Kaibin Li

Mercury biomagnification in the aquaculture pond ecosystem in the Pearl River Delta.

This is the first study to investigate the rate of mercury (Hg) biomagnification in the aquaculture pond ecosystem of the Pearl River Delta (PRD), China, by analyzing total mercury (THg) and methyl mercury (MeHg) concentrations in various species of fish at different trophic levels (TLs). Species representing a gradient of trophic positions in the aquaculture pond food chains were chosen for analyzing THg and MeHg concentrations. In this study, there were two kinds of the aquaculture pond food chains: (1) omnivorous (fish feeds, zooplankton, grass carp [Ctenopharyngodon idellus], and bighead carp [Aristichthys nobilis]) and (2) predatory (zooplankton, mud carp [Cirrhina molitorella], and mandarin fish [Siniperca kneri]). Bighead carp and mandarin fish had the highest MeHg and THg concentrations, i.e., an order of magnitude higher than other species, in their respective food chains. More than 90% of the THg concentrations detected in bighead carp, mandarin fish, and mud carp were in the methylated form. In this study, %MeHg increased with TLs and MeHg concentrations, reflecting that MeHg is the dominant chemical species of Hg accumulated in higher concentrations in biota, especially biota associated with higher TLs in the food chains. The trophic magnification factors were 2.32 and 2.60 for MeHg and 1.94 and 2.03 for THg in omnivorous and predatory food chains, respectively, in PRD. Hg concentrations in fish tissue correlated to Hg levels in the ambient environment, and sediment seemed to be the major source for Hg accumulated in fish. In addition, feeding habit also affected Hg accumulation in different fish species. Four significant linear relationships were obtained between log-THg and δ15N and between log-MeHg and δ15N. The slope of the regression equations, as biomagnification power, was smaller in magnitude compared with those reported for temperate and arctic marine and freshwater ecosystems, indicating that THg and MeHg biomagnifications were lower in this PRD subtropical aquaculture pond ecosystem. This was probably due to low Hg bioavailability at lower TLs as well as individual feeding behavior of fish.

Assessment of typical pollutants in waterborne by combining active biomonitoring and integrated biomarkers response.

Organic pollutants, heavy metals and pharmaceuticals are continuously dispersed into the environment and have become a relevant environmental emerging concern. In this study, a situ assay to assess ecotoxicity of mixed pollutants was carried out in three typical sites with different priority contaminations in Guangzhou, China. Chemical analysis of organic pollutants, metals and quinolones in three exposure sites were determined by GC-ECD/MS, ICP-AES and HPLC, as well as, a combination of biomarkers including: ethoxyresorufin O-deethylase (EROD); aminopyrine N-demethylase (APND); erythromycin N-demethylase (ERND); glutathione S-transferase (GST); malondialdehyde (MDA); CYP1A; and P-glycoprotein (P-gp) mRNA expressions were evaluated in Mugilogobius abei. Results of chemical analysis in sediment samples revealed that the dominant chemicals were organic pollutants and heavy metals in Huadi River while quinolones in the pond. Bioassays indicated that differences among sites were in relation to some specific biomarkers. EROD and GST activities significantly increased after 72 h in situ exposure, but no difference was observed among the exposure sites. APND, ERND and MDA exhibited dissimilar change patterns for different priority pollutants. CYP1A and P-gp mRNA expressions were significantly induced at all exposure sites, whilst P-gp activity was typical for S2 with the highest levels of quinolones. The molecular biomarkers seemed to be more susceptible than enzyme activities. These assays confirmed the usefulness of applying a large array of various combined biomarkers at different levels, in assessing the toxic effects of mixed pollutants in a natural aquatic environment.

Effects of norfloxacin on hepatic genes expression of P450 isoforms (CYP1A and CYP3A), GST and P-glycoprotein (P-gp) in Swordtail fish (Xiphophorus Helleri).

The presence of antibiotics including norfloxacin in the aquatic environment may cause adverse effects in non-target organisms. But the toxic mechanisms of fluoroquinolone to fish species are still not completely elucidated. Thus, it is essential to investigate the response of fish to the exposure of fluoroquinolone at molecular or cellular level for better and earlier prediction of these environmental pollutants toxicity. The sub-chronic toxic effects of norfloxacin (NOR) on swordtail fish (Xiphophorus helleri) were investigated by measuring mRNA expression of cytochrome P450 1A (CYP1A), cytochrome P450 3A (CYP3A), glutathione S-transferase (GST) and P-glycoprotein (P-gp) and their corresponding enzyme activities (including ethoxyresorufin O-deethylase, erythromycin N-demethylase and GST. Results showed that NOR significantly affected the expression of CYP1A, CYP3A, GST and P-gp genes in swordtails. The gene expressions were more responsive to NOR exposure than their corresponding enzyme activities. Moreover, sexual differences were found in gene expression and enzyme activities of swordtails exposed to NOR. Females displayed more dramatic changes than males. The study further demonstrated that the combined biochemical and molecular parameters were considered as useful biomarkers to improve our understanding of potential ecotoxicological risks of NOR exposure to aquatic organisms.

Ontogenetic Development of the Digestive Tract in Larvae of American Shad

Abstract The American Shad Alosa sapidissima was introduced into China for aquaculture in 2003. The histological characteristics of the digestive tract of American Shad larvae were examined from hatching to 33 d after hatching (DAH) with the aim of cultivating the larvae efficiently. The fertilized American Shad eggs were imported from Oregon and incubated in barrels with spring water maintained at 20.3–21.9°C in Qingyuan, Guangdong Province, China. The larvae were transferred to cement pools (water temperature at 24.0–25.0°C) at 13 DAH. Larvae were fed Artemia nauplii starting at 3 DAH, Artemia nauplii supplemented with gradually increasing proportions of commercial formulated feed after 18 DAH, and then only the formulated feed by 30 DAH. Based on the source of nutrition and structural changes in the digestive tract, larval development was divided into three stages: (1) lecitotrophic (0–2 DAH), (2) lecitoexotrophic (3 DAH), and (3) exotrophic (4–33 DAH). At 0 DAH of the lecitotrophic stage, the digestiv...

Effects of simvastatin on the PXR signaling pathway and the liver histology in Mugilogobius abei

Simvastatin is one of the most commonly cholesterol-lowering prescribed drugs all over the world. With the increase of consumption of these pharmaceuticals and subsequent their discharge into the aquatic environment in recent years, they are present at detectable levels in most sewage effluents. Unfortunately, limited information is provided about their potential impacts on aquatic organisms, especially on the detoxification-related metabolism in fish. In the present study, one local native benthic fish (Mugilogobius abei) in southern China was employed as test species and exposed to SV (0.5 μg L-1, 5 μg L-1, 50 μg L-1 and 500 μg L-1) for 72 h. The transcriptional expression of nucleus transcriptional factor pregnane X receptor (PXR) and its downstream targeted genes including multixenobiotics resistance protein or permeability glycoprotein (P-gp), cytochrome 1A (CYP1A), cytochrome P450 3A (CYP3A), glutathione-S-transferase (GST) and the expression of associated microRNA such as miR-27, miR-34 and miR-148 in Mugilogobius abei were investigated. Result showed that the expressions of P-gp, CYP 1A, CYP 3A, GST and PXR were induced to some extend under simvastatin exposure for 72 h. A positive correlation was observed between PXR and CYP1A, CYP3A and P-gp. While for microRNA, a negative relationship was found between miR-34a and CYP3A, CYP1A. The expression of miR-148a was significantly induced under the exposure of SV (50 μg L-1), which was positive related to the transcriptional expression of PXR. For enzyme activity, erythromycin N-demethylase (ERND) significantly increased at 24 h and the activity of catalase (CAT) and superoxide dismutase (SOD) exhibited different trends. CAT was slightly inhibited at 24 h exposure but SOD was significantly induced in high concentration. Glutathione-S-transferase (GST) activity was significant inhibited after 72 h exposure. The reductive small molecule glutathione (GSH) content showed obvious decrease, while the quantity of malondialdehyde (MDA) increased significantly in high concentrations of SV exposure. GSH and MDA showed a typical negative correlation to some degree. Moreover, simvastatin caused histological changes in the liver tissues of M. abei, especially the size of adipocyte significantly decreased. The present study indicated that environmentally relevant concentration SV may affect the PXR signaling pathway in M. abei and pose potential ecological risks to non-target organisms like fish.

Genetic Variation of Channa maculata , Channa argus and Their Hybrid by AFLP Analysis

In this paper, we adopted AFLP molecular marker technique to analyze the genetic differences of 85 individuals of Channa maculata , Channa algus and their hybrid ( C. maculata ♀× C. argus ♂), among which Channa maculata and Chonna argus was 30 respectively, their hybrid was 25. The results showed that tota1 of 459 bands were obtained by 11 primer combinations, of which 350 were polymorphic bands, the percentage of polymorphic loci was 76.25%, the average of polymorphic bands per primer combination was 31.8. There were 169 discrepant bands could be distinguished C. maculata and C. argus steadily, 78 of those were paternal ( C. argus ) specific bands and 72 were entailed on hybrid, 89 of those were maternal ( C. maculata ) specific bands and 71 were entailed on hybrid. In addition, there were 3 nonparental bands in hybrid. The results of analysis of molecular variance (AMOVA) found that the Nei’s unbiased measures of genetic identity between C. maculata and C. argus was 0.516 1, while those between hybrid and C. maculata , hybrid and C. argus was 0.718 9 and 0.747 6. And their Nei’s unbiased measures of genetic distance were respectively 0.661 5, 0.330 0 and 0.290 9, respectively, the analysis of molecular variance analysis (AMOVA) displayed that. There was significantly genetic differentiation among C. maculata , C. argus and the hybrid. On the other hand, the UPGMA cluster analysis revealed that, individuals of C. maculata and C. argus could be distinguished into two populations, but most individuals of hybrid scattered in populations of C. maculata and C. argus . In populations cluster analysis hybrid and C. argus populations were cluster firstly, then clustered with C. maculata . The preliminary analysis result indicated that the hybrid was supposed to be isolation cultivated because of high promiscuous possibility among C. maculata, C. argus and their hybrid. The results of this article would provide experimental evidence for genetic assaying of C. maculata , C. argus and their hybrid and the refference for reasonable utilization of their germplasms.