Distribution patterns of the two genetic groups of Corbicula fluminea in a lotic-lentic system.

Differences in local habitat conditions are often implicated as drivers for morphological and genetic divergence in natural populations. However, there are still relatively few studies regarding how divergent habitats influence patterns for morphotypes and genetic lineages in aquatic invertebrates. In this study, we explored the morphological patterns, genetic divergence, and distributions of a bivalve, Corbicula fluminea, in a lotic-lentic system. Sampling locations included lotic, ecotone, and lentic habitats. First, we found two lineages (Lineages A and B) with significant genetic divergence that primarily corresponded to two morphotypes (Morphs D and C) of C. fluminea. Lineage A consisted of 88.68% Morph D (shell sculpture: 8-14 ridges/cmsh) and 11.32% Morph C (shell sculpture: 15 ridges/cmsh) individuals and had genetic similarity to invasive populations. Lineage B consisted of only Morph C (shell sculpture: 15-23 ridges/cmsh). Second, we revealed clear effects of habitat on the spatial distribution patterns for the two lineages of C. fluminea. Lineage A was dominant in lotic habitats, with a significantly higher density than that of Lineage B in these locations. Lineage B was dominant in lentic habitats. However, both lineages had their highest densities in the ecotone habitat, without clear dominance and no significant difference in density between groups. Individuals of Lineages A and B are different in shell morphology, which may be related to a benefit trade-off between shell shapes that allow for rapid burrowing and holding position in different flow conditions. The distribution patterns indicate that Lineages A and B may not prefer uniquely lotic and lentic habitats, but each lineage is more tolerant to one habitat type, respectively. Generally, our study established a correlation among morphotypes, lineages, and different habitats for C. fluminea along a lotic-lentic gradient system, which has important implementations for fisheries management units and for understanding the role of habitat preference for this species in monitoring for pioneer dispersal in invasive species management.

Preparation and catalytic properties of polydopamine-modified polyacrylonitrile fibers functionalized with silver nanoparticles.

Fiber-supported catalysts have attracted much attention due to their large specific surface area, high catalytic activity, and good recyclability. Functional polyacrylonitrile fibers were prepared by immersion of polyacrylonitrile fibers at room temperature in an alkaline dopamine (pH = 8.5) aqueous solution which can undergo self-polymerization and reduce silver ions to silver nanoparticles with mild reducibility and adsorption. The surface of the polyacrylonitrile fiber (PAN) was wrapped with a layer of polydopamine (PDA), and silver nanoparticles (Ag NPs) were adsorbed on the surface of PDA, forming an efficient fiber catalyst. The morphology and chemical composition of the catalyst material were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) patterns, and Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The catalytic activity of the nanocomposite was evaluated for the reduction reaction of 4-nitrophenol using sodium borohydride (NaBH4) at 35 °C with a material molar ratio of 1 : 10 and a fiber loaded catalysis dosage of 40 mg. The liquid phase yield can reach 98% in 30 minutes and can be reused after washing with ethanol. Moreover, the composite material exhibited a good stability up to 10 cycles without a significant loss of its catalytic activity. The results show that the catalyst is easy to recover from the reaction system and has maintained good stability and catalytic activity after many cycles.

Thiol-suppressed I2-etching of AuNRs: acetylcholinesterase-mediated colorimetric detection of organophosphorus pesticides.

For the first time it is demonstrated that sulfhydryl compounds can suppress longitudinal etching of gold nanorods via consuming oxidizers, which provides a new signaling mechanism for colorimetric sensing. As a proof of concept, a colorimetric assay is developed for detecting organophosphorus pesticides, which are most widely used in modern agriculture to improve food production but with high toxicity to animals and the ecological environment. Triazophos was selected as a model organophosphorus pesticide. In the absence of triazophos, the active acetylcholinesterase can catalyze the conversion of acetylthiocholine iodide to thiocholine whose thiol group can suppress the I2-induced etching of gold nanorods. When triazophos is present, the activity of AchE is inhibited, and I2-induced etching of gold nanorods results in triazophos concentration-dependent color change from brown to blue, pink, and red. The aspect ratio of gold nanorods reduced with gradually blue-shifted longitudinal absorption. There was a linear detection range from 0 to 117 nM (R2 = 0.9908), the detection limit was 4.69 nM, and a good application potential was demonstrated by the assay of real water samples. This method will not only contribute to public monitoring of organophosphorus pesticides but also has verified a new signaling mechanism which will open up a new path to develop colorimetric detection methods. It has been first found that sulfhydryl compounds can suppress longitudinal etching of gold nanorods (AuNRs) via consuming oxidizers, which provides a new signaling mechanism for colorimetric sensing. As a proof of concept, a colorimetric assay is developed for sensitively detecting organophosphorus pesticides (OPs). It will not only contribute to public monitoring of OPs but also has verified a new signaling mechanism which will open up a new path to develop multicolor colorimetric methods.