Olive flounder (Paralichthys olivaceus) is an important commercially cultured marine flatfish in China, Korea, and Japan, of which female grows faster than male. In order to explore the molecular mechanism of flounder sex determination and development, we used RNA-seq technology to investigate transcriptomes of flounder gonads. This produced 22,253,217 and 19,777,841 qualified reads from ovary and testes, which were jointly assembled into 97,233 contigs. Among them, 23,223 contigs were mapped to known genes, of which 2,193 were predicted to be differentially expressed in ovary and 887 in testes. According to annotation information, several sex-related biological pathways including ovarian steroidogenesis and estrogen signaling pathways were firstly found in flounder. The dimorphic expression of overall sex-related genes provides further insights into sex determination and gonadal development. Our study also provides an archive for further studies of molecular mechanism of fish sex determination.

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BackgroundLimited information on epidemiologic patterns of KSHV, with none focusing on heterosexual transmission, is available in mainland China. To clarify this, a cross-sectional study was conducted among a group of female sex workers (FSW) and general population women (GW) in Shanghai, China.MethodsAn anonymous questionnaire interview was administrated among 600 FSW and 600 GW. Blood samples were collected and tested for antibodies to KSHV, HSV-2, HIV, syphilis and HBsAg. Correlates of KSHV and HSV-2 were examined using multiple logistic regression analysis.ResultsNone of the study participants were tested positive for HIV. The seroprevalence of KSHV, HSV-2 , HBV and syphilis was 10.0%, 52.2%, 12.3% and 10.5%, respectively for FSW, and was 11.0%, 15.3%, 9.8% and 2.8%, respectively for GW. KSHV seropositivity was not associated with syphilis and HSV-2 infection as well as sexual practices among either FSW or GW. Nevertheless, HSV-2 infection among FSW was independently associated with being ever married (OR = 1.59; 95%CI: 1.04-2.45), >5 years of prostitution (OR = 2.06; 95%CI: 1.16-3.68) and being syphilis positive (OR = 2.65; 95%CI: 1.43-4.93). HSV-2 infection among GW was independently associated with an age of >35 years (OR = 2.29; 95%CI: 1.07-4.93), having had more than 2 sex partners in the prior 12 months (OR = 6.44; 95%CI: 1.67-24.93) and being syphilis positive (OR = 3.94; 95%CI: 1.38-11.23). A gradual increase of prevalence with the prostitution time group was also detected for HSV-2 and syphilis, but not for KSHV.ConclusionsKSHV is moderately and equivalently prevalent among FSW and GW. Heterosexual contact is not a predominant route for KSHV transmission among Chinese women.

To better understand the effects of DNA methylation on the expression patterns of dmrt1 (Doublesex and Mab-3-related transcription factor 1) and cyp19a (Cytochrome P450 19a) in the Japanese flounder Paralichthys olivaceus, quantitative expressions, cellular distributions and cytosine-p-guanine (CpG) methylation patterns of these two genes in the gonads were analysed. The results showed that P. olivaceus dmrt1 expression was 70 times higher in the testis than in the ovary (P < 0·05). Its mRNA was detected clearly in spermatocytes and Sertoli cells of the testis, but weakly in the ovary. Paralichthys olivaceus cyp19a expression was 40 times higher in the ovary than in the testis (P < 0·01). Its mRNA was detected clearly in follicular cells of the ovary, but weakly in spermatocytes of the testis. The dmrt1 promoter CpGs were not methylated in the testis, whereas 57·69% were methylated in the ovary. For the cyp19a promoter CpGs, 97·5% were methylated in the testis and 73·33% were methylated in the ovary. These findings demonstrate that P. olivaceus dmrt1 and cyp19a are sex-related genes with sexual dimorphic expression, CpG methylation levels of the two genes are consistent with their expression quantities, and this epigenetic modification can influence the differential expression of genes in the gonads of P. olivaceus.

The olive flounder (Paralichthys olivaceus) is an economically important flatfish in marine aquaculture with a broad thermal tolerance ranging from 14 to 23°C. Cold-tolerant flounder that can survive during the winter season at a temperature of less than 14°C might facilitate the understanding of the mechanisms underlying the response to cold stress. In this study, the transcriptional response of flounder to cold stress (0.7±0.05°C) was characterized using RNA sequencing. Transcriptome sequencing was performed using the Illumina MiSeq platform for the cold-tolerant (CT) group, which survived under the cold stress; the cold-sensitive (CS) group, which could barely survive at the low temperature; and control group, which was not subjected to cold treatment. In all, 29,021 unigenes were generated. Compared with the unigene expression profile of the control group, 410 unigenes were up-regulated and 255 unigenes were down-regulated in the CT group, whereas 593 unigenes were up-regulated and 289 unigenes were down-regulated in the CS group. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that signal transduction, lipid metabolism, digestive system, and signaling molecules and interaction were the most highly enriched pathways for the genes that were differentially expressed under cold stress. All these pathways could be assigned to the following four biological functions for flounder that can survive under cold stress: signal response to cold stress, cell repair/regeneration, energy production, and cell membrane construction and fluidity.

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Rongcheng Bay is a coastal bay of the Northern Yellow Sea, China. To investigate and monitor the fish resources in Rongcheng Bay, 187 specimens from 41 different species belonging to 28 families in nine orders were DNA-barcoded using the mitochondrial cytochrome c oxidase subunit I gene (COI). Most of the fish species could be discriminated using this COI sequence with the exception of Cynoglossus joyneri and Cynoglossus lighti. The average GC% content of the 41 fish species was 47.3%. The average Kimura 2-parameter genetic distances within the species, genera, families, and orders were 0.21%, 5.28%, 21.30%, and 23.63%, respectively. Our results confirmed that the use of combined morphological and DNA barcoding identification methods facilitated fish species identification in Rongcheng Bay, and also established a reliable DNA barcode reference library for these fish. DNA barcodes will contribute to future efforts to achieve better monitoring, conservation, and management of fisheries in this area.

The water characteristics of the Gucheng Lake, such as eutrophication, health and spatial distribution, were investigated. On the basis of the trophic state index (TSI) and entropy weight, a synthesized trophic state index (STSI) model was established to assess lake eutrophication condition through calculating STSI, choosing TP, TN, COD, BOD and NH 3 -N as trophic variables. The STSI ranged from 50.58 to 62.44, which showed that the water has been between eutrophic and supereutrophic. A histogram was applied to health risk assessment which was analyzed from carcinogenic substances (Cr ?6 , As and Cd) and non-carcinogenic substances (hydroxybenzene, Pb, Hg, CN -and NH 3 ), and the results showed that the former was much greater than the latter for effect. The total risk for each resident caused by all pollutants ranged from 5.18E-05 to 8.34E-05, which is far higher than the standard, recommended by Sweden Bureau of Environment Protection and Holland Ministry of Building and Environment Protection (1.0E-05). Cluster analysis was used to detect similarities and dissimilarities among the seven sampling sites and explain the observed clustering in terms of affected conditions. Twenty-one variables were used to divide seven sampling sites into three groups, namely, north lake, south lake and lake center.