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.

Main drivers of dragonflies and damselflies (Insecta; Odonata) metacommunities in streams inside protected areas in the Brazilian Amazon.

The evaluation of environmental and spatial influence in freshwater systems is crucial for the conservation of aquatic diversity. So, we evaluated communities of Odonata in streams inside and outside sustainable use areas in the Brazilian western Amazon. We predicted that these streams would differ regarding habitat integrity and species α and ß diversity. We also predict that environmental and spatial variables will be important for both suborders, but with more substantial effects on Zygoptera species, considering their nature of forest-specialist. The study was conducted in 35 streams, 19 inside and 16 outside sustainable use areas. The streams outside presented high species richness, abundance, and number of exclusive forest-specialist species from Zygoptera and higher scores of habitat integrity. In contrast, one sustainable use area presented the lowest values of these metrics. Besides, we found that environmental and spatial variables were significantly associated to Zygoptera species composition, but not with Anisoptera, which can be explained by their cosmopolitan nature. Our results indicated that an interplay between environmental and spatial processes determines the structure of the metacommunities of Zygoptera. The less effective dispersal rates and narrow ecological tolerance of Zygoptera species make them more influenced by local conditions and dispersal limitation, and more sensible to habitat modifications. We highlight the importance of improving the local management of the sustainable use areas by environmental agencies, mainly on areas that are losing their capacity to maintain the aquatic fauna, and implementation of social policies toward traditional people.

Amazonian Odonata Trait Bank.

Discussion regarding the gaps of knowledge on Odonata is common in the literature. Such gaps are even greater when dealing with basic biological data for biodiverse environments like the Amazon Rainforest. Therefore, studies that address, classify, and standardize functional traits allow the elaboration of a wide range of ecological and evolutionary hypotheses. Moreover, such endeavors aid conservation and management planning by providing a better understanding of which functional traits are filtered or favored under environmental changes. Here, our main goal was to produce a database with 68 functional traits of 218 Odonata species that occur in the Brazilian Amazon. We extracted data on behavior, habit/habitat (larvae and adults), thermoregulation, and geographic distribution from 419 literature sources classified into different research areas. Moreover, we measured 22 morphological traits of approximately 2500 adults and categorized species distributions based on approximately 40,000 geographic records for the Americas. As a result, we provided a functional matrix and identified different functional patterns for the Odonata suborders, as well as a strong relationship between the different trait categories. For this reason, we recommend the selection of key traits that represent a set of functional variables, reducing the sampling effort. In conclusion, we detect and discuss gaps in the literature and suggest research to be developed with the present Amazonian Odonata Trait Bank (AMO-TB).

Impact of environmental changes on the behavioral diversity of the Odonata (Insecta) in the Amazon.

The odonates are insects that have a wide range of reproductive, ritualized territorial, and aggressive behaviors. Changes in behavior are the first response of most odonate species to environmental alterations. In this context, the primary objective of the present study was to assess the effects of environmental alterations resulting from shifts in land use on different aspects of the behavioral diversity of adult odonates. Fieldwork was conducted at 92 low-order streams in two different regions of the Brazilian Amazon. To address our main objective, we measured 29 abiotic variables at each stream, together with five morphological and five behavioral traits of the resident odonates. The results indicate a loss of behaviors at sites impacted by anthropogenic changes, as well as variation in some morphological/behavioral traits under specific environmental conditions. We highlight the importance of considering behavioral traits in the development of conservation strategies, given that species with a unique behavioral repertoire may suffer specific types of extinction pressure.

After 10 years the myth of Crotalaria spp. and dragonflies remains alive / Após 10 anos, o mito de Crotalaria spp. e libélulas permanece vivo

Abstract The struggle to control insect-borne diseases can lead to make rash decisions. For instance, the controversial method of planting of Crotalaria spp. to attract predatory dragonflies can be used to control insect vectors of dengue fever and several other medically significant insect-borne diseases. Nevertheless, there is no scientific support for this assumption. Despite the lack of evidence, in Brazil, there remains a multitude of online articles and grey literature sources still promote Crotalaria planting as a means to prevent dengue fever. Here we discuss the reasons why Odonata would not be attracted by Crotalaria and, therefore, it cannot not be considered as an efficient method for vector control. Finally, the best practice to avoid the spread of insect-borne diseases in the tropics is to avoid the accumulation of standing water in urban areas.

Resumo A luta contra doenças pode levar as pessoas a tomar decisões precipitadas. Um método controverso que estamos discutindo é o da Crotalaria atraindo libélulas, porém nenhuma pesquisa científica apoia essa premissa. As libélulas são predadoras generalistas e, eventualmente, são empregadas de uma maneira incorreta como predadoras de mosquitos vetores. No Brasil, depois de dez anos, ainda encontramos pessoas que estão plantando Crotalaria com a tentativa de evitar a propagação da dengue. Discutimos as razões pelas quais os Odonata não seriam atraídos pela Crotalaria e, portanto, não poderiam ser utilizados como método eficiente de controle de vetores. Por fim, não deixar a água parada é a maneira mais eficaz de evitar doenças tropicais.