Correlations of life-span variation parameters in 128 successive generations of Drosophila melanogaster with changes in atmospheric pressure and geomagnetic activity

A Link between Atmospheric Pressure and Fertility of Drosophila Laboratory Strains

Simple Summary

The researchers usually keep insects under study under thoroughly controlled conditions. However, sometimes they encounter a situation where the data they obtained under such conditions demonstrate an obvious side effect of some unaccounted factor. Here we provide evidence that changes in atmospheric pressure could be responsible for some such cases.

Abstract

Standardization of conditions under which insects are kept is of great importance when studying their physiology and researchers do their best to maintain it. Nevertheless, sometimes an obvious side effect of some unaccounted factor affecting insects’ reproduction can be revealed even under thoroughly controlled laboratory conditions. We faced such a phenomenon when studying the fertility level in two wild type Drosophila melanogaster strains. For fertility analysis, 50 newly emerged females and 50 males of each strain under study were transferred to fresh medium daily within 10 days. We found out that fertility of both strains was stable on days 2–10 after the oviposition onset in one experiment, while in another one it was significantly decreased during days 5–10. When compared to publicly available meteorological data, these changes in the fertility level demonstrated a strong association with one weather factor: barometric pressure. Thus, we conclude that changes in atmospheric pressure can be considered a factor affecting insects reproduction and discuss a possible mechanism of their influence on fertility.

Low Barometric Pressure Enhances Tethered-Flight Performance and Reproductive of the Oriental Armyworm, Mythimna separata (Lepidoptera: Noctuidae)

Barometric pressure is an important factor influencing several insect traits. Most studies have been conducted on the behavior of insects in relation to rapid and slight changes in pressure magnitudes or short-term pressure trends, but there is little information on the effect of long-term and large pressure variations on insect traits. Here, we assessed the effects of static low barometric pressure on the tethered flight, lifespan and reproductive performance of Mythimna separata (Walker), a long-distance migratory insect, using an apparatus simulating low barometric pressure at altitudes of 500 m above sea level. We found that both the flight distance and flight duration of M. separata moths were significantly longer under low barometric pressure conditions. Exposure to low barometric pressure conditions for 24 and 48 h significantly shortened the lifespan of female moths but had no influence on male moths. The ovaries of female moths developed earlier, and the preoviposition and oviposition periods were significantly shortened under low atmospheric pressure. Moreover, low atmospheric pressure reduced the respiration rate of female moths. However, there was an increase in the respiration rate of female moths after being returned to standard barometric pressure conditions. Our results show that the behavior and physiological traits of insects are affected by the low-pressure environment during migration. The low barometric pressure conditions at high altitudes is one of important factors accelerating reproductive behavior of M. separata after migration.

Extremely-low frequency magnetic field exposure for simulating geomagnetic pulsations in Alexandrium pacificum and Gymnodinium catenatum cultures

Growth and chain formation in cultures of the chain-forming dinoflagellates Alexandrium pacificum and Gymnodinium catenatum were previously found to be susceptible to space weather variables. A clock drive was used to deliver a frequency of 0.5 Hz and central amplitude of 7 µT in order to perform in vitro simulation of geomagnetic pulsations (composed of extremely low-frequency magnetic fields, ELFMF) which occur during high geomagnetic activity (GMA) periods. Short-term exposure (hours) to this ELFMF increased relative cell growth around 10 nT of naturally occurring GMA. Relative growth outside these intervals gradually approached 0% or was negative for G. catenatum. Differential survival to a subsequent shock was inversely related to growth, and minimal survival coincided with the same 10 nT interval. Relative growth and survival displayed opposite hormetic curves towards GMA: inverted U-shaped for growth, and J-shaped for survival. After exposure to this ELFMF, positive phototaxis response was not lost, but the percentage of cells swimming was slightly reduced. Long-term exposure (days) increased relative growth in A. pacificum but reduced in G. catenatum when low GMA was taking place. These alterations in growth were both associated with a reduction in the cellular pool of mycosporine-like amino acids (MAAs). MAAs that are more susceptible to oxidation were more reduced than those resistant, highlighting that an ELFMF can act by increasing cellular oxidative stress status. The higher susceptibility of G. catenatum found is in compliance with the previous association of its natural populations at the western Iberia coast with periods of solar activity minima and GMA minima.

Impact of light quality and space weather in Alexandrium catenella (Dinophyceae) cultures

The chain-forming dinoflagellate Alexandrium catenella was grown with LED or fluorescent light. With LED light, the pool of mycosporine-like amino acids (MAAs) with strong antioxidant properties, such as mycosporine-glycine and palythene, was reduced in comparison to fluorescent light. The conjugated MAAs M-320 and M-335/360 presented similar stability to light and oxidation than their respective more sensitive moiety: mycosporine-glycine and palythene, respectively. A. catenella was exposed to extracellular hydrogen peroxide under LED or fluorescent light. It triggered an increase in chain formation at a final concentration of 98 and 196 µM, typical of an inverted U-shaped hormetic response, and reduced cell survival above 294 µM. LED light, minimizing UV-stress photoprotection, was chosen to render cells more susceptible to space weather. Cultures were exposed to 490 µM H₂O₂ multiple times between November 2017 and February 2018, close to the minimum of solar cycle 24. Cell survival was dependent on temperature, geomagnetic activity, solar X-rays and neutron flux. Geomagnetic activity originated an inverted U-shaped survival curve and X-ray flux a J-shaped survival curve, this second type of hormetic response being more rarely found. The percentage of cells in chains increased moderately with temperature, and more significantly with solar X-ray flux. Chain formation reduced along culture growth, but these observations were dependent on the occurring X-ray flux.

Solar activity during gestation does not affect human lifespan: evidence from national data

Human lifespan has been reported to relate to solar activity during prenatal development. The likely key mechanism behind this association is increased mutagenic ultraviolet (UVB) radiation during high solar activity that damages DNA. Here, the aim was to replicate the findings of those previous few studies that have suggested a reduced lifespan of individuals born during the years of high solar activity, measured as the sunspot numbers. We used data on annual cohort life expectancy at birth of both women and men born between 1751 and 1915, obtained from ten nations located mainly in Europe. These data, however, provided no evidence that human life expectancy at birth was related to solar activity during gestation among the countries studied.

Date of eclosion modulates longevity: insights across dietary-restriction gradients and female reproduction in the mexfly Anastrepha ludens

We use unique experimental data on daily reproduction and survival of individual fruit flies from eight cohorts eclosed at different dates in 2004 and 2005 who were treated with varying proportions of sugar and yeast and subject to different caloric restrictions (CR). We investigate the relationship between eclosion date and longevity across diets and reproduction in Anastrepha ludens. We show that eclosion date can be associated with uncontrolled external or internal factor(s) which can modulate longevity of males and females independently of diet and reproduction to the extent similar to the effect of diet on longevity. The effect of diet manipulation on longevity is sensitive to date of eclosion with the role of CR in life extension ranging from beneficial to harmful. Interaction of date of eclosion with compositional changes of sugar and yeast but not with CR is responsible for life extension. Highly protein-enriched diets reliably maximize reproduction but not life span. Decreased longevity of flies treated with high-protein diets may be associated with harmful consequences of protein ingestion but is unlikely a result of high reproduction rates. We present evidence for the presence of two frailty-sensitive weakly interacting mechanisms of longevity in female flies associated with differences in predisposed fitness.