Freshwater Insects Research Articles

A landscape conservation perspective of state Species of Greatest Conservation Need

AbstractState Wildlife Action Plans (SWAPs), including lists of Species of Greatest Conservation Need (SGCN), outline state strategies for protecting species and habitats in the United States. In developing the current, second revision SWAPs, states are increasingly pursuing coordinated landscape conservation approaches. Analyzing SGCN lists in the first revision SWAPs, we found evidence that they already support multistate conservation. Most states address a common set of vertebrate and invertebrate groups, include most of the imperiled species from these groups, do not prioritize endemics over non‐endemics, and often include most imperiled species that are shared with neighboring states. Also, a regional SGCN coordination effort was successful. Although 65% of animals on each SGCN list were assessed as at elevated risk of extirpation by state authorities, only 43% of the combined national list were at elevated risk of global extinction. Over 40% of the combined animal SGCNs are considered globally apparently secure. Plants, snails, freshwater shrimps, and freshwater insects were poorly represented in SGCN lists. For the current SWAP revisions, we recommend improving foundational data on taxonomy, range‐wide distribution, and conservation status; expanded taxonomic coverage in SGCN lists; supporting existing and establishing new interstate initiatives; and diversifying funding mechanisms that target regional cooperation.

Coleopteran burrows from foreshore settings in Florianópolis, Brazil

While insects are versatile animals capable of occupying harsh environmental conditions, not many are present in the marine environment, and has generally been discounted as trace makers in such settings. During the intra-congress field trip of ICHNIA 2024, however, we observed multiple surficial burrows on foreshore sediments that were constructed by beetle larvae. While there are several reports of insect burrows from backshores, eolian dunes, salt marshes, tidal creeks, washover fans, and distributary channels, we are not aware of ichnological studies of these burrows from the foreshore. Moreover, some of these studies failed to identify or mention the entity of the trace makers, and have not stressed enough the significance of burrowing marine insects on palichnology and paleoecology. Some entomologists on the other hand have recognized insects in marine environments, and some insect groups (such as Coleoptera and Diptera) have burrowing larvae in brackish to marine environments. Understanding the burrow morphologies of marine insects compared to freshwater insects or other marine invertebrates may help us understand the ecological significance and evolutionary history of insects in marine habitats.

A Review of the Density, Biomass, and Secondary Production of Odonates.

Freshwater insects are highly significant as ecosystem service providers, contributing to provisioning services, supporting services, and cultural services. Odonates are dominant predators in many freshwater systems, becoming top predators in fishless ecosystems. One service that odonates provide is the export of matter and energy from aquatic to terrestrial ecosystems. In this study, we provide a review of the literature aiming to estimate the density, biomass, and secondary production of odonates and discuss to what extent this order of insects is relevant for the fertilization of terrestrial ecosystems. We found published data on 109 species belonging to 17 families of odonates from 44 papers. Odonata larvae are abundant in freshwater systems, with a mean density of 240.04 ± 48.01 individuals m-2 (±SE). Lentic habitats show much higher densities (104.40 ± 55.31 individuals m-2, N = 118) than lotic systems (27.12 ± 5.09, N = 70). The biomass estimations for odonates indicate values of 488.56 ± 134.51 mg m-2 y-1, with similar values in lentic and lotic habitats, which correspond to annual secondary productions of 3558.02 ± 2146.80 mg m-2 y-1. The highest biomass is found in dragonflies of the Aeshnidae, Corduliidae, and Gomphidae families. The available evidence suggests a significant potential contribution of Odonata to the exportation of material from water bodies to land. This is further strengthened by the ability of adult odonates to migrate and to colonize different types of water bodies.

The spatiotemporal profile and adaptation determine the joint effects and interactions of multiple stressors

BackgroundBiodiversity is declining worldwide as ecosystems are increasingly threatened by multiple stressors associated with anthropogenic global change. Stressors frequently co-occur across scales spatially and temporally, resulting in joint effects that are additive or non-additive, i.e., antagonism or synergism. Forecasting and counteracting threats from intensifying stressors requires improved mechanistic understanding of joint effects, which is currently relatively low. To date, research on multiple stressors has been biased toward simplified scenarios, emphasized classification of interactions over realized joint effects, and mostly ignored adaptation (i.e., phenotypic plasticity or evolving life-history traits) of organisms. To investigate if more a realistic scenarios design incorporating complex spatiotemporal stressor profiles and adaption change joint effects and interactions of multiple stressors compared to simplified scenarios, we modified a spatially explicit meta-population model for a generic freshwater insect. We used the model to simulate different, hypothetical spatiotemporal profiles of a continuous and a discrete stressor and evaluated their joint effects and interactions. Agricultural land use represented the continuous stressor impacting meta-population patch quality and network connectivity and related scenarios implied different trajectories. Climatic events represented the discrete stressor impacting all patches simultaneously by temporary mortality events, with related scenarios implying different event severity. Adaptation mitigated the effects of climatic events based on previous events.ResultsExcluding adaptation, we found that at higher levels of the discrete stressor (i.e., strong and frequent climatic events) it strongly dominates the joint effects, while at a low level (i.e., weak and infrequent climatic events) of the discrete stressor, the continuous stressor (i.e., land use) dominates. Yet, the continuous stressor always defined the interaction type, with decreasing land use stress leading to antagonism, and increasing land use stress leading to synergism. Adaptation reduced joint effects under decreasing land use stress, yet had little compensatory influence under increasing land use stress. Moreover, adaptation changed interaction sizes inconsistently across the different land use and climate scenarios, with change depending on the climate scenario. Here, interactions decreased in the moderate scenario but increased in the severe and intense scenarios.ConclusionsWe highlight that realistic stressor scenarios accounting for potential adaptation are critical for a mechanistic understanding of how species respond to global change. To our knowledge, this is the first modeling study to show that stressor interactions depend on complex spatiotemporal stressor profiles and adaptation, following general principles.

Diversity and abundance of mayflies (Insecta: Ephemeroptera) in Achenkovil River, southern Western Ghats, Kerala, India

Freshwater insects like Ephemeroptera are more comprehensive and direct indicators of the biological impacts of pollution. During the study period (2018–2020), a total of 4,374 individuals of mayflies were collected and categorized under nine families, 27 genera, and 36 species. The family Leptophlebiidae was found dominant with 13 species. In the post-monsoon season, a higher species diversity of Ephemeroptera was noticed in the river’s upstream section with a Shannon-Wiener index value of H’ = 1.814. ANOVA revealed a significant difference (p <0.05) except for Ephemeridae (p >0.05). Protecting rivers requires a holistic approach and collaboration among stakeholders is essential for successful implementation.

Variation in Freshwater Insect Osmoregulatory Traits: A Comparative Approach.

AbstractFreshwater salinity regimes vary naturally and are changing in response to anthropogenic activities. Few insect species tolerate saline waters, and biodiversity losses are associated with increasing salinity in freshwater. We used radiotracers (22Na, 35SO4, and 45Ca) to examine ion uptake rates across concentration gradients in mayflies (Ephemeroptera), caddis flies (Trichoptera), and mosquitoes (Diptera) and made observations for some traits in seven other taxa representing mayflies, stone flies (Plecoptera), true flies (Diptera), and true bugs (Hemiptera). We further assessed the permeability of the cuticle to 3H2O influx and 22Na efflux when faced with deionized water in these same taxa. We hypothesized a relationship between uptake rates and reported saline tolerances, but our data did not support this hypothesis, likely because acclimatory responses were not part of this experimental approach. However, we found several common physiological traits across the taxa studied, including (i) ionic uptake rates that were always positively correlated with dissolved concentrations, (ii) generally low Ca uptake rates relative to other freshwater taxa, (iii) greater Na loss than Na uptake in dilute conditions, (iv) ion uptake that was more variable in ion-rich conditions than in dilute conditions, and (v) 3H2O influx that occurs quickly (but this rapidly exchangeable pool of body water accounts for a surprisingly small percentage of the water content of species tested). There remains much to learn about the physiology of these important organisms in the face of changing salinity regimes worldwide.

Automated identification of aquatic insects: A case study using deep learning and computer vision techniques

Deep learning techniques have recently found application in biodiversity research. Mayflies (Ephemeroptera), stoneflies (Plecoptera) and caddisflies (Trichoptera), often abbreviated as EPT, are frequently used for freshwater biomonitoring due to their large numbers and sensitivity to environmental changes. However, the morphological identification of EPT species is a challenging but fundamental task. Morphological identification of these freshwater insects is therefore not only extremely time-consuming and costly, but also often leads to misjudgments or generates datasets with low taxonomic resolution. Here, we investigated the application of deep learning to increase the efficiency and taxonomic resolution of biomonitoring programs. Our database contains 90 EPT taxa (genus or species level), with the number of images per category ranging from 21 to 300 (16,650 in total). Upon completion of training, a CNN (Convolutional Neural Network) model was created, capable of automatically classifying these taxa into their appropriate taxonomic categories with an accuracy of 98.7 %. Our model achieved a perfect classification rate of 100 % for 68 of the taxa in our dataset. We achieved noteworthy classification accuracy with morphologically closely related taxa within the training data (e.g., species of the genus Baetis, Hydropsyche, Perla). Gradient-weighted Class Activation Mapping (Grad-CAM) visualized the morphological features responsible for the classification of the treated species in the CNN models. Within Ephemeroptera, the head was the most important feature, while the thorax and abdomen were equally important for the classification of Plecoptera taxa. For the order Trichoptera, the head and thorax were almost equally important. Our database is recognized as the most extensive aquatic insect database, notably distinguished by its wealth of included categories (taxa). Our approach can help solve long-standing challenges in biodiversity research and address pressing issues in monitoring programs by saving time in sample identification.

Bigger is not necessarily better: empirical tests show that dispersal proxies misrepresent actual dispersal ability.

Tests for the role of species' relative dispersal abilities in ecological and biogeographical models rely heavily on dispersal proxies, which are seldom substantiated by empirical measures of actual dispersal. This is exemplified by tests of dispersal-range size relationships and by metacommunity research that often features invertebrates, particularly freshwater insects. Using rare and unique empirical data on dispersal abilities of caddisflies, we tested whether actual dispersal abilities were associated with commonly used dispersal proxies (metrics of wing size and shape; expert opinion). Across 59 species in 12 families, wing morphology was not associated with actual dispersal. Within some families, individual wing metrics captured some dispersal differences among species, although useful metrics varied among families and predictive power was typically low. Dispersal abilities assigned by experts were either no better than random or actually poorer than random. Our results cast considerable doubt on research underpinned by dispersal proxies and scrutiny of previous research results may be warranted. Greater progress may lie in employing innovative survey and experimental design to measure actual dispersal in the field.

Modeling temperature-dependent life-cycle toxicity of thiamethoxam in Chironomus riparius using a DEB-TKTD model

The neonicotinoid insecticide thiamethoxam (TMX) is widely used to protect crops against insect pests. Despite some desirable properties such as its low toxicity to birds and mammals, concerns have been raised about its toxicity to non-target arthropods, including freshwater insects like chironomids. Whereas multiple studies have investigated chronic effects of neonicotinoids in chironomid larvae at standardized laboratory conditions, a better understanding of their chronic toxicity under variable temperatures and exposure is needed for coherent extrapolation from the laboratory to the field. Here, we developed a quantitative mechanistic effect model for Chironomus riparius, to simulate the species’ life history under dynamic temperatures and exposure concentrations of TMX. Laboratory experiments at four different temperatures (12, 15, 20, 23 °C) and TMX concentrations between 4 and 51 µg/L were used to calibrate the model. Observed concentration-dependent effects of TMX in C. riparius included slower growth, later emergence, and higher mortality rates with increasing concentrations. Furthermore, besides a typical accelerating effect on the organisms’ growth and development, higher temperatures further increased the effects associated with TMX. With some data-informed modeling decisions, most prominently the inclusion of a size dependence that makes larger animals more sensitive to TMX, the model was parametrized to convincingly reproduce the data. Experiments at both a constant (20 °C) and a dynamically increasing temperature (15–23 °C) with pulsed exposure were used to validate the model. Finally, the model was used to simulate realistic exposure conditions using two reference exposure scenarios measured in Missouri and Nebraska, utilizing a moving time window (MTW) and either a constant temperature (20 °C) or the measured temperature profiles belonging to each respective scenario. Minimum exposure multiplication factors leading to a 10% effect (EP10) in the survival at pupation, i.e., the most sensitive endpoint found in this study, were 25.67 and 21.87 for the Missouri scenario and 38.58 and 44.64 for the Nebraska scenario, when using the respective temperature assumptions. While the results illustrate that the use of real temperature scenarios does not systematically modify the EPx in the same direction (making it either more or less conservative when used as a risk indicator), the advantage of this approach is that it increases the realism and thus reduces the uncertainty associated with the model predictions.

The thermal breadth of temperate and tropical freshwater insects supports the climate variability hypothesis.

Climate change involves increases in mean temperature and changes in temperature variability at multiple temporal scales but research rarely considers these temporal scales. The climate variability hypothesis (CVH) provides a conceptual framework for exploring the potential effects of annual scale thermal variability across climatic zones. The CVH predicts ectotherms in temperate regions tolerate a wider range of temperatures than those in tropical regions in response to greater annual variability in temperate regions. However, various other aspects of thermal regimes (e.g. diel variability), organisms' size and taxonomic identity are also hypothesised to influence thermal tolerance. Indeed, high temperatures in the tropics have been proposed as constraining organisms' ability to tolerate a wide range of temperatures, implying that high annual maximum temperatures would be associated with tolerating a narrow range of temperatures. We measured thermal regimes and critical thermal limits (CTmax and CTmin) of freshwater insects in the orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) along elevation gradients in streams in temperate and tropical regions of eastern Australia and tested the CVH by determining which variables were most correlated with thermal breadth (T br = CTmax - CTmin). Consistent with the CVH, T br tended to increase with increasing annual temperature range. T br also increased with body size and T br was generally wider in Plecoptera than in Ephemeroptera or Trichoptera. We also find some support for a related hypothesis, the climate extreme hypothesis (CEH), particularly for predicting upper thermal limits. We found no evidence that higher annual maximum temperature constrained individuals' abilities to tolerate a wide range of temperatures. The support for the CVH we document suggests that temperate organisms may be able to tolerate wider ranges of temperatures than tropical organisms. There is an urgent need to investigate other aspects of thermal regimes, such as diel temperature cycling and minimum temperature.

Sites and species contribution to the β-diversity of Odonata assemblages in Haiti: Implications for conservation

Understanding the ecological determinants of assemblage diversity in freshwater insects is of crucial importance for conservation biology and environmental management. This is particularly true in Haiti, where severe and ongoing environmental degradation of aquatic ecosystems is a major threat to the local invertebrate fauna. Here, using Odonates assemblages sampled from 67 waterbodies belonging to 14 different Haitian watersheds, we assessed species uniqueness (U) from both rarity based on spatial occupancy and taxonomic species distinctness (TSD), and species contribution to total β diversity (SCBD). We assessed between-site variation in species richness (SR), relative taxonomic distinctness (RTD), mean species uniqueness per site (Mean U), and the contribution of individual sites to total β diversity (LCBD), based on presence-absence data. We then examined the relationships between these variables and the physico-chemical characteristics of the sites. In total, we recorded 49 different odonate species (including two endemic species of conservation interest), belonging to 40 genera and 7 families, with a relatively high percentage (69.4%) of rare species (i.e. occurring in 10% or less of sampled water bodies). TSD was negatively correlated with spatial occupancy, while U was significantly higher in Zygopeteran species compared to Anisopteran species. SR varied among the 67 sites, ranging from 2 to 17 species, while SCBD was positively correlated with site occupancy. Differences in assemblage composition between sites were mainly due to species replacement, while only a few sites had assemblages consisting of a subset of larger assemblages found at other sites. The observed positive correlation between dissimilarity and geographic distance between sites further suggests that the turnover of species may take place over some ecological gradient and/or might be explained by species ecological requirements and limited ability to disperse. LCBD and Mean U increased with increasing altitude and decreasing temperature and conductivity, whereas SR and RTD did not. All variables were independent of pH. Overall, SR and RTD were higher in lotic than in lentic sites, and in sites with natural riparian vegetation compared to sites with anthropogenic or mixed riparian vegetation. Mean U provided a relevant index for site selection for odonates conservation in Haiti, whereas β diversity appeared to be of limited interest for this purpose. Globally, our results advocate the importance of conserving a wide diversity of waterbodies to protect Odonate diversity in Haïti, and particularly in forested areas at > 1000 m altitude.

Mammal communities of primeval forests as sentinels of global change.

Understanding the drivers and consequences of global environmental change is crucial to inform predictions of effects on ecosystems. We used the mammal community of Białowieża Forest, the last lowland near-primeval forest in temperate Europe, as a sentinel of global change. We analyzed changes in stable carbon (δ13 C) and nitrogen (δ15 N) isotope values of hair in 687 specimens from 50 mammal species across seven decades (1946-2011). We classified mammals into four taxonomic-dietary groups (herbivores, carnivores, insectivores, and bats). We found a significant negative trend in hair δ15 N for the mammal community, particularly strong for herbivores. This trend is consistent with temporal patterns in nitrogen deposition from (15 N depleted) industrial fertilizers and fossil fuel emissions. It is also in line with global-scale declines in δ15 N reported in forests and other unfertilized, non-urban terrestrial ecosystems and with local decreases in N foliar concentrations. The global depletion of 13 C content in atmospheric CO2 due to fossil fuel burning (Suess effect) was detected in all groups. After correcting for this effect, the hair δ13 C trend became non-significant for both community and groups, except for bats, which showed a strong decline in δ13 C. This could be related to an increase in the relative abundance of freshwater insects taken by bats or increased use of methane-derived carbon in food webs used by bats. This work is the first broad-scale and long-term mammal isotope ecology study in a near-primeval forest in temperate Europe. Mammal communities from natural forests represent a unique benchmark in global change research; investigating their isotopic temporal variation can help identify patterns and early detections of ecosystem changes and provide more comprehensive and integrative assessments than single species approaches.

Systematics expertise and taxonomic status of New Zealand’s freshwater insects

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Respirometry reveals major lineage-based differences in the energetics of osmoregulation in aquatic invertebrates.

All freshwater organisms are challenged to control their internal balance of water and ions in strongly hypotonic environments. We compared the influence of external salinity on the oxygen consumption rates (ṀO2) of three species of freshwater insects, one snail and two crustaceans. Consistent with available literature, we found a clear decrease in ṀO2with increasing salinity in the snail Elimia sp. and crustaceans Hyalella azteca and Gammarus pulex (r5=-0.90, P=0.03). However, we show here for the first time that metabolic rate was unchanged by salinity in the aquatic insects, whereas ion transport rates were positively correlated with higher salinities. In contrast, when we examined the ionic influx rates in the freshwater snail and crustaceans, we found that Ca uptake rates were highest under the most dilute conditions, while Na uptake rates increased with salinity. In G. pulex exposed to a serially diluted ion matrix, Ca uptake rates were positively associated with ṀO2(r5=-0.93, P=0.02). This positive association between Ca uptake rate and ṀO2was also observed when conductivity was held constant but Ca concentration was manipulated (1.7-17.3 mg Cal-1) (r5=0.94, P=0.05). This finding potentially implicates the cost of calcium uptake as a driver of increased metabolic rate under dilute conditions in organisms with calcified exoskeletons and suggests major phyletic differences in osmoregulatory physiology. Freshwater insects may be energetically challenged by higher salinities, while lower salinities may be more challenging for other freshwater taxa.

The colour temperature and placement of LED lighting near rivers can reduce attraction of flying adult caddisflies

Abstract Artificial light at night (ALAN), which can confuse and distract insects, has been implicated as a contributor of their decline worldwide. Changes in artificial light technology has led to a widespread conversion of outdoor lighting to light‐emitting diode (LED) bulbs, which are more energy efficient than older high‐intensity discharge or fluorescent lamps. However, many outdoor LED lights emit a proportion of short‐wavelength blue light, to which insects are commonly sensitive. The potential to reduce flying insect attraction to outdoor lights by using LEDs that emit different amounts of blue light, or by placing lights further from insect sources has not been well‐studied, particularly for freshwater insects. We tested whether four blue‐white LEDs that varied in their emittance of blue light intensity (3000, 4000, 5650, 6500 Kelvin [K] colour temperature) differed in their attractiveness to flying insects, particularly adult caddisflies (Trichoptera) over distances up to 100 m from a river. LEDs were deployed at a lit urban river and a predominantly unimpacted braided river in Canterbury, New Zealand. We expected a greater abundance and species richness of adult caddisflies to be attracted to LEDs that emit more blue light (cooler white LEDs [6500, 5650 K]) than those that emit less (warmer colour temperatures [3000 K, 4000 K]). We also expected the abundance and species richness of adult caddisflies in light traps to decline rapidly with increasing distance from the river, regardless of colour temperature. Moths, flies and a total of 26 caddisfly species were collected from both rivers. Significantly more caddisflies were attracted to higher than lower colour temperature LEDs. For example, a more than 1.6‐fold number of caddisflies were caught by the bluer‐white 6500 K LEDs than the warmer‐white 3000 K LEDs. This trend was consistent across most caddisfly taxa and both rivers. The number of caddisflies attracted to LEDs significantly declined with increasing distance from the river edge for the two most abundant caddisfly families and the four most abundant species; 65% of all caddisflies were caught by 20 m from the river margin. In order to reduce the attraction of caddisflies to outdoor lights such as streetlights, our study highlights the importance of considering a low LED colour temperature (3000 K or 4000 K) or those that emit less blue light and the benefit of positioning lights further back from waterways, where possible. Our results indicate that plans for urban outdoor lighting should consider the ecological implications of different colour temperature LEDs and their spatial position as project design considerations.

Genetic diversity and climatic suitability over time of Baetodes huaico (Ephemeroptera: Baetidae)

In the Neotropical region, the genetic diversity and bioclimatic preferences of Ephemeroptera are poorly known mainly due to the lack of studies. We used the 16S rRNA mitochondrial gene to examine the genetic structure of Baetodes huaico, an aquatic insect distributed in the Northwest of Argentina. Also, we performed an ecological niche modeling (ENM) to understand bioclimatic preferences and combine with the genetic data to understand historical dynamic distribution of B. huaico. We found that B. huaico populations are genetically structured into two distinct geographic groups. The ENM showed a distributional shift from south to north through time. Also, we recovered a stable region over time in the Southwest of Tucumán with the highest value of suitability and high genetic diversity; this region was previously proposed as a Pleistocene refuge. Our result suggests that the northern group was stable over time and underwent a recent demographic expansion coincident with a glacial refugium, whereas the southern group could have been affected by climatic fluctuations during. The results emphasize possible climatic influences in genetic population differentiation, and contributes to the knowledge of the genetic diversity of Ephemeroptera from subtropical Argentina laying the groundwork for future work for other freshwater insects in our region.

Anticipating where are unknown aquatic insects in Europe to improve biodiversity conservation

AbstractAimUnderstanding biodiversity patterns is crucial for prioritizing future conservation efforts and reducing the current rates of biodiversity loss. However, a large proportion of species remain undescribed (i.e. unknown biodiversity), hindering our ability to conduct this task. This phenomenon, known as the ‘Linnean shortfall’, is especially relevant in highly diverse, yet endangered, taxonomic groups, such as insects. Here we explore the distributions of recently described freshwater insect species in Europe to (1) infer the potential location of unknown biodiversity hotspots and (2) determine the variables that can anticipate the distribution of unknown biodiversity.LocationThe European continent, including western Russia, Cyprus and Turkey.MethodsGeoreferenced information of all sites where new aquatic insect species were described across Europe from 2000 to 2020 was compiled. In order to understand the observed spatial patterns in richness of recently described species, spatial units were defined (level 6 of HydroBASINS) and associated with a combination of a set of socioeconomic, environmental and sampling effort descriptors. A zero‐inflated Poisson regression approach was used to model the richness of newly described species within each spatial unit.ResultsNine hundred and sixty‐six recently described species were found: 398 Diptera, 362 Trichoptera, 105 Coleoptera, 66 Plecoptera, 28 Ephemeroptera, 3 Neuroptera, 2 Lepidoptera and 2 Odonata. The Mediterranean Basin was the region with the highest number of recently described species (74%). The richness of recently described species per spatial unit across Europe was highest at mid‐elevation areas (between 400 and 1000 m), latitudes between 40 and 50° and in areas with yearly average precipitation levels of 500–1000 mm, a medium intensity of sampling effort and low population density. The percentage of protected areas in each study unit was not significantly related to the richness of recently described species. In fact, 70% of the species were found outside protected areas.Main conclusionsThe results highlight the urgent need to concentrate conservation efforts in freshwater ecosystems located at mid‐altitude areas and out of protected areas across the Mediterranean Basin. The highest number of newly described species in those areas indicates that further monitoring efforts are required to ensure the aquatic biodiversity is adequately known and managed within a context of growing human impacts in freshwater ecosystems.

Ingestion and egestion of microplastic by aquatic insects in Egypt wastewater

AbstractMicroplastics (MPs) are frequently regarded as environmental and biota contaminants. Yet, research on the accumulation of MPs in living entities, particularly aquatic insects that serve as food resources in the aquatic food chain, is limited. This study to investigate the accumulation of MPs in aquatic insects from water and sediment in an Egyptian wastewater basin. Four typical freshwater insect groups were used. The highest MP load per gram wet weight was reported by collector‐gatherers (Chironomus sp. and Hydrophilus sp.), followed by collector‐filterers (Culex sp.) with the second highest MP load. However, Predators (Aeshna sp.) had the lowest values. Also, the present results showed a reduction in the number of MPs in all insect taxa tested after a 24 h depuration time, with differences in the observed egestion ability. The mean number of MPs per individual significantly reduced after 24 h in both Chironomus sp. and Culex sp. larvae, where 53% and 40% of MPs particles were ejected from them, respectively. However, the ability of MP egestion decreases in Aeshna sp. nymph (25%), and the lowest proportion of ejection was observed in Hydrophilus sp. adults (9%). Polyethylene terephthalate fibers were the most abundant type of MP in both sediment and water, followed by fragments (polyethylene and polypropylene). Yet, only polyester fibers were detected in the various insect species. The average length of fibers in the various insects was somewhat shorter than in the surrounding environment. The current study reveals that MP ingestion by aquatic insects is not always related to levels of pollution in the environment, since other factors such as feeding strategies may play a role in MP ingestion. Based on these observations, further studies should be carried out on studies on toxicological impacts of MPs on freshwater/aquatic biota.

Historical land use patterns provide insight into contemporary insect diversity loss.

Healthy insect populations are vital for maintaining natural ecosystems and essential to global food security. The ongoing dramatic loss of insect species and biomass is thus a global cause for concern, with much focus on this topic in the media. Yet, determining the mechanism behind these declines remains difficult, particularly when attempting to differentiate between anthropogenic drivers of biodiversity loss and long-term natural fluctuations. In a From the Cover manuscript in this issue of Molecular Ecology, Crossley et al. (2022) examined the long-term impact of land use change on freshwater insects by estimating levels of genetic diversity with publicly available data for the cytochrome c oxidase subunit 1 (CO1) mitochondrial locus from >700 aquatic insect species across the United States. Contemporary genetic diversity measures reflect both current and past demography and therefore are related to both past and present habitat change. Crossley et al. found that environments with greater cropland extent over the last 200 years were associated with lower genetic diversity in contemporary aquatic insect populations. This indicates that historical land use is an important factor in contemporary population dynamics. Most critically, in regions of historical cropland cover that have been converted towards other uses (such as urban environments) more recently, aquatic insect populations exhibited higher levels of genetic diversity, indicating a possible rebound in insect populations after cessation of agricultural activity. This study highlights the power of using publicly available data to answer crucial questions regarding the current biospheric emergency.

Freshwater insect communities in urban environments around the globe: a review of the state of the field

Urbanization is a key stressor of freshwater habitats, possibly contributing to global insect declines. However, scientific understanding of urbanization's effects on aquatic insect communities has largely been based on studies of temperate streams. We reviewed global urban freshwater macroinvertebrate community studies, classifying habitat type, location, urbanization metrics, biodiversity metrics, and focal taxa, drawing from 114 studies in 32 different countries. Our goals were to: (1) investigate the extent of research on urbanization across a variety of freshwater habitats, (2) examine the representation in empirical literature across the globe by comparing cities in different geographic regions, and (3) highlight how study approaches including taxonomic resolution and the inclusion of trait data impact interpretation of these patterns. Most studies were conducted in North America and Europe, but there is growing representation from other continents. Additionally, lentic environments were underrepresented in the literature on community responses to urbanization compared to lotic studies. Therefore, we suggest that lentic habitats should be investigated more thoroughly. We suggest that future empirical studies should incorporate traits of the taxa investigated to better predict how communities respond to urban stressors. The lack of consistent results from the reviewed studies showed that there is no single, predictable effect of urbanization, indicating that future meta-analyses and review papers should consider the potential context-dependency of freshwater insect responses to anthropogenic pressures. Our goal in highlighting understudied environmental and regional contexts is to move toward holistically addressing the ongoing challenges of urban freshwater insect conservation and freshwater ecology research.