Odonate Nymphs Research Articles

Taxonomical studies of dragonfly nymphs (Odonata, Libellulidae) by using their exuviae

Taxonomic studies of dragonfly nymphs were done up to species level using their exuviae. Exuviae, being the last instar larval skin, possess all larval features. These features can be used for the identification of odonate nymphs up to species level. Seven species belonging to the family Libellulidae were identified using the features present on exuviae. This is a non-invasive method that can be used for the taxonomic studies of dragonfly nymphs without rearing them in the laboratory. The study describes the morphological features of seven species of dragonfly nymphs belonging to family Libellulidae using exuviae. A taxonomic key for the identified exuviae were also provided.

The role of selected odonate nymphs in biological control of Culex quinquefasciatus larvae, and effect of glyphosate herbicide on their predatory performance

The role of selected odonate nymphs in biological control of Culex quinquefasciatus larvae, and effect of glyphosate herbicide on their predatory performance

Ontogenetic shift in the trophic role of the invasive killer shrimp Dikerogammarus villosus: a stable isotope study

The introduction of the amphipod Dikerogammarus villosus in European fresh waters is to date recognized as a threat to the integrity of invaded communities. Predation by D. villosus on native benthic invertebrates is assumed as the key determinant of its ecological impact, yet available information describe the species as a primary consumer as well as a carnivore depending on local conditions. Here, we assessed the trophic position (TP) of D. villosus in Lake Trasimeno, a recently invaded lentic system in central Italy, using the CN isotopic signatures of individuals captured in winter spanning two orders of magnitude in body size. TP estimations were compared with those characterizing the native amphipod Echinogammarus veneris and other representative invertebrate predators. On average, D. villosus showed a trophic position higher than E. veneris, and comparable with that of odonate nymphs. An in-depth analysis revealed that large-sized individuals had a trophic position of 3.07, higher than odonates and close to that of the hirudinean predator Erpobdella octoculata, while small-sized specimens had a trophic position of 2.57, similar to that of E. veneris (2.41). These findings indicate that size-related ontogenetic shifts in dietary habits may per se vary the nature of the interaction between Dikerogammarus villosus and native invertebrates from competition to predation. Information collated from published isotopic studies corroborated the generality of our results. We conclude that intra-specific trophic flexibility may potentially amplify and make more multifaceted the impact of the species on other invertebrate species in invaded food webs.

Crayfish Eating in Snakes: Testing How Anatomy and Behavior Affect Prey Size and Feeding Performance.

SynopsisQuantifying the performance of animals is a powerful methodology for determining the functional consequences of morphological variation. For example, snakes consume prey whole, and variation in the anatomy of their trophic apparatus directly affects gape and limits maximal prey size. However, for the foraging ecology of snakes and other systems, scant data exist regarding how often maximal capacities are taxed in nature. Hence, we quantified: (1) maximal gape, (2) the size of prey relative to maximal gape, and (3) how the type and relative size of prey affected behavior and prey handling times (HTs) for two species of natricine snakes that primarily eat soft- (Regina septemvittata) or hard-shelled (Liodytes alleni) crayfish. Liodytes alleni had significantly larger maximal gape than R. septemvittata with equal snout–vent length. The percentages of large prey (>60% maximal gape area) consumed in the field were low in both R. septemvittata (22%) and L. alleni (2%). However, R. septemvittata, especially juveniles, ate relatively larger prey than L. alleni. Strategies for dealing with the seasonal scarcity of small crayfish differed as juvenile R. septemvittata commonly removed and ate only chelipeds from crayfish too large to swallow whole, whereas juvenile L. alleni ate many small odonate nymphs. During laboratory trials, unlike R. septemvittata, L. alleni usually used its body to restrain prey with behaviors that depended on relative prey size and prey hardness. Liodytes alleni consumed soft-shelled crayfish significantly faster than R. septemvittata and significantly faster than hard-shelled crayfish. Several of the differences in gape, prey size, and prey HTs and behavior between the crayfish-eating snakes resemble those between two phylogenetically distant species of homalopsid snakes that consume either hard- or soft-shelled crabs. In both groups of crustacean-eating snakes, the decreased capture success in captivity and the rare consumption of relatively large hard-shelled crustaceans in the field suggest that the ability to capture this type of prey constrains prey size more commonly than maximal gape. Based on data integrating snake size and gape with the relative mass of intact prey, the predicted potential feeding performance R. septemvittata consuming intact prey exceeded that of the other three species.

Effect of environment on functional traits of co-occurring water beetles

We investigated trait-environment relationships of co-occurring aquatic Coleoptera specifically true water beetles in anthropogenic ponds from the Western Ghats, India for the first time. Our objectives were to: (1) identify species assemblages; (2) study species traits; (3) study trait-environment relationships of co-occurring species. We analysed 132 samples collected using standardised quantitative method during the years 2016 and 2017. We found 16 significant assemblages using Fager's index, where most of the pairs have body size ratio of 1.3 or more. For example,Laccophilus parvulus and Hydaticus satoipair has body size ratio of 3.98, and both are predators, indicating that body size is a function of food size. Moreover, factor analysis revealed three major swimming categories of studied beetles, namely fast swimmers, maneuverers and poor swimmers. Further, the RLQ analysis, and combined approach of RLQ and fourth-corner analysis showed that environmental variables affected species traits. For instance, odonate nymphs and submerged vegetation were positively associated with fast swimmers likeLaccophilusinefficiensandHydaticus satoi. The assemblage of congenersHydroglyphus inconstansandH. flammulatuscan be predator-mediated as these beetles showed negative association with odonate nymphs as well as competitive to obtain resource by showing positive association with chironomid larvae. Therefore, the traits studied were important for ecological performances of species in ponds. This study has also highlighted the importance of anthropogenic ponds in the Western Ghats as biodiversity refuges of ecologically unique and evolutionary old major extant lineages of water beetles.

Predation of Dragonfly Nymphs by Passerines

Avian predation of dragonflies and damselflies (Odonata) is fairly well-documented, but most observations are restricted to non-passerine birds eating adult odonates. As nymphal odonates are aquatic, most passerine birds would not encounter them while foraging but instead are more likely to catch teneral adults on their maiden flights. Photographs taken by naturalists over the past several years suggest that passerine predation on odonate nymphs, while apparently rare, occurs across a wider range of species than previously documented.

Miniaturized QuEChERS based methodology for multiresidue determination of pesticides in odonate nymphs as ecosystem biomonitors

The impacts of the modern, agrochemicals based agriculture that threatens the overall systems sustainability, need to be monitored and evaluated. Seeking for agroecosystems monitors, the present article focus in the occurrence and abundance of aquatic macroinvertebrates, that have been frequently used as bioindicators of water quality due to their relationship with land use. Some of these organisms are on the top of the food chain, where bioaccumulation and biomagnification processes can be observed, and they can turn into secondary pollution sources of systems and terrestrial organisms as well. Odonate nymphs, which belong to the functional group of predators, were selected for this study. A methodology to determine 73 pesticide residues in odonate nymphs by LC-MS/MS and GC-MS/MS was developed. A QuEChERS sample preparation strategy was adapted. As it is complex to obtain samples especially in disturbed ecosystems, the method was minimized to a sample size of 200mg of fresh nymphs. The method was validated and good recoveries (71–120%) with RSDs below 20% for the majority of the studied pesticides at least at two of the assayed levels 1, 10 and 50µgkg−1 were obtained. For 32 analytes the limit of quantitation was 1µgkg−1 and 10µgkg−1 for the others. The lineal range was observed between 1–100µgkg−1 in matrix-matched and solvent calibration curves for most of the assessed pesticides. LC-MS/MS matrix effects were evaluated, 40% of the analytes presented low or no signal suppression. Only flufenoxuron presented high matrix effects. The obtained methodology is adequate for pesticide multiresidue analysis in aquatic macroinvertebrates (odonates) aiming to contribute to the ecological state evaluation of freshwater ecosystems.

Nanofabrication of Graphene Quantum Dots with High Toxicity Against Malaria Mosquitoes, Plasmodium falciparum and MCF-7 Cancer Cells: Impact on Predation of Non-target Tadpoles, Odonate Nymphs and Mosquito Fishes

Recently, it has been highlighted an overlooked connection between the biting activity of Anopheles mosquitoes and the spread of cancer. The excellent physico-chemical properties of graphene quantum dots (GQDs) make them a suitable candidate for biomedical applications. We focused on the toxicity of GQDs against Plasmodium falciparum and its vector Anopheles stephensi, and their impact on predation of non-target mosquito predators. Biophysical methods, including UV–vis, photoluminescence, FTIR and Raman spectroscopy, XRD analysis and TEM, confirmed the effective GQD nanosynthesis. LC50 against A. stephensi ranged from 0.157 (larva I) to 6.323 ppm (pupa). The antiplasmodial activity of GQDs was evaluated against CQ-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of P. falciparum. IC50 were 82.43 (CQ-s) and 85.17 μg/ml (CQ-r). In vivo experiments conducted on Plasmodium berghei infecting albino mice showed moderate activity of GQDs if compared to chloroquine. Concerning non-target effects, the predation efficiency of Gambusia affinis, Anax immaculifrons and Hoplobatrachus tigerinus post-treatment with GQDs was enhanced. Lastly, GQDs were toxic against MCF-7 breast cancer cell lines with an IC50 = 24.81 μg/ml, triggering apoptosis in treated cells. Overall, we highlighted the multipurpose potential of GQDs for the development of newer drugs in the fight against Anopheles vectors, Plasmodium parasites and breast cancer cells.

Indirect Interactions Limit the Efficiency of Odonata as Natural Control Agents for Mosquito Larvae

Odonate nymphs are voracious predators and may be useful natural control agents. However, odonates are normally found in complex guilds with a high degree of conspecific and inter specific predation that may reduce their overall predation efficiency. The present study investigates whether indirect interactions, mediated via chemical predation signals, inhibit the consumption of mosquito larvae by two common odonates: Crocothemis erythraea and Ischnura evansi. Our results show that the predation rate of C. erythraea is reduced by chemical cues from Anax imperator, but the response of I. evansi to C. erythraea was statistically non-significant. This study shows that intra-guild interactions may limit the effectiveness of odonates as predators of mosquitoes.

Effects of environmental factors on the species composition of aquatic insects in irrigation ponds

AbstractAlthough irrigation ponds contribute to the conservation of aquatic biodiversity, they have experienced declines in recent years. We therefore examined the relationships between various environmental factors and the community composition of aquatic insects, specifically insect predators, in irrigation ponds to gain knowledge that would aid in the conservation and restoration of biodiversity. We selected Odonata, Hemiptera and Coleoptera as target taxonomic groups and conducted censuses of these groups in 21 ponds in Shiga, central Japan. In total, we collected 30 and 10 species (or species groups) of Odonata and Hemiptera, respectively, and 17 species of Coleoptera. A partial canonical correspondence analysis revealed that the following four environmental factors significantly affected the species composition of aquatic insect communities: the number of emergent plant species, percent concrete revetment, presence of litter and peripheral length. Among these variables, the number of emergent plant species was the most potent factor, perhaps because emergent plants serve as sites for oviposition and emergence, and provide refugia for aquatic insects (odonate nymphs in particular). In contrast, some species specifically inhabited sites poor in emergent plants. This study shows that reductions in concrete revetments are necessary for the conservation of biodiversity. This would lead to increases in the number of aquatic plant species, which provide habitats and oviposition sites for many aquatic insects. Furthermore, to enrich the local biodiversity of aquatic insects, groups of irrigation ponds with different environments are needed.

The Nymphal Odonate Fauna of Two Watersheds in the Lower Potomac River Basin, Maryland, with Emphasis on Rare Taxa

Sixty percent of Maryland's odonate species are considered to be in need of conservation. To prioritize areas for the protection of biodiversity, the Maryland Department of Natural Resources (MD DNR) has identified 10 watersheds with the highest rates of occurrence of imperiled and rare stream species, including odonates. We examined the lotic-breeding odonate fauna of two of these high priority watersheds to determine the distribution and status of several imperiled odonate species in Maryland. Odonate nymphs from two Lower Potomac River basin watersheds, Zekiah Swamp Run and Breton Bay, were collected by volunteers and MD DNR's Maryland Biological Stream Survey from 2000–2010 and were identified to species level when possible. Thirty-four species were collected during this survey, 10 of which are state-listed species. The data collected in this survey detail the distributions, habitats, and microhabitats of rare odonates in two priority watersheds in Maryland that can be used to aid in the conservation of these species and their habitats.

Habitat complexity reduces prey vulnerability: An experimental analysis using aquatic insect predators and immature dipteran prey

The effects of alternative prey and structural complexity of habitat on the selection of mosquito larvae by aquatic insect predators were evaluated in the laboratory. The water bugs Anisops bouvieri, Diplonychus ( = Sphaerodema) rusticus, and D. annulatus, and the odonate nymphs, Ceriagrion coromandelianum and Brachydiplax chalybea chalybea, selected mosquito larvae based on their abundance relative to chironomid larvae and on the levels of habitat complexity. The effect of one prey species on the other was asymmetrical, as indicated through prey selectivity values. Compared to open habitat, the presence of macrophytes reduced the vulnerability of mosquito larvae while the effect was reverse in the presence of sediments. When both sediment and macrophytes were present in habitats, all the predators except D. annulatus consumed more mosquito larvae than chironomid larvae. The clearance rate, an indicator of predatory efficiency, varied among the predator species and habitat types. The results suggest that the outcome of the interactions between insect predators and mosquito immatures was context-dependent and that it was mediated by the presence of alternative controphic species and the habitat complexity.

Top-down control by insect predators in an intermittent pond – a field experiment

The role of predation in the regulation of freshwater communities is predicted to decrease along a habitat-duration gradient, from permanent to episodic waters. We tested the role of invertebrate predation in shaping the community structure in a fishless temperate intermittent pond with a three month long hydroperiod by comparing the community structure in two large field enclosures (4.2 m2) with added predators to two enclosures without added predators. The added predators reflected the density and composition of top predators in the pond and comprised weekly additions of dytiscid larvae (for three weeks) followed by weekly additions of odonate nymphs (for five weeks). Compared with the enclosure controls, the predator addition enclosures had fewer dipterans and crustaceans, higher concentrations of benthic ciliates and other protozoans, higher chlorophyll a and bacterial counts, and lower abundance of rotifers. Many treatment effects were temporally variable and this appeared to be linked to predator identity, predator size, and prey availability. Compared with the surrounding pondwater, the enclosed areas had lower abundance of molluscs, ostracods and cladocerans but higher abundance of cyclopoids and higher concentrations of phytoplankton and ciliates. Despite high productivity and seasonally variable predator and prey assemblages, which likely buffered against strong top-down control, we conclude that the top-predators regulate the dipterans and zooplankton in this intermittent pond and that the effects propagated down through the food web to lower trophic levels.

Biocontrol efficiency of odonate nymphs against larvae of the mosquito, Culex quinquefasciatus Say, 1823

An estimation of the predatory efficiency of the nymphs of five coexisting odonate species Aeshna flavifrons, Coenagrion kashmirum, Ischnura forcipata, Rhinocypha ignipennis and Sympetrum durum using the fourth-instar larvae of Culex quinquefasciatus as prey, was made under laboratory and semi-field conditions. The daily feeding rate varied among the odonate species, at laboratory conditions. The mean number of IV instars Cx. quinquefasciatus larvae killed per day, ranged between 14 and 64 (64 mosquito larvae for I. forcipata, 57 for A. flavifrons, 45 for R. ignipennis, 25 for S. durum and 14 for C. kashmirum). The prey consumption was linearly related to the number of predators and prey available but inversely related with space. It was also noted that the feeding rates varied significantly between dark and light conditions, in all the odonate species. The presence of nymphs in semi-field conditions significantly lowered the mosquito larval density in dipper samples after 15 days from the introduction, followed by a significant increase of larval mosquito density after 15 days from the withdrawal of the nymphs. The results of the present observations are suggestive of the use of odonate nymphs in temporary pools or larger habitats where they can be a potential biological resource in regulating the larval population of the vector and pest mosquitoes.

Diversity, Abundance, and Disturbance Response of Odonata Associated with Breeding Sites of <I>Anopheles pseudopunctipennis</I> (Diptera: Culicidae) in Southern Mexico

Odonate nymphs are important predators of the immature aquatic stages of mosquitoes. Populations of the malaria vector Anopheles pseudopunctipennis Theobald (Diptera: Culicidae) can be efficiently reduced by extraction of filamentous algae from river pools in southern Mexico. Here, we examined the influence of this intervention on the diversity of odonates associated with mosquito breeding pools after annual extractions of algae from river pools in a 3-km section of the Coatan River, over a period of 2 yr. Odonate sampling was performed at monthly intervals in control and treated sections of the river for 4–5 mo after extraction in both years and before extraction in 1 yr. In total, 16 species, 10 genera, and 6 families of odonates were collected. Shannon diversity index values declined significantly during a period of 1 mo in 2001 and >5 mo in 2002. However, the abundance of odonates captured was not affected by algal extraction. In contrast, year-to-year variation in the diversity and abundance of the odonate community was strongly influenced by precipitation and river volume. Despite the importance of algae in river ecology, we conclude that the mosquito control intervention resulted in minimal impact on the odonate community in southern Mexico.

Diversity, Abundance, and Disturbance Response of Odonata Associated with Breeding Sites of Anopheles pseudopunctipennis (Diptera: Culicidae) in Southern Mexico

Odonate nymphs are important predators of the immature aquatic stages of mosquitoes. Populations of the malaria vector Anopheles pseudopunctipennis Theobald (Diptera: Culicidae) can be efficiently reduced by extraction of filamentous algae from river pools in southern Mexico. Here, we examined the influence of this intervention on the diversity of odonates associated with mosquito breeding pools after annual extractions of algae from river pools in a 3-km section of the Coatán River, over a period of 2 yr. Odonate sampling was performed at monthly intervals in control and treated sections of the river for 4–5 mo after extraction in both years and before extraction in 1 yr. In total, 16 species, 10 genera, and 6 families of odonates were collected. Shannon diversity index values declined significantly during a period of 1 mo in 2001 and >5 mo in 2002. However, the abundance of odonates captured was not affected by algal extraction. In contrast, year-to-year variation in the diversity and abundance of the odonate community was strongly influenced by precipitation and river volume. Despite the importance of algae in river ecology, we conclude that the mosquito control intervention resulted in minimal impact on the odonate community in southern Mexico.

The roles of natural temporal and spatial variation versus biotic influences in shaping the physicochemical environment of intermittent ponds: a case study

The importance of top-down and bottom-up mechanisms in lentic systems has largely been explored in stable systems; however, their influence is likely to change along a habitat duration gradient. Using a case study of four intermittent ponds, we test the generality of these paradigms in systems nearing the extreme short end of this gradient. Intermittent ponds fill up with water on a seasonally predictable basis, and are considered more regulated by physicochemical constraints than by biological factors. We found that natural spatial (i.e., pond-to-pond) and temporal variations (i.e., seasonal and annual) were more important than food-web manipulations (i. e., exclusion of aerial colonization, addition of top-predators [beetle larvae and odonate nymphs], and addition versus removal of allochthonous resources [leaf litter] in field enclosures) in shaping the physicochemical environment. Spatial variation included mainly depth-related variables (e. g., conductivity and pH), whereas annual variation included variables associated with hydroperiod length and productivity (e. g., weeks after flooding, pH, nutrients, and chlorophyll-a). Seasonal variation was pronounced but lower in ponds with longer hydroperiod and in mid-season. Enhanced invertebrate predation pressure increased levels of chlorophyll-a. Exclusion of aerial colonizers increased levels of chlorophyll-a and phosphorus, and affected levels of dissolved oxygen (increasing in one pond and decreasing in another). Addition of leaf litter resulted in lower concentrations of dissolved oxygen, higher phosphorus, and lower pH. Leaf litter removal led to increased levels of dissolved oxygen, changed chlorophyll-a (increasing in one pond and decreasing in another), and higher pH (in one pond). We conclude that although pond characteristics, seasonal development, and annual differences were of greater importance than biological factors for shaping the physicochemical characteristics of these intermittent ponds, bottom-up and top-down effects were also influential.

First record of Phyllognathopus bassoti Rouch, 1972 from India, with remarks on the family Phyllognathopodidae Gurney, 1932 (Crustacea, Copepoda, Harpacticoida)

Phyllognathopus bassoti Rouch, 1972, originally described from Long Island, Papua New Guinea, and later reported from the Philippines, is found for the first time in India. This subterranean species is redescribed and its ecology and zoogeography are discussed. Also, the systematics of the family Phyllognathopodidae is discussed and a key to genera and species is given. As a result of the taxonomic analysis, three species are here synonymized: Phyllognathopus insularis Chappuis, 1940 and P. camptoides Bozic, 1965 with P. chappuisi Delachaux, 1924; and P. volcanicus Barclay, 1969 with P. viguieri (Maupas, 1892). It has been observed that odonate nymphs prey on adults and copepodids of P. bassoti, an interaction not known until now.

Habitat Distribution, Dietary Composition and Life History Characteristics of Odonate Nymphs in a Blackwater Coastal Plain Stream

The ecology and life histories of odonates were studied in a headwater, sand-bottomed coastal plain stream in Virginia. Quantitative sampling of odonates in sand and silt sediments, on submerged snags and in debris dams was conducted monthly for 13 mo. Six species of odonates were common in the stream. Calopteryx maculata (Calopterygidae) had a univoltine life history, whereas Boyeria vinosa (Aeshnidae) Cordulegaster maculata (Cordulegastridae), Gomphus cavillaris, Hagenius brevistylus and Progomphus obscurus (Gomphidae) were semivoltine. The odonates were most abundant in debris dams, less abundant in silt and sand sediments and least abundant on snags. Habitat-specific production of odonates was 1.3 g m−2 y−1 in debris dams and 0.1 − 0.3 g m−2 y−1 in the sand, silt and snag habitats. The production to biomass ratio (P/B) for Calopteryx was 5.9, whereas ratios for semivoltine species ranged from 2.0 − 4.0.Analysis of overlap in the use of habitat, food and time showed that greatest ecological separation of the species was in their different use of habitat. Boyeria vinosa and Calopteryx maculata primarily inhabited debris dams, Hagenius brevistylus and Gomphus cavillaris were most abundant in silt and Progomphus obscurus was found almost exclusively in sand. Cordulegaster maculata occurred throughout the stream except on snags. Narrow niche breadths for B. vinosa, C. maculata and P. obscurus based on their use of habitat suggest high fidelity of these species to one habitat, whereas Cordulegaster maculata, with the broadest habitat niche breadth, was a habitat generalist. There was little difference among the species in prey items. Trophic niche breadths of all species were broad, all species feeding on a wide variety of invertebrates, in particular Chironomidae, Ephemeroptera and Plecoptera. Little ecological separation of the species occurred based on their use of time, all species occurring in the stream throughout the year with little staggering of life history events or growth patterns. Seasonal patterns of changing resource availability and the dynamic nature of the stream environment likely are important in regulating the distribution, abundance and interactions of the odonate community in this stream.

Diet of Two Freshwater Turtles, Chelodina rugosa and Elseya dentata (Testudines: Chelidae) from the Wet-Dry Tropics of Northern Australia

Chelodina rugosa occupies seasonally ephemeral waterholes on the coastal freshwater floodplains of the wet-dry tropics of northern Australia. It is an obligate carnivore and feeds primarily on fish, fast-moving aquatic invertebrates, and carrion. Differences between wet-season and dry-season diets, notably an increase in fish consumption and a decrease in consumption of odonate nymphs, reflect changes in abundance or accessibility of prey items. Elseya dentata occupies permanent water riverine habitats and is primarily herbivorous. The bulk of its diet consists of fruit and leaves of riparian rainforest trees, and seasonal changes in fruit species consumed reflected fruiting patterns. Filamentous algae comprised 30% by mass of the dry-season diet but was absent from the river during wet-season flooding and hence was absent from the diet. Elseya dentata readily feed on meat and fish carrion when available, but animal prey such as shrimp (Macrobrachium sp.) and freshwater sponge formed only a small proportion of their diet. Because E. dentata relies on riparian trees for most of its dietary intake, it is extremely vulnerable to land management practices that have adverse impacts on riparian forests.