Shiyong Zhang

To advance the efficient all-male breeding of channel catfish, Ictalurus punctatus (Rafinesque, 1818), this study utilized YY pseudofemales obtained through hormone-induced sex reversal. Morphological traits and body weight were systematically compared among YY pseudofemales ( n = 50), XX females ( n = 50), XY males ( n = 50), YY supermales ( n = 50), and XY pseudofemales ( n = 50) at 6 months of age. Using correlation analysis, path analysis, and multiple regression, the relationships between morphological traits and body weight were elucidated. The results showed that YY pseudofemales exhibited significantly lower values for several morphological indicators than males, but no significant differences were observed relative to females or XY pseudofemales. This provides key phenotypic evidence supporting the feasibility of using YY pseudofemales as female broodstock in the “YY supermale × YY pseudofemale” breeding system. The analysis revealed strong correlations between morphological traits and body weight; however, the key traits affecting body weight showed significant population-specific patterns. Specifically, weight gain in pseudofemale channel catfish primarily depended on increased body depth at the anus, exhibiting a “body depth-dominant” pattern, whereas male channel catfish showed a “standard length-dominant” or “total length-dominant” pattern. This finding offers direct theoretical guidance for implementing precise population-differentiated selection strategies tailored to distinct breeding objectives. Furthermore, a reliable predictive model for body weight in YY pseudofemales was established based on key morphological traits. This model may facilitate early screening of broodstock and accelerate genetic progress in all-male breeding, although its broader applicability requires validation across independent populations and rearing systems.

Understanding the genetic architecture underlying growth variation is central to improving aquaculture species through genomic selection. Here, we performed a genome-wide association study (GWAS) on 303 individuals from a G₂ breeding population of channel catfish (Ictalurus punctatus) using whole-genome resequencing data. After stringent quality control, 5.64 million high-confidence single nucleotide polymorphisms (SNPs) were retained for association analyses of two key growth traits—monthly weight gain (MWG) and body depth (BH). We identified 15 and 28 loci significantly associated with MWG and BH, respectively, with the majority concentrated on chromosome 20. Two SNPs (Chr20:14,657,971 and Chr20:14,658,012) located in exon 9 of the rrp44 gene were significantly associated with both traits. Functional annotation and enrichment analyses revealed that the rrp44 gene, encoding an exoribonuclease subunit of the RNA exosome complex, participates in mitotic spindle regulation and post-transcriptional RNA decay, processes critical for cellular growth and metabolic homeostasis. We propose that rrp44 may influence growth through the modulation of feeding rhythm and circadian regulation, providing a potential molecular basis for growth heterogeneity in channel catfish. These findings enrich our understanding of growth-related genomic variation and offer valuable molecular markers for precision breeding and genetic improvement of catfish.

To elucidate the temporal dynamics of genetic diversity across successive breeding generations of channel catfish (Ictalurus punctatus) and enhance subsequent breeding efficiency, we systematically evaluated the genetic variation in four consecutive generations using ten highly polymorphic microsatellite loci. The number of alleles (Na), effective alleles (Ne), and Shannon’s index (I) all declined with increasing generations. The mean expected heterozygosity (He) decreased gradually from 0.822 to 0.805 but remained above 0.80, indicating that all generations maintained relatively high genetic diversity. Allele frequency analysis revealed the progressive fixation of alleles potentially linked to target traits, while some rare alleles were gradually lost. Analysis of molecular variance (AMOVA) demonstrated that 98% of the genetic variation occurred within generations, with weak differentiation among generations (Fst = 0.016). UPGMA clustering further indicated that later generations diverged from the base stock, whereas genetic distances among adjacent generations progressively narrowed, suggesting increasing convergence and stabilization of genetic structure. These findings provide both theoretical insights and practical guidance for the continuous selective breeding and germplasm conservation of channel catfish.

Throughout their life cycles, many fish alternate between periods of fasting and feeding due to the temporal and geographical variability of food availability in aquatic environments. The ability to adapt to fasting and restore internal balance after refeeding is fundamental to the long‐term survival and symbiotic relationships of aquatic species. However, our understanding of the mechanisms by which the fish adapt to fasting and refeeding remains limited. We looked at the growth performance, intestinal and liver histology, and liver gene expression patterns of channel catfish, a significant commercial species, during three weeks of fasting stress and three weeks of refeeding, respectively, in order to clarify the molecular response mechanisms to these two events. Our study revealed that fasting significantly impacts growth, histological characteristics and physiological metabolism. During the fasting period, catfish growth performance was greatly inhibited, but growth compensation was observed after refeeding. Histological analysis showed that liver and intestinal tissues experienced varying degrees of apoptotic injury during fasting, with a modest number of TUNEL‐positive cells still present in the liver after refeeding. We identified 787 significant differentially expressed genes (DEGs) in the control group in three weeks (CG3) groups versus the fasting‐refeeding group inthree week (EG3) group, while only 35 DEGs were defined in the CG6 group versus the EG6 group. Gene Ontology functional annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses suggested that fasting stress affected gene expression related to the mitotic cell cycle, cell cycle processes, amino acid metabolism, steroid biosynthesis, fatty acid metabolism and immune responses. Metabolism and cellular process response genes were significantly downregulated in the fasting group. Significant alterations in the expression levels of genes related to metabolism and apoptosis were validated by quantitative Real‐time PCR (qRT‐PCR) . This study provides insights into the physiological mechanisms underlying fish adaptation to fasting or nutritional deficiency stress, shedding light on how channel catfish respond to fasting stress and refeeding.

Rhythms, regulated by core clock genes like the period (per) gene family, are crucial for maintaining physiological processes in animals. In teleost fish, including channel catfish (Ictalurus punctatus), these genes have evolved distinct functions. However, the evolutionary characteristics and functional roles of period genes, particularly in response to environmental cues such as feeding, remain unclear. This study aimed to investigate the evolutionary divergence and functional specialization of the period gene family in channel catfish, with a focus on feeding-induced rhythmicity. Four period genes, Ipper1b, Ipper2, Ipper2l, and Ipper3, were identified in channel catfish. Phylogenetic analysis revealed distinct evolutionary paths for these genes, with Ipper2l forming a separate clade from Ipper2. Tissue-specific expression analysis showed differential expression of period genes across tissues, with Ipper1b exhibiting the highest expression in the intestine and Ipper2 being predominantly expressed in the liver. Statistical analysis confirmed significant differences in the expression levels between tissues (p < 0.05), supporting the tissue-specific roles of these genes. Notably, under strict feeding schedules, we observed significant modulation of rhythmic expression in both the brain and liver, with a notable shift in the peak expression times and amplitude changes aligned with the feeding time. These results suggest that feeding serves as a critical Zeitgeber, entraining circadian rhythms in key tissues and potentially enhancing metabolic efficiency. These results demonstrated that feeding schedules play a key role in modulating circadian gene expression in channel catfish. This study provides insights into the evolutionary divergence and functional roles of the period gene family in channel catfish, showing how feeding schedules modulate circadian gene expression in the brain and liver. These findings have potential applications in optimizing feeding strategies for improving fish health and growth in aquaculture.

With the expansion of farming regions and changing environmental conditions, the genetic structure of yellow catfish populations in different geographic areas may have undergone new changes. This study assessed the genetic diversity and population genetic structure of six yellow catfish populations from the Yangtze River, Huaihe River, and Ussuri River basins in China using ten microsatellite markers. The results showed that the average number of alleles per population ranged from 9.0 to 11.5, with observed heterozygosity ranging from 0.614 to 0.667 and expected heterozygosity from 0.588 to 0.727. The Ussuri River population (WSLR) exhibited the lowest genetic diversity (PIC = 0.569), while the population from Hongze Lake had the highest (PIC = 0.710). Analysis of molecular variance (AMOVA) revealed that 91% of genetic variation was within individuals, and only 3% was between populations. F_st values ranged from 0.014 to 0.069, indicating low genetic differentiation between populations. Clustering analysis, including principal coordinate analysis (PCoA), unweighted pair-groups method using arithmetic averages (UPGMA) dendrogram, and ancestral lineage analysis showed genetic separation between the northern Ussuri River population and the five southern populations. The results highlight the influence of geographic isolation on genetic differentiation. These findings provide valuable insights into the conservation and breeding strategies of yellow catfish germplasm resources.

Salinity is an important environmental factor affecting fish growth and development. To investigate the effects of salinity stress on the growth performance, tissue structures, and expression of genes related to apoptosis and immune response in large‐sized channel catfish (Ictalurus punctatus) juveniles, an 8‐week salinity stress experiment was conducted. Six salinity levels (3, 3.8, 4.7, 5.9, 7.3, and 9 psu) were set according to an equal logarithmic concentration gradient method, along with a control group (0), and growth performance and physicochemical indices were measured. The survival rate of channel catfish in all salinity groups was 100%. Body length, body weight, weight gain rate, and specific growth rate decreased with increasing salinity, with higher salinity levels resulting in more significant reductions in growth performance. At 9 psu, both the specific growth rate (SGR) and weight gain rate (WGR) decreased significantly to 0.61%/day and 40.86%, respectively (p < 0.05). Histological analysis results indicated that with the increase in salinity, the number of intestinal mucosal folds relatively increased, while the number of goblet cells gradually decreased. Hepatocytes became more densely packed, and the hepatic lobule gaps widened. Apoptosis detection results revealed that in the liver, the number of apoptotic cells at 4.7 psu salinity was more than that in the control group and at 9 psu salinity. In the intestine, the number of apoptotic cells at 9 psu salinity was significantly higher than in the other two groups (p < 0.05). Quantitative polymerase chain reaction (qPCR) analysis of the expression patterns of genes related to apoptosis and immunity showed that the expression levels of caspase 3, caspase 8, INF‐I, IL‐1β, and bax genes in the liver and intestinal tissues were higher in the experimental groups than in the control group, while the expression of bcl‐2 decreased with increasing salinity in liver tissue but increased in intestinal tissue. These findings can provide theoretical guidance for the aquaculture of channel catfish in saline‐alkali land.