A mixture of mesotrione and atrazine harms adults and larvae of the predatory wasp Polistes satan.

Herbicides have been intensively used for weed control, raising concerns about their potentially adverse effects on non-target organisms. Research on the effects of these common agrochemicals on beneficial insects and the ecosystem services they provide (e.g., predation and pollination) is scarce. Therefore, we tested whether a commercial formulation comprising a mixture of mesotrione and atrazine was detrimental to adult females and larvae of the Neotropical predatory social wasp Polistes satan, which is an effective natural enemy of crop pests. Wasps were individually fed syrups contaminated with different concentrations of the herbicide above and below the maximum label rate (MLR = 12 mL/L). Survival was assessed. The locomotor activity, immune response, and midgut morphology of adults as well as the immune response of the larvae were also studied. Herbicide concentrations far above the MLR (12, 40, and 100 times) caused adult mortality, whereas lower concentrations (0.5, 1, and 6 times) did not. Herbicide exposure at 0.5 to 12 times the MLR increased adult activity. Adult exposure at 0.1 or 0.5 times the MLR did not affect melanotic encapsulation of foreign bodies but led to changes in the morphology of the midgut epithelium and peritrophic matrix. In larvae, the ingestion of herbicide at 0.1 or 0.2 times the MLR (corresponding to 9.6 and 19.2 ng of herbicide per individual) did not cause mortality but decreased their melanization-encapsulation response. Increased locomotor activity in herbicide-exposed adults can affect their foraging activity. The altered midgut morphology of adults coupled with the decreased immune response in larvae caused by herbicide exposure at realistic concentrations can increase the susceptibility of wasps to infections. Therefore, herbicides are toxic to predatory wasps.

Morphological characterization of antennal sensilla in Toxorhynchites theobaldi, Toxorhynchites violaceus, and Lutzia bigoti adults: a comparative study using scanning electron microscopy.

Some mosquitoes, including species of the genus Toxorhynchites, are known for actively preying on other mosquito larvae, making these predators valuable allies in the fight against vector-borne diseases. A comprehensive understanding of the anatomy and physiology of these potential biological control agents is helpful for the development of effective strategies for controlling vector populations. This includes the antennae, a crucial component in the search for hosts, mating, and selection of oviposition sites. This study utilized scanning electron microscopy to characterize the sensilla on the antennae of adult mosquitoes from two species that are exclusively phytophagous, including Toxorhynchites theobaldi and Toxorhynchites violaceus, as well as Lutzia bigoti, which females are allegedly hematophagous. The types of sensilla in each species were compared, and five basic types of antennal sensilla were identified: trichoid, chaetic, coeloconic, basiconic, and ampullacea. The analysis also found that they were morphologically similar across the three species, regardless of feeding habits or sex. The identification and characterization of basic types of antennal sensilla in T. theobaldi, T. violaceus, and L. bigoti suggest that these structures, which play a crucial role in the behavior and ecology, have common functions across different mosquito species, despite differences in feeding habits or sex.

Heat stress negatively affects physiology and morphology during germination of Ormosia coarctata (Fabaceae, Papilionoideae).

Research on the morphophysiological behavior of forest seeds during germination with respect to climate change is scarce. To date, there have been no studies on the biochemical or morphological aspects of Ormosia spp. In this study, we subjected Ormosia coarctata seeds to various temperature conditions to investigate temperature-dependent impacts on morphology, reactive oxygen species (ROS) generation, antioxidant systems, and storage systems. Analyses were performed on seeds exposed to 25, 35, and 40 °C for 48, 96, and 144 h. The morphology was evaluated by radiation using a Faxitron MX-20 device. ROS production (superoxide anion and hydrogen peroxide), malonaldehyde (MDA), carbonylated proteins, antioxidant enzyme activity (superoxide dismutase [SOD], ascorbate peroxidase [APX], catalase [CAT], and peroxidase [POX]), ß-carotene, lycopene, glucose, and reserve enzyme activity (α- and ß-amylase, lipase, and protease) were analyzed by spectrophotometry. Heat stress (40 °C) decreased germination by 76.2% and 78.1% (compared to 25 and 35 °C, respectively), caused damage to the external morphology of the seed, increased the content of ROS, MDA, and carbonylated proteins, and reduced APX, CAT, and POX activity. Furthermore, heat stress decreased glucose content and α-amylase activity. These results suggest that an increase of 5 °C in temperature negatively affects germination, promotes oxidative stress, and induces deterioration in O. coarctata seeds.

Impact of copper sulfate on survival, behavior, midgut morphology, and antioxidant activity of Partamona helleri (Apidae: Meliponini).

Copper sulfate (CuSO4) is widely used in agriculture as a pesticide and foliar fertilizer. However, the possible environmental risks associated with CuSO4 use, particularly related to pollinating insects, have been poorly studied. In this study, we evaluated both lethal and sublethal effects of CuSO4 on the stingless bee Partamona helleri. Foragers were orally exposed to five concentrations of CuSO4 (5000, 1666.7, 554.2, 183.4, 58.4 µg mL-1), and the concentration killing 50% (LC50) was estimated. This concentration (142.95 µg mL-1) was subsequently used in behavioral, midgut morphology, and antioxidant activity analyses. Bee mortality increased with the ingestion of increasing concentrations of CuSO4. Ingestion at the estimated LC50 resulted in altered walking behavior and damage to the midgut epithelium and peritrophic matrix of bees. Furthermore, the LC50 increased the catalase or superoxide dismutase activities and levels of the lipid peroxidation biomarker malondialdehyde. Furthermore, the in situ detection of caspase-3 and LC3, proteins related to apoptosis and autophagy, respectively, revealed that these processes are intensified in the midgut of treated bees. These data show that the ingestion of CuSO4 can have considerable sublethal effects on the walking behavior and midgut of stingless bees, and therefore could pose potential risks to pollinators including native bees. Graphical abstract.

Heat stress-mediated effects on the morphophysiological, biochemical, and ultrastructural parameters of germinating Melanoxylon brauna Schott. seeds.

KEY MESSAGE: The present study showed that the heat stress (40 °C) caused changes in morphophysiological, biochemical, and ultrastructural parameters to the seeds Melanoxylon brauna, ultimately leading to loss of germination capacity. Temperature is an abiotic factor that influences seed germination. In the present study, we investigated morphophysiological, biochemical, and ultrastructural changes during the germination of Melanoxylon brauna seeds under heat stress. Seed germination was evaluated at constant temperatures of 25 and 40 °C. The samples consisted of seeds soaked in distilled and ionized water for 48 and 96 h at both temperatures. For the evaluation of internal morphology, the seeds were radiographed. Ultrastructural parameters were assessed using transmission electron microscopy (TEM). The production of reactive oxygen species (ROS), content of malondialdehyde (MDA) and glucose, carbonylated proteins, and activity of the enzymes (superoxide dismutase-SOD, ascorbate peroxidase-APX, catalase-CAT, peroxidase-POX, glucose-6-phosphate dehydrogenase-G6PDH, lipase, α- and ß-amylase, and protease) were measured by spectrophotometric analysis. An 82% reduction in the germination of M. brauna seeds was observed at 25 °C, and 0% at 40 °C. TEM showed that seeds submitted to heat stress (40 °C) had poorly developed mitochondria and significantly reduced respiration rates. The content of ROS and protein carbonylation in seeds subjected to 40 °C increased compared to that at 25 °C. The activity of antioxidant enzymes, namely SOD, APX, CAT, and POX, was significantly reduced in seeds subjected to heat stress. Glucose content, G6PDH, and lipase activity also decreased when the seeds were exposed to heat stress. Conversely, α- and ß-amylase enzymes and the protease increased due to the increase in temperature. Our data showed that the increase in temperature caused an accumulation of ROS, increasing the oxidative damage to the seeds, which led to mitochondrial dysfunction, ultimately leading to loss of germination.