Flight tone characterisation of the South American malaria vector Anopheles darlingi (Diptera: Culicidae)

Abstract

BACKGROUND Flight tones play important roles in mosquito reproduction. Several mosquito species utilise flight tones for mate localisation and attraction. Typically, the female wingbeat frequency (WBF) is lower than males, and stereotypic acoustic behaviors are instrumental for successful copulation. Mosquito WBFs are usually an important species characteristic, with female flight tones used as male attractants in surveillance traps for species identification. Anopheles darlingi is an important Latin American malaria vector, but we know little about its mating behaviors. OBJECTIVES We characterised An. darlingi WBFs and examined male acoustic responses to immobilised females. METHODS Tethered and free flying male and female An. darlingi were recorded individually to determine their WBF distributions. Male-female acoustic interactions were analysed using tethered females and free flying males. FINDINGS Contrary to most mosquito species, An. darlingi females are smaller than males. However, the male’s WBF is ~1.5 times higher than the females, a common ratio in species with larger females. When in proximity to a female, males displayed rapid frequency modulations that decreased upon genitalia engagement. Tethered females also modulated their frequency upon male approach, being distinct if the interaction ended in copulation or only contact. MAIN CONCLUSIONS This is the first report of An. darlingi flight acoustics, showing that its precopulatory acoustics are similar to other mosquitoes despite the uncommon male:female size ratio, suggesting that WBF ratios are common communication strategies rather than a physical constraint imposed by size.

Synchronized swarming: Harmonic convergence and acoustic mating dynamics in the malaria mosquito Anopheles gambiae

“…Fewer studies have examined mating activity in swarms 6,86,87 or performed audio recordings of swarming individuals in free flight 10,35,36,39,47,49,62,66,85 , and none prior to the present study have done so simultaneously or over an entire swarm sequence. Overall, the findings presented in this study, along with other recent mosquito acoustics work 10,39,47,48,66 , underscores the importance of examining mosquito flight tones and mating activity in free-flying individuals, ideally during their swarming period.…”

“…albimanus 47 , An. darlingi 48 , and Culex quinquefasciatus 10,66 , and increases in flight speed in response to artificial tone playback were observed in another study in An. gambiae males and Ae.…”

“…S4). To be considered a mating interaction tone, male tones had to display each of the following three criteria: 1) a ≥ 25 Hz increase in frequency relative to background swarming male frequencies; 2) a ≥10 dB increase in amplitude relative to background male tones; and 3) rapid frequency modulation, a distinctive behavioral feature of male mosquito mating interaction flight 10,39,40,47,48,66 . Harmonic overtones and flight tone harmonic differences were estimated based on sampling from fundamental flight tone frequencies as previously described 67 .…”

“…flight acoustics . Numerous studies have reported mosquito flight tones from single, pairs, or groups of tethered adults 26,[28][29][30][31]45,79,[82][83][84] , free-flying adults 24,32,[35][36][37]49,66,85 , or a combination of tethered and free-flying adults 10,21,25,[39][40][41][42]47,48,62,67,80 . Fewer studies have examined mating activity in swarms 6,86,87 or performed audio recordings of swarming individuals in free flight 10,35,36,39,47,49,62,66,85 , and none prior to the present study have done so simultaneously or over an entire swarm sequence.…”

“…Despite these discoveries, much of the previous work on harmonic convergence has examined tethered, rather than free-flying males and females. Although tethered flight analysis offers an experimentally tractable means of dissecting the mechanics and biological significance of this behavior, tethering restricts natural flight patterns and alters flight tones 10,21,[44][45][46][47][48] . Analysis on flight tone acoustics and harmonic convergence over the course of a complete swarm sequence would therefore provide valuable insights and context for these phenomena, as studies examining convergence in free-flight are limited 10,39,47,49 .…”