Weather Forecasting by Insects: Modified Sexual Behaviour in Response to Atmospheric Pressure Changes

Ana Cristina Pellegrino,Wayne Bezner-Kerr,Cristiane Nardi,José Maurício Simões Bento,Jeremy N Mcneil,Maria Fernanda Gomes Villalba Peñaflor,Christopher G Guglielmo,Claudio R Lazzari

doi:10.1371/journal.pone.0075004

Ana Cristina Pellegrino, Wayne Bezner-Kerr + Show 6 more

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https://doi.org/10.1371/journal.pone.0075004

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Abstract

Prevailing abiotic conditions may positively or negatively impact insects at both the individual and population levels. For example while moderate rainfall and wind velocity may provide conditions that favour development, as well as movement within and between habitats, high winds and heavy rains can significantly decrease life expectancy. There is some evidence that insects adjust their behaviours associated with flight, mating and foraging in response to changes in barometric pressure. We studied changes in different mating behaviours of three taxonomically unrelated insects, the curcurbit beetle, Diabrotica speciosa (Coleoptera), the true armyworm moth, Pseudaletia unipuncta (Lepidoptera) and the potato aphid, Macrosiphum euphorbiae (Hemiptera), when subjected to natural or experimentally manipulated changes in atmospheric pressure. In response to decreasing barometric pressure, male beetles exhibited decreased locomotory activity in a Y-tube olfactometer with female pheromone extracts. However, when placed in close proximity to females, they exhibited reduced courtship sequences and the precopulatory period. Under the same situations, females of the true armyworm and the potato aphid exhibited significantly reduced calling behaviour. Neither the movement of male beetles nor the calling of armyworm females differed between stable and increasing atmospheric pressure conditions. However, in the case of the armyworm there was a significant decrease in the incidence of mating under rising atmospheric conditions, suggesting an effect on male behaviour. When atmospheric pressure rose, very few M. euphorbiae oviparae called. This was similar to the situation observed under decreasing conditions, and consequently very little mating was observed in this species except under stable conditions. All species exhibited behavioural modifications, but there were interspecific differences related to size-related flight ability and the diel periodicity of mating activity. We postulate that the observed behavioral modifications, especially under decreasing barometric pressure would reduce the probability of injury or death under adverse weather conditions.

Highlights

Abiotic factors, such as temperature, photoperiod, wind speed and rainfall, play important roles in determining the geographic distribution and population dynamics of insect species, as well as the diel periodicity of individuals
The locomotory activity of D. speciosa males in the Y-tube olfactometer with female pheromone extracts was affected by barometric pressure (Figure 1A, df = 2, x2 = 13.38, P,0.001), being significantly lower when pressure decreased compared to stable or increasing pressure conditions (Figure 1A, stable vs. decreasing df = 1, x2 = 56.38, P,0.001; increasing vs. decreasing df = 1, x2 = 40.93, P,0.001)
The atmospheric conditions tested in our experiments are well within the range changes in atmospheric pressure that insects would encounter under natural field conditions

Summary

Introduction

Abiotic factors, such as temperature, photoperiod, wind speed and rainfall, play important roles in determining the geographic distribution and population dynamics of insect species, as well as the diel periodicity of individuals. Rainfall is important, with the peak populations of many insect species observed during wet-seasons [1,2], as precipitation directly provides water essential for development and reproduction, [3,4,5], and indirectly through increased food availability [6]. Due to the general small size and fragile nature of insects the heavy rains and strong winds associated with storms are potentially important mortality factors [11,12]. Adaptations allowing individuals to detect imminent changes in weather conditions would be beneficial and a limited number of studies have shown that insects [13], like mammals [14], birds [15], reptiles [16] and fish [17], modify different behaviours [18,19,20,21,22] in response to the rapid drop in atmospheric pressure (.4 mbars) in the hours preceding a storm [23]

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