Harmonic convergence coordinates swarm mating by enhancing mate detection in the malaria mosquito Anopheles gambiae

The mosquito Anopheles gambiae is a major African malaria vector, transmitting parasites responsible for significant mortality and disease burden. Although flight acoustics are essential to mosquito mating and present promising alternatives to insecticide-based vector control strategies, there is limited data on mosquito flight tones during swarming. Here, for the first time, we present detailed analyses of free-flying male and female An. gambiae flight tones and their harmonization (harmonic convergence) over a complete swarm sequence. Audio analysis of single-sex swarms showed synchronized elevation of male and female flight tones during swarming. Analysis of mixed-sex swarms revealed additional 50 Hz increases in male and female flight tones due to mating activity. Furthermore, harmonic differences between male and female swarm tones in mixed-sex swarms and in single-sex male swarms with artificial female swarm audio playback indicate that frequency differences of approximately 50 Hz or less at the male second and female third harmonics (M2:F3) are maintained both before and during mating interactions. This harmonization likely coordinates male scramble competition by maintaining ideal acoustic recognition within mating pairs while acoustically masking phonotactic responses of nearby swarming males to mating females. These findings advance our knowledge of mosquito swarm acoustics and provide vital information for reproductive control strategies.

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

The mosquito Anopheles gambiae is a major African malaria vector, transmitting parasites responsible for significant mortality and disease burden. Malaria declines have stagnated recently due to widespread insecticide resistance among vector populations. Flight acoustics are essential to mosquito mating biology and represent promising alternative targets for mosquito control. However, mosquito swarm acoustics data are limited. Here, for the first time, we present detailed analyses of free-flying male and female An. gambiae flight tones and their harmonization (harmonic convergence) over a complete swarm sequence. Audio analysis of single-sex swarms showed elevated male or female flight tone frequencies and amplitudes during swarming flight with gradual declines to pre-swarm levels over an approximately 35-min period. Analysis of mixed-sex swarms revealed additional increases in flight tone frequencies and amplitudes due to mating activity. Data from mixed-sex swarms suggest harmonic convergence during swarming enhances the efficiency of female detection by synchronizing male and female baseline swarm tones. Further, data from experiments using female swarm tone playbacks to males indicate that harmonic convergence during mating interactions coordinates male scramble competition by acoustically masking mating couple flight tones. These findings advance our knowledge of mosquito swarm acoustics, providing vital information for reproductive control strategies.

Experimental size- and sex-specific predation on dung flies by amphibian and arthropod predators

Because predator-prey interactions in nature are multifarious, linking phenomenological predation rates to underlying behavioral or ecological mechanisms is challenging. Size- and sex-specific predation has been implicated as a major selective force keeping animals small, directing the evolution of body size and sexual size dimorphism. We experimentally assessed predation by 4 amphibian and 3 arthropod species (bug, fly, spider) on 3 species of dung flies with similar ecology but contrasting body sizes, sexual size dimorphism, and coloration. Predators were offered a size range of male and/or female individuals of one prey species. As expected based on optimal foraging theory, some anurans (Bufo bufo) preferred larger prey individuals, others (Bombina variagata, Rana esculenta) showed no preference. Small juvenile Rana temporaria metamorphs preferred small prey, as did all arthropod predators, a pattern that may be explained by gape limitation or larger prey escaping better. Presumably more mobile males were not preyed upon more frequently or faster than cryptic females, even when conspicuously colored. Contrary to expectation, predation rates on flies in mixed groups facilitating mating activity were not higher, nor was predation generally sex-specific, hence contributing little to sexual dimorphism. We conclude that the size-selectivity of predators, and hence the viability selection pattern exerted on their prey, depends foremost on the relative body sizes of the two in a continuous fashion, in addition to any specific prey defense mechanisms. Therefore, the mechanistic study of predation requires integration of both the predator and prey perspectives, and phenomenological field studies of predation remain indispensable.

Biostatistics of fall armyworm Spodoptera frugiperda in maize plants in Bogor, West Java, Indonesia

Russianzi W, Anwar R, Triwidodo H. 2021. Biostatistics of fall armyworm Spodoptera frugiperda in maize plants in Bogor, West Java, Indonesia. Biodiversitas 22: 3463-3469. Fall Armyworm (FAW) Spodoptera frugiperda (J.E. Smith) is an invasive species that has become important pest of maize in Indonesia since 2019. This research was aimed to study the biology and demographic statistics of FAW in maize at Bogor. Daily observations of 132 FAW individuals from egg to death were carried out as the basis for compiling biology and life table. The demographic statistics of FAW were calculated using the Jackknife approach from the basic life table data. ImagoFAW actives at night. Mating activity occurs between 06.00 pm – 04.00 am, while egg-laying activity occurs between 06.00 pm-10.00 pm. Most hatching occurs between 00.00 am - 02.00 am. FAW has 6 larvae instars and there is no difference in stage between larvae that develop into male and female, which is around 15 days. The male pupae stage was longer than the female pupae, 8.78 ± 0.12 days and 7.81 ± 0.15 days. Male and female imagoes have the same life cycle, which is about 10 days. The life cycle of FAW was 32.26 ± 0.41 days, with a preoviposition period of 2.56 ± 0.45 days. Fecundity of FAW reaches 1012.62 ± 99.12 eggs per female imago. The population of FAW in Bogor has an intrinsic growth rate of 0.154 ± 0.001 individuals/day, with gross reproduction rate of 0.154 ± 0.001 individuals per generation, and net reproduction rate of 104.781 ± 0.155 individuals per imago per generation and a generation time of 30.114 ± 0.002 days.

PRELIMINARY OBSERVATIONS ON GESTATION LENGTH, AGE AT FIRST CALVING AND BIRTH WEIGHT OF MUTURU CATTLE

The gestation length, age at first calving and birth weight of muturu cattle were studied in a small herd of Muturu hiefers maintained at the Research Farm. The animals were grazed twice daily from 0830hr to 1200 hr and 1430 hr to 1800 hr either in open natural grassland mixture of guinea grass (Panicum maximum) and giant star grass. (Cynodon dactylon). During the dry season, all animals received nutritional supplementation consisting of a mixture of brewer’s spent grain and palm kernel cake in a ratio of 3:1. When the heifers were between the age of 16 and 18 months, a mature, fertile Muturu bull was introduced into the herd and the mating activity of the animals was closely monitored daily. No attempt was made to limit the number of services which a heifer on heat received from the bull. Results showed that gestation length average 280.0 ± 2.34 days, mean age of first calving was 29.39 ± 1.5 months and mean birth weight was 11.3 ± 0.68 kg. There were no significant differences (P > 0.05) in the gestation length and birth weight of male and female calves.

INTERCROPPING TO IMPROVE EGG FERTILISATION RATES

In assessing the productivity of the parent flock, one of the most important indicators is the productivity of brood males. For the productive use of brood males, the interspiking method is used. Interspiking is the exchange of 25–30% of males between sections of the house of the same flock, which produces a similar response to increased mating activity as in normal stocking. The effect lasts for 6-8 weeks. The advantage of interspiking is that the males that are swapped are already trained to mate, have the same mass and maturity as the bulk of the males in the house, which significantly increases their chances of success. During the research period, two groups of birds of the parent flock of the Cobb-500 cross were formed using the analog pair method. In the first group, normal mating was used. And in the second group, the interspiking method was used at the age of 36 weeks, in which 25% of the males from the total population were exchanged between poultry houses. The conditions for keeping and feeding the parent flock were the same. Live weight indicators in the second group slightly exceed those of the first group. Thus, the live weight of females after entering the parent herd workshop in the first group was 2194 g, and males - 2793 g, in the second group - 2240 and 2997 g, respectively. At the age of 36 weeks, the live weight of chickens in the second group was higher by 1.8% (3420 g), cockerels - by 0.8%, and amounted to 4012 g. Fertility of eggs in group II is higher by 1.2% (84.9%) than in the first (83.7%), hatchability in group II slightly exceeds this indicator by 0.5% than in group I and amounted to 87, 2 and 86.7%, respectively. The hatching of day-old chickens in group I was 72.6%, in group II it increased by 1.4% and amounted to 74%. Safety in both groups was at a high level and amounted to 92.9 and 93.2%. The gross collection of eggs in group I amounted to 2087.83 thousand pieces, in group II - 2272.34 thousand pieces.