In recent years, bisphenol AF (BPAF) in aquatic environments has drawn attention to its ecological risks. This study aims to investigate the toxic effects of BPAF (188.33 μg/L) exposure for 30 days on female marine medaka (Oryzias melastigma). On the 10th and 30th day of exposure, the toxicity was evaluated using histological analysis of the liver and ovaries and the transcription levels of genes related to the antioxidant system, immune system, and hypothalamic-pituitary-gonadal (HPG) axis. Findings revealed that (1) BPAF exposure caused vacuolation, karyopyknosis and karyolysis in the liver of marine medaka, and the toxic impact augmented with duration; (2) exposure to BPAF for 10 days facilitated the growth and maturation of primary ova, and this exposure had a comparatively inhibitory effect after 30 days; (3) exposure to BPAF resulted in a biphasic regulation of the transcriptional abundance of genes involved in antioxidant and inflammatory response (e.g., il-8, cat), with an initial up-regulation followed by down-regulation. Additionally, it disrupted the transcriptional pattern of HPG axis-related genes (e.g., 3βhsd, arα). In conclusion, 188.33 μg/L BPAF can alter the expression levels of functionally related genes, impair the structural integrity of marine organisms, and pose a threat to their overall health.

Lutjanus fulgens (Valenciennes, 1830) is a teleost species classified under the family Lutjanidae which is a native of the Eastern Atlantic Ocean. Though highly commercialized due to its abundance and good taste, the production output has declined in recent years. This is an indication of the need for effective management and conservation measures. However, accurate species identification will ensure strategic management and conservation measure. DNA‐based species identification has proven its reliability in this regard via precise species identification. Several researchers have confirmed the accuracy of DNAbarcode as a species identification tool as well as species phylogeny analysis based on both the complete mitogenome and COI gene. Currently, nine specimens of L. fulgens were sampled from Ghana and subjected to DNA‐based analysis, namely, complete mitochondrial DNAand COI gene (DNA barcoding) analyses. The mitogenomic result revealed that L. fulgens is made up of a 16,500 base pairs (bp) mtDNA which consists of 22 transfer RNAs, 13 protein‐coding genes, and two ribosomal RNAs (GenBank Accession Number: MN398650). Furthermore, a sequence polymorphism analysis of the COIgene (MN986442–MN986450) detected two haplotypes. These haplotypes were both collected from the same fish landing site which suggests a possible cryptic linage diversity in the L. fulgens population at Vodza. According to the phylogeny examination, a close taxonomic relationship exists between L. fulgens and Lutjanus buccanella caused by a recent evolution termed as sympatric speciation. This study serves as a novel study for this species, building the foundation for future molecular‐based study for this species and as a DNA barcode reference data.

Hainan medaka (Oryzias curvinotus) is distributed in the coastal waters of the South China Sea and is able to adapt to a wide range of salinities. In this study, we characterized O. curvinotus in Sanya River (SY-medaka), which lacks dmy (a male sex-determining gene in O. latipes and O. curvinotus). In a comparison of SY-medaka and Gaoqiao medaka (GQ-medaka), the morphological difference between the two populations does not reach the subspecies level and they can be considered two geographic populations of O. curvinotus. A mitochondrial cytochrome oxidase subunit I (CoI) sequence alignment showed that the sequence identities between SY-medaka and other geographic populations of O. curvinotus are as high as 95%. A phylogenetic analysis of the mitochondrial genome also indicated that SY-medaka belongs to O. curvinotus. Molecular marker-based genetic sex assays and whole genome re-sequencing showed that SY-medaka does not contain dmy. Further, in RNA-Seq analyses of the testis and ovaries of sexually mature SY-medaka, dmy expression was not detected. We speculate that high temperatures resulted in the loss of dmy in SY-medaka during evolution, or the lineage has another sex-determining gene. This study provides a valuable dataset for elucidating the mechanism underlying sex determination in Oryzias genus and advances research on functional genomics or reproduction biology in O. curvinotus.