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Gábor Horváth - One of the best experts on this subject based on the ideXlab platform.
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Polarization Vision of Aquatic Insects
Polarized Light and Polarization Vision in Animal Sciences, 2014Co-Authors: Gábor Horváth, Zoltán CsabaiAbstract:In this chapter we show that primary Aquatic Insects fly predominantly in mid-morning, and/or around noon and/or at nightfall. We describe the different types of their diurnal flight activity rhythm characterised by peaks at low and/or high solar elevations. We present here experimental evidence that the polarization visibility Q(θ) of water surfaces is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation θ for dark waters, while Q(θ) is maximal at dawn and dusk (low solar elevations) for bright waters both under clear and partly cloudy skies. The θ-dependent reflection-polarization patterns, combined with an appropriate air temperature, clearly explain why polarotactic Aquatic Insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. This phenomenon is called the “polarization sundial” of dispersing Aquatic Insects. We also show that non-biting midges (Chironomidae, Diptera) are positively polarotactic and like many other Aquatic Insects, their females are attracted to horizontally polarized light. We present here measured thresholds (i.e., the minimum degrees of linear polarization of reflected light that can elicit positive polarotaxis) of the ventral polarization sensitivity in mayflies, dragonflies and tabanid flies. The mayflies Palingenia longicauda swarm exclusively over the river surface; thus, they need not search for water. It could be assumed that this species is not polarotactic. We show here that also P. longicauda has positive polarotaxis, which, however, can be observed only when the animals are displaced from the water and then released above artificial test surfaces. P. longicauda is the first species in which polarotactic water detection was demonstrated albeit it never leaves the water surface, and thus, a polarotactic water detection seems unnecessary for it. The yellow fever mosquito, Aedes aegypti, has been thought to locate its breeding habitats exclusively by chemical cues. We demonstrate here that horizontally polarized light can also attract ovipositing Ae. aegypti females when they are deprived of chemical cues. Aedes aegypti is the first known water-associated species in which polarotaxis exists, but does not play a dominant role in locating water bodies and can be constrained in the presence of chemical cues. Finally, we deal with the negative polarotaxis in the desert locust, Schistocerca gregaria, the ventral eye region of which detects the horizontally polarized water-reflected light, and thus can navigate towards or away from large water surfaces.
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a polarisation sun dial dictates the optimal time of day for dispersal by flying Aquatic Insects
Freshwater Biology, 2006Co-Authors: Zoltán Csabai, Pál Boda, Balázs Bernáth, György Kriska, Gábor HorváthAbstract:SUMMARY 1. Daily changes in the flight activity of Aquatic Insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of Aquatic Insects and the environmental factors governing it are poorly understood. 2. We found that primary Aquatic Insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid-morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in Aquatic Insects, characterised by peak(s): (i) in mid-morning; (ii) in the evening; (iii) both in mid-morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic. 3. We found experimental evidence that the proportion (%) P(h) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (h) for dark reflectors while P(h) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies. 4. From the temporal coincidence between peaks in the diel flight activity of primary Aquatic Insects and the polarotactic detectability P(h) of water surfaces we conclude that the optimal times of day for Aquatic Insects to disperse are the periods of low and high solar elevations h. The h-dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic Aquatic Insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun-dial’ of dispersing Aquatic Insects.
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A ‘polarisation sun‐dial’ dictates the optimal time of day for dispersal by flying Aquatic Insects
Freshwater Biology, 2006Co-Authors: Zoltán Csabai, Pál Boda, Balázs Bernáth, György Kriska, Gábor HorváthAbstract:SUMMARY 1. Daily changes in the flight activity of Aquatic Insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of Aquatic Insects and the environmental factors governing it are poorly understood. 2. We found that primary Aquatic Insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid-morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in Aquatic Insects, characterised by peak(s): (i) in mid-morning; (ii) in the evening; (iii) both in mid-morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic. 3. We found experimental evidence that the proportion (%) P(h) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (h) for dark reflectors while P(h) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies. 4. From the temporal coincidence between peaks in the diel flight activity of primary Aquatic Insects and the polarotactic detectability P(h) of water surfaces we conclude that the optimal times of day for Aquatic Insects to disperse are the periods of low and high solar elevations h. The h-dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic Aquatic Insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun-dial’ of dispersing Aquatic Insects.
Zoltán Csabai - One of the best experts on this subject based on the ideXlab platform.
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Polarization Vision of Aquatic Insects
Polarized Light and Polarization Vision in Animal Sciences, 2014Co-Authors: Gábor Horváth, Zoltán CsabaiAbstract:In this chapter we show that primary Aquatic Insects fly predominantly in mid-morning, and/or around noon and/or at nightfall. We describe the different types of their diurnal flight activity rhythm characterised by peaks at low and/or high solar elevations. We present here experimental evidence that the polarization visibility Q(θ) of water surfaces is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation θ for dark waters, while Q(θ) is maximal at dawn and dusk (low solar elevations) for bright waters both under clear and partly cloudy skies. The θ-dependent reflection-polarization patterns, combined with an appropriate air temperature, clearly explain why polarotactic Aquatic Insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. This phenomenon is called the “polarization sundial” of dispersing Aquatic Insects. We also show that non-biting midges (Chironomidae, Diptera) are positively polarotactic and like many other Aquatic Insects, their females are attracted to horizontally polarized light. We present here measured thresholds (i.e., the minimum degrees of linear polarization of reflected light that can elicit positive polarotaxis) of the ventral polarization sensitivity in mayflies, dragonflies and tabanid flies. The mayflies Palingenia longicauda swarm exclusively over the river surface; thus, they need not search for water. It could be assumed that this species is not polarotactic. We show here that also P. longicauda has positive polarotaxis, which, however, can be observed only when the animals are displaced from the water and then released above artificial test surfaces. P. longicauda is the first species in which polarotactic water detection was demonstrated albeit it never leaves the water surface, and thus, a polarotactic water detection seems unnecessary for it. The yellow fever mosquito, Aedes aegypti, has been thought to locate its breeding habitats exclusively by chemical cues. We demonstrate here that horizontally polarized light can also attract ovipositing Ae. aegypti females when they are deprived of chemical cues. Aedes aegypti is the first known water-associated species in which polarotaxis exists, but does not play a dominant role in locating water bodies and can be constrained in the presence of chemical cues. Finally, we deal with the negative polarotaxis in the desert locust, Schistocerca gregaria, the ventral eye region of which detects the horizontally polarized water-reflected light, and thus can navigate towards or away from large water surfaces.
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a polarisation sun dial dictates the optimal time of day for dispersal by flying Aquatic Insects
Freshwater Biology, 2006Co-Authors: Zoltán Csabai, Pál Boda, Balázs Bernáth, György Kriska, Gábor HorváthAbstract:SUMMARY 1. Daily changes in the flight activity of Aquatic Insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of Aquatic Insects and the environmental factors governing it are poorly understood. 2. We found that primary Aquatic Insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid-morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in Aquatic Insects, characterised by peak(s): (i) in mid-morning; (ii) in the evening; (iii) both in mid-morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic. 3. We found experimental evidence that the proportion (%) P(h) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (h) for dark reflectors while P(h) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies. 4. From the temporal coincidence between peaks in the diel flight activity of primary Aquatic Insects and the polarotactic detectability P(h) of water surfaces we conclude that the optimal times of day for Aquatic Insects to disperse are the periods of low and high solar elevations h. The h-dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic Aquatic Insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun-dial’ of dispersing Aquatic Insects.
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A ‘polarisation sun‐dial’ dictates the optimal time of day for dispersal by flying Aquatic Insects
Freshwater Biology, 2006Co-Authors: Zoltán Csabai, Pál Boda, Balázs Bernáth, György Kriska, Gábor HorváthAbstract:SUMMARY 1. Daily changes in the flight activity of Aquatic Insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of Aquatic Insects and the environmental factors governing it are poorly understood. 2. We found that primary Aquatic Insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid-morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in Aquatic Insects, characterised by peak(s): (i) in mid-morning; (ii) in the evening; (iii) both in mid-morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic. 3. We found experimental evidence that the proportion (%) P(h) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (h) for dark reflectors while P(h) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies. 4. From the temporal coincidence between peaks in the diel flight activity of primary Aquatic Insects and the polarotactic detectability P(h) of water surfaces we conclude that the optimal times of day for Aquatic Insects to disperse are the periods of low and high solar elevations h. The h-dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic Aquatic Insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun-dial’ of dispersing Aquatic Insects.
Jesper Givskov Sørensen - One of the best experts on this subject based on the ideXlab platform.
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Upper thermal tolerance in Aquatic Insects.
Current opinion in insect science, 2015Co-Authors: Steven L. Chown, Grant A. Duffy, Jesper Givskov SørensenAbstract:•Owing to the characteristics of their contrasting habitats, Aquatic and terrestrial Insects will respond differently to global environmental change.•A synthesis of Aquatic insect thermal tolerance studies identified a weak latitudinal pattern of upper thermal traits.•Average upper thermal tolerances of Aquatic Insects are generally lower than those of terrestrial species.•Immature life-stages have lower thermal tolerances than adults.•Geographic biases in Aquatic insect physiological studies highlight the need for further experimental work.Given global climate change, much attention has been given to the extent to which upper thermal tolerance limits in terrestrial and marine metazoans might be constrained. A quantitative synthesis of the available information indicates that Aquatic Insects, and especially immature life stages, have a broader range of thermal tolerances, and a lower average thermal tolerance, than their terrestrial counterparts. The pronounced incidence of oxygen and capacity limitation of thermal tolerance in Aquatic-dwelling stages and species is likely responsible for this pattern. A combination of high temperature and low water oxygen content is likely to be especially problematic for Aquatic species. Maximum limits to upper thermal tolerance are similar among terrestrial and Aquatic Insects, verifying the generality of constrained upper thermal tolerances. These findings are, however, limited by the narrow geographic and taxonomic scope of assessments.
Jeff Scott Wesner - One of the best experts on this subject based on the ideXlab platform.
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Seasonal variation in the trophic structure of a spatial prey subsidy linking Aquatic and terrestrial food webs: Adult Aquatic Insects
Oikos, 2010Co-Authors: Jeff Scott WesnerAbstract:Research over the past decade has established spatial resource subsidies as important determinants of food web dynamics. However, most empirical studies have considered the role of subsidies only in terms of magnitude, ignoring an important property of subsidies that may affect their impact in recipient food webs: the trophic structure of the subsidy relative to in situ resources. This may be especially important when subsidies are composed of organisms, as opposed to nutrient subsidies, because the trophic position of subsidy organisms may differ from in situ prey. I explored the relative magnitude and trophic structure of a cross-habitat prey subsidy, adult Aquatic Insects, in terrestrial habitats along three streams in the south2013central United States. Overall, adult Aquatic Insects contributed more than one-third of potential insect prey abundance and biomass to the terrestrial habitat. This contribution peaked along a permanent spring stream, reaching as high as 94% of abundance and 86% of biomass in winter. Trophic structure of adult Aquatic and terrestrial Insects differed. Nearly all adult Aquatic Insects were non-consumers as adults, whereas all but one taxon of terrestrial Insects were consumers. Such a difference created a strong relationship between the relative contribution of the prey subsidy and the trophic structure of the prey assemblage: as the proportion of adult Aquatic Insects increased, the proportion of consumers in the prey assemblage declined. Specific effects varied seasonally and with distance from the stream as the taxonomic composition of the subsidy changed, but general patterns were consistent. These findings show that adult Aquatic insect subsidies to riparian food webs not only elevate prey availability, but also alter the trophic structure of the entire winged insect prey assemblage.
Blair D. Siegfried - One of the best experts on this subject based on the ideXlab platform.
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Comparative toxicity of pyrethroid insecticides to terrestrial and Aquatic Insects
Environmental Toxicology and Chemistry, 1993Co-Authors: Blair D. SiegfriedAbstract:The acute toxicities of three pyrethroid insecticides (permethrin, cypermethrin, and bi-fenthrin) and one organophosphate insecticide (chlorpyrifos) were compared by topical application and static exposure to a variety of terrestrial and Aquatic Insects. Mayflies and damselflies were the most susceptible taxa tested by both exposure methods. The Aquatic Insects were generally more susceptible than the terrestrial Insects when compared on a dose per body weight basis, although the differences were smaller than expected, given the extremely low concentrations that produce toxic effects by static exposure.