Understanding the biodiversity of aquatic communities and the underlying mechanisms that shape biodiversity patterns and community dynamics is crucial for the effective conservation and management of freshwater ecosystems. However, traditional survey methods often fail to comprehensively capture species diversity, particularly for low-abundance taxa. Moreover, studies integrating both metazoan and fish communities at fine spatial scales remain limited. To address these gaps, we employed a multi-marker eDNA metabarcoding approach, targeting both the 12S and 18S rRNA gene regions, to comprehensively investigate the composition of metazoan and fish communities in the Yujiang River. A total of 12 metazoan orders were detected, encompassing 15 families, 21 genera, and 19 species. For the fish community, 32 species were identified, belonging to 25 genera, 10 families, and 7 orders. Among these, Adula falcatoides and Coptodon zillii were identified as the most prevalent and abundant metazoan and fish species, respectively. Notably, the most prevalent fish species, C. zillii and Oreochromis niloticus, are both recognized as invasive species. The Bray–Curtis distance of metazoa (average: 0.464) was significantly lower than that of fish communities (average: 0.797), suggesting higher community heterogeneity among fish assemblages. Beta-diversity decomposition indicated that variations in the metazoan and fish communities were predominantly driven by species replacement (turnover) (65.4% and 70.9% for metazoa and fish, respectively) rather than nestedness. Mantel tests further revealed that species turnover in metazoan communities was most strongly influenced by water temperature, while fish community turnover was primarily affected by water transparency, likely reflecting the physiological sensitivity of metazoans to thermal gradients and the dependence of fish on visual cues for foraging and habitat selection. In addition, a co-occurrence network of metazoan and fish species was constructed, highlighting potential predator-prey interactions between native species and Corbicula fluminea, which emerged as a potential keystone species. Overall, this study demonstrates the utility of multi-marker eDNA metabarcoding in characterizing aquatic community structures and provides new insights into the spatial dynamics and species interactions within river ecosystems.

Although the expression of miRNAs has been widely applied to investigate on gonads, the role of miRNAs in the gonadal development of white Pacific shrimp (Litopenaeus vannamei) remains unknown. In this study, we performed high-throughput sequencing to identify the sex-related microRNAs (miRNAs) that elucidated the regulatory mechanisms on the gonadal differentiation of L. vannamei. We obtained a total of 29,671,557 and 28,526,942 raw reads from the ovaries and testes library, respectively. We then mapped 26,365,828 (92.73%) of the ovarian clean sequences and 23,694,294 (85.65%) of the testicular clean sequences for a transcriptome reference sequence of L. vannamei. After blasting the miRNA sequences against the miRBase database, we identified 153 significantly differentially expressed miRNAs between the ovaries and testes. To confirm the high-throughput sequencing results, we used a reverse transcriptase–quantitative polymerase chain reaction (RT-qPCR) to verify the expression patterns of the seven most differentially expressed miRNAs (i.e., novel_mir23, miR-92b-3p_3, miR-12-5p_2, novel_mir67, miR-279_1, let-7-5p_6, miR-263a-5p_1). According to the results of RT-qPCR, most of the miRNAs were expressed consistently with the high-throughput sequencing results. In addition, the target genes significantly enriched several Kyoto Encyclopedia of Genes and Genome (KEGG) pathways that were closely related to gonadal differentiation and development, including extracellular matrix–receptor interaction, Hedgehog signaling pathway, protein digestion and absorption and cell adhesion molecules (CAMs). This study revealed the first miRNAs sequencing of L. vannamei gonads. We identified sex-related differentially expressed miRNAs and KEGG pathways, which will be helpful to facilitate future research into the regulatory mechanism on the gonadal differentiation of L. vannamei.

Bellamya limnophila is a mollusk of significant medical and economic value in China. Understanding the complete mitochondrial genome of this species will better establish a foundation for systematic classification research on Viviparidae. Therefore, we sequenced the complete mitochondrial genome of B. limnophila, conducted a comprehensive analysis of its structural characteristics, and constructed a phylogenetic tree using maximum likelihood and Bayesian methods. The results showed that the genome sequence is 16,991 bp in length, including 13 protein-coding genes (PCGs), 20 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs), and 1 non-coding region (D-loop). In summary, the Ka/Ks ratios of all PCGs were <1, indicating that purifying selection dominated the evolutionary process of these snails. The entire genome structure exhibited conservative features, such as the majority of start codons being the standard ATG codon and the majority of tRNA genes having the standard cloverleaf secondary structure. B. limnophila and B. quadrata showed collinearity in terms of sequence homology. Phylogenetic analysis indicates that the clade formed by the genera Margarya, Cipangopaludina, and Bellamya is the sister group of the genus Viviparus; Bellamya limnophila is more closely related to B. quadrata than to other species. This study contributes to the mitochondrial genome database of the family Viviparidae and provides valuable insights into the phylogenetic relationships of related snails.

This study investigated the potential effects of Bellamya purificata polysaccharide (BPP) supplementation in feed on Cherax quadricarinatus, aiming to elucidate its impact on immune function and the underlying regulatory mechanisms. A 60-day feeding trial was conducted to evaluate the effects of varying dietary BPP concentrations (0‰, 2‰, 4‰, 6‰, and 8‰) on growth performance, histopathology, immune function, and transcriptomic profiles of C. quadricarinatus. Dietary BPP significantly increased the final body length and body weight of C. quadricarinatus. Furthermore, BPP inclusion improved the histological damage of hepatopancreatic tissues, alleviated physiological stress, and enhanced antioxidant capacity, antibacterial activity, and anti-inflammatory function, as evidenced by alterations in relevant enzyme activities and gene expression levels. Transcriptomic analysis revealed 957 differentially expressed genes (DEGs), which were predominantly enriched in GO terms and KEGG pathways associated with BPP-mediated immune regulation, such as the PPAR signaling pathway, peroxisome, steroid hormone biosynthesis, and lysosome. In addition, 14 candidate genes were identified, including Acox3, ACOX1, SCP2, and PPT1. Integrated analysis of GO, KEGG, and Short Time-Series Expression Miner (STEM) data supported the development of a mechanistic model illustrating how C. quadricarinatus modulates immune function in response to BPP supplementation. RT-qPCR validation confirmed the accuracy and reliability of the high-throughput sequencing results. Collectively, these findings highlight the potential of BPP as a functional feed additive in aquaculture and provide novel insights into disease prevention strategies for the C. quadricarinatus farming industry.