Ecotoxicological effects of commercial herbicides on the reproductive system of aquatic arthropod Limnocoris submontandoni (Hemiptera: Naucoridae)

Worldwide, conventional agriculture makes extensive use of pesticides. Although the effects of herbicides are relatively well known in terms of environmental impacts on non-target organisms, there is very little scientific evidence regarding the impacts of herbicide residues on aquatic arthropods from tropical conservation areas. This study evaluates for the first time the toxicity of the herbicides ametryn, atrazine, and clomazone on the aquatic insect Limnocoris submontandoni (Hemiptera: Naucoridae). The lethal concentration (LC50) of herbicides was evaluated for these insects, as well as the effect of the herbicides on the insects’ tissues and testicles. The estimated LC50 was 1012.41, 192.42, and 46.09 mg/L for clomazone, atrazine, and ametryn, respectively. Spermatocyte and spermatid changes were observed under the effect of atrazine, and effects on spermatogenesis were observed for some concentrations of clomazone, with apparent recovery after a short time. Our results provide useful information on the effects of herbicide residues in aquatic systems. This information can help minimize the risk of long-term reproductive effects in non-target species that have been previously overlooked in ecotoxicology studies.

Nutrient composition and bioaccumulation of an edible aquatic insect, Pantala sp. (Odonata: Libellulidae) from the rice field

Numerous edible aquatic insects have unanticipated nutraceutical potential and are consumed in a variety of Thai locations. The proximate composition, amino acid, fatty acid, mineral, and heavy metal content of Pantala sp. (Odonata: Libellulidae) aquatic edible nymphs were determined using standard analytical methods in this study. Pantala sp. had a proximate protein content of 445.14±0.04%, a fat content of 4.93±0.05%, an ash content of 5.24±0.03%, a moisture content of 35.11±0.09%, and a total carbohydrate content of 9.60±0.11%. Total energy was 263.25±0.20 kcal/100 g, with fat energy accounting for 44.37±0.43 kcal/100 g. Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis revealed that this insect was high in phosphorus, iron, and copper for human consumption. In comparison to other edible insects studied, they were also excellent calcium sources. Agilent 7890B Gas Chromatograph (GC) analysis revealed that it contains 236.67 mg/100g of omega-3 and 523.32 mg/100g of omega-6. While the amino acids examined using High Performance liquid Chromatography contained all essential amino acids. ICP-OES was used to determine the levels of cadmium (Cd), lead (Pb), and arsenic (As). Pantala sp. had the highest concentration of As (average = 2.827 ± 0.289 mg kg -1 ), followed by Cd (0.164 ± 0.007 mg kg -1 ) and Pb (0.158 ± 0.015 mg kg -1 ). Although the insects have nutraceutical potential, they also have toxic heavy metals in trace amounts, with the exception of As. This work could serve as a nutritional reference for local consumers interested in entomophagy.

Water Quality Assessment with Biotic Index Based on Abundance and Diversity of Aquatic Insects in a Hilly Stream, Bangladesh

Study of stream insect fauna provide valuable insights into aspects of the stream channel ecosystem. The present study was conducted to investigate the aquatic stream living insect community, abundance and diversity in a hilly stream, Balukhali chora of Chittagong University campus to determine the water quality. The insects were collected with bottom dredge net from the edge and benthic regions of the Riffle zone and the Pool zone of the stream from January 2018 to December 2018. Insects were sampled using standard entomological method and determined their tolerance value. A total of 2535 insects were recorded, belonging to six insect orders, 30 families and 45 genera. The abundance ratio was higher in all the months in the Pool zone excepting the months of April, May, June and October. The orders Ephemeroptera, Odonata and Diptera were abundant in the Pool zone, while Hemiptera, Coleoptera and Lepidoptera were abundant in the Riffle zone. On the basis of Biotic Index, the most dominating orders Odonata and Hemiptera indicated good water quality, though the dipteran genus Chironomus spp. indicated poor quality in some of the months. The stream insect community structure of the two zones indicated that the overall water quality of the stream water was very good. Both manmade and natural interruption occurred in the stream channel due to human settlement, agricultural runoff and natural disasters. The study was conducted to know the abundance and diversity of aquatic insect community which indicated the water quality of the stream.

Description of Some Aquatic Insect Genera in Greater Zab River Branches, North of Iraq

Aquatic insects samples were collected from 6 sites along the Greater Zab River in the northern Iraq from Duhok and Erbil governorates over 12 months during September 2016 to August2017, which belong to seven orders (Ephemeroptera, Plecoptera, Trichoptera, Odonatan, Diptera, Coleoptera, and Megaloptera). Clustering mitochondrial DNA cytochrome c oxidase and 16S rDNA genes, morphological keys, and matches in the Barcode of Life Database, we identified 24 species return to 7 orders and 12 families, as indicated in the results. The reported species were: Ephemeroptera 5 members of the family Heptageniidae (Maccaffertium meririvulanum, Raptoheptagenia cruentata, Ecdyonurus dispar, Anepeorus rusticus, Stenonema femoratum), 1 Ephemerellidae (Seratella ignita), 1 Arthropleidae (Arthroplea bipunctata), 6 Baetidae (Baetis alpinus, Baetis braaschi, Baetis noa, Baetis harrisoni, Iswaeon anoka, Heterocloeon amplum), 1 member for each of Diptera, Coleoptera, Megaloptera and Odonatan orders, while Plecoptera 2 members Leuctridae (Leuctra hippopoides, Leuctra inermis) and Tricoptera 4 members 3 Hydropsychidae (Leptonema albovirens, Hydropsyche simulans, Arctopsyche irrorate), 1 Hydroptilidae (Ochrotrichia tenuata). Most of these recorded species and genera were mentioned for the first time and represent new records in Iraq. Presence and distribution of identified species varied between studied sites, as a result of differences in biogeographical and physical conditions.

Effects of experimental multi-season drought on abundance, richness, and beta diversity patterns in perennially flowing stream insect communities

Freshwater systems are projected to experience increased hydrologic extremes under climate change. To determine how small streams may be impacted by shifts in flow regimes, we experimentally simulated flow loss over the span of three summers in nine 50 m naturally fed stream channels. The aquatic insect community of these streams was sampled before, during, and after experimental drought treatments as well as following one unforeseen flood event. Abundance, richness, and beta diversity were measured as indicators of biotic effects of altered flow regimes. Abundance declined in proportion to flow loss. In contrast, we observed a threshold response in richness where richness did not decrease except in channels where losses of surface flow occurred and disconnected pools remained. The flood reset this pattern, but communities continued their prior trajectories shortly thereafter. Beta diversity partitions suggested no strong compositional shifts, and that the effect of drought was largely experienced uniformly across taxa until flow cessation. Pools served as a refuge, maintaining stable abundance gradients and higher richness longer than riffles. Upon flow resumption, abundance and richness returned to pre-treatment levels within one year. Our results suggest that many taxa present were resistant to drought conditions until loss in surface flow occurred.

Trajectories of aquatic insect functional groups along the resistance/resilience axis when facing water flow changes

1. Understanding how differences in intensity and frequency of hydrological disturbances affect the resistance and resilience of aquatic organisms is key to manage aquatic systems in a fast-changing world. Organisms’ responses to environmental changes can be influenced by different life strategies. Some aquatic organisms have strategies that improve the permanence in aquatic systems, while others use strategies that enhance colonization. 2. Therefore, we carried out a manipulative experiment to understand the resistance/resilience of aquatic insects based on their functional characteristics to hydrological disturbances in streams in the Cerrado hotspot. 3. We placed 200 artificial substrates in five streams and submitted them to changing water flow regimes that differed both in frequency and intensity. Then we observed the response of the aquatic community for 39 days. We used a Hierarchical Bayesian strategy approach to estimate the probabilities of permanence and colonization of each life strategy group (nine groups). 4. We observe that the most intense changes in the water flow tend to affect the permanence of almost all groups. However, this effect was reduced in intensity over time. On the other hand, less frequent disturbances, regardless of intensity, tend to reduce the permanence of most groups of aquatic insects over time. The difference in the effect of disturbance regarding intensity (higher or lower) may be related to a greater dispersal capacity of some groups. 5. These results are worrisome in a scenario of reduced riparian vegetation around streams and with the expectation of precipitation to become more concentrated in shorter periods of time due to climate change in the Cerrado hotspot. Together, these anthropogenic changes tend to increase the effect of runoff on the lotic systems and, consequently, reduces the permanence of many groups of aquatic insects in their habitat, particularly those with traits associated with permanence.

Extreme suction attachment performance from specialised insects living in mountain streams (Diptera: Blephariceridae)

Suction is widely used by animals for strong controllable underwater adhesion but is less well understood than adhesion of terrestrial climbing animals. Here we investigate the attachment of aquatic insect larvae (Blephariceridae), which cling to rocks in torrential streams using the only known muscle-actuated suction organs in insects. We measured their attachment forces on well-defined rough substrates and found that their adhesion was less reduced by micro-roughness than that of terrestrial climbing insects. In vivo visualisation of the suction organs in contact with microstructured substrates revealed that they can mould around large asperities to form a seal. We have shown that the ventral surface of the suction disc is covered by dense arrays of microtrichia, which are stiff spine-like cuticular structures that only make tip contact. Our results demonstrate the impressive performance and versatility of blepharicerid suction organs and highlight their potential as a study system to explore biological suction mechanisms.