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Microplastics have become a worldwide pollutant, widely discovered in soil, air and aquatic environment. Microplastics have been found in habitats where crayfish (Procambarus clarkii) cultivated, but the impact of microplastics on crayfish remains unclear. In this study, after 21-day dietary exposure, polyethylene (PE) particles were found to accumulate in intestine, hepatopancreas, gills and hemolymph of crayfish. Furthermore, PE particles can still be detected in these tissues after a 7-day depuration in clean water. PE retained in these tissues caused oxidative stress responses, as indicated by the change of oxidative-stress-related index, such as the increase of H 2 O 2 level and SOD activity. PE exposure also caused hemocytic encapsulation in crayfish hepatopancreas and increase of mucus secretion in intestine. Moreover, PE exposure affected the microbiota balance in crayfish, by reducing the total microbiota abundance and altering the proportions of many bacterial families. Interestingly, results showed that PE exposure led to of lower numbers of hemocytes and declination of phenoloxidase activity. Finally, PE exposure induced the expression of immune-related genes, including transcription factors and antimicrobial peptides. Taken these together, we conclude that PE microplastics exert considerable toxic effects on crayfish and are a potential threat to crayfish aquaculture and consumption. This study provides basic toxicological data toward quantifying and illuminating the impact of PE microplastics on freshwater animals. [Display omitted] • Polystyrene microplastics accumulated in several tissues of crayfish and caused histopathological changes. • Polystyrene microplastics induced oxidative stress and immune responses in crayfish. • Polystyrene microplastics induced gut microbiota dysbiosis in crayfish. [ABSTRACT FROM AUTHOR]

A numerical procedure that couples the Runge–Kutta discontinuous Galerkin method (RKDG), the boundary element method (BEM) and the finite element method (FEM) is developed to study the dynamics of an underwater explosion bubble near a sandwich structure efficiently and accurately. The numerical approach is validated by a near-field underwater explosion experiment. The numerical predicted bubble shape, cavitation and the free field pressure are in good agreement with the experimental results. The validated code is then used to determine the effects of the foam core strengths, the stand-off distances and the boundary condition of the back face sheet on the fluid response, the bubble behaviors, and the deformation of the sandwich structure. The results are beneficial for guiding the design of the protection structures. • Dynamics of an underwater explosion bubble near a sandwich structure is studied. • A numerical procedure that couples RKDG, BEM and FEM is developed. • Deformation of sandwich structures has significant effects on the bubble behaviors. [ABSTRACT FROM AUTHOR]

In previous studies, the response of sandwich structures to water blast is solved by envisaging the plate adjacent to water as a rigid one, while the effects of the elasticity in the longitudinal direction of the plate are rarely studied. In this paper, a monolithic elastic coating with varying stiffness and thickness is investigated by a one-dimensional analytical approach, based on linear wave motion theory, to reveal the elastic effect of the plate on the incident wave. One side of the coating is loaded by a planar shock wave; on the opposite side, rigid boundary or air-backed boundary is imposed. The fluid–structure interaction (FSI), cavitation phenomenon and large deformation of the coating are taken into account. In particular, the initiation and evolution of cavitation, including the propagations of breaking fronts and closing fronts, as well as the pressure histories of radiated wave by the closing front, are examined. The analytical solution has been compared with finite element (FE) predictions. The results are found to be in excellent agreement for the propagation of breaking front and closing front, as well as the pressure and particle velocity histories at the wet face before the cavitation reaches the wet face. However, when the wet face cavitates, the predictions provided by the analytical method are less accurate and the analytically-computed particle velocity can only be compared in an average sense with the FE predictions. For air-backed case, Taylor׳s model prior to cavitation becomes a trivial case of the analytical model and the comparison also indicates the validity of the analytical model. The validated analytical model is used to determine the dependence of the peak pressure at the wet face and the impulse transmitted to the coating on the coating properties, including the wave impedance and thickness. [ABSTRACT FROM AUTHOR]

Understanding the structure and functional mechanisms of cyanobacterial halorhodopsin has become increasingly important, given the report that Synechocystis halorhodopsin (Sy HR), a homolog of the cyanobacterial halorhodopsin from Mastigocladopsis repens (Mr HR), can take up divalent ions, such as SO 4 2−, as well as chloride ions. Here, the crystal structure of Mr HR, containing a unique "TSD" chloride ion conduction motif, was determined as a homotrimer at a resolution of 1.9 Å. The detailed structure of Mr HR revealed a unique trimeric topology of the light-driven chloride pump, with peculiar coordination of two water molecules and hydrogen-mediated bonds near the TSD motif, as well as a short B–C loop. Structural and functional analyses of Mr HR revealed key residues responsible for the anion selectivity of cyanobacterial halorhodopsin and the involvement of two chloride ion-binding sites in the ion conduction pathway. Alanine mutant of Asn63, Pro118, and Glu182 locating in the anion inlet induce multifunctional uptake of chloride, nitrate, and sulfate ions. Moreover, the structure of N63A/P118A provides information on how Sy HR promotes divalent ion transport. Our findings significantly advance the structural understanding of microbial rhodopsins with different motifs. They also provide insight into the general structural framework underlying the molecular mechanisms of the cyanobacterial chloride pump containing Sy HR, the only molecule known to transport both sulfate and chloride ions. Unlabelled Image • The structure of the cyanobacterial chloride pump containing a unique "TSD" motif was solved at 1.9 Å resolution. • The homotrimeric topology and key ion-conducting residues of MrHR differ with general halorhodopsins. • Mutations in the chloride inlet induce multifunctional uptake of Cl−, NO 3 −, SO 4 2− ions. • The mutant structure of chloride inlet provides structural evidence on different anion accessibilities. [ABSTRACT FROM AUTHOR]

C-type lectins (CTLs) function as pattern recognition receptors (PRRs) by recognizing invading microorganisms, thereby triggering downstream immune events against infected pathogens. In this study, a novel CTL containing a low-density lipoprotein receptor class A (LDLa) domain was obtained from Litopenaeus vannamei , designed as LvLDLalec. Stimulation by the bacterial pathogen Vibrio anguillarum (V. anguillarum) resulted in remarkable up-regulation of LvLDLalec, as well as release of LvLDLalec into hemolymph. The rLvLDLalec protein possessed broad-spectrum bacterial binding and agglutinating activities, as well as hemocyte attachment ability. Importantly, LvLDLalec facilitated the bacterial clearance in shrimp hemolymph and protected shrimp from bacterial infection. Further studies revealed that LvLDLalec promoted hemocytes phagocytosis against V. anguillarum and lysosomes were involved in the process. Meanwhile, LvLDLalec participated in humoral immunity through activating and inducing nuclear translocation of Dorsal to regulate phagocytosis-related genes and antimicrobial peptides (AMPs) genes, thereby accelerated the removal of invading pathogens in vivo and improved the survival rate of L. vannamei. These results unveil that LvLDLalec serves as a PRR participate in cellular and humoral immunity exerting opsonin activity to play vital roles in the immune regulatory system of L. vannamei. • LvLDLalec is activated by V. anguillarum and promotes bacterial clearance. • LvLDLalec binds to the surface of hemocytes to promote phagocytosis and lysis of ingested V. anguillarum in phagosomes. • LvLDLalec regulates the expression of immune-related genes by promoting the nuclear translocation of Dorsal. • LvLDLalec protectes shrimp from infection from V. anguillarum to improve the survival rate of L. vannamei. [ABSTRACT FROM AUTHOR]