The early developmental stages of fish exhibit the highest mortality and greatest environmental sensitivity throughout their life cycle. This period encompasses a series of crucial biological events, including morphogenesis, organ differentiation, and nutritional mode transition from fertilized eggs to newly hatched larvae. Although largemouth bass (Micropterus nigricans) is a commercially important fish species in China, the molecular regulatory mechanisms governing its endogenous nutritional stage remain largely unexplored. To elucidate the molecular basis of this critical period, we performed transcriptomic profiling across six consecutive developmental stages (Multicellular, Blastula, Gastrula, Neurula, Organogenesis, and 5 day post hatching larvae). Our results reveal stage-specific transcriptional programs: the multicellular-to-blastula transition is characterized by stage-specific enrichment of by cell cycle and DNA replication pathways, with MCM complex (mcm2-5) upregulation accelerating proliferation; the blastula-to-gastrula transition features activation of bmp4, fgfr2, and lft1 for germ layer induction; the neurula stage exhibits transcriptional bursts and enrichment of neural tube-related pathways; organogenesis involves simultaneous activation of focal adhesion (col1a1b, col4a5, tnc) and Wnt signaling (wnt1, wnt4, wnt3a) pathway; and 5 dph larvae show visual function maturation, with light transduction genes (gnat1, gnat2, gucy2f, pde6b) identified as hub genes. Mfuzz analysis further reveals sustained upregulation of Cluster 14 (igf2r、napin、vamp7、il1b、aco2) indicating functional maturation, while Cluster 29 (mcm10, espl1, cep152, cep44, cep295) confirms declining cell division activity. Collectively, this study provides a transcriptomic resource for understanding largemouth bass embryonic development and offers molecular insights for improving hatchery practices.
Jixiang Hua, Yi-Fan Tao, Hui Sun et al.· Comparative Biochemistry and...· 0 citations
Growing freshwater scarcity in China is driving aquaculture interests toward saline‐tolerant fish species. Red tilapia (Oreochromis spp.) is a euryhaline species with strong osmoregulatory capacity, making it an ideal model for investigating stress‐induced physiological changes. In this study, we examined the gill responses of red tilapia subjected to acute salinity stress. Fish were maintained in either (0 h, Ctrl group) or saline water (17.7‰ ± 0.1‰) for 192 h; time points (0, 24, 48, 96, 192 h). Gill samples were collected over a time course for integrated histopathological and physiological analyses. Exposure to saline water induced histopathological alterations, including lamellar shortening and thickening, as well as a significant increase in the apoptotic index. Using qRT‐PCR, we confirmed the significant activation in gills under salinity stress of genes associated with apoptosis (tnfsf1, birc5a, casp6, ddit3), ABC transporters (cftr, tap1), and Toll‐like receptor (TLR) signaling (irak1, nfkbiaa). These molecular responses reflect three key processes: osmoregulation (ABC transporters), immune and inflammatory regulation (TLR signaling), and cell fate control (apoptosis). Collectively, they underpin the disruption of homeostasis, immune activation, and oxidative stress observed during acute salinity exposure. Biochemical profiling revealed a dynamic osmoregulatory response: early upregulation of Na+/K+‐ATPase, NKCC1, and antioxidant enzymes (SOD, CAT, GSH‐Px) was followed by a late‐stage oxidative imbalance, characterized by sustained elevation of malondialdehyde (MDA) and reduced antioxidant capacity. Ion homeostasis became progressively disrupted, with significant alterations in Na+ and Cl− levels. Molecular analysis further uncovered a coordinated transcriptional sequence: an initial anti‐apoptotic phase, succeeded by delayed upregulation of pro‐apoptotic and immune‐related pathways (including IgM and LZM), occurring alongside modulation of osmoregulatory genes. Together, these findings provide a mechanistic basis for understanding salinity adaptation in red tilapia.
Moustafa Saleh, Rahma Aboueleila, M. Badran et al.· Journal of the World Aquacul...· 0 citations
The genetic mechanisms of salinity tolerance in grass carp are revealed, which might be optimized through genomic selection, and provides insights for selectively breeding new varieties with greater salinity tolerance.
