Substrate vibrations during courtship in three Drosophila species

Abstract

While a plethora of studies have focused on the role of visual, chemical and near-field airborne signals in courtship of Drosophila fruit flies, the existence of substrate-borne vibrational signals has been almost completely overlooked. Here we describe substrate vibrations generated during courtship in three species of the D. melanogaster group, from the allegedly mute species D. suzukii, its sister species D. biarmipes, and from D. melanogaster. In all species, we recorded several types of substrate vibrations which were generated by locomotion, abdominal vibrations and most likely through the activity of thoracic wing muscles. In D. melanogaster and D. suzukii, all substrate vibrations described in intact males were also recorded in males with amputated wings. Evidence suggests that vibrational signalling may be widespread among Drosophila species, and fruit flies may provide an ideal model to study various aspects of this widespread form of animal communication.

Figure 1. Behaviours accompanying emission of substrate vibrations in the three Drosophila species (D. suzukii, D. biarmipes and D. melanogaster).

Coloured dots (red, blue and yellow) indicate different species. During chasing, males and females alternate phases of running with temporary stops during which (a) in D. melanogaster males vibrate one wing and emit pulse and sine songs, in D. suzukii males stand with wings semi-open, whereas in D. biarmipes males flutter their wings. During the phase of running, males may follow the females either from the back (D. melanogaster, D. biarmipes) (b), along the side (D. biarmipes) (c) or circle 45-90° around (D. biarmipes) or intercept (D. suzukii) them while extending either one or both wings (d, e). Toot emission in D. suzukii was always accompanied by wing extension and fast forward wing vibration (d), whereas in D. biarmipes it was accompanied by wing fluttering (a, b, c). For detailed information about vibrational signals emitted during these behavioural stages see Table 1.

Figure 2. Oscillograms of abdominal quivering and wing ticking in three Drosophila species.

a, b: abdominal quivering in D. suzukii. b shows accelerated quivering before emission of a "toot". c: abdominal quivering in D. biarmipes. d: wing ticking in D. biarmipes. e: abdominal quivering in D. melanogaster.

Figure 3. Oscillograms (above) and spectrograms (below) of vibrational components of (a) "toot" in D. suzukii, (b) "toot" in D. biarmipes, (c) sine song in D. biarmipes, (d) a sequence recorded in D. melanogaster which includes abdominal quivering, sine and pulse song.