Aphelocheirus Aestivalis Research Articles

Effects of Different Types of Agricultural Land Use on the Occurrence of Common Aquatic Bugs (Nepomorpha, Heteroptera) in Habitats with Slow Flowing Water in Bulgaria, Southeast Europe

Agricultural activities can have a significant impact on aquatic organisms, including aquatic insects. Most of the aquatic Heteroptera are known as moderately tolerant to low oxygen and high nutrient concentrations. Nevertheless, the complex effects of agriculture (source of both pesticides and nutrient loads) on this group are still unclear. Therefore, the relationship between six agricultural land use classes and the occurrence of common aquatic bugs in Bulgaria was studied. In order to avoid detection bias, presence-only models were applied; Maxent algorithm was used. According to the results, land use practices connected to arable land (annual crops) have stronger influence on the occurrence of the selected aquatic Heteroptera species than those connected to perennial crops (vineyards and fruit trees). Higher sensitivity to the effects of agriculture was indicated for species preferring microhabitats without macrophyte vegetation, Aphelocheirus aestivalis (Fabricius, 1794) and Micronecta griseola Horváth, 1899, compared to species preferring macrophyte dominated sites, Nepa cinerea Linnaeus, 1758, Ilyocoris cimicoides (Linnaeus, 1758) and Sigara striata (Linnaeus, 1758).

Preliminary Study on Water Quality and Heteropterans Diversity in a Semi-Urban Stream (Central Region of Cameroon)

A study was conducted in the Konglo stream for six months to make an inventory of aquatic heteroptera, following a monthly sampling frequency. Some hydrological and physicochemical parameters such as water width, current velocity, and water flow, water temperature and pH, electrical conductivity, dissolved oxygen, total hardness, phosphates, nitrates, and ammonia were measured according to standard methods. For an inventory of the heteropterans, the multihabitat approach was used during sampling, but only heteropterans representing 3.15 % of total abundance are considered in this study. The hydrological variables were different in each station. The water width and flow were increased from upstream to downstream. The results showed that pH, total hardness, nitrites, phosphates, and ammonia values ​​were weak and no significant differences were observed. Among physicochemical variables, only dissolved oxygen and electrical conductivity were different between upstream and downstream. The conductivity increased from upstream to downstream while the dissolved oxygen was very low downstream. 62 individuals were collected and counted belonging to 11 taxa, the most abundant being Ranatra linearis. The other taxa such as Anisops sp., Aphelocheirus aestivalis, Gerris sp., Gerridae Nd., Hydrometra sp., Ilyocoris cimicoides, Naucoris sp., Nepa sp., Notonectidae Nd., and Velia sp. were poorly represented. High abundance was recorded at the upstream (38 individuals), but the taxonomic richness (3 taxa) and diversity (0.24 bits/ind) remain low, unlike the stations located downstream (7 taxa and 1.82 bits/ind).

On the presence of Aphelocheirus aestivalis (Fabricius, 1794) in the Iberian Peninsula: new records with morphological and molecular data (Hemiptera: Aphelocheiridae)

The presence of Aphelocheirus aestivalis (Fabricius, 1794) (Hemiptera: Aphelocheiridae) in the Iberian Peninsula has been on the spot in the last decades. New records collected in northern inner plateau (Riaza River, Duero Basin) provide new insights about the presence of this species in the Iberian Peninsula. Morphological and molecular analyses confirmed the presence of A. aestivalis. Moreover, male and female genital structures and habitus illustrations are provided. As a whole, our results highlight the complex scenario of Aphelocheirus species in the Iberian Peninsula, involving three currently valid species (two of them very similar based on morphological studies) plus a cryptic undescribed lineage.

New evidences on the presence of Aphelocheirus aestivalis in the Iberian Peninsula, its ecology and description of two northeastern Iberian populations

New evidences on the presence of Aphelocheirus aestivalis in the Iberian Peninsula, its ecology and description of two northeastern Iberian populations

First report onWolbachiaendosymbiosis in freshwaterAphelocheirus aestivalis(Heteroptera: Aphelocheiridae) and its potential impact on genetic diversity of host

AbstractAlphaproteobacteriaWolbachiahave been described as endosymbionts of approximately half of all aquatic insect species. These bacteria might affect not only reproduction but also the genetic diversity of its hosts. In the present study we identifiedWolbachiaendosymbiosis in freshwater true bugAphelocheirus aestivalisF., 1794 (Heteroptera: Aphelocheiridae). Despite the fact thatA. aestivalisis widely distributed in Europe, it occurs rather locally, often in isolated populations. Taking into account thatWolbachia, close relationships and past demographic phenomena could affect the genetic diversity of its host, we analyzed mitochondrial (COIand 16S) and nuclear (internal transcribed spacer 2) markers determined forA. aestivalisindividuals collected from five populations. Moreover, we compared obtainedCOIsequences with those deposited in GenBank. Analyses revealed low genetic differentiation among samples tested, as well as low variation among determinedCOIsequences and those downloaded from the database. AlthoughWolbachiainfection could correlate with decreasing mitochondrial diversity of its host, we suggest that low genetic variation observed in testedA. aestivalissamples (at both mitochondrial and nuclear levels) is a result of populations’ close relationships, past demographic phenomena or is characteristic for this species. Detailed analysis of thewspgene fragment revealed two distinct strains ofWolbachiainfectingA. aestivalis.Both of them belong to supergroup A, also found in other arthropods.

The effects of temperature, activity and convection on the plastron PO2 of the aquatic bug Aphelocheirus aestivalis (Hemiptera; Aphelocheiridae)

The aquatic bug Aphelocheirus aestivalis (Fabricius 1794) utilises a plastron, a thin bubble layer on the surface of its body to extract O2 from the water. Millions of tiny hairs keep the bubble from collapsing, enabling the bug to remain submerged indefinitely. The development of fibre optic O2-probes has allowed measurements of O2 pressure (PO2) surrounding the plastron, and within the plastron although only for short periods. Here we developed methods to continuously measure plastron PO2, and investigate how it is affected by temperature (15, 20, 25°C), activity, and water circulation. We also made measurements of water PO2, temperature and velocity in the field and swimming velocity at the treatment temperatures. Results show that plastron PO2 is inversely related to temperature, associated with differences in metabolic demand, and that small bouts of activity or changes in water convection result in rapid changes in plastron PO2. A model was developed to calculate the conditions under which Aphelocheirus would exist without becoming O2-limited in relation to water temperature, PO2 and boundary layer thickness. This suggests that Aphelocheirus at one of two field sites may have a reduced metabolic scope even in well convected water in association with low PO2 and moderate temperature, and that in well convected, air-saturated water, bugs may have a reduced metabolic scope where water temperatures are between 20 and 25°C. If exposed to 5kPa PO2, Aphelocheirus cannot sustain resting metabolic rate even in well-convected water and would die at temperatures above approximately 25°C.

Karyotype, sex determination and male meiosis in three benthic water bugs (Hemiptera: Nepomorpha: Aphelocheiridae)

ABSTRACTWe report here the first chromosome numbers for benthic water bugs (Nepomorpha: Aphelocheiridae). All three studied species, Aphelocheirus aestivalis (Fabricius, 1794), A. murcius Nieser and Millán, 1989 and Aphelocheirus sp. from Ebro River (northern Spain), have karyotype 2n = 22 + XX/X(0) and inverted sequence of the X chromosome divisions in male meiosis. The similarity and difference in cytogenetic traits between Aphelocheiridae and other families of Nepomorpha are shortly discussed.

The Effect of Dredging of a Small Lowland River on Aquatic Heteroptera

Rehabilitation of river beds is sometimes necessary, particularly when a substantial amount of bottom sediment causes unnaturally slow water flow. However, it is difficult to predict whether such procedures will negatively affect biodiversity and species composition of organisms inhabiting these sites. The effects of such procedures were analysed in the Krąpiel river in northwestern Poland. It was postulated that dredging would not reduce Heteroptera diversity, but would alter the habitat significantly and create lotic habitats for rheophilous species. It was also postulated that conditions would become less favourable for taxa preferring a bottom with accumulated mud and abundant vegetation. According to our results, dredging did not significantly affect species diversity of Heteroptera, but did cause an increase in abundances of several species. Dredging increased the number of available habitats, which were mainly inhabited by abundant pioneer species. Aquarius najas, Aphelocheirus aestivalis, Plea min...

Oxygen limited thermal tolerance is seen in a plastron breathing insect, and can be induced in a bimodal gas exchanger

ABSTRACTThermal tolerance has been hypothesized to result from a mismatch between oxygen supply and demand. However, the generality of this hypothesis has been challenged by studies on various animal groups, including air-breathing adult insects. Recently, comparisons across taxa have suggested that differences in gas exchange mechanisms could reconcile the discrepancies found in previous studies. Here, we test this suggestion by comparing the behaviour of related insect taxa with different gas exchange mechanisms, with and without access to air. We demonstrate oxygen-limited thermal tolerance in air-breathing adults of the plastron-exchanging water bug Aphelocheirus aestivalis. Ilyocoris cimicoides, a related, bimodal gas exchanger, did not exhibit such oxygen-limited thermal tolerance and relied increasingly on aerial gas exchange with warming. Intriguingly, however, when denied access to air, oxygen-limited thermal tolerance could also be induced in this species. Patterns in oxygen-limited thermal tolerance were found to be consistent across life-history stages in these insects, with nymphs employing the same gas exchange mechanisms as adults. These results advance our understanding of oxygen limitation at high temperatures; differences in the degree of respiratory control appear to modulate the importance of oxygen in setting tolerance limits.

Respiratory function of the plastron in the aquatic bug Aphelocheirus aestivalis (Hemiptera, Aphelocheiridae).

The river bug Aphelocheirus aestivalis is a 40 mg aquatic insect that, as an adult, relies totally on an incompressible physical gill to exchange respiratory gases with the water. The gill (called a 'plastron') consists of a stationary layer of air held in place on the body surface by millions of tiny hairs that support a permanent air-water interface, so that the insect never has to renew the gas at the water's surface. The volume of air in the plastron is extremely small (0.14 mm(3)), under slightly negative pressure and connected to the gas-filled tracheal system through spiracles on the cuticle. Here, we measure PO2 of the water and within the plastron gas with O2-sensing fibre optics to understand the effectiveness and limitations of the gas exchanger. The difference in PO2 is highest in stagnant water and decreases with increasing convection over the surface. Respiration of bugs in water-filled vials varies between 33 and 296 pmol O2 s(-1), depending on swimming activity. The effective thickness of the boundary layer around the plastron was calculated from respiration rate, PO2 difference and plastron surface area, according to the Fick diffusion equation and verified by direct measurements with the fibre-optic probes. In stagnant water, the boundary layer is approximately 500 μm thick, which nevertheless can satisfy the demands of resting bugs, even if the PO2 of the free water decreases to half that of air saturation. Active bugs require thinner boundary layers (∼ 100 μm), which are achieved by living in moving water or by swimming.

Prewintering Aquatic and Semiaquatic True Bugs in the Timiş River Valley: Adaptations, Diversity, Community Structure and the Role of Antropic Impact

ABSTRACT In November 2011 during a normal overwintering period, a small number of active, aquatic and semiaquatic adult insects were collected from several habitats along the Timiș River basin. This active state for the insects was closely related to higher temperatures found in certain deeper, stagnant water habitats, which also had greater amounts of aquatic vegetation and more stable living conditions. Most such habitats seem to be of anthropic origin, emphasizing the role of human impacts on the life of the discussed group of insects and the need to consider anthropic activities in the conservation of certain species of insects. The state of Aphelocheirus aestivalis is also discussed, along with a proposal to study the species on a larger scale and its possible inclusion on the Romanian Red List.

Physical gills prevent drowning of many wetland insects, spiders and plants

Insects, spiders and plants risk drowning in their wetland habitats. The slow diffusion of O(2) can cause asphyxiation when underwater, as O(2) supply cannot meet respiratory demands. Some animals and plants have found a common solution to the major challenge: how to breathe underwater with respiratory systems evolved for use in air? Hydrophobic surfaces on their bodies possess gas films that act as a 'physical gill' to collect O(2) when underwater and thus sustain respiration. In aquatic insects, this feature/process has been termed 'plastron respiration'. Here, we demonstrate the similarities in function between underwater respiration of insect (Aphelocheirus aestivalis) plastrons and gas films on leaves of wetland plants (Phalaris arundinacea) and also show the importance of these physical gills by the resulting changes upon their removal. The gas films provide an enlarged gas-water interface to enhance O(2) uptake underwater that is above that if only spiracles (insects) or stomata (plants) provided the gas-phase contact with the water. Body-surface gas films contribute to the survival of many insects, spiders and plants in aquatic and flood-prone environments.

New records of suctorians (Ciliophora: Suctoria) as epibionts of aquatic true bugs (Hemiptera: Prosorrhyncha: Nepomorpha) from two regions: Mexico and Eastern Europe

Here, we provide new records of suctorians (Ciliophora: Suctoria), epibionts of aquatic true bugs (Hemiptera: Prosorrhyncha: Nepomorpha) collected in Ukraine, Belarus and Mexico. The worldwide distribution of the 16 species we found is updated, from which, 15 species are new records as epibionts of 15 species of aquatic true bugs. Only for the suctorian Discophrya gessneri Matthes, we confirm the previous record (epibiont of Aphelocheirus aestivalis Fabricius). We conclude that the relationship between the suctorians and aquatic true bugs is poorly studied and some suctorian genera (Dis- cophrya Lachmann and Periacineta Collin) inhabit as nepomorphans as other aquatic insects (Coleoptera). However the high degree of specificity at the species level of these genera is evident, for which we provide some possible explanations according to the group of basibiont.

The first decapeptide adipokinetic hormone (AKH) in Heteroptera: A novel AKH from a South African saucer bug, Laccocoris spurcus (Naucoridae, Laccocorinae)

A novel peptide of the adipokinetic hormone (AKH)/red pigment-concentrating hormone (RPCH) family has been elucidated by mass spectrometry from the corpora cardiaca of an African saucer bug species, Laccocoris spurcus. It is the first decapeptide member found in the species-rich taxon Heteroptera, has the primary sequence pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp-Gly-Gly amide and is denoted as Lacsp-AKH. The first eight amino acids are identical to the octapeptide Anaim-AKH of the European saucer bug, Ilyocoris cimicoides. The synthetic peptide Lacsp-AKH elevates lipids upon injection into the hemolymph of L. spurcus at a low dose of 3 pmol. Swimming activity in this saucer bug also causes a significant increase in the lipid concentration in the hemolymph. Thus, both results point to an apparent function of the endogenous new decapeptide Lacsp-AKH in L. spurcus, namely, to regulate lipid mobilization. Isolation of an AKH peptide from the corpora cardiaca of the water bug Aphelocheirus aestivalis (Aphelocheiridae) resulted in the assignment of the octapeptide Anaim-AKH, supporting current phylogenies on the infraorder Nepomorpha.

Allometric analysis beyond heterogeneous regression slopes: use of the Johnson-Neyman technique in comparative biology.

Allometry (or scaling) is a common technique used to evaluate and compare physiological, morphological, and other variables in organisms of different size. The relationship between many variables (Y) and body mass (X) is well described by a power function of the form . Typically, the procedure involves b Y p aX log-transforming both the variable and body mass and calculating a linear regression of the form log (Y ) p log (a) . An advantage of log-linear analysis is that it allows b log (X) calculation of associated 95% confidence intervals for the regression mean and 95% prediction intervals. Furthermore, allometric regressions for two or more groups can be compared. This is often accomplished by ANCOVA (Fisher 1932), a statistical procedure that combines ANOVA and analysis of variance of regressions (ANOVAR) to compare treatment means (groups) after accounting for and removing their relationship with the covariate (often body mass). Generally, ANCOVA is more appropriate for most data than is ANOVA, carried out on ratios of the variable and covariate, because many variables do not have an isometric relationship with body mass (Huxley 1932; Gould 1966; Packard and Boardman 1987, 1988, 1999). A requirement of ANCOVA is that the relationship with the covariate is uniform across groups; that is, the regression slopes (b) must be identical. In practice, before commencing ANCOVA it must therefore be demonstrated that the slopes are not significantly different between groups. When the slopes differ, regression elevations (a) cannot be statistically compared using ANCOVA (Zar 1999). The standard texts on allometry (Peters 1983; Calder 1984; Schmidt-Nielsen 1984; Brown and West 2000) provide little advice on how to continue analysis

Ventilatory structures in Cryphocricos barozzii Signoret (Heteroptera, Naucoroidea).

Plastron and spiracular features strongly resemble those of Aphelocheirus aestivalis (Fab.), described by Messner et al. (1981). Plastronal foliose hairs, somewhat irregular shaped are regularly distributed in the plastron. Very numerous tiny openigs on sternites an tergites connect platronal air with a subcuticular air film limited internally apparently by a membrane. Aplicated, radial, structure at the proximal end of the tracheae, almost occluding the extremely fine spiracular openings, appear with lesser variations in both species, suggesting close relationships than accepted until now.

Monte Carlo Simulations of Benthic Macroinvertebrate Populations: Estimates Using Random, Stratified, and Gradient Sampling

Accuracy, precision, and cost are major concerns in optimizing a sampling strategy to estimate population sizes of benthic macroinvertebrates. We used Monte Carlo simulations to compare precision and accuracy for various efforts (= cost) to predict density of cohorts and total populations of the water but Aphelocheirus aestivalis (Fabr.) from 3 German rivers. We compared density predictions of this hemipteran made from simultaneously collected physical variables to density predictions made from random sampling. The joint preference factor (JPF) method predicted Aphelocheirus densities from combined preference gradients for depth, velocity, and substratum size. It clearly yielded the most powerful predictions of all physical approaches tested. However, the JPF method sometimes predicted bug density better or worse than random sampling, depending on 1) the mean density of a cohort or total population, 2) the degree of spatial patchiness (contagion), 3) the affordable sample number to predict from, and 4) whether all or only dominant size components of the substratum were considered. We concluded that benthic macroinvertebrate sampling should be optimized using a flexible strategy, depending on the study objectives and the budget. This approach can save considerable time for the given error level required in predictions, and/or can yield a considerable reduction of the error of predictions (up to 50%) with a comparable effort. Optimization of sampling strategies in studies of lotic benthos is appropriate, logical, and timely, because large expenditures for stream management may be based on data provided by lotic ecologists.

Prey Selection by the Water Bug Aphelocheirus aestivalis Fabr. (Heteroptera: Aphelocheiridae)

AbstractFeeding experiments were conducted in situ in flow through boxes to determine the vulnerability of different prey types (the mayfly larvae Baetis, Ephemerella and Ecdyonurus spp., the caddisfly larva Hydropsyche spp. and the crustacean Gammarus spp.) to the predaceous water bug Aphelocheirus aestivalis and to estimate the predation impact of Aphelocheirus on prey populations. Experiments with equal densities of mixed prey and experiments where each prey was tested individually revealed that Baetis and Ephemerella were most vulnerable to Aphelocheirus predation: Hydropsyche, Ecdyonurus and Gammarus were little/not preyed upon. The present results suggest that vulnerability of prey depends mainly upon prey mobility and microhabitat overlap between predator and prey and that feeding behaviour of Aphelocheirus resembles more that of megalopterans than of stoneflies. Experiments with different prey densities (120–720 prey m−2) showed that the predation rate of Aphelocheirus increased with increasing prey density. Experiments with different substrates documented that mortality rates of prey decreased with increasing substrate complexity. When substrate conditions were complex mortality rates in the control and in the experimental boxes were the same which suggest little importance of Aphelocheirus predation on mayflies in the study site.

Regeneration of Floodplain Biotopes on the Upper Rhine – The “Polder Altenheim” Case

The floodplain of the Upper Rhine and its biocoenoses have, through different river-regulatory activities over the last 175 years, undergone large scale degradation. At the same time flood protection for the downstream inhabitants has been greatly reduced. For reasons of flood protection, the “Polder Altenheim” in Baden-Württemberg, Germany southwest of Strasbourg, France, with so called retention flooding, was put into operation in 1987. The original floodplain had been diked for the previous 17 years, during which no flooding occurred. Since 1989 “ecological flooding” also is carried out. This has assisted in the regeneration of floodplain biotopes and promoted the floodplain biotic communities and the readaption of the bioceonosis to a regular flooding regime. The creation of new floodplain biotopes of early succession stages, particularly through geomorphodynamic processes, has followed the more than ten flood ocassions and typical biotic communities have colonised these sites. This will be presented together with selected examples of terrestrial and limnical species and communities. The following species and communities will be discussed: kingfisher Alcedo atthis, carabid communities (Coleoptera), the red alga Hildenbrandia rivularis (Rhodophyceae), the freshwater snail Theodoxus fluviatilis (Neritacea) and the freshwater bug Aphelocheirus aestivalis (Hydrocorisae).

Hydraulic Stream Ecology: Observed Patterns and Potential Applications

Although it is well known that metabolism, feeding, and behaviour of lotic organisms is influenced by various flow characteristics, hydraulic variables usually are not accurately measured in lotic ecology studies. Using an approach we call "hydraulic stream ecology", we link organismic responses to a more comprehensive treatment of the physical environment. Since a unified analytical solution for all important hydraulic variables in running waters does not exist at the moment, we advocate a simpler view of the physical system. We demonstrate methods for estimating complex hydraulic key characteristics, like turbulence in the free flow, turbulence close to the stream bottom, and the force of flow prevailing at the bottom. Calculations of these complex key characteristics require measurement of simple hydraulic characteristics like mean velocity, water surface slope, depth, bottom roughness, kinematic viscosity, and density of the water. The hydraulic environment shows characteristic patterns within whole catchments or within reaches of different types of running waters (e.g., high gradient mountain stream, lowland stream, mid-order river). Examples from lotic macroinvertebrates, in particular original data on the water bug Aphelocheirus aestivalis (Fabr.), demonstrate how organismic responses are linked to the hydraulic environment. The body shapes of many lotic zoobenthos are not well adapted to minimize forces of flow, as has been generally believed. Indeed, flow forces are rather stressful for these animals. Critical resources in swift flowing microzones can often be exploited by zoobenthos for only restricted periods, a view that is consistent with the temporal, vertical migration patterns observed for most stream invertebrates. The stress of flow and temporal exposure to it may be correlated with the distribution of lotic zoobenthos. Substratum characteristics, usually perceived as a major factor explaining the distribution of lotic macroinvertebrates, is less important than mean velocity and the complex hydraulic key characteristics. Complex hydraulic characteristics are most useful in modeling specific relationships between the distribution of zoobenthos within a stream reach and the physical habitat, which differ depending on developmental stage of the organism, season, and site. On the catchment scale, the distribution of zoobenthos, and, consequently, longitudinal zonation are also largely dependent on hydraulics. Other groups of organisms found in running waters (e.g., microorganisms and fish) show responses to hydraulics that are comparable to those of lotic macroinvertebrates. There is evidence that some species can alter the hydraulic environment for other individuals (or species). Hydraulic stream ecology provides methods to scale flow in lotic research, which will lead to an increase in replicability and predictability in studies of running water ecosystems. We suggest that researchers who have measured relevant simple hydraulic characteristics in many past studies reevaluate their data considering the role of complex hydraulic key characteristics for the distribution of organisms.