Effect of Cameraria ohridella feeding on Aesculus hippocastanum photosynthesis

The complex of invasive species of phytophagous insects that can adapt to novel living conditions is constantly increasing. The ecological effect of their vital activity in the new environment is almost impossible to predict. As a result, invasions undesirable in the economic sense are often observed. The horse -chestnut leaf miner (Cameraria ohridella Deschka & Dimič, 1986, Gracillariidae) is one of these problematic invader species in the introduced range of the horse chestnut (Aesculus hippocastanum (Linnaeus, 1753), Sapindaceae). We studied the effect of C. ohridella on the state of the photosynthetic apparatus in Ae. hippocastanum leaves. Photosynthesis is the one of the processes most vulnerable to stress factors, so information about the state of photosynthetic apparatus in a plant under the influence of phytophage feeding obtained with fluorescence analysis can be significant. The feeding effect of C. ohridella caterpillars on the functional state and activity of Ae. hippocastanum photosynthetic apparatus was studied. We studied critical parameters of chlorophyll fluorescence induction reflecting the effect of a single C. ohridella generation (feeding the caterpillar for the five stages of this species’ development) on the functional links of the photosystem II in Ae. hippocastanum leaves. The data obtained show a decrease in PS II quantum efficiency (inhibition of photosynthetic activity) in the leaves from different parts of the crown; it suggests the destructive effect of C. ohridella caterpillar feeding on Ae. hippocastanum photosynthetic apparatus. Values of all key parameters of chlorophyll fluorescence indication evidence inhibition of photophysical and photochemical processes of photosynthesis and impaired coherence of Calvin cycle reactions. Study of the feeding effect of C. ohridella caterpillars on the efficiency of the main enzyme in the Calvin cycle (which closely correlates with the coefficient of fluorescence induction that characterizes the efficiency of dark photosynthetic processes) showed a significant decrease in its activity in the leaves of both the illuminated and shaded parts of the crown. Our study has shown that the method of chlorophyll fluorescence induction allows one to determine the general state of a plant in an express regime by evaluating the main process of plant life as photosynthesis. Analysis of chlorophyll fluorescence parameters is a powerful and effective tool for determining the effect of phytophages on the plant body. The obtained data allow us to apply the method of analyzing chlorophyll fluorescence induction in practice to establish the physiological state of tree flora in forests and garden farms.

Feeding and growth coupling during different development larvae phases of the Mediterranean mussel Mytilus galloprovincialis L. from Amsa Bay

Spat supply for mussel farming in Morocco is essentially based on seed capture and collection from natural beds. However, natural irregularity recruitment in exploited areas and encountered difficulties during spat collection operations have led to develop and improve reproduction techniques under controlled conditions in hatcheries. The present study focused on the larvae phase aiming at assessing growth rate varies between different development stages. Trocophore larva stage had a size of 63.25 μm and reached the pedivilegere stage with a size of 272.56 μm in 18 culture days. Length growth was more significant than width growth for both H-batch and T-batch. For instance, larvae grew in terms of length quickly in H-batch than T-batch (11.10± 1.30 and 9.67 ± 1.17 μm day-1), and the same pattern was observed for T-batch larvae. Inversely, the total biomass consumed was higher during T-batch larvae rearing than H-batch ones. In contrast, the effect of feeding on growth was observed more significantly for H-batch larvae (t=7.55, df=23, p<0.001) than T-batch ones (t=4.13, df=23, p<0.001). However, the specific feeding effect was revealed higher for I. galbana for both batches rather than C. calcitrans and T. suecica. However, the larvae growth reduction is linked to the beginning of tissue synthesis.

Effect of Dinotefuran, Permethrin, and Pyriproxyfen (Vectra® 3D) on the Foraging and Blood-Feeding Behaviors of Aedes albopictus Using Laboratory Rodent Model

Dinotefuran-Permethrin-Pyriproxyfen (DPP) is used to kill and repel mosquitoes from dogs. However, the influence of the product on the host-seeking behavior of mosquitoes remains unknown. The interference of DPP with the host selection of unfed female Aedes albopictus was investigated. A total of 18 animals (9 mice and 9 rats) were divided into three groups of six animals each. DU: DPP treated rats (n = 3) with untreated mice (n = 3), UD: DPP treated mice (n = 3) with untreated rats (n = 3) and control UU: untreated mice (n = 3) and untreated rats (n = 3). In each group, the rats and mice were placed 30 cm apart. After sedation, the animals in each group were exposed twice (Day 1 and Day 7 post-treatment) for one hour to 71 ± 3 female mosquitoes. Mosquitoes were categorized after the 2-h post-exposure period as dead or alive. Blood-meal origin was determined from mosquitoes using a newly customized duplex qPCR. The highest values of forage ratio (1.36 ≥ wi ≤ 1.88) and selection index (0.63 ≥ Bi ≤ 0.94) for rat hosts indicates a preference of mosquitoes for this species as compared to mice when co-housed during the exposure. The mosquitoes only seldom fed on mice, even in the untreated group. The anti-feeding effect of DPP was therefore only assessed on rat’s hosts. The results showed that DPP, when directly applied on rats, provided a direct protection of 82% and 61% on Day 1 and Day 7, respectively, while when applied on mice hosts (UD), the DPP provided an indirect protection of 21% and 10% on Day 1 and Day 7, respectively. The results showed also that DPP, when applied on rats, provided a direct protection against Ae. albopictus bites. This effect did not result in increased exposure of the untreated host placed in the same cage at a distance of 30 cm.

Effects of Zn content on Hot Tearing Susceptibility of Mg–7Gd–5Y–0.5Zr Alloy

Mg–7Gd–5Y–0.5Zr alloy has excellent mechanical properties but poor hot tearing resistance. The latter makes it difficult to cast billets, which limits the size of subsequently processed parts. Therefore, the hot tearing susceptibility of Mg–7Gd–5Y–xZn–0.5Zr (x = 0, 3, 5, 7 wt%) alloys was studied. It was found that Zn can significantly reduce hot tearing susceptibility of Mg–7Gd–5Y–0.5Zr alloy, which almost linearly decreased with Zn content. When Zn content was 3 wt%, 5 wt% and 7 wt%, hot tearing susceptibility will be reduced by 27%, 83% and 100%, respectively. It was further revealed that the solid solubility of Gd and Y in α-Mg decreased with the increase of Zn content, and the nucleation temperature decreased accordingly, which resulted in the increase of nucleation rate and the refinement of final grains. On the macro level, it showed that the dendrite coherency temperature decreased, the solidification shrinkage stress of α-Mg slowed down, and the residual liquid channel became shorter and hot tearing susceptibility decreased. It was also found that with the increase of Zn content, the content of Zn, Gd and Y enriched on the grain boundary increased, the content of residual liquid phase between dendrites increased after α-Mg crystallization, and the solidified precipitated second phase also changed from Mg5RE phase to long-period stacking ordered phase + W-phase (a little), long-period stacking ordered phase + W-phase (much) and finally to W-phase only. The feeding effect of sufficient intergranular residual liquid on the shrinkage of α-Mg dendrite and the bridging effect of the precipitated phase at the grain boundary (especially long-period stacking ordered phase which is coherent with the parent phase) also led to the decrease of hot tearing susceptibility.