Aquatic Life Stages Research Articles

Assessing recovery of stream insects from pesticides using a two-patch metapopulation model

Pesticides can exert lethal and sublethal effects on streams organisms. Field studies have shown that non-polluted upstream patches promote population recovery from such effects. Nevertheless, the dynamics and potential carryover effects on the upstream patch are largely unknown. We used a metapopulation model with 2 patches to simulate lethal and sublethal effects on the downstream population of an insect with one generation per year, which was structured into early and late instars aquatic life stages, and an adult terrestrial life stage. We examined the implications for the recovery time of a range of scenarios covering different pesticide effect combinations, migration and exposure types. We found that recovery time responded most strongly to a reduction in reproduction in terms of the reduction of the intrinsic growth rate during the early instar aquatic life stage. For 60 of 96 scenarios with pesticide exposure in consecutive years, no recovery occurred within one year if the intrinsic growth rate was reduced by 50% or more. Without migration between patches (32 scenarios), the polluted downstream population went extinct in 5 of these scenarios. Migration lead overall to slightly faster recovery, albeit this was scenario dependent, but also to a carryover of the pesticide effect from the polluted downstream to the non-polluted upstream patch (up to 25% reduction in the minimal population size). A sensitivity analysis revealed that recovery time was most sensitive to the parameters length of the intrinsic growth phase during early instar aquatic life stage and to migration mortality of the late instar aquatic larvae, and least sensitive to the adult emigration rate and timing of pesticide application. Our study highlights the important role of sublethal effects for population responses to pesticides and that migration buffers against effects, but also carries effects over to non-polluted patches.

Sampling and comparing odonate assemblages by means of exuviae: statistical and methodological aspects

Freshwater species are in serious decline all over the world. Thus, monitoring of freshwater ecosystems and species is crucial to guide policy actions and dragonflies are generally considered to be good indicators for these systems. The aquatic life stage of the Odonata is inherently more susceptible to changes in water quality than the imago and therefore exuviae give better insights into site-specific effects. However, utilizing exuviae for monitoring purposes introduces a number of problems. For example, they often do not persist long in the environment. Some of these problems have been addressed. However, there are no published data that distinguish the influence of sampling frequency and total sampling effort on the faunal completeness. Also the number of exuviae necessary to define local assemblages has not been investigated. These questions were addressed by analyzing the data on exuviae collected in seven sites and we found that for any given total amount of time invested, it was always preferable to conduct more short surveys, rather than fewer surveys lasting longer. The study also showed that a sample size of 300 exuviae allowed us to reliably estimate the similarity of two assemblages from different sites. However, when collecting 40 exuviae or less, the reliability was low. Based on our findings we recommend sampling exuviae for a minimum of 5 days, evenly spread out over the entire season during which Odonata emerge, to sample each time for approximately 60 min and aim to collect not less than 300 exuviae in total.

Selenium speciation influences bioaccumulation in Limnodynastes peronii tadpoles

Despite being essential for animal health and fitness, Se has a relatively narrow range between deficiency and toxicity, and excess Se can cause a variety of adverse effects in aquatic organisms. Amphibians are particularly vulnerable to contaminants during larval aquatic life stage, because they can accumulate toxic ions through various routes including skin, gills, lungs and digestive tract. Few attempts have been made to understand the tissue-specific accumulation of trace elements, including the impacts of chemical speciation in developing amphibian larvae. We used radiolabelled 75Se to explore the biokinetics and tissue distributions of the two dominant forms occurring in surface waters, selenite (SeIV) and selenate (SeVI). Tadpoles of the native Australian frog Limnodynastes peronii were exposed to Se in both forms, and live-animal gamma spectroscopy was used to track accumulation and retention over time. Tissue biodistributions were also quantified at the end of the uptake and depuration phases. Results showed the bioconcentration of SeIV to be 3 times greater compared to SeVI, but rates of elimination were similar for both forms. This suggests a change of Se speciation within the organism prior to excretion. Depuration kinetics were best described by a one-phase exponential decay model, and tadpoles retained approximately 19% of the accumulated Se after 12 days of depuration in clean water. Selenium bioaccumulation was greatest in digestive and excretory organs, as well as the eye, which may directly relate to previously reported Se-induced impairments. Results demonstrate how the use of radiotracing techniques can significantly improve our understanding of trace element toxicokinetics and tissue distributions in developing amphibians. From an environmental monitoring perspective, the findings highlight the importance of considering chemical speciation as this could influence the accuracy of risk assessment.

A Flow-through Exposure System for Evaluating Suspended Sediments Effects on Aquatic Life.

This paper describes the Fish Larvae and Egg Exposure System (FLEES). The flow-through exposure system is used to investigate the effects of suspended sediment on various aquatic species and life stages in the laboratory by using pumps and automating delivery of sediment and water to simulate suspension of sediment. FLEES data are used to develop exposure-response curves between the effects on aquatic organisms and suspended sediment concentrations at the desired exposure duration. The effects data are used to evaluate management practices used to reduce the interactions between aquatic organisms and anthropogenic causes of suspended sediments. The FLEES is capable of generating total suspended solids (TSS) concentrations as low as 30 to as high as 800 mg/L, making this system an ideal choice for evaluating the effects of TSS resulting from many activities including simulating low ambient levels of TSS to evaluating sources of suspended sediments from dredging operations, vessel traffic, freshets, and storms.

Inference of Timber Harvest Effects on Survival of Stream Amphibians Is Complicated by Movement

The effects of contemporary logging practices on headwater stream amphibians have received considerable study but with conflicting or ambiguous results. We posit that focusing inference on demographic rates of aquatic life stages may help refine understanding, as aquatic and terrestrial impacts may differ considerably. We investigated in-stream survival and movement of two stream-breeding amphibian species within a before-after timber harvest experiment in the Oregon Coast Range. We used recaptures of marked individuals and a joint probability model of survival, movement, and capture probability, to measure variation in these rates attributed to stream reach, stream gradient, pre- and post-harvest periods, and the timber harvest intensity. Downstream biased movement occurred in both species but was greater for Coastal Tailed Frog (Ascaphus truei) larvae than aquatic Coastal Giant Salamanders (Dicamptodon tenebrosus). For D. tenebrosus, downstream biased movement occurred early in life, soon after an individual's first summer. Increasing timber harvest intensity reduced downstream movement bias and reduced survival of D. tenebrosus, but neither of these effects were detected for larvae of A. truei. Our findings provide insight into the demographic mechanisms underlying previous nuanced studies of amphibian responses to timber harvest based on biomass or counts of larvae.

A newly developed dispersal metric indicates the succession of benthic invertebrates in restored rivers

Dispersal capacity plays a fundamental role in the riverine benthic invertebrate colonization of new habitats that emerges following flash floods or restoration. However, an appropriate measure of dispersal capacity for benthic invertebrates is still lacking. The dispersal of benthic invertebrates occurs mainly during the aquatic (larval) and aerial (adult) life stages, and the dispersal of each stage can be further subdivided into active and passive modes. Based on these four possible dispersal modes, we first developed a metric (which is very similar to the well-known and widely used saprobic index) to estimate the dispersal capacity for 802 benthic invertebrate taxa by incorporating a weight for each mode. Second, we tested this metric using benthic invertebrate community data from a) 23 large restored river sites with substantial improvements of river bottom habitats dating back 1 to 10years, b) 23 unrestored sites very close to the restored sites, and c) 298 adjacent surrounding sites (mean±standard deviation: 13.0±9.5 per site) within a distance of up to 5km for each restored site in the low mountain and lowland areas of Germany. We hypothesize that our metric will reflect the temporal succession process of benthic invertebrate communities colonizing the restored sites, whereas no temporal changes are expected in the unrestored and surrounding sites. By applying our metric to these three river treatment categories, we found that the average dispersal capacity of benthic invertebrate communities in the restored sites significantly decreased in the early years following restoration, whereas there were no changes in either the unrestored or the surrounding sites. After all taxa had been divided into quartiles representing weak to strong dispersers, this pattern became even more obvious; strong dispersers colonized the restored sites during the first year after restoration and then significantly decreased over time, whereas weak dispersers continued to increase. The successful application of our metric to river restoration might be promising in further applications of this metric, for example, in analyzing metacommunity structure or community's recovery from extreme events such as floods, droughts or catastrophic pollution episodes.

Spatial scale and dispersal influence metacommunity dynamics of benthic invertebrates in a large river

AbstractTaxon-specific dispersal ability can affect community composition, but little is known about how it influences metacommunity dynamics, particularly for taxa with large ontogenetic changes in dispersal mode and ability. The spatial scale of a study also can affect perceived or sampled community composition, but our understanding of the artifacts resulting from the spatial extent sampled is limited, and artifacts are difficult to differentiate from real metacommunity processes. We assessed community composition of benthic macroinvertebrates at nested spatial scales in a large river and used differences in dispersal as immature aquatic life stages and winged terrestrial adults to explain patterns in community structure. Spatial distribution of patches alone (space), followed by synergistic effects of space and environmental factors, and then environmental factors alone were the best predictors of community structure. As predicted by metacommunity theory, the local environment was a better predictor t...

Acute oral toxicity of chemicals in terrestrial life stages of amphibians: Comparisons to birds and mammals

Amphibians are currently the most threatened and rapidly declining group of vertebrates and this has raised concerns about their potential sensitivity and exposure to plant protection products and other chemicals. Current environmental risk assessment procedures rely on surrogate species (e.g. fish and birds) to cover the risk to aquatic and terrestrial life stages of amphibians, respectively. Whilst a recent meta-analysis has shown that in most cases amphibian aquatic life stages are less sensitive to chemicals than fish, little research has been conducted on the comparative sensitivity of terrestrial amphibian life stages. Therefore, in this paper we address the questions “What is the relative sensitivity of terrestrial amphibian life stages to acute chemical oral exposure when compared with mammals and birds?” and “Are there correlations between oral toxicity data for amphibians and data for mammals or birds?” Identifying a relationship between these data may help to avoid additional vertebrate testing. Acute oral amphibian toxicity data collected from the scientific literature and ecotoxicological databases were compared with toxicity data for mammals and birds. Toxicity data for terrestrial amphibian life stages are generally sparse, as noted in previous reviews. Single-dose oral toxicity data for terrestrial amphibian life stages were available for 26 chemicals and these were positively correlated with LD50 values for mammals, while no correlation was found for birds. Further, the data suggest that oral toxicity to terrestrial amphibian life stages is similar to or lower than that for mammals and birds, with a few exceptions. Thus, mammals or birds are considered adequate toxicity surrogates for use in the assessment of the oral exposure route in amphibians. However, there is a need for further data on a wider range of chemicals to explore the wider applicability of the current analyses and recommendations.

NightLife: A cheap, robust, LED based light trap for collecting aquatic insects in remote areas.

Inland waters cover less than 1% of our planet's surface, yet provide habitat to approximately one hundred thousand aquatic insect species, i.e. those with at least one aquatic lifestage (Balian et al. 2008, Dijkstra et al. 2014). Considering the taxonomic deficit in these groups this figure is likely a significant underestimate of the true aquatic insect diversity (Dijkstra et al. 2014). The majority of aquatic insect diversity is comprised of true flies (Diptera), followed by caddisflies (Trichoptera), beetles (Coleoptera), dragonflies (Odonata), stoneflies (Plecoptera) and mayflies (Ephemeroptera) (Balian et al. 2008, Dijkstra et al. 2014). The ecology of these groups has been the focus of significant study due to their role as bioindicators of water quality, as many species are sensitive to pollution and sudden changes in their environment (Rosenberg and Resh 1993). In addition many aquatic dipteran species are vectors of disease (e.g. Currie and Adler 2008, Rueda 2008). Aquatic insects are surveyed using a variety of methods including light trapping (e.g. Collier et al. 1997) which attracts emergent adults, and often mayfly subadults, using mercury vapour (MV) bulbs or actinic fluorescent tubes. Light trapping can be either active: attended light sheets, or passive: a combination of a light with a trap (Hardwick 1968, Hienton 1974). Passive traps allow samples from multiple sites to be collected in parallel by an individual in the field, with the number of sampling sites limited by the size and weight of each trap. Current Lights Mercury vapour (MV) bulbs work by passing an arc of electric current through ionised mercury vapour; as a result these bulbs require a relatively high current to maintain the arc and thus are limited to use with either mains power or a petrol / diesel powered generator. Remote areas therefore cannot be sampled without significant effort. In addition MV bulbs are excessively bright for attracting aquatic insects, and tend to draw large numbers of night flying lepidoptera and other non-target species. MV bulbs are also delicate, easily damaged in transport and liable to break if exposed to rain during operation due to thermal fracture of the glass, and their high operating temperature is a waste of power. Actinic fluorescent tubes also use mercury, but their method of operation requires a smaller current draw. While an improvement over MV bulbs, the current draw of fluorescent tubes does still require sizeable batteries if they are to be used in remote locations. For example a single 4W flourescent tube requires a 6v 12Ah battery weighing up to 2kg for an approximate 12hr run time. Fluorescent tubes are also delicate and liable to damage under field conditions. Both MV bulbs and actinic fluorescent tubes contain mercury, which if released in the field can be hazardous for the environment. An ideal aquatic insect light trap would have these properties: Be able to run from small, standard, [potentially] rechargeable batteries. Use low power light sources, at frequencies targeted for insect vision. Be robust enough for field use without special packing or travel arrangements. Be capable of autonomous operation. Light Emitting Diodes Light Emitting Diodes (LEDs) are semiconductor devices that are used in a wide range of scientific, home and commercial lighting solutions due to the following properties: low power / high-efficiency (compared to incandescent / fluorescent) narrow spectral emissions (i.e. specific colours) long-life low-operating temperature durable (enclosed in a solid epoxy case rather than hollow glass) small size and weight These same properties also lend themselves to the use of LEDs in insect collection.

Landscape context influences the abundance of amphibians and the strength of their food web interactions in small ponds

Many species, including most amphibians, undergo an ontogenetic niche shift (ONS) from an aquatic larval stage to a terrestrial adult stage. We use the ratio of aquatic to terrestrial habitat in a landscape as a tool to understand the influence of landscape context on the population growth of ONS species. The aquatic to terrestrial ratio (ATR) of habitats can be viewed as an analog to the influence of resource ratios on the population growth of consumers and depends on the degree to which each habitat type limits the growth of a given population. Population growth rates of shorter‐lived species tend to be more limited by demographic rates in early (aquatic) life stages. As a result, increasing the ATR should lead to a higher total population size in the landscape (and higher densities in the terrestrial habitat), but have little influence on the density of individuals in any given aquatic habitat. Alternatively, population growth rates of longer‐lived species tend to be more limited by demographic rates in later (terrestrial) life stages and increasing the ATR should have little influence on the total population size in the landscape, but decrease the density of individuals in any given aquatic habitat. We show that among‐landscape variation in the breeding‐pond densities of three widespread amphibians with contrasting life histories is consistent with this framework. Within‐pond densities of Pseudacris crucifer, a species with short‐lived adults, were not influenced by ATR, whereas within‐pond densities of Hyla versicolor, a longer‐lived member of the same family (Hylidae), declined as ATR increased. Ambystoma maculatum, a long‐lived salamander, also had lower densities in ponds with higher ATR. Because A. maculatum larvae are important predators in ponds, we use structural equation modeling to show that landscape context (ATR) can moderate community structure via direct (amphibian abundances) and indirect (prey species richness) effects.

Food Web Linkages Demonstrate Importance of Terrestrial Prey for the Threatened California Red-Legged Frog

Restoration efforts are ongoing to protect the threatened California Red-Legged Frog (Rana draytonii) from further decline, but conserving species that have aquatic and terrestrial life stages can be challenging. For example, although it is clear that aquatic habitat must be protected for breeding, less is known about the importance of terrestrial habitat. Food web linkages remain largely unknown for this species yet would offer insight on the source of prey items and, thus, the importance of each type of habitat. We used three methods to analyze food web linkages for the California Red-Legged Frog: 1) stable isotopes collected from frogs and key species in their ecosystem; 2) stomach contents sampled from live frogs in the wild; and 3) stomach contents sampled from museum specimens. The stable isotope mixing model found 99.7% of R. draytonii diet came from terrestrial prey. Wet and dry season stomach content samples flushed from captured frogs had 90% terrestrial prey, and museum specimens contained 82% terrestrial prey. These data suggest that conservation efforts should protect riparian and upland habitats adjacent to aquatic habitats in addition to aquatic habitats.

Using Hexagenia in sediment bioassays: Methods, applicability, and relative sensitivity

The majority of sediment toxicity and aquatic bioaccumulation assessments are conducted using standardized species, such as Hyalella azteca, Chironomus dilutus, and Lumbriculus variegatus. The burrowing mayfly, Hexagenia sp., may serve as an ideal supplemental organism for both toxicity and bioaccumulation studies for several reasons. Hexagenia are recognized as sensitive species, have a long aquatic life stage (up to 2 yr), and have large bodies, which aid in retrieval from sediments and for residue analysis. The present study outlines the authors' established method for collecting and hatching eggs, raising nymphs, and using these animals for toxicity testing. Furthermore, the relative sensitivity of 3 size classes of Hexagenia to a representative contaminant (bifenthrin) was examined and compared with laboratory-derived median lethal concentrations for the more traditionally used Hyalella and Chironomus. Finally, sublethal end points, including immobilization and suspended solids, were defined for this species. This provides guidance for the use of this species in toxicological bioassays.

Damselfly larvae select quick release lamellae for survival

Adult damselflies are a spectacular vision of summer, streaking through the air above pond surfaces. Yet survival through their earlier aquatic life stages is extremely precarious. Equipped with leaf-like lamellae hinged at the end of the abdomen for propulsion, the structures provide the perfect appendages for passing predators to grab onto. But the larval insects have a self-preservation mechanism that helps them to escape hungry predators: they self amputate – autotomize – trapped lamellae. Jennifer Gleason, Douglas Fudge and Beren Robinson from the University of Guelph, Canada, explain that the ability of a larva to shed its lamellae with ease improves its chances of survival, which might lead larvae that inhabit heavily predated waters to develop relatively fragile lamellar joints to increase their chances of survival (p. 185). To test the theory, the Canadians measured the force required to break damselfly larvae lamellar joints, as well as the size and cuticle thickness of the joint. They discovered that the joints of damselfly larvae from fishless ponds – where carnivorous dragonfly larvae flourish – were much more fragile than the joints of larvae from ponds where there were few dragonfly larvae. ‘This suggests that autotomy may evolve in larval damselflies under selection from small grasping predators like larval dragonflies by favouring smaller joint size or reduced cuticle area of lamellae joints’, says the team.

Upland Habitat Quality and Historic Landscape Composition Influence Genetic Variation of a Pond-Breeding Salamander

Understanding the temporal and spatial scale at which habitat alteration impacts populations is important for conservation and management. Amphibians have declined more than other vertebrates, and pond-breeding species are particularly susceptible to habitat loss and fragmentation because they have terrestrial and aquatic life stages. One approach to management of pond-breeding species is protection of core upland habitat surrounding the breeding pond. We used genetic variation as an indicator of population status in a common amphibian species, spotted salamanders (Ambystoma maculatum), to determine how amount of suitable upland habitat relates to population status in the greater Charlotte, North Carolina, USA metropolitan area. We developed candidate models to evaluate the relative influence of historical and contemporary forested habitat availability on population genetic variation at two spatial scales of upland area (164 m and 2000 m) at four time intervals over the past seven decades (1938, 1978, 1993, 2005). We found that historical land cover best predicted contemporary allelic richness. Inbreeding coefficient and observed heterozygosity were not effectively predicted by forest cover at either spatial or temporal scales. Allelic richness was best predicted at the smaller spatial scale in the 1993 time interval. Predicting and understanding how future landscape configuration affects genetic variation of common and rare species is imperative for the conservation of amphibian and other wildlife populations.

Life Cycle Complexity Influences Intraguild Predation and Cannibalism in Pond Communities

Predation risk is an important contributor to community structure that varies in response to abiotic and biotic factors. In aquatic habitats, predation risk is often linked to hydroperiod as the latter directly influences predator identity within these ecosystems. For pond-breeding salamanders, intraguild predation (IGP) and cannibalism are prevalent interactions in larval communities, but the frequency of each type of agonistic interaction, as well as changes in their pervasiveness along hydroperiod gradients are not well understood. Size-structured populations of aquatic life stages (paedomorphic adults and overwintered larvae) of mole salamanders (Ambystoma talpoideum) have the potential to be dominant IG predators and cannibals in permanent ponds because of large size advantages over successive cohorts, but the species exists as only a single larval cohort in temporary ponds with reduced predatory abilities on guild members. Thus, both the potential for and intensity of predation by this species is li...

The macroinvertebrate seedbank promotes community persistence in temporary rivers across climate zones

Summary Aquatic macroinvertebrates inhabiting temporary rivers are typically described as having low resistance to riverbed drying. However, little research has examined the ‘seedbank’ within dry riverbed sediments, which comprises aquatic life stages that survive in dewatered sediments and from which active organisms may develop only after surface water returns. We synthesised published and unpublished data from studies that had experimentally rehydrated sediments collected from dry riverbeds, to establish the importance of the seedbank in promoting macroinvertebrate community resistance. Studies from across climate zones were included, to examine seedbank importance in relation to environmental harshness and, in particular, sediment moisture. We also assessed the importance of the seedbank relative to alternative habitats promoting persistence of the flowing river (FR) assemblage. We predicted that the proportion of the FR assemblage present in rehydrated sediments (RS) would decrease with environmental harshness, due to conditions within the sediments becoming less conducive to the survival of biota. A negative relationship between the proportion of FR taxa present in RS and harshness was observed, and this contributed to a reduction in the compositional similarity of FR and RS assemblages as harshness increased. Significant positive correlations were identified between sediment moisture content and macroinvertebrate community metrics (density and taxon richness) in some systems. Habitats external to the dry reach, which contribute to community resilience, were invariably inhabited by a greater number of FR taxa than rehydrated sediments. However, rehydrated sediments included several FR taxa that were not found in any other habitats during the dry phase, including families of Coleoptera and Diptera. Our results indicate the importance of the seedbank as a resistance mechanism for temporary river macroinvertebrates. With climate change scenarios predicting an increase in riverbed drying, maintaining habitats that facilitate the persistence of instream communities during dry phases is an increasing priority. We identified strong relationships between sediment moisture and taxon richness, and river management and rehabilitation activities should therefore aim to retain moisture in drying sediments, by manipulating parameters such as riparian shading.

High prevalence of infection in tadpoles increases vulnerability to fungal pathogen in high-Andean amphibians

The amphibian pathogen Batrachochytrium dendrobatidis (Bd) is causing population declines and species extirpations worldwide. Montane amphibians in tropical and temperate regions are especially vulnerable to chytridiomycosis. High-elevation amphibian assemblages typically include few species, so that epizootics should be limited once high frog mortality hinders transmission of the pathogen. We hypothesized that tadpoles of a high-elevation frog in the Peruvian Andes, Telmatobius jelskii, could function as reservoir for Bd in Andean streams. We postulated that, for tadpoles to function as an efficient reservoir of Bd, they should inhabit streams over extended periods of time, and have high prevalence of Bd. We surveyed streams between 2400 and 4850m in the wet and dry seasons of 2010, where we captured, swabbed and determined the developmental stage of 458 tadpoles. We found that cohorts of tadpoles overlap continuously in these streams, as a consequence of multiple breeding events throughout the year. Prevalence of Bd among tadpoles averaged 53.1% (95% confidence interval: 49.8–56.3%); 8 out of 13 streams inhabited by T. jelskii had a prevalence greater than 50%. Prevalence of Bd was also higher during the dry season and increased with the age of the tadpoles. Our results support the hypothesis that the year-long presence of infected tadpoles in streams makes high-Andean Telmatobius frogs especially vulnerable to chytridiomycosis. The genus is already extirpated in Ecuador, and has been observed to decline rapidly in Peru, Bolivia and Argentina. Conservation strategies to mitigate the impact of Bd on populations of Telmatobius should consider aquatic life-stages.

Toxicity of pesticides to aquatic and terrestrial life stages of amphibians and occurrence, habitat use and exposure of amphibian species in agricultural environments

The aim of this study was to provide EFSA with information relating to assessment of the risk to amphibians posed by pesticide exposure. In the first part of the study the European amphibian species associated with agricultural habitats were identified with the aim of collating information for representative species such as body size and life-cycle. Also collated were the results of studies of amphibians in European agricultural habitats to provide information on activity in areas where they may be at risk of exposure to pesticides. Several studies of the use of agricultural habitats were found providing information on migration distances and associations with particular crops although the data is patchy. The second part of the study collated information useful to risk assessment for terrestrial habitats. Information was presented on possible assessment of dietary exposure but methods for estimating dermal exposure have not yet been developed due to lack of necessary information. Other routes of exposure such as soil ingestion and inhalation were considered but no methods specific to amphibians were found. Finally, toxicity data for both the aquatic and terrestrial stages were gathered for comparison with fish and bird/mammal data respectively. A substantial quantity of data was found for aquatic exposure and after quality assessment data for each time period were presented. Far less information was found for terrestrial amphibians and what is available is of variable quality. More information is required to allow the assesment of exposure, particularly dermal exposure and the relative toxicity of pesticides to terrestrial amphibians and other vertebrate groups.

All the better to see you with: a review of odonate color vision with transcriptomic insight into the odonate eye

Although dragonflies and damselflies (Insecta: Odonata) represent some of the most advanced visual systems among insects, odonate visual systems are not as well understood as those of model or more economically important insects. Yet, with their large and complex eyes, aquatic and terrestrial life stages, entirely carnivorous lifestyle, exceptional mating behaviors, diversity in coloration, occupancy of diverse light environments, and adult success that is completely dependent on vision, it would seem studying the visual system of Odonata at the molecular level would yield highly rewarding scientific findings related to predator/prey interactions, the physiological and molecular shifts associated with ecological shifts in light environments, and the role of vision on behavioral ecology. Here, we provide a review of odonate color vision. The first odonate opsin sequences are published using a degenerate PCR approach for both dragonfly and damselfly lineages as well as a transcriptome approach for a single species of damselfly. These genetic data are combined with electrophysiology data from odonates to examine genotype/phenotype relationships in this visual system. Using these data, we present the first insights into the evolution and distribution of the visual pigments (opsins) among odonates. The integration of molecular and behavioral studies of odonate vision will help answer long-standing questions about how sensory systems and coloration may coevolve.

Spatial and temporal aquatic–terrestrial transitions in the temporary Albarine River, France: responses of invertebrates to experimental rewetting

Summary1. In temporary rivers, viewed as coupled terrestrial–aquatic ecosystems, spatial and temporal transition zones between aquatic and terrestrial conditions are common and occur simultaneously.2. The effects of artificial rewetting on terrestrial and aquatic invertebrate assemblages were examined in dry sediments collected from the Albarine River, France. Rewetted sediments had previously been dry for between 0.1 and 142 days. Dry sediments were collected directly from the streambed (DS) and from riparian gravel bars (RGB).3. We first predicted that invertebrate responses to rewetting would vary with the duration of the preceding dry period. Second, we predicted convergence of the invertebrate assemblages in DS and RGB sediments with increasing duration of the dry period. Third, we predicted that an aquatic ‘invertebrate seedbank’ (aquatic life stages that persist within streambed sediments during dry periods) would contribute substantially to the resilience of benthic assemblages.4. Results indicated that the duration of the dry period was the primary driver of aquatic and terrestrial responses to artificial rewetting. The density and richness of aquatic taxa decreased with the duration of the dry period in both DS and RGB sediments, whereas the density of terrestrial invertebrates increased in DS sediments.5. No convergence between DS and RGB assemblage composition was observed with an increasing dry period. Although there were more aquatic organisms in DS sediments than in RGB sediments, there was no difference in taxonomic richness between sediment types. Even after prolonged dry periods (142 days), there was typically a lower density and taxonomic richness of terrestrial invertebrates in DS sediments than in adjacent RGB sediments.6. The results suggest that the aquatic invertebrate seedbank could contribute substantially to the resilience of benthic assemblages in the Albarine River, in addition to other mechanisms such as drift and oviposition. Of the taxa in the benthos before and after the summer dry period, 65% were also recovered from artificially rewetted DS sediments. The simultaneous presence of temporal and spatial terrestrial–aquatic transition zones in temporary rivers increases successional diversity (i.e. mosaics of dry and saturated streambed patches at various stages of terrestrial and aquatic succession). This contribution to biodiversity emphasises the need to protect dry reaches of temporary rivers.