Larimichthys crocea is an economically important marine fish in China. To date, the molecular mechanisms underlying testicular development and spermatogenesis in L. crocea have not been thoroughly elucidated. In this study, we conducted a comparative transcriptome analysis between testes (TES) and pooled multiple tissues (PMT) (liver, spleen, heart, and kidney) from six male individuals. More than 54 million clean reads were yielded from TES and PMT libraries. After mapping to the draft genome of L. crocea, we acquired 25,787 genes from the transcriptome dataset. Expression analyses identified a total of 3853 differentially expressed genes (DEGs), including 2194 testes-biased genes (highly expressed in the TES) and 1659 somatic-biased genes (highly expressed in the PMT). The dataset was further annotated by blasting with multi-databases. Functional genes and enrichment pathways involved in spermatogenesis and testicular development were analyzed, such as the neuroactive ligand–receptor interaction pathway, gonadotropin-releasing hormone (GnRH) and mitogen-activated protein kinase (MAPK) signaling pathways, cell cycle pathway, and dynein, kinesin, myosin, actin, heat shock protein (hsp), synaptonemal complex protein 2 (sycp2), doublesex- and mab-3-related transcription factor 1 (dmrt1), spermatogenesis-associated genes (spata), DEAD-Box Helicases (ddx), tudor domain-containing protein (tdrd), and piwi genes. The candidate genes identified by this study lay the foundation for further studies into the molecular mechanisms underlying testicular development and spermatogenesis in L. crocea.

Disease outbreaks in aquaculture have recently intensified. In particular, visceral white-nodules disease, caused by Pseudomonas plecoglossicida, has severely hindered the small yellow croaker (Larimichthys polyactis) aquaculture industry. However, research on this disease is limited. To address this gap, the present study employed a 100K SNP chip to genotype individuals from an F1 full-sib family, identify single nucleotide polymorphisms (SNPs), and construct a genetic linkage map for this species. A high-density genetic linkage map spanning a total length of 1395.72 cM with an average interval of 0.08 cM distributed across 24 linkage groups was obtained. Employing post-infection survival time as an indicator of disease resistance, 13 disease resistance-related quantitative trait loci (QTLs) were detected, and these regions included 169 genes. Functional enrichment analyses pinpointed 11 candidate disease resistance-related genes. RT-qPCR analysis revealed that the genes of chmp1a and arg1 are significantly differentially expressed in response to P. plecoglossicida infection in spleen and liver tissues, indicating their pivotal functions in disease resistance. In summary, in addition to successfully constructing a high-density genetic linkage map, this study reports the first QTL mapping for visceral white-nodules disease resistance. These results provide insight into the intricate molecular mechanisms underlying disease resistance in the small yellow croaker.

Housefly maggot larvae (HML) have been identified as a potential alternative animal diet for the fattening process of the Chinese mitten crab (Eriocheir sinensis). However, the feasibility and potential impacts of HML supplementation require further investigation. The present study evaluated the effects of dietary HML on the growth indices, nutrient compositions, antioxidant activity, and texture profiles of edible tissues of E. sinensis. The results showed that dietary HML supplementation effectively improved the hepatic steatosis index of both genders and sweet amino acid content of edible tissues (except for male gonad) (p < 0.05). Additionally, dietary HML significantly increased the total antioxidant capacity in the gonad and female muscle (p < 0.05). For the textural properties, HML feeding significantly improved the adhesiveness in the male muscle, and the cohesiveness, chewiness, and resilience in the female muscle (p < 0.05). Furthermore, HML feeding significantly decreased the levels of the equivalent umami concentration of the male gonad, male muscle, and hepatopancreas (p < 0.05). Conversely, HML feeding significantly increased the sweetness value in the muscle, hepatopancreas, and female gonad (p < 0.05). Our findings indicate that HML could serve as a viable alternative feed for fattening to improve the edible yield and change the flavor characteristics in E. sinensis.

Anthropogenic acidification is a long-term challenge to marine ecosystems. Though coastal acidification is intensifying, the large yellow croaker (Larimichthys crocea) exhibits good adaptability to pH fluctuations, the underlying mechanisms of which remain poorly understood. This study investigated the morphology, antioxidant enzyme activity, and gene expression of L. crocea under varying acidification conditions (pH 8.1 (H group), 7.8 (M group), and 7.4 (L group)). Water pH fluctuations were also monitored to explore the physiological responses and potential adaptive molecular mechanisms of L. crocea under various acidified environments. The results indicated that the water pH decreased in the H group, significantly increased in the L group (p < 0.05), and remained stable in the M group during the experiment. The lowest MDA content and the highest antioxidant enzyme activities (CAT, SOD, GSH-Px) were observed in L. crocea at pH 7.8, suggesting pH 7.8 was optimal for L. crocea. Transcriptomic analysis revealed distinct gene expression patterns between the gills and kidneys under acidification stress. Differentially expressed genes (DEGs) in the gills were primarily observed between the M and L groups (62.3%), whereas in the kidneys, the majority of DEGs were observed between the M and H groups (43.2%). These findings suggested that the gills play a critical role in adapting to low pH in L. crocea, while the kidneys were more responsive to high pH. Enrichment analysis identified critical pathways, including vasopressin-regulated water reabsorption, mineral reabsorption, and aldosterone-regulated sodium reabsorption, which are associated with water and ion metabolism. These pathways play a pivotal role in the acid–base homeostasis and metabolism of L. crocea. These results provide insights into the adaptive mechanisms of L. crocea to acidified environments, with implications for aquaculture management and future ocean acidification adaptation.

High temperatures present considerable challenges to global fish growth and production, yet the genetic basis of heat tolerance remains underexplored. This study combines quantitative trait locus (QTL) mapping and genome-wide association studies (GWAS) to examine the genetics of heat tolerance in Larimichthys polyactis. As a result, a genetic linkage map was constructed with 3237 bin markers spanning 24 linkage groups and totaling 1900.84 centimorgans, using genotyping-by-sequencing of a full-sib family comprising 120 progeny and their two parents. Based on this genetic linkage map, QTL mapping identified four QTLs associated with heat tolerance, which encompassed 18 single nucleotide polymorphisms and harbored 648 genes within the QTL intervals. The GWAS further disclosed 76 candidate genes related to heat tolerance, 56 of which overlapped with the QTL results. Enrichment analysis indicated that these genes are involved in immune response, development, lipid metabolism, and endocrine regulation. qPCR validation of 14 prioritized genes, which were simultaneously enriched in Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways, confirmed significant upregulation of smpd5, polr3d, rab11fip2, and gfpt1, along with downregulation of gpat4 and grk5 after 6 h of heat stress. These findings demonstrate their responsiveness to elevated high temperatures. This meta-analysis of QTL mapping and GWAS has successfully identified functional genes related to heat tolerance, enhancing understanding of the genetic architecture underlying this critical trait in L. polyactis. It also provides a molecular breeding tool to improve genetic traits associated with heat tolerance in cultured L. polyactis.

Commercial feeds formulated for Larimichthys crocea are commonly used in intensive farming of Larimichthys polyactis; however, their nutritional composition is suboptimal for the latter. The study evaluated the effects of dietary chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA) supplementation on mitigating nutritional mismatch-induced growth retardation and hepatopancreatic–intestinal metabolic disorders in L. polyactis. Fish were fed seven feeds: a commercial feed (control) and feeds supplemented with 300, 600, and 1200 mg/kg of CDCA or UDCA. Results showed that both bile acids (BAs) supplementation improved growth, altered thyroid hormone metabolism, with significant changes in hepatopancreatic–intestinal types of deiodination. Both BAs increased hepatopancreatic energy metabolism and cholic acid synthesis, while inducing hepatopancreatic oxidative damage. Notably, 300 mg/kg CDCA and 600 mg/kg UDCA significantly reduced hepatopancreatic vacuolation and lipid accumulation, which was associated with enhanced protease and lipase activities (p < 0.05). Dietary both BAs supplementation enhanced intestinal antioxidant capacity, but contributed to the inflammation, with 300 mg/kg UDCA improving intestinal mucosal morphology (p < 0.05). These findings suggest that supplementation with dietary 300 mg/kg CDCA, 300 and 600 mg/kg UDCA could alleviate growth restriction and liver–intestinal structural damage caused by nutritional mismatch, reduce hepatic fat accumulation, and enhance intestinal antioxidant capacity of L. polyactis.