Freshwater Insects Research Articles

Assessment of thiamethoxam toxicity to Chironomus riparius

The insecticide thiamethoxam (TMX) is a systemic neonicotinoid widely used for pest control in several agricultural crops. TMX mimics the action of acetylcholine causing uncontrolled muscular contraction eventually leading to insect death. TMX is being found in freshwater ecosystems at concentrations of up to 225µg/L. Still, chronic toxicity data for freshwater invertebrates is limited. Therefore, the aim of this study was to evaluate the acute and chronic effects (at organismal and biochemical levels) of TMX on the freshwater insect Chironomus riparius. C. riparius life history responses were significantly affected by TMX exposure, namely with a decrease in growth and delay in emergence. Concerning the biochemical responses, after a short exposure (48h) to TMX, our results showed that low concentrations of TMX significantly reduced CAT activity and LPO levels of C. riparius. No effects were observed in AChE, GST and ETS activities. Effects in terms of survival, development rates and biochemical responses of C. riparius exposed to low concentrations of TMX observed in this study suggest potential deleterious effects of this neonicotinoid on aquatic insects inhabiting freshwaters environments near agricultural areas.

Acute toxicity of arsenic to larvae of four New Zealand freshwater insect taxa

ABSTRACTArsenic, often found in gold deposits, can enter aquatic systems. The toxicity of arsenate (As(V)), the most common valence state of arsenic in freshwater, was assessed on the larvae of four freshwater insect taxa from naturally acidic (pH 5.9) and circumneutral (pH 7.4) New Zealand streams. Insects from the acidic stream were more sensitive to arsenate-spiked water than those from the circumneutral stream. Early instars (<3 mm) of the mayfly Deleatidium spp. (Leptophlebiidae) were the most sensitive compared to later instars (3–6 mm) (4-d LC50 1.5 and 3.5 mg/L, respectively) or to the stonefly Zelandobius spp. (Gripopterygidae) (4-d LC50 2.5 mg/L). The cased caddisflies Pycnocentria spp. (Conoesucidae) and Helicopsyche spp. (Helicopsychidae) from circumneutral stream were the most tolerant (4-d LC50 45.4 and 113 mg/L, respectively). The 14-day arsenic LC10 and LC50 for Deleatidium spp. late instars exposed to mining-impacted water were 0.12 and 0.36 mg/L, respectively.

Living on the edge: trophic ecology of Alligator mississippiensis (American alligator) with access to a shallow estuarine impoundment

I used a combination of stomach content and stable isotope analyses to examine intrapopulation and temporal variation in use of estuarine prey resources by Alligator mississippiensis (American Alligator) with access to a shallow estuarine impoundment located on the northeast Atlantic coast of Florida. I used a multi-tissue stable isotope approach to examine temporal trends in trophic interactions. This study took place within the Guana River Wildlife Management Area located in Ponte Vedra, Florida. From 2010 to 2012, I collected stomach contents from 44 A. mississippiensis and stable isotope samples from a total of 127 individuals. Stomach contents indicated the principal prey taxa consumed on a short-term basis were invertebrates (i.e., insects and crustaceans) and small baitfish. Individuals of all sizes used estuarine, as well as freshwater prey resources; however, the importance of estuarine prey to the diet increased through ontogeny. Juvenile and sub-adult stomach contents predominantly contained freshwater insects, while adult diets mainly contained estuarine baitfish and crustaceans. I used stable carbon and nitrogen isotope ratios (δ13C and δ15N) measured in three tissues (blood plasma, red blood cells, scute keratin) differing in turnover rates to assess overlap and temporal variation in the isotopic niche and inferred trophic interactions of A. mississippiensis sub-populations. Isotopic niche and inferred trophic interactions of A. mississippiensis varied among size classes, sexes, years, and capture habitats. Overlap in isotopic niches of sub-populations was highest between sexes of similar body size and for individuals captured in similar habitats within the same years. Temporal shifts in trophic interactions were most prevalent for juveniles and sub-adults, while adults demonstrated a higher degree of temporal stability in trophic interactions and niche specialization. These findings represent one of the few studies to examine intrapopulation variation in use of estuarine prey resources by A. mississippiensis. Results of this study should be useful to habitat managers designing and implementing conservation programs for coastal ecosystems in the southeastern United States, especially in light of the expected alterations in coastal habitat structure due to sea level rise and global climate change.

Toxic effects of nitrite on freshwater organisms: a review

AbstractHigh nitrite concentrations may occur mainly in recirculating aquaculture systems, but can also be found under certain conditions in natural waters. Among studied freshwater organisms, molluscs and worms followed by fish are the most resistant to nitrite. On the other hand, crustaceans and aquatic insects followed by amphibians are the most sensitive. Wide interspecific differences in nitrite susceptibility can be found within freshwater insects, crustaceans and amphibians. Chloride concentration in water is supposed to be the most important factor influencing nitrite toxicity. Generally, a positive chloride effect on nitrite toxicity reduction can be expected in all aquatic animals (or their early stages) employing gills for breathing and ion exchange. This phenomenon has already been observed in an amphipod (Eulimnogammarus toletanus, Pinkster &amp; Stock), a planarian (Polycelis felina, Dalyell), two species of crayfish, several fish species and in amphibians in early development stages. A relatively huge amount of data on nitrite effects is available for fish, but other freshwater organisms were less frequently studied. Information on chronic effect of nitrite is nearly completely missing.

Habitat recovery and restoration in aquatic ecosystems: current progress and future challenges

Abstract Aquatic ecosystems are degraded by a variety of pressures as a result of the growing human population. Global‐scale impacts include homogenization of biological communities, removal of top predators and ecosystem engineers, chemical pollution by excess nutrients and contaminants as well as deteriorating structural diversity, connectivity and process dynamics. There is a pressing societal need to reverse the decline in biodiversity and replace lost ecosystem functioning and services in aquatic ecosystems by enabling natural recovery or by active restoration. Common concepts and approaches for conservation, recovery and restoration in freshwater and marine ecosystems, aided by recent advances in ecological theory, include decision criteria on priorities for conservation, harnessing natural recovery by cessation of impacts, restoring connectivity and meso‐habitat diversity as well as the geomorphological structural template including hydrodynamic processes. Re‐oligotrophication at catchment or regional sea‐scale benefits from integrating freshwater and marine restoration. Species or assemblages that convey biogenic structure or act as ecosystem engineers and keystone species should be given priority. Top‐down control can be reinstated in closed systems. Differences between freshwater and marine ecosystems include the greater spatial restriction of many species in fresh water, the importance of rooted vegetation and insects in freshwater, and the much greater dispersal and connectivity in marine systems. These differences dictate different approaches, with more scope for active restoration work in fresh water and harnessing natural recovery in marine systems. Restoration schemes need clearly defined target states. They should generally take a process‐oriented and stepwise adaptive management approach judging success against reference or control sites. Societal and political expectations need to be managed and restoration schemes should not promise too much. Even minor rehabilitation of degraded ecosystems can put back some biodiversity and key services. Sometimes ´Ersatz´‐ecosystems are better than nothing and the best that can be achieved, especially in urban settings. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Rates and patterns of molecular evolution in freshwater versus terrestrial insects.

Insect lineages have crossed between terrestrial and aquatic habitats many times, for both immature and adult life stages. We explore patterns in molecular evolutionary rates between 42 sister pairs of related terrestrial and freshwater insect clades using publicly available protein-coding DNA sequence data from the orders Coleoptera, Diptera, Lepidoptera, Hemiptera, Mecoptera, Trichoptera, and Neuroptera. We furthermore test for habitat-associated convergent molecular evolution in the cytochrome c oxidase subunit I (COI) gene in general and at a particular amino acid site previously reported to exhibit habitat-linked convergence within an aquatic beetle group. While ratios of nonsynonymous-to-synonymous substitutions across available loci were higher in terrestrial than freshwater-associated taxa in 26 of 42 lineage pairs, a stronger trend was observed (20 of 31, pbinomial = 0.15, pWilcoxon = 0.017) when examining only terrestrial-aquatic pairs including fully aquatic taxa. We did not observe any widespread changes at particular amino acid sites in COI associated with habitat shifts, although there may be general differences in selection regime linked to habitat.

Diet reconstruction using next-generation sequencing increases the known ecosystem usage by a shorebird

ABSTRACT Molecular scatology and next-generation sequencing identified previously unknown linkages among ecosystems in the diet of Semipalmated Sandpipers (Calidris pusilla) in the Bay of Fundy, Canada. During their annual migratory stopover, the birds consumed a wider range of prey items than previously reported, which suggests that they are not selecting for the amphipod Corophium volutator and are acting as generalist foragers. Our analysis identified several novel prey items—arachnids, crabs, bivalves, several terrestrial and freshwater insect species, ctenophores, cnidarians, and fish (likely eggs or juveniles)—indicating that Semipalmated Sandpipers consume prey from marine, freshwater, and terrestrial ecosystems. Connections between Semipalmated Sandpipers and freshwater and terrestrial ecosystems were previously unknown in the Bay of Fundy. Current conservation efforts for this species are focused on beach and intertidal habitats; however, we may also need to consider the surrounding freshwater an...

Strong land‐use effects on the dispersal patterns of adult stream insects: implications for transfers of aquatic subsidies to terrestrial consumers

Summary The dispersal of terrestrial adults of freshwater insects is a key process regulating the transfer resources from aquatic habitats to terrestrial consumers, including high‐quality lipids synthesised in the aquatic environment. However, the efficiency of these transfers depends strongly on both subsidy production in the aquatic source habitat and permeability of the aquatic–terrestrial boundary. We assessed how land use (agriculture versus forest) affects stream riparian habitats and the dispersal of adult aquatic insects. Flying insects were sampled alongside eight streams (four agricultural, four forested) in central Sweden using sticky traps, placed from 1 up to 100 m from the stream edge. Environmental variables including temperature, wind, vegetation structure and canopy cover were also quantified. Abundances of adult aquatic insects were greater at agricultural than at forested sites, but most (64%) were caught close to the stream edge. In contrast, catches of adult aquatic insects declined relatively little with increasing distance from the forest streams. Overall, dispersal of the dominant aquatic insect order (Diptera) was positively associated with greater tree density and canopy shading and negatively associated with higher wind speeds and soil temperatures, more open habitats and steeper topographies. Taxonomic differences among assemblages, reflecting differing dispersal capacities, were also important, but less so than environmental factors. Our results indicate that adult aquatic insects in our forested landscapes are more likely to subsidise near‐ground food webs at a greater distance from stream channels, whereas the abundant subsidy emerging from the agricultural sites is likely to be most influential near the stream channel. A key question for future research is whether the deposition of large quantities of aquatic subsidy in agricultural riparian habitats exceeds the resource requirements and processing capacities of terrestrial consumers.

Salinized rivers: degraded systems or new habitats for salt-tolerant faunas?

Anthropogenic salinization of rivers is an emerging issue of global concern, with significant adverse effects on biodiversity and ecosystem functioning. Impacts of freshwater salinization on biota are strongly mediated by evolutionary history, as this is a major factor determining species physiological salinity tolerance. Freshwater insects dominate most flowing waters, and the common lotic insect orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) are particularly salt-sensitive. Tolerances of existing taxa, rapid adaption, colonization by novel taxa (from naturally saline environments) and interactions between species will be key drivers of assemblages in saline lotic systems. Here we outline a conceptual framework predicting how communities may change in salinizing rivers. We envision that a relatively small number of taxa will be saline-tolerant and able to colonize salinized rivers (e.g. most naturally saline habitats are lentic; thus potential colonizers would need to adapt to lotic environments), leading to depauperate communities in these environments.

Phylogeographic origin ofApatania zonella(Trichoptera) in Iceland

AbstractThe purpose of our study was to analyze the origin of the Icelandic population of the Holarctic caddisfly Apatania zonella, a species with a highly skewed sex ratio. Biological diversity in Iceland, as in the Arctic, has been shaped by the glacial periods of the Pleistocene, but Iceland’s geographic isolation contributes to its low diversity. Many species at high latitudes in the northern hemisphere have diverged allopatrically during glacial periods and expanded their distribution following the retreat of the glaciers. Genetic patterns of various species reflect these climate changes, but freshwater insects show patterns that differ from those of many vertebrate and terrestrial species. To analyze the origin of the Icelandic population we assessed sequence variation of the mitochondrial cytochrome c oxidase subunit I (COI) gene in specimens from Iceland and throughout its distribution range. We included sequences from different species for a further comparison. We also assessed sequence variation...

WATER. Saving freshwater from salts.

Ion-specific standards are needed to protect biodiversity

Are insect repellents toxic to freshwater insects? A case study using caddisflies exposed to DEET

Stream ecosystems face ever-increasing pressures by the presence of emergent contaminants, such as, personal care products. N, N-diethyl-3-methylbenzamide (DEET) is a synthetic insect repellent that is being found in surface waters environments in concentrations up to 33.4 μg/L. Information concerning DEET's toxicity in the aquatic environment is still limited and focused only on its acute effects on model species. Our main objective was to assess the effects of DEET exposure to a caddisfly non-target species using sub-lethal endpoints. For that, we chose Sericostoma vittatum, an important shredder in Portuguese freshwaters that has been already used in different ecotoxicological assays. Besides acute tests, S. vittatum were exposed during 6 days to a gradient of DEET concentrations (8, 18 and 40.5 mg/L) to assess effects on feeding behaviour and biochemical responses, such as, lipid peroxidation levels (LPO), catalase and acetylcholinesterase (AChE) activities, and also assess effects on energy reserves and consumption. Acute tests revealed a 48 h-LC50 of 80.12 mg/L and DEET exposure caused feeding inhibition with a LOEC of 36.80 mg/L. Concerning the biochemical responses, DEET caused no effects in LPO nor on catalase activity. A non-significant decrease in AChE activity was observed. Regarding energetic reserves, exposure to DEET caused a significant reduction in S. vittatum carbohydrates levels. These results add important information for the risk assessment of insect repellents in the aquatic environment and suggest that reported environmental concentrations of DEET are not toxic to non-target freshwater insects.

Aeromonas chitinase degrades chironomid egg masses.

Chironomids are freshwater insects that undergo a complete metamorphosis of four life stages. Chironomid egg masses can be degraded by Vibrio cholerae and some Aeromonas species. Egg mass degradation by V. cholerae requires haemagglutinin protease activity. Our aim was to identify the egg mass degrading (EMD) factor secreted by Aeromonas dhkanesis 3K1C15. Following the hypothesis that the EMD factor of A. dhkanesis is also a protease, secreted proteases were screened, but none of them proved to have the same properties as the EMD factor. Using conventional protein purification methods, we found that the active fraction included chitinases. We further confirmed chitin as a building block of the egg masses. Interestingly, by supplementing bacterial growth media with chitin, we observed unexpected EMD factor activity in Aeromonas isolates that initially were not able to degrade egg masses. Accordingly, we concluded that although strain 3K1C15 secretes chitinases constitutively, most Aeromonas strains secrete chitinases inductively. Induction of chitinases in nature presumably occurs when bacteria are attached to the egg mass habitat, in which chitin is abundant. Considering that chitinases are highly conserved across bacteria phyla, we assume that the role of this enzyme in the bacteria-insect interplay could be wider than is currently thought.

Aquatic insects of a lowland rainforest in Papua New Guinea: assemblage structure in relation to habitat type

AbstractPapua New Guinea is one of the most valuable tropical regions but ecological research of its freshwater invertebrates has been lacking. The goal of this paper is to evaluate the species richness, diversity and structure of aquatic insect assemblages in different habitats in the Wanang River catchment in a well-preserved lowland rainforest. Assemblage structure was studied on two spatial scales - in different habitats (river, streams and stagnant pools) and in three mesohabitats in the river (slow and fast sections and submerged wood). The results show that headwater streams had the highest morphospecies diversity, while the river had the highest insect abundance. Slow and fast sections of the river differed both in terms of insect abundance and diversity. Furthermore, a number of unique wood-associated species was found on submerged wood. The most notable feature of the assemblage structure was scarcity of shredders and dominance of predators. However, predatory beetles, bugs and dragonfly larvae exhibited contrasting habitat preferences. This study shows that Papua New Guinean lowland rainforests host diverse and distinctly structured freshwater insect assemblages.

Ethanol: A simple and effective RNA‐preservation for freshwater insects living in remote habitats

AbstractThe often proposed preservation method “snap‐freezing” is rather unpractical for sampling in remote areas. Therefore, the effectiveness, feasibility and affordability of alternative fixatives were investigated. Larvae of Orthocladius sp. (Diptera, Chironomidae) were fixed in RNAlater®, RNAfix (self‐made), acetone and ethanol of two different qualities (methylated and molecular grade). Samples were first kept at room temperature for 24 h, then at −20°C for 1 week, at −80°C for 1 month and at −80°C for 6 months. Additionally, long term storage at −20°C for up to 18 months was tested for methylated ethanol and RNAfix. Subsequently evaluated RNA quality and quantity did not differ significantly between the preservation methods. Methylated ethanol, being the most economical alternative, was chosen to be tested in a field trip. Diamesa latitarsis larvae (Diptera, Chironomidae) and Baetis alpinus nymphs (Ephemeroptera, Baetidae) were collected in two remote streams at 2208 m a.s.l. Samples were cooled (∼ 4°C) for 23 up to 30 h during sampling and transportation. Organisms were identified and photographed in ethanol at room temperature and then stored at −80°C for 6 months until RNA isolation. RNA quality was high and the yield was suitable for down‐stream applications such as cDNA synthesis and real‐time quantitative PCR. Due to these results we recommend methylated ethanol as an inexpensive but reliable RNA‐fixative for sampling in remote areas even if time‐consuming species identification has to be done prior to RNA‐extraction.

A time-calibrated phylogeny of southern hemisphere stoneflies: Testing for Gondwanan origins

For more than two centuries biogeographers have attempted to explain why terrestrial or freshwater lineages have geographic distributions broken by oceans, with these disjunct distributions either attributed to vicariance associated with Gondwanan fragmentation or trans-oceanic dispersal. Stoneflies (order: Plecoptera) are a widespread order of freshwater insects whose poor dispersal ability and intolerance for salt water make them ideal candidates for Gondwanan relicts – taxa whose distribution can be explained by vicariant isolation driven by the breakup of Gondwana. Here we reconstruct the phylogenetic relationships among southern hemisphere stoneflies (5 families; 86 genera) using 2864bp of mitochondrial (COI) and nuclear (18S, H3) DNA, with a calibrated relaxed molecular clock used to estimate the chronology of diversification. Our analysis suggests that largely antitropical stonefly sub-orders, Arctoperlaria (northern hemisphere) and Antarctoperlaria (southern hemisphere), were formed approximately 121Ma (95% prior probability distribution 107–143Ma), which may reflect the vicariant rifting of the supercontinent Pangaea. Subsequently, we infer that a single Arctoperlaria lineage has dispersed into southern hemisphere 76Ma (95% range 65–98Ma). The majority of divergences between South American and Australian stonefly lineages appear to coincide with the opening of Drake Passage around 40Ma, suggesting vicariant isolation of these landmasses may be responsible for these biogeographic disjunctions. In contrast, divergences between New Zealand lineages and their sister taxa appear to post-date vicariant timeframes, implying more recent dispersal events.

More than just fish food: ecosystem services provided by freshwater insects

1. Freshwater ecosystems cover less than 1% of the planet's surface but support up to 10% of known species. Around 25% of freshwater invertebrate species are under threat of extinction. Such a decline in species richness is likely to lead to adverse effects on the delivery of services. However, the effect of species loss on ecosystem goods and services can only be assessed once the link between species diversity and ecosystem goods and services has been established and better understood.2. Using a flexible systematic literature review search protocol, we were able to identify a range of ecosystem goods and services provided by freshwater insects in the categories of provisioning, supporting, and cultural services.3. The ecosystem services and benefits provided by freshwater insects are diverse and unexpectedly wide‐ranging including decomposition and nutrient cycling, food for a wider range of species including humans, and the inspiration for art, music, and literature. Several of these have clear economic values but are not currently fully exploited.4. The identification of goods and services may bring greater appreciation and impetus to understanding the scale of their importance, economic value, and conservation. In the absence of freshwater insects, few other service providers could replicate the same level and degree of service.

Molecular data extend AustralianCricotopusmidge (Chironomidae) species diversity, and provide a phylogenetic hypothesis for biogeography and freshwater monitoring

Resolving species relationships and confirming diagnostic morphological characters for insect clades that are highly plastic, and/or include morphologically cryptic species, is crucial for both academic and applied reasons. Within the true fly (Diptera) family Chironomidae, a most ubiquitous freshwater insect group, the genera CricotopusWulp, 1874 and ParatrichocladiusSantos-Abreu, 1918 have long been taxonomically confusing. Indeed, until recently the Australian fauna had been examined in just two unpublished theses: most species were known by informal manuscript names only, with no concept of relationships. Understanding species limits, and the associated ecology and evolution, is essential to address taxonomic sufficiency in biomonitoring surveys. Immature stages are collected routinely, but tolerance is generalized at the genus level, despite marked variation among species. Here, we explored this issue using a multilocus molecular phylogenetic approach, including the standard mitochondrial barcode region, and tested explicitly for phylogenetic signal in ecological tolerance of species. Additionally, we addressed biogeographical patterns by conducting Bayesian divergence time estimation. We sampled all but one of the now recognized Australian Cricotopus species and tested monophyly using representatives from other austral and Asian locations. Cricotopus is revealed as paraphyletic by the inclusion of a nested monophyletic Paratrichocladius, with in-group diversification beginning in the Eocene. Previous morphological species concepts are largely corroborated, but some additional cryptic diversity is revealed. No significant relationship was observed between the phylogenetic position of a species and its ecology, implying either that tolerance to deleterious environmental impacts is a convergent trait among many Cricotopus species or that sensitive and restricted taxa have diversified into more narrow niches from a widely tolerant ancestor.

Odonata of maharashtra, India with notes on species distribution.

Odonata are freshwater insects spread world-wide. Tropical areas are high Odonata diversity areas. However, there has not been accumulation of extensive baseline data on spatial distribution of these insects from such places. Maharashtra, the third largest state of India, harbors a variety of land-use and occupies six biogeographic provinces. We carried out Odonata surveys in Maharashtra during 2006–2014. Compilation of all these studies along with other authenticated records resulted in a checklist of 134 species of Odonata belonging to 70 genera representing 11 families. The highest numbers of species were recorded from the Libellulidae (48 species) and Gomphidae (22 species) families. A previous study had reported 99 species of Odonata from the Maharashtra state considering records from early 1900’s to 2012. Our observations across the state add 33 species to this list. Maharashtra forms a unique source of Odonata diversity and our observations support the importance of this region in providing valuable habitats for Odonata. Here, we discuss several of the new records, how global surveys might help fill the local gap in species distributions, how secondary data deposited through crowd-sourcing can help and what it offers to conservation.

An Observation of the Overwintering Aquatic Insects in a Prairie Pond in Saskatchewan, Canada

In temperate regions freshwater insects annually face the challenge of surviving the winter months or otherwise perishing. Ice formation presents a substantial danger to all life stages, from the eggs to adults. Accordingly, some species have adapted to overwinter within ice and emerge during the spring thaw. The diversity of aquatic species encased in the ice and frozen sediment of a prairie pond in Saskatchewan, Canada and their survival rate upon thawing was assessed in the winter of 2013. A total of 164 specimens were retrieved from the ice and sediment, 73 of which survived after thawing. Survival rate was greatest for Cymatia americana (Corixidae, Hemiptera) at 79.6%. Corixids were found in distinct clusters encased in pond ice, a phenomenon not well documented in previous literature. A higher rate of survival was expected among the chironomids, although the value falls within ranges observed in previous studies. Additionally, members of other taxa including Notonectidae (Hemiptera), Haliplidae (Coleoptera), Ceratopogonidae (Diptera), and Coenagrionidae (Odonata) were recovered; however, these specimens exhibited much lower rates of survival.