Localized and Long-Lasting Adaptation in Dragonfly Target-Detecting Neurons.

Some visual neurons in the dragonfly (Hemicordulia tau) optic lobe respond to small, moving targets, likely underlying their fast pursuit of prey and conspecifics. In response to repetitive targets presented at short intervals, the spiking activity of these "small target motion detector" (STMD) neurons diminishes over time. Previous experiments limited this adaptation by including intertrial rest periods of varying durations. However, the characteristics of this effect have never been quantified. Here, using extracellular recording techniques lasting for several hours, we quantified both the spatial and temporal properties of STMD adaptation. We found that the time course of adaptation was variable across STMD units. In any one STMD, a repeated series led to more rapid adaptation, a minor accumulative effect more akin to habituation. Following an adapting stimulus, responses recovered quickly, though the rate of recovery decreased nonlinearly over time. We found that the region of adaptation is highly localized, with targets displaced by ∼2.5° eliciting a naive response. Higher frequencies of target stimulation converged to lower levels of sustained response activity. We determined that adaptation itself is a target-tuned property, not elicited by moving bars or luminance flicker. As STMD adaptation is a localized phenomenon, dependent on recent history, it is likely to play an important role in closed-loop behavior where a target is foveated in a localized region for extended periods of the pursuit duration.

Temperature modulates the tuning properties of small target motion detector neurons in the dragonfly visual system.

Dragonflies are poikilothermic animals with limited thermoregulation; therefore, their entire bodies, including the brain, experience a range of temperatures during their daily activities.1,2 These flying insects exhibit hunting prowess, pursuing prey or conspecifics whether in direct sunlight or under the cover of cloud.3,4 Likely to underlie these aerobatic feats are the small target motion detector (STMD) neurons.5 These visual neurons are sensitive to target contrast and tuned to the target's size and velocity, with some neurons exhibiting complex predictive and selective properties, well suited for prey interception and feeding amid swarms.3,4,6,7,8,9 Increased temperature can modulate the biochemical processes underlying neuronal processing, increasing sensitivity and quickening the responsiveness of insect photoreceptors and downstream optic flow neurons,10,11,12 while in other neuronal pathways, compensatory processes have been shown to account for temperature changes.13,14 We determined the ethological range of temperatures experienced by the dragonfly, Hemicordulia tau, in its natural environment. Across this behaviorally relevant range, we showed increased temperatures having a large 8.7-fold increase in the contrast sensitivity of STMD neurons. However, suppression of responses to larger targets was unaltered. STMD tuning for target velocities was changed remarkably, not only increasing the optimum but extending the fastest velocities encoded by an order of magnitude. These results caution against interpreting functionality underlying spike rates at constrained, experimental temperatures. Moreover, they raise intriguing new questions about how information is represented within the brain of these flying insects, given the relationship between visual stimulus parameters and neuronal activity varies so dramatically depending on current environmental conditions.

A novel measure for long-term sediment reduction inspired by dragonfly wings.

The sediment accumulation in drainage pipes has long been recognized as a significant concern in the environmental field. This study addresses sediment accumulation in drainage pipes by introducing an innovative bioinspired approach using various shapes and angles of plates for long-term sediment reduction. Through experiments and numerical simulations, the velocity field, the turbulent kinetic energy, the head loss, and the dynamic pressure distribution in the pipeline with plates are analyzed. Results demonstrate significant increases in local velocity, dynamic pressure, and turbulence energy due to the presence of plates. The sediment reduction performance shows a positive correlation with the angle for folded plates and a non-linear relation with curvature for curved plates. Notably, the superior performance of folded plates is attributed to their exceptional ability to induce vortex formation. The head loss due to sediment reduction measures increases linearly as the angle and the curvature increase. Furthermore, the intentional induction of strong eddies and high shear flow using the undulating topography created by the locally installed folding plates in the pipeline was the main cause of sediment reduction. This novel approach holds promise for more efficient and sustainable sediment reduction in drainage systems.

Is the local environment more important than within-host interactions in determining coinfection?

Host populations often vary in the magnitude of coinfection they experience across environmental gradients. Furthermore, coinfection often occurs sequentially, with a second parasite infecting the host after the first has established a primary infection. Because the local environment and interactions between coinfecting parasites can both drive patterns of coinfection, it is important to disentangle the relative contributions of environmental factors and within-host interactions to patterns of coinfection. Here, we develop a conceptual framework and present an empirical case study to disentangle these facets of coinfection. Across multiple lakes, we surveyed populations of five damselfly (host) species and quantified primary parasitism by aquatic, ectoparasitic water mites and secondary parasitism by terrestrial, endoparasitic gregarines. We first asked if coinfection is predicted by abiotic and biotic factors within the local environment, finding that the probability of coinfection decreased for all host species as pH increased. We then asked if primary infection by aquatic water mites mediated the relationship between pH and secondary infection by terrestrial gregarines. Contrary to our expectations, we found no evidence for a water mite-mediated relationship between pH and gregarines. Instead, the intensity of gregarine infection correlated solely with the local environment, with the magnitude and direction of these relationships varying among environmental predictors. Our findings emphasize the role of the local environment in shaping infection dynamics that set the stage for coinfection. Although we did not detect within-host interactions, the approach herein can be applied to other systems to elucidate the nature of interactions between hosts and coinfecting parasites within complex ecological communities.

Semi-field evaluation of aquatic predators for the control of Anopheles funestus in rural south-eastern Tanzania.

BACKGROUND: Biological control is a promising alternative or complementary approach for controlling vector populations in response to the spread of insecticide resistance in malaria vectors. This study evaluated the efficacy of three selected potential predators on the density and fitness parameters of Anopheles funestus larvae in rural Tanzania. METHODS: Common predator families Aeshnidae (dragonflies), Coenagrionidae (damselflies), and Notonectidae (backswimmers) and An. funestus group larvae were collected from natural aquatic habitats in rural south-eastern Tanzania. Predators were starved for 12-h while An. funestus larvae were given fish food before starting the experiment. Anopheles funestus larvae were placed into artificial habitats containing predators, exposing them to potential predation. The number of surviving An. funestus larvae were counted every 24-h. An emergence traps were placed at the top of artificial habitats to capture emerging mosquitoes. Emerged mosquitoes were monitored until they died. Female wings were measured and used as a proxy for body size. Generalized linear mixed models (GLMM) with binomial variates at 95% CI and Cox proportional hazard models were used to assess the proportion of dead mosquitoes and the daily survival determined. RESULTS: There were significant differences in the number of emerged mosquitoes between the treatment and control groups (P < 0.001). Thus, all predator species played a significant role in reducing the density of An. funestus mosquitoes (P < 0.001). Furthermore, these predators had notable effects on the fitness parameters and survival of emerged mosquitoes (P < 0.001). Among the three predators studied, Coenagrionidae (damselflies) were most efficient followed by Notonectidae (backswimmers), with Aeshnidae (dragonflies) being the least efficient. CONCLUSION: Selected aquatic predators have the potential to reduce the survival and density of An. funestus larvae. They might eventually be included within an integrated malaria vector control strategy, ultimately leading to a reduction in malaria transmission.

A molecular phylogeny of the Petaluridae (Odonata: Anisoptera): A 160-Million-Year-Old story of drift and extinction.

Petaluridae (Odonata: Anisoptera) is a relict dragonfly family, having diverged from its sister family in the Jurassic, of eleven species that are notable among odonates (dragonflies and damselflies) for their exclusive use of fen and bog habitats, their burrowing behavior as nymphs, large body size as adults, and extended lifespans. To date, several nodes within this family remain unresolved, limiting the study of the evolution of this peculiar family. Using an anchored hybrid enrichment dataset of over 900 loci we reconstructed the species tree of Petaluridae. To estimate the temporal origin of the genera within this family, we used a set of well-vetted fossils and a relaxed molecular clock model in a divergence time estimation analysis. We estimate that Petaluridae originated in the early Cretaceous and confirm the existence of monophyletic Gondwanan and Laurasian clades within the family. Our relaxed molecular clock analysis estimated that these clades diverged from their MRCA approximately 160 mya. Extant lineages within this family were identified to have persisted from 6 (Uropetala) to 120 million years (Phenes). Our biogeographical analyses focusing on a set of key regions suggest that divergence within Petaluridae is largely correlated with continental drift, the exposure of land bridges, and the development of mountain ranges. Our results support the hypothesis that species within Petaluridae have persisted for tens of millions of years, with little fossil evidence to suggest widespread extinction in the family, despite optimal conditions for the fossilization of nymphs. Petaluridae appear to be a rare example of habitat specialists that have persisted for tens of millions of years.

Zygoptera / Anisoptera (Insecta: Odonata) ratio as a tool to assess anthropogenic changes in Brazilian Cerrado streams.

Aquatic ecosystems are among the most affected by anthropogenic impacts, and the rapid detection and measurement of these impacts are of great importance for the maintenance of such environments. The order of aquatic insects Odonata has emerged as an important bioindicator of environmental quality due to its sensitivity to environmental changes and its ecophysiological requirements, which make them closely associated with habitat conditions. The aim of this study was to test whether the Zygoptera/Anisoptera ratio can be used as an effective tool to assess anthropogenic changes in Cerrado streams. Our hypothesis is that the proportion of Zygoptera/Anisoptera is an efficient tool for measuring environmental alterations in Cerrado streams, with a positive relationship between habitat integrity and the proportion of Zygoptera and an inverse relationship with the proportion of Anisoptera. Adults were collected in 44 streams of the Cerrado Biome in the eastern Maranhão state. The Habitat Integrity Index (HII) was used to verify the environmental gradient. Our hypothesis was corroborated, with a positive relationship between the richness and abundance of Zygoptera and HII, while an inverse relationship was observed for Anisoptera. According to our results, streams exhibiting a Zygoptera abundance of 68% or higher and richness of 58% or higher can be classified as preserved, while those showing an Anisoptera abundance and richness surpassing 31% and 41%, respectively, may be deemed altered. The patterns detected in the Cerrado were similar to those found in studies of the Amazon Biome and the Atlantic Forest, confirming the effectiveness of this method even for naturally open environments, such as the Cerrado. We conclude, therefore, that this method can be used as a tool to generate rapid results in monitoring studies, with low cost and easy application, enabling the development of mitigation, control, and conservation measures for extremely threatened environments such as those found in the Cerrado Biome.

Behavioral Diversity Among Odonata Larvae Increases in Water with Greater Turbidity Under Captivity Conditions.

Various factors, including environmental variables, influence the behavior of aquatic insects. However, our understanding of insect behavior and their relationships with these variables remains limited. One important variable is water turbidity, which may be exacerbated by soil erosion, directly impacting visibility in the water and potentially affecting the organism's behaviors. In this study, we investigated larval behavior across seven Odonata species under controlled conditions, examining variations in behavioral diversity (frequency and type) associated with sex and three levels of water turbidity. Our findings revealed that heightened water turbidity correlated with increased behavior frequency, possibly attributable to predator avoidance in darker, seemingly safer habitats. Furthermore, behavior diversity differed between sexes, being higher for males in certain categories and for females in others. Anisoptera species predominantly displayed behaviors like resting, eating, and prey capture, whereas Zygoptera larvae were often observed perching and walking, possibly indicative of distinct predator response strategies. Behaviors shared by Anisoptera larvae could be associated with similar responses to predators and capture of prey. Our study found an increased frequency of behaviors when the larvae are in water with higher turbidity. Behavior frequency disparities between the sexes were observed across various behaviors, likely influenced by species-specific activity levels and individual behavioral plasticity in response to environmental cues. Overall, individuals exhibited heightened behavioral activity in environments with elevated turbidity, potentially reflecting a perceived lower risk environment.

Global changes in the odonate family ratios in response to the tropical forest degradation.

Odonates (dragonflies and damselflies) can indicate the ecological health of aquatic biota within the rich but vulnerable biodiversity of tropical forests. The reaction of odonates to deforestation can be measured by changes in coarse taxonomic ratios. Suborder Zygoptera are thermal conformers susceptible to overheating, having the affinity with shaded, intact sites. Anisoptera have exothermic regulation and better dispersal capacities, suggesting their association with more altered, open environments. Similarly, with an increasing degradation, the proportion of Anisoptera species in assemblages should increase. However, based on the data from different continents, the Zygoptera/Anisoptera ratio may be too simple, strongly biased, and not applicable at the global scale. The main reason is that the most diverse, abundant, and cosmopolitan families, Coenagrionidae (Zygoptera) and Libellulidae (Anisoptera), comprise a great proportion of habitat generalists with high migratory capacity and affinity with open habitats. In this study, we sampled odonates from three bioregions (Indomalaya, Afrotropics, and Neotropics) over the gradient of tropical forest degradation with a comparable sampling effort to assess the suitability of species richness and suborder-based (Zygoptera/Anisoptera) and family-based (Libellulidae/other Anisoptera and Coenagrionidae/other Zygoptera) ratios and their abundance-weighted versions for monitoring tropical forest degradation. Our results show that simple Odonata as well as Zygoptera and Anisoptera richness are poor indicators of the forest biota alteration. Family-level indices weighted by relative abundance, especially those involving Coenagrionidae, were more sensitive to changes in forest conditions compared to suborder-level indices. Collectively, our results suggest that for biomonitoring, where financial resources and time are commonly critical, family-level ratio metrics may be effective tools to indicate even slight alterations of aquatic biota resulting from forest degradation. Although these indices have the potential for broader application, their effectiveness across tropical bioregions warrants further validation.

Trophic effects of Bti-based mosquito control on two top predators in floodplain pond mesocosms.

Chironomid (Diptera: Chironomidae) larvae play a key role in aquatic food webs as prey for predators like amphibian and dragonfly larvae. This trophic link may be disrupted by anthropogenic stressors such as Bacillus thuringiensis var. israelensis (Bti), a biocide widely used in mosquito control. In a companion study, we recorded a 41% reduction of non-target larval chironomids abundance in outdoor floodplain pond mesocosms (FPMs) treated with Bti. Therefore, we examined the diet of two top predators in the FPMs, larvae of the palmate newt (Salamandridae: Lissotriton helveticus) and dragonfly (Aeshnidae: predominantly Anax imperator), using bulk stable isotope analyses of carbon and nitrogen. Additionally, we determined neutral lipid fatty acids in newt larvae to assess diet-related effects on their physiological condition. We did not find any effects of Bti on the diet proportions of newt larvae and no significant effects on the fatty acid content. We observed a trend in Aeshnidae larvae from Bti-FPMs consuming a higher proportion of large prey (Aeshnidae, newt, damselfly larvae; ~42%), and similar parts of smaller prey (chironomid, mayfly, Libellulidae, and zooplankton), compared to controls. Our findings may suggest bottom-up effects of Bti on aquatic predators but should be further evaluated, for instance, by using compound-specific stable isotope analyses of fatty acids or metabarcoding approaches.

Bimodal response strategy in Daphnia to ambush predation risk.

Predation's consequences can manifest through either consumptive or nonconsumptive effects, but the prey response may also vary depending on the predator hunting strategy. Considerable attention has been paid to coursing predators, whereas less information is available regarding responses to ambush predators. To remedy this paucity, we utilized a three-dimensional tracking platform to record groups of Daphnia magna under predation risk from the ambush invertebrate predator red-eyed damselfly, Erythromma najas. This design allowed us to test individual antipredator responses in multiple metrics of swimming behaviors. We demonstrate that predation risk was greatest for those that swam at 85% of the available depth and averaged 8.1 mm/s. Examining the swimming behavior of each individual separately showed that predation risk did not affect any of the prey response metrics. Interestingly, however, Daphnia did conform to one of two strategies while under predation risk: either swim fast high up in the water column or swim slowly close to the bottom. Hence, this dichotomous behavior is driven by strategies combining speed and depth in different constellations. In a broader context, our findings highlight the importance of considering both the spatial and temporal dimensions of predation events in order to correctly detect antipredator responses.

Induced Power Scaling Alone Cannot Explain Griffenfly Gigantism.

Paleozoic skies were ruled by extinct odonatopteran insects called "griffenflies," some with wingspans 3 times that of the largest extant dragonflies and 10 times that of common extant dragonflies. Previous studies suggested that flight was possible for larger fliers because of higher atmospheric oxygen levels, which would have increased air density. We use actuator disk theory to evaluate this hypothesis. Actuator disk theory gives similar estimates of induced power as have been estimated for micro-air vehicles based on insect flight. We calculate that for a given mass of griffenfly, and assuming isometry, a higher density atmosphere would only have reduced the induced power required to hover by 11%, which would have supported a flyer 3% larger in linear dimensions. Steady-level forward flight would have further reduced induced power but could only account for a flier 5% larger in linear dimensions. Further accounting for the higher power available due to high-oxygen air and assuming isometry, we calculate that the largest flyer hovering would have been only 1.19 times longer than extant dragonflies. We also consider known allometry in dragonflies and estimated allometry in extinct griffenflies. But such allometry only increases flyer size to 1.22 times longer while hovering. We also consider profile and parasite power, but both would have been higher in denser air and thus would not have enhanced the flyability of larger griffenflies. The largest meganeurid griffenflies might have adjusted flight behaviors to reduce power required. Alternatively, the scaling of flight muscle power may have been sufficient to support the power demands of large griffenflies. In literature estimates, mass-specific power output scales as mass0.24 in extant dragonflies. We need only more conservatively assume that mass-specific muscle power scales with mass0, when combined with higher oxygen concentrations and induced power reductions in higher-density air to explain griffenflies 3.4 times larger than extant odonates. Experimental measurement of flight muscle power scaling in odonates is necessary to test this hypothesis.

Human-modified habitats imperil ornamented dragonflies less than their non-ornamented counterparts at local, regional, and continental scales.

Biologists have long wondered how sexual ornamentation influences a species' risk of extinction. Because the evolution of condition-dependent ornamentation can reduce intersexual conflict and accelerate the fixation of advantageous alleles, some theory predicts that ornamented taxa can be buffered against extinction in novel and/or stressful environments. Nevertheless, evidence from the wild remains limited. Here, we show that ornamented dragonflies are less vulnerable to extinction across multiple spatial scales. Population-occupancy models across the Western United States reveal that ornamented species have become more common relative to non-ornamented species over >100 years. Phylogenetic analyses indicate that ornamented species exhibit lower continent-wide extinction risk than non-ornamented species. Finally, spatial analyses of local dragonfly assemblages suggest that ornamented species possess advantages over non-ornamented taxa at living in habitats that have been converted to farms and cities. Together, these findings suggest that ornamented taxa are buffered against contemporary extinction at local, regional, and continental scales.

A review of applications and limitations of using aquatic macroinvertebrate predators for biocontrol of the African malaria mosquito, Anopheles gambiae sensu lato.

Macroinvertebrate predators such as backswimmers (Heteroptera: Notonectidae), dragonflies (Odonata: Aeshnidae), and predatory diving beetles (Coleoptera: Dytiscidae) naturally inhabit aquatic ecosystems. Some aquatic ecosystems inhabited by these macroinvertebrate predator taxa equally form malaria vector larval habitats. The presence of these predators in malaria vector larval habitats can negatively impact on development, adult body size, fecundity, and longevity of the malaria vectors, which form important determinants of their fitness and future vectorial capacity. These potential negative impacts caused by aquatic macroinvertebrate predators on malaria vectors warrant their consideration as biocontrol agents in an integrated program to combat malaria. However, the use of these macroinvertebrate predators in malaria biocontrol is currently constrained by technical bottlenecks linked to their generalist predatory tendencies and often long life cycles, demanding complex rearing systems. We reviewed the literature on the use of aquatic macroinvertebrate predators for biocontrol of malaria vectors from the An. gambiae s.l. complex. The available information from laboratory and semi-field studies has shown that aquatic macroinvertebrates have the potential to consume large numbers of mosquito larvae and could thus offer an additional approaches in integrated malaria vector management strategies. The growing number of semi-field structures available in East and West Africa provides an opportunity to conduct ecological experimental studies to reconsider the potential of using aquatic macroinvertebrate predators as a biocontrol tool. To achieve a more sustainable approach to controlling malaria vector populations, additional, non-chemical interventions could provide a more sustainable approach, in comparison with the failing chemical control tools, and should be urgently considered for integration with the current mosquito vector control campaigns.

Flow sensing on dragonfly wings.

One feature of animal wings is their embedded mechanosensory system that can support flight control. Insect wings are particularly interesting as they are highly deformable yet the actuation is limited to the wing base. It is established that strain sensors on insect wings can directly mediate reflexive control; however, little is known about airflow sensing by insect wings. What information can flow sensors capture and how can flow sensing benefit flight control? Here, we use the dragonfly (Sympetrum striolatum) as a model to explore the function of wing sensory bristles in the context of flight control. Combining our detailed anatomical reconstructions of both the sensor microstructures and wing architecture, we used computational fluid dynamics simulations to ask the following questions. (1) Are there strategic locations on wings that sample flow for estimating aerodynamically relevant parameters such as the local effective angle of attack? (2) Is the sensory bristle distribution on dragonfly wings optimal for flow sensing? (3) What is the aerodynamic effect of microstructures found near the sensory bristles on dragonfly wings? We discuss the benefits of flow sensing for flexible wings and how the evolved sensor placement affects information encoding.

How to train your dragon: absolute conditioning in larval dragonflies.

Insects, despite possessing relatively small brains, exhibit noteworthy adaptive behaviors, making them intriguing subjects for understanding learning mechanisms. This study explores the learning capabilities of dragonfly larvae (Anisoptera: Aeshnidae) in conditioning experiments, shedding light on the cognitive processes that underpin their remarkable abilities. As apex predators, dragonflies play a crucial role in ecosystems, necessitating a diverse range of learning behaviors for survival and reproductive success. We addressed whether dragonfly larvae can differentiate between different colored stimuli and associate color with prey. Our experimental design demonstrated that dragonfly larvae are able to recognize conditioning stimuli. The findings contribute valuable insights into the cognitive abilities of dragonflies, suggesting that these insects can learn and discriminate colors of stimuli. Overall, this research broadens our understanding of insect learning and cognition, contributing to the broader field of animal behavior and memory.

Effects of overwintering on the transcriptome and fitness traits in a damselfly with variable voltinism across two latitudes.

Winter diapause consists of cessation of development that allows individuals to survive unfavourable conditions. Winter diapause may bear various costs and questions have been raised about the evolutionary mechanisms maintaining facultative diapause. Here, we explored to what extent a facultative winter diapause affects life-history traits and the transcriptome in the damselfly Ischnura elegans, and whether these effects were latitude-specific. We collected adult females at central and high latitudes and raised their larvae in growth chambers. Larvae were split into a non-diapausing and post-winter (diapausing) cohort, were phenotyped and collected for a gene expression analysis. At the phenotypic level, we found no difference in survival between the two cohorts, and the post-winter cohort was larger and heavier than the non-winter cohort. These effects were mostly independent of the latitude of origin. At the transcriptomic level, wintering affected gene expression with a small fraction of genes significantly overlapping across latitudes, especially those related to morphogenesis. In conclusion, we found clear effects of diapause on the phenotype but little evidence for latitudinal-specific effects of diapause. Our results showed a shared transcriptomic basis underpinning diapause demonstrated, here, at the intraspecific level and supported the idea of evolutionary convergence of the response to diapause across organisms.

On the wings of dragons: Wing morphometric differences in the sexually dichromatic common whitetail skimmer dragonfly, Plathemis lydia (Odonata: Libellulidae).

Sexual dimorphism is common throughout the animal kingdom, leading to sex-specific phenotypic differences. The common whitetail skimmer dragonfly, Plathemis lydia (Drury, 1773), is sexually dichromatic, where males of this species display a conspicuous white abdomen and females display a dark brown abdomen. Differences in abdomen conspicuousness between male and female P. lydia are likely attributed to differences in selective pressure where males use their white conspicuous abdomen during male-male territorial chases. We hypothesized that male P. lydia would exhibit wing morphology adaptations to better offset the costs of predation and territoriality and that these adaptations would differ from females. We used field-collected images to quantify differences in body length, wing length, wing area, wing shape, and wing loading between male and female P. lydia. Our results show that male P. lydia have significantly shorter fore and hind wings relative to body size with a higher wing loading when compared to females. We also found that male P. lydia have narrower and pointier fore and hind wings compared to females. These results are consistent with the idea that males are adapted for faster flight, specifically higher acceleration capacity, and higher agility whereas females are adapted for higher maneuverability.

Total environment sentinels: Dragonflies as ambivalent/amphibiotic bioindicators of damage to soil and freshwater.

Discerning the impact of anthropogenic impacts requires the implementation of bioindicators that quantify the susceptibilities and vulnerabilities of natural terrestrial and aquatic ecosystems to perturbation and transformation. Although legal regulations in Brazil recognize the value of bioindicators in monitoring water quality, the depreciation of soil conditions has yet to receive adequate attention. Thus, our study aimed to evaluate the potential of odonates (dragonflies and damselflies) as amphibiotic bioindicators to reflect the correlation between the degradation of aquatic and terrestrial habitats in pasture-dominated landscapes. We assessed the relationship between the biotic indices of Odonata and the conservation status of preserved riparian landscapes adjacent to anthropogenically altered pastures in 40 streams in the Brazilian savannah. Our results support the hypothesis that Odonata species composition may be a surrogate indicator for soil and water integrity, making them promising sentinels for detecting environmental degradation and guiding conservation strategies in human-altered landscapes. Importantly, while the Zygoptera/Anisoptera species ratio is a useful bioindicator tool in Brazilian forest, it is less effective in the open savannah here, and so an alternative index is required. Importantly, while the Zygoptera/Anisoptera species ratio is a useful bioindicator tool in Brazilian forest, it is less effective in the open savannah here, and so an alternative index is required. On the other hand, our results showed the Dragonfly Biotic Index to be a suitable tool for assessing freshwater habitats in Brazilian savannah. We also identified certain bioindicator species at both ends of the environment intactness spectrum.

Research of biomimetic corrugation on the blade flutter suppression in large-scale wind turbine systems.

Aiming at the blade flutter of large horizontal-axis wind turbines, a method by utilizing biomimetic corrugation to suppress blade flutter is first proposed. By extracting the dragonfly wing corrugation, the biomimetic corrugation airfoil is constructed, finding that mapping corrugation to the airfoil pressure side has better aerodynamic performance. The influence of corrugation type, amplitudeλ, and intensity on airfoil flutter is analyzed using orthogonal experiment, which determines that theλhas the greatest influence on airfoil flutter. Based on the fluctuation range of the moment coefficient ΔCm, the optimal airfoil flutter suppression effect is obtained when the type is III,λ= 0.6, and intensity is denser (n= 13). The effective corrugation layout area in the chord direction is determined to be the leading edge, and the ΔCmof corrugation airfoil is reduced by 7.405%, compared to the original airfoil. The application of this corrugation to NREL 15 MW wind turbine 3D blades is studied, and the influence of corrugation layout length in the blade span direction on the suppressive effect is analyzed by fluid-structure interaction. It is found that when the layout length is 0.85 R, the safety marginSfreaches a maximum value of 0.3431 Hz, which is increased 2.940%. The results show that the biomimetic corrugated structure proposed in this paper can not only improve the aerodynamic performance by changing the local flow field on the surface of the blade, but also increase the structural stiffness of the blade itself, and achieve the effect of flutter suppression.