Skin color is an important phenotypic feature of vertebrate fitness under natural conditions. Celestial goldfish, a common goldfish breed in China, mainly shows three kinds of skin colors including white, yellow and brown. However, the molecular genetic basis of this phenotype is still unclear. In this study, high-throughput sequencing was carried out on the back skin tissues of celestial goldfish with different skin colors. About 58.46 Gb of original data were generated, filtered and blasted, and 74,297 mRNAs were obtained according to the reference transcriptome. A total of 4653 differentially expressed genes were screened out among the brown, yellow and white groups, and the expression of melanogenesis related genes in brown goldfish was significantly higher than the other two groups. There are 19 common differentially expressed genes among three groups, of which eight genes are related to pigment production, including tyrp1a, slc2a11b, mlana, gch2, loc113060382, loc113079820, loc113068772 and loc113059134. RT-qPCR verified that the expression patterns of randomly selected differentially expressed transcripts were highly consistent with those obtained by RNA sequencing. GO and KEGG annotation revealed that these differentially expressed genes were mostly enriched in pathways of the production of pigment, including melanogenesis, tyrosine metabolism, Wnt signaling pathway, MAPK signaling pathway etc. These results indicated that the external characteristics of goldfish are consistent with the analysis results at transcriptome level. The results of this study will lay a foundation for further study on the expression characteristics and gene network analysis of pigment related genes.

Sulfamethoxazole (SMZ), a widely used broad-spectrum antibiotic in aquaculture, lacks comprehensive research on its residual elimination kinetics in tilapia. This study investigated SMZ residue depletion, withdrawal periods, and dietary risks in 1-year-old GIFT tilapia (Genetically Improved Farmed Tilapia Oreochromis niloticus) weighing 500 ± 50 g, following oral gavage administration of a loading dose (200 mg/kg BW on day 1) and then 100 mg/kg BW daily for 6 more days, at 22 ± 2 °C. Tissue samples (plasma, muscle, skin, liver, kidney, gill, and remaining tissues) were collected from five fish per time point at intervals from 0.33 to 30 days post-administration, with SMZ residues quantified via HPLC-MS/MS. Results revealed peak SMZ concentrations at 0.33 days (8 h), ordered as liver > skin > plasma > kidney > remaining tissues > gill > muscle. Muscle residues fell below the maximum residue limit (MRL, 100 μg/kg) by day 3, while skin required 10 days. Kidney residues dropped below the limit of detection (LOD) earliest (16 days), followed by muscle, gill, and remaining tissues (25 days), whereas plasma, liver, and skin retained detectable levels until day 30. Elimination equations for SMZ across tissues exhibited first-order kinetics. Based on the specific conditions of this study, a minimum 11-day withdrawal period is recommended for edible tissues (muscle + skin) after SMZ administration. Hazard quotient (HQ) values for all tissues remained below the safety threshold (HQ = 1), indicating low dietary risk. These findings support SMZ use standardization in tilapia aquaculture to ensure food safety compliance.

The aim of this study was to examine and understand the physiological and biochemical components of the blood and vitreous humor of goldfish (Carassius auratus). Blood was drawn from the arterial (static) line and vitreous humour was extracted using a syringe from healthy goldfish. An automatic haematology analyzer was used to detect 17 physiological indicators, including white blood cells and red blood cells. At the same time, 20 biochemical indexes, including albumin, calcium, and glutamic pyruvic transaminase, were found in the automatic biochemical analyzer. Experiments were also conducted on the effect of blood and vitreous fluid collection on the subsequent survival rate of the celestial goldfish. The findings demonstrated that there were values for 17 physiological indicators in the blood of the goldfish, including red blood cells (2.19 × 1012), white blood cells (62.21 × 109), hemoglobin (138.25g/L), and no eosinophils or basophils. However, no data for 17 physiological indications of vitreous humor were discovered. The quantities of total protein, glutamic oxaloacetic transaminase, and potassium in the vitreous humor were substantially lower than those in the serum (P < 0.01) according to the results of 20 biochemical indexes in the serum and vitreous humor of goldfish. Alkaline phosphatase, chlorine, and creatinine between vitreous humor and serum did not differ significantly(P > 0.05). The levels of glutamic pyruvic transaminase and γ-glutamyl transpeptide in vitreous humor were significantly higher than those in serum (P < 0.01). This experiment provides basic datas for the healthy culture of goldfish and the perfection of hematology in goldfish, and the results will be convenient for the further study of development and formation of celestial eye traits.

Within-cohort growth heterogeneity constrains aquaculture productivity, and its molecular correlates in carnivorous teleosts are poorly described. We compared the three heaviest and the three lightest individuals (n = 3 biological replicates per group, one fish per replicate) from a single cohort of mandarin fish (Siniperca chuatsi) at 90 days post-hatch, which differed 3.09-fold in body mass (p = 7.1 × 10⁻⁵), by combining muscle RNA sequencing with label-free quantitative proteomics of muscle and liver. Muscle transcriptomics identified 827 differentially expressed genes. The proteasome (ko03050) was the only KEGG pathway reaching significance, with all 14 contributing subunits being more abundant in slow-growing fish, and GO enrichment recovered proteasome, peptidase and endopeptidase complexes alongside serine-type peptidase activities in the same direction. Proteomics identified 37 differentially abundant proteins in muscle and 24 in liver at a nominal threshold. Protein-level gene set enrichment analysis showed negative enrichment of oxidative phosphorylation (NES = −1.96, adjusted p = 0.001) and of mitochondrial proteins (NES = −1.77, adjusted p = 0.005) in fast-growing muscle. Haemoglobin subunits were more abundant in fast-growing muscle and liver at the protein level, while muscle haemoglobin transcripts showed paralog-specific differences. The cross-sectional extreme-phenotype design identifies molecular signatures associated with the observed growth phenotype without establishing causality. The dataset provides candidate genes and proteins for functional study in S. chuatsi.

This study layed the groundwork for the creation of haploid and triploid celestial goldfish, presenting essential data derived from preliminary investigations. The research delved into three main areas: the short-term preservation of celestial goldfish gametes, the interaction between oocytes and foreign sperm, and the effects of temperature on fertilized eggs concerning hatching rates and late-stage ocular development. Initially, the study explored the optimal semen dilution ratio for celestial goldfish under microscopic examination. And the hybridization of the largemouth bass and celestial goldfish was investigated: largemouth bass sperm was crossbred with celestial goldfish eggs, and it was found that their sperm could not stimulate the development of celestial eye eggs. At last, celestial goldfish fertilized eggs were stimulated at 4 °C and −20 °C, respectively, to observe their impact on the hatching rate and later celestial eye rate. The results revealed no significant differences in hatching rate and celestial eye rate between the cold stimulus groups and the control group, but numerically, the 4 °C cold stimulation reduced the celestial eye rate of celestial goldfish fertilized eggs. The research provided fundamental data for artificial breeding and hybridization experiments in celestial goldfish.

Large variation in body weight poses a major challenge to the development and industrialization of formulated-feed aquaculture in Siniperca chuatsi. Breeding varieties that combine formulated-diet adaptation, rapid growth, and uniform body weight is therefore important for improving production efficiency. However, the genetic architecture of body weight and optimal genomic selection (GS) strategies remain poorly understood. Here, whole-genome resequencing was performed on 522 formulated-diet-adapted individuals. Genome-wide association study (GWAS) identified 21 significant loci, with candidate genes associated with lipid metabolism, endocrine regulation, and neuroendocrine signaling. Genomic prediction was evaluated using genome-wide single-nucleotide polymorphisms (SNPs) and GWAS-prioritized SNP panels with Bayesian and machine-learning models. Prediction accuracy increased with marker number and generally plateaued at approximately 30,000 SNPs. Random forest using GWAS-prioritized markers achieved the highest accuracy, improving prediction accuracy by 4.8% over genome-wide genomic best linear unbiased prediction (GBLUP) while using fewer markers. These findings demonstrate the potential of GWAS-informed marker prioritization to reduce marker requirements and improve GS efficiency for body weight in formulated-diet-adapted S. chuatsi.