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The Opalinida comprise ciliated protists that live as intestinal endoparasites in poikilothermic vertebrates. They are classified as one group of colourless Stramenopiles, the Opalinata, along with Proteromonadida (Proteromonas and Karotomorpha). The validity of certain opalinid genera is questionable, and their genetic relationships remain unclear. In this study, we conducted complete ribosomal DNA gene sequencing of nine opalinid species (belonging to Opalina , Protoopalina , Zelleriella , and Cepedea) from China. We compared the primary sequences, secondary structures, and characteristics of short tandem repeats within the expansion segments of the sequences. Additionally, a TimeTree analysis was performed to estimate divergence times. Our findings suggest that opalinids diverged from proteromonads ~250–220 Mya, with Protoopalina being the ancient genus. There is no genetic evidence supporting the differentiation of Cepedea and Bezzenbergeria as distinct genera, and they have been synonymized: Opalina (= Cepedea) and Protoopalina (= Bezzenbergeria); new combinations of species names are listed. Opalinid rDNA sequences exhibit greater length compared with other groups owing to A-T insertions within the expansion segments. These insertions consist of short tandem repeats and appear to be associated with speciation events that led to genus differentiation. [ABSTRACT FROM AUTHOR]

Lipids are an essential component of living beings and an important group of nutrients. As the gut microbiota plays important roles in the intestinal absorption and extraintestinal metabolism of dietary lipids, the current review addresses the recent progress regarding the interactions between the gut microbiota and lipid metabolism in aquatic animals, with a focus on fish. We discuss in detail how dietary lipid sources and content affect the composition of the gut microbiome and the mechanism by which the gut microbiota affects the lipid metabolism of the host. This interaction is largely mediated via microbial lipases, short‐chain fatty acids and the gut‐liver axis. The latter refers to the metabolism of biliary salts and acids, the regulation of their synthesis by gut microbes and their impact on the lipid metabolism. Finally, we briefly discuss how probiotic supplementation modulates the host's microbiome, and how probiotics have a beneficial effect on health and welfare of farmed aquatic animals. Although the influence of intestinal microbiota on lipid metabolism has been explored before, further research is needed to profoundly investigate the molecular mechanisms by which microbial metabolites (SCFAs and bile acids) induce lipid metabolism. [ABSTRACT FROM AUTHOR]

The quality of welding is directly related to the performance and life of the welding structure. The nondestructive testing technology is mainly used for welding defect defection, while the X-ray testing technology can directly and reliably reflect the shape, location and size of defects. For X-ray images, manual inspection is used at present, and it is easily caused by subjective factors, such as professional level, which may lead to low accuracy. This paper focuses on establishing an end-to-end automatic detection model of X-ray welding defects to improve the accuracy and efficiency of detection based on a deep learning algorithm. Considering the feature information of welding defects, this paper improves on the basis of Faster R-CNN and uses the deep residual network Res2Net to enhance the original backbone network to improve the feature extraction ability. And the weighted feature fusion module is studied, which combines the high-level semantic information and the low-level high-resolution edge detail information to predict the feature map of each layer respectively, to improve the detection performance, especially for small targets. The experimental data show that this method can effectively improve the accuracy and efficiency of welding defect detection. [ABSTRACT FROM AUTHOR]

Copepoda is a large and diverse group of crustaceans, which is widely distributed worldwide. It encompasses roughly 9 orders, whose phylogeny remains unresolved. We sequenced the complete mitochondrial genome (mitogenome) of Sinergasilus major (Markevich, 1940) and used it to explore the phylogeny and mitogenomic evolution of Copepoda. The mitogenome of S. major (14,588 bp) encodes the standard 37 genes as well as a putative control region, and molecular features are highly conserved compared to other Copepoda mitogenomes. Comparative analyses indicated that the nad2 gene has relatively high nucleotide diversity and evolutionary rate, as well as the largest amount of phylogenetic information. These results indicate that nad2 may be a better marker to investigate phylogenetic relationships among closely related species in Copepoda than the commonly used cox1 gene. The sister-group relationship of Siphonostomatoida and Cyclopoida was recovered with strong support in our study. The only topological ambiguity was found within Cyclopoida, which might be caused by the rapid evolution and sparse taxon sampling of this lineage. More taxa and genes should be used to reconstruct the Copepoda phylogeny in the future. [ABSTRACT FROM AUTHOR]