A comparison of digestive strategies for fishes with different feeding habits: Digestive enzyme activities, intestinal morphology, and gut microbiota.

Fish feeding habit determines the digestive tract structure and intestinal microflora. However, the relationship between feeding habit, digestive intestinal morphology, and microbial diversity of omnivorous, herbivorous, plankton feeder, and carnivorous fish from the same environment has not been compared. This study compared the digestive enzyme activities, intestinal morphology, and intestinal microflora of omnivorous (Carassius auratus), herbivorous (Ctenopharyngodon idellus), carnivorous (Siniperca chuatsi), and plankton feeder (Schizothorax grahami) fishes and predicted the potential functions of specific microflora on different nutrients. Twelve intestine samples were collected from each of the four fishes from Dianchi Lake. The composition and diversity of microbial communities were determined by using high-throughput sequencing of 16S rDNA. The results showed that the carnivorous fish (S. chuatsi) had higher trypsin and pancrelipase activities in the hepatopancreas and enteropeptidase in the intestine, but lower amylase activities in the intestine. The carnivorous fish intestine had more microvilli branches and complex structures than other fish species in the order carnivorous > herbivorous > plankton feeder > omnivorous. The intestinal microflora diversity was higher in the omnivorous fish and followed the order omnivorous > herbivorous > plankton feeder > carnivorous. Acinetobacter species and Bacteroides species were the most dominant flora in the carnivorous and herbivorous fishes, respectively. Acinetobacter species and Pseudomonas species might help the host to digest protein, while Bacteroidetes species may help the host to digest cellulose. Taken together, feeding habit determines the digestive enzyme activities, intestinal tissue morphology, and differential colonization of fish intestinal flora. The knowledge obtained is useful in feed formulation and feeding practices for the studied fish species.

Cyhexatin causes developmental toxic effects by disrupting endocrine system and inducing behavioral inhibition, apoptosis and DNA hypomethylation in zebrafish (Danio rerio) larvae.

Cyhexatin (CYT), an organotin acaricide, is extensively utilized in developing countries to mitigate plant diseases caused by mites and minimize agricultural crop losses. However, the comprehensive mechanisms underlying the developmental stage of non-target organisms remain largely unexplored. In this study, zebrafish embryos were firstly exposed to CYT (0.06, 0.12, and 0.20 ng/mL, referred to as CYTL, CYTM, and CYTH, respectively) from 2 hpf (hours post fertilization) to 30 dpf (days post fertilization). No developmental toxicity was observed in the CYTL and CYTM groups, except for induced deformed phenotypes in the CYTM group at 120 hpf. However, exposure to CYTH resulted in significant reductions in spontaneous movement (24 hpf), heart rate (48 hpf), hatching rate (48 and 72 hpf), body weight (30 dpf), whole body length (30 dpf), and locomotion (30 dpf). Additionally, CYTH exposure induced morphological malformations, including spinal curvature, pericardial edema, and tail curvature in zebrafish larvae. Moreover, CYTH treatment induced apoptosis, increased reactive oxygen species (ROS) production, and resulted in significant reductions in free T3, cholesterol, estradiol, and testosterone levels in zebrafish larvae, while free T4 levels were increased. RNA-Seq analysis indicated that CYTH exposure led to significant alterations in the genome-wide gene expression profiles of zebrafish, particularly in the thyroid hormone and steroid biosynthesis signaling pathways, indicating endocrine disruption. Furthermore, CYTH exposure induced global DNA hypomethylation, reduced S-adenosylmethionine (SAM) levels and the SAM/S-adenosylhomocysteine (SAH) ratio, elevated SAH levels, and suppressed the mRNA expression of DNA methyltransferases (DNMTs) while also downregulating DNMT1 at both the gene and protein levels in zebrafish larvae. Overall, this study partially elucidated the developmental toxicity and endocrine disruption caused by CYT in zebrafish, providing evidence of the environmental hazards associated with this acaricide.

Multiphase holdup measurement of oil-gas-water flow using new dual receiver fiber-optical probe array multiphase logging tool.

To solve the problem of multiphase holdup measurement, a new dual-receiver fiber-optical probe array multiphase logging tool (NDRFOPA_MLT) is designed and developed. This paper first constructed the mechanism model of an NDRFOP for phase holdup measurement by using the ray tracing method and theoretically analyzed the feasibility of NDRFOP to measure phase holdup; considering the shortcomings of NDRFOP local measurement, a NDRFOPA sensor for oil production three-phase flow is designed and developed. At the same time, the volume of fluid model was used to simulate the distribution characteristics of the medium in the NDRFOPA_MLT measurement pipeline under the working conditions of oil-gas-water flow with a total flow rate range of 0.42-1.25 m3/h, water holdup range of 50%-80%, oil holdup range of 10%-30%, and gas holdup range of 10%-40%. In addition, the NDRFOPA_MLT measurement models for different multiphase flow conditions were established by the ZEMAX ray tracing method, and the sensitivity distribution, response characteristics, and phase holdup measurement methods were studied to obtain the phase holdup measurement results under multiphase flow conditions. Finally, a multiphase flow experimental platform with a measurement pipe diameter of 20 mm and a measurement pipe length of 300 mm was established, and experiments were conducted under multiphase flow conditions, such as a gas flow rate range of 0.04-0.16 m3/h, oil flow rate range of 0.64-1.70 m3/h, and water flow rate range of 0.53-2.58 m3/h. The experimental results showed that phase holdup measurement error was mainly kept within 10%.

Acute polyethylene microplastic (PE-MPs) exposure activates the intestinal mucosal immune network pathway in adult zebrafish (Danio rerio).

Polyethylene is one of the most important plastic types with the highest consumption in the world. Plastics are prone to photodegradation and turn into microplastics, which are magnified as they move across trophic levels. Microplastics would be able to penetrate into lymph even cross cell membranes, causing harm to the lymphatic and/or circulatory systems, accumulating in secondary organs, and impacting the immune system and cell health. The objective of this study was to test that the activation of the intestinal immune network might be caused by disruption of intestinal microbiota after exposure to different polyethylene microplastics (PE-MPs) concentrations (1, 10, 100, and 1000 µg/mL) in adult zebrafish (Danio rerio) for 7 days. The concentrations of PE-MPs (100 and 1000 µg/mL) exposure decreased the goblet cell coverage. The intestinal microbial diversity index (Shannon and Simpson) was increased at 100 and 1000 µg/mL PE-MPs concentrations. The relative abundance of intestinal dominant microbiota phylum Proteobacteria and Actinobacteria increased significantly (P < 0.05); however, phylum Fusobacteria decreased significantly (P < 0.05). The relative abundance of intestinal microbiota at level of genera showed varying degrees of elevation such as Acinetobacter (6.31-fold), Plesiomonas (4.80-fold), Flavobacterium (10.54-fold) and Pseudomonas (5.17-fold) in 1000 µg/mL PE-MPs. Intestinal innate immunity-complement C3 and C4 content first increased and then declined in a dose-dependent manner. Expression of genes from the intestinal immune network for mucosal immunoglobulin production were increased also in a dose-dependent manner. The expression of immune-related genes (pigr, il10 and ighv4-5) were positively correlated with the relative abundance of genera Plesiomonas. In conclusion, PE-MPs increase the infection probability in the intestinal mucosa by altering the abundance of intestinal dominant microbiota at the level of phylum. PE-MPs exposure activated the intestinal immune network pathway for mucosal immunoglobulin production at a concentration of 100 or 1000 µg/mL for 7 days.

Excitation emission matrix fluorescence spectroscopy and parallel factor framework-clustering analysis for oil pollutants identification.

Serious ecological damage can be caused due to increased oil pollution. Identifying the source of oil can inform effective mitigation strategies and policies. A novel method for oil pollutants identification has been presented based on excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor framework-clustering analysis (PFFCA). First, the EEM spectroscopy of the oil samples was measured by a FS920 steady-state fluorescence spectrometer. Second, EEM was analyzed and characterized by PFFCA. A total 90 EEM were decomposed into six components using excitation wavelengths from 260 to 400 nm and emission wavelengths from 280 to 450 nm. Finally, oil samples were classified and matched by using concentration vectors. The results were compared with those obtained by using linear discriminant analysis (LDA) employing parallel factor analysis (PARAFAC) scores, and partial least squares discriminant analysis (PLS-DA). The best classification result was obtained by using LDA employing concentration vectors with 96.7% accuracy. The results indicate that PFFCA-LDA offers a robust approach for the oil samples, which is of great significance in discrimination of oil pollutants.

Growth influence of juvenile golden trout (Oncorhynchus mykiss) in different osmotic conditions: implications for tissue histology, biochemical indicators, and genes transcription involved in GH/IGF system.

The objectives of this study were to evaluate the effects of different salinity levels on tissue histology, blood biochemistry, and genes transcription of the GH/IGF system in juvenile golden trout (Oncorhynchus mykiss). Five experimental salinity levels (0, 8, 16, 24, and 32‰) were selected to domesticate juvenile O. mykiss for 7 days. Histological characteristics changed with salinity, including higher ionocites area and epithelium thickness in gills, narrow lumen of collecting tubules in kidneys, and high numbers of goblet cells in the intestines. Similarly, increments in slits, degenerate hepatocytes, and individualization of hepatocytes have been shown in fish reared in the 32‰ salinity group. The lowest triglyceride (TG) and the highest level of total protein (TP) were detected in fish reared at the 32‰ group. The genes transcription of the GH/IGF system altered in response to the increase of salinity. The present results add to the understanding of the physiological responses of O. mykiss on salinity stress and would be helpful in formulating strategies to optimize the aquaculture of this species in environments with fluctuating patterns of salinity.

Classification of oil pollutants based on excitation-emission matrix fluorescence spectroscopy and two-dimensional discriminant analysis.

Excitation-Emission Matrix (EEM) Fluorescence spectroscopy and two-dimensional (2D) discriminant analysis were used to classify oil pollutants. Firstly, the EEM fluorescence spectroscopy of the oil samples was collected using the FS920 steady-state fluorescence spectrometer, and EEM was preprocessed by removing scattering and normalization. Secondly, EEM was analyzed and characterized by parallel factor analysis (PARAFAC). Finally, all the collected samples were divided into training and test sets by the Kennard-Stone algorithm. The classification models of the training set samples were established by using 2D-PCA, 2D-LDA, PARAFAC-2DPCA, PARAFAC-2DLDA, PARAFAC-LDA and NPLS-DA algorithms, respectively. These models were then used to classify test set samples. The classification performance of the used models was assessed by accuracy, sensitivity and specificity. The best classification results in the used models were obtained by using 2D-PCA and 2D-LDA with 95% and 95% accuracy, respectively. These results provide an important reference for classification of oil pollutants.

Design and numerical simulation on an auto-cumulative flowmeter in horizontal oil-water two-phase flow.

In order to accurately measure the flow rate under the low yield horizontal well conditions, an auto-cumulative flowmeter (ACF) was proposed. Using the proposed flowmeter, the oil flow rate in horizontal oil-water two-phase segregated flow can be finely extracted. The computational fluid dynamics software Fluent was used to simulate the fluid of the ACF in oil-water two-phase flow. In order to calibrate the simulation measurement of the ACF, a novel oil flow rate measurement method was further proposed. The models of the ACF were simulated to obtain and calibrate the oil flow rate under different total flow rates and oil cuts. Using the finite-element method, the structure of the seven conductance probes in the ACF was simulated. The response values for the probes of the ACF under the conditions of oil-water segregated flow were obtained. The experiments for oil-water segregated flow under different heights of the oil accumulation in horizontal oil-water two-phase flow were carried out to calibrate the ACF. The validity of the oil flow rate measurement in horizontal oil-water two-phase flow was verified by simulation and experimental results.

The Finite Element Analysis for a Mini-Conductance Probe in Horizontal Oil-Water Two-Phase Flow.

Oil-water two-phase flow is widespread in petroleum industry processes. The study of oil-water two-phase flow in horizontal pipes and the liquid holdup measurement of oil-water two-phase flow are of great importance for the optimization of the oil production process. This paper presents a novel sensor, i.e., a mini-conductance probe (MCP) for measuring pure-water phase conductivity of oil-water segregated flow in horizontal pipes. The MCP solves the difficult problem of obtaining the pure-water correction for water holdup measurements by using a ring-shaped conductivity water-cut meter (RSCWCM). Firstly, using the finite element method (FEM), the spatial sensitivity field of the MCP is investigated and the optimized MCP geometry structure is determined in terms of the characteristic parameters. Then, the responses of the MCP for the oil-water segregated flow are calculated, and it is found that the MCP has better stability and sensitivity to the variation of water-layer thickness in the condition of high water holdup and low flow velocity. Finally, the static experiments for the oil-water segregated flow were carried out and a novel calibration method for pure-water phase conductivity measurements was presented. The validity of the pure-water phase conductivity measurement with segregated flow in horizontal pipes was verified by experimental results.

Improving the growth performance and cholesterol metabolism of rainbow trout (Oncorhynchus mykiss) fed soyabean meal-based diets using dietary cholesterol supplementation.

A 9-week feeding trial was conducted to evaluate the effects of dietary cholesterol supplementation at different levels (0, 0·3, 0·6, 0·9, 1·2 and 1·5 %) on growth and cholesterol metabolism of rainbow trout (Oncorhynchus mykiss) fed soyabean meal (SBM)-based diets. Daily growth coefficient (DGC) steadily increased when the supplemental cholesterol was increased by up to 1·2 %, but declined upon further addition. The total cholesterol (TC), HDL-cholesterol (HDL-C) and LDL-cholesterol (LDL-C) levels in plasma generally increased when the supplemental cholesterol was increased by up to 1·2 %. Thereafter, the TC level reached a plateau, the LDL-C level showed a marked decline, whereas the HDL-C level continued to increase. Dietary cholesterol supplementation generally increased the total lipid and cholesterol levels in liver; the total lipid and TAG levels in muscle; the TC, free cholesterol, cholesteryl ester and total bile acid levels in intestinal contents; and the triiodothyronine and Ca levels in plasma. However, significant differences were mainly observed with high levels of supplemental cholesterol (0·9-1·5 %). Low levels of supplemental cholesterol (0·3-0·9 %) decreased hepatic 3-hydroxy-3-methyl-glutaryl-CoA reductase and cholesterol 7α-hydroxylase activities, but high levels of supplemental cholesterol (1·5 %) increased hepatic acyl-CoA:cholesterol acyl transferase and cholesterol 7α-hydroxylase activities. These results suggest that rainbow trout fed SBM-based diets have a certain 'cholesterol-buffering capacity', which in turn suggests the possibility of the inhibition of exogenous cholesterol absorption and/or inadequate endogenous production of cholesterol in trout fed SBM-based diets. DGC increased steadily with increasing supplemental cholesterol level up to 1·2 %, and the growth-promoting effects might be related to the alleviation of the negative effects caused by a soyabean diet and/or make up for the deficiency of endogenous cholesterol in rainbow trout.

Effect of ethanolic extract of propolis on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss).

This study was conducted to evaluate the effect of ethanolic extract of propolis (EEP) on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss). Graded levels of EEP [0 (control), 1, 2, and 4 g kg(-1) diet] were fed to trout juveniles (mean weight 7.73 ± 0.17 g) for 10 weeks. Dietary EEP supplementation regardless of inclusion level significantly improved the specific growth rate of fish. Similarly, supplemental EEP generally improved the feed efficiency ratio and protein efficiency ratio, but no significant differences were observed between the 1 g kg(-1) EEP group and the control group. In addition, dietary EEP supplementation generally increased the plasma superoxide dismutase, lysozyme, total antioxidant capacity, glutathione peroxidase, and catalase activities, but decreased the plasma malondialdehyde level. The plasma triglycerides level was significantly lower in the 1 or 4 g kg(-1) EEP group as compared with the control group. Dietary EEP supplementation generally decreased the plasma aspartate aminotransferase and alanine aminotransferase activities, but increased the hepatic aspartate aminotransferase and alanine aminotransferase activities. These results indicate the potential to use the EEP as a growth promoter, hepatoprotective agent, and immunostimulant for rainbow trout.