0, 1, and 3 hours) before the assay are shown. (D) The time of courtship towards virgin females before copulation in the immediate assay are shown and the proportion and number of males copulated during 300 seconds of observation are provided under the columns. (E) CIs towards virgin and mated females by experienced males trained with mated females 24 hours after isolation from the mixed group are shown. The comparison group consists of experienced males placed in a chamber without a female during the training stage (sham control). See legends in Figs 1 and 2.

Fig 4. Studies of short-term courtship suppression and its mechanisms in various combinations of trainer and tester flies (female if not otherwise indicated).

(A) Combinations described in the literature [9, 12, 13, 17, 43, 45, 47, 48, 53, 54] are illustrated where the trainer and/or tester flies are immobilized. (B) Combinations described in the literature [12, 13, 28, 52] and all other possible combinations are illustrated where both the trainer and tester flies are mobile. A review of the objects, conditions, and conclusions of the mentioned studies can be found in a previous review [49].