Zhuang Xue

In fish artificial breeding, adhesive eggs present a significant challenge for fertilization and reduce hatching success rates. Understanding the specific factors and mechanisms that influence egg adhesiveness, as well as developing effective de‐adhesion methods, is crucial for improving fish reproduction efficiency. Fat greenling ( Hexagrammos otakii ), a typical marine teleost species that produces adhesive eggs, is widely distributed in the northwest Pacific Ocean and is considered a promising candidate for aquaculture. In this study, H. otakii eggs were used as a model to qualitatively analyse the effects of different pH levels (6.0, 7.0, 8.0 and 9.0), osmotic pressures (100, 400 and 1000 mOsm kg ⁻¹ ) and metal ions (Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ , Mn ²⁺ and Cu ²⁺ ) on egg adhesiveness. In addition, scanning electron microscopy was employed to examine the ultrastructural changes on the egg surface under different conditions. The results indicated that Ca ²⁺ and Mg ²⁺ are the primary factors in seawater that induce egg adhesiveness in H. otakii , while changes in pH and osmotic pressure neither triggered adhesiveness nor altered the underlying adhesive mechanism. Furthermore, the study evaluated the effectiveness of protease treatment for chemical de‐adhesion. The results showed that treating the eggs with a 10 mg/L protease solution for 2 min successfully removed their adhesiveness, confirming the feasibility of chemical de‐adhesion. This research provides significant theoretical insights for optimizing the artificial breeding techniques of H. otakii .

Mixed lineage kinase domain‐like pseudokinase (MLKL) is a key effector of necroptosis. We identified an MLKL homologue from Hexagrammos otakii , named Ho MLKL. The open reading frame (ORF) of Ho MLKL contained 1497 nucleotides and encoded a protein with 498 amino acids (Mw = 57.15 kDa). Bioinformatic analysis revealed that Ho MLKL is highly conserved. In the experiments, fish were exposed to 16°C (control), 24°C, and 28°C for up to 24 h, and samples were taken at 0, 6, 12, and 24 h. We used quantitative real‐time polymerase chain reaction (qRT‐PCR), Western blot, and immunohistochemistry (IHC) to quantify Ho MLKL and related protein in the cardiac tissue of H. otakii . Cardiac injury was evaluated by histopathology and biochemical assays. The results showed that Ho MLKL may play an important role in heat‐stress‐induced cardiac injury in H. otakii . Heat stress significantly upregulated Ho MLKL, receptor‐interacting protein kinase 1 (RIPK1), and receptor‐interacting protein kinase 3 (RIPK3) expression ( p < 0.05), indicating activation of the necroptosis pathway. Cardiac damage was characterized by elevated creatine kinase (CK) and lactate dehydrogenase (LDH), myocardial disorganization, vascular congestion, chromatin condensation, and inflammatory cell infiltration. Increased expression of inflammatory factors and reduced glucose levels suggested concomitant inflammation and metabolic dysfunction. These findings demonstrate that Ho MLKL likely cooperates with RIPK1/RIPK3 to mediate necroptosis, linking heat stress to cardiac injury and inflammation in H. otakii , and provide insight into stress‐induced necroptosis in fish.

Hypoxic stress is an important environmental challenge for aquatic organisms, which is detrimental to fish survival and growth. Specifically, the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) has emerged as a pivotal regulator, with accumulating evidence underscoring its central role in inflammatory processes. However, the regulatory functions of NLRP3 during hypoxic stress in fat greenling (Hexagrammos otakii) remain elusive. In this study, we systematically analyzed the molecular features of HoNLRP3 and elucidated its biphasic regulatory mechanism under hypoxic stress in H. otakii using phylogenetic analysis, qRT-PCR, Western blot, and immunofluorescence. Its phylogeny is significantly different from that of mammals and carries FISNA and related motifs specific to bony fishes. Hypoxia induced predominant nlrp3 expression in the brain, peaking at 12–24 h, with strong positive correlation to hif-1α activation. NLRP3-ASC-Caspase1 inflammasomes assembly drove IL-1β maturation, while prolonged hypoxia (48 h) activated Caspase3/GSDME-mediated pyroptosis, accompanied by elevated LDH activity. Reoxygenation partially reversed inflammatory and pyroptosis markers, indicating that NLRP3 balances defense and injury through a biphasic regulatory mechanism. This study provides new insights into the hypoxic adaptation mechanisms in bony fish.

Cinnamaldehyde is an ideal feed additive with good immune enhancement and anti‐inflammatory regulation effects. However, the anti‐inflammatory regulation mechanism in fat greenling (Hexagrammos otakii, H. otakii) remains unclear. The nine targets of cinnamaldehyde were gathered in identified by the Traditional Chinese Medicine Systems Pharmacology database and Uniprot database, and 1,320 intestinal inflammation disease (IIF)‐related proteins were screened from DrugBank, Online Mendelian Inheritance in Man (OMIM), Genecards, and Pharmacogenetics and Pharmacogenomics Knowledge Base (PHARMGKB) Databases. According to the Gene Ontology enrichment results and Kyoto Encyclopedia of Genes and Genomes pathway results, cinnamaldehyde may regulated the responses to bacteria, lipopolysaccharide, an inflammatory cytokine, and external stimuli via the nuclear factor kappa‐B (NFκB) signaling pathway within on inflammatory network. In addition, the protein–protein interaction analysis assisted in obtaining the closely related inflammatory regulatory proteins, including the C5a anaphylatoxin chemotactic receptor 1 (C5aR1), transcription factor p65 (RELA), prostaglandin G/H synthase 2 (PTGS2), and toll‐like receptor 4 (TLR4), which were confirmed as the bottleneck nodes of the network to be more deeply verified via the molecular docking. Moreover, a cinnamaldehyde feeding model was established for evaluating the anti‐inflammatory effect of cinnamaldehyde in vivo. According to the current findings implied that cinnamaldehyde may play a protective role against IIF H. otakii by reducing inflammation through the C5 complement (C5)/C5aR1/interleukin‐6 (IL‐6) and TLR4/NFκB/PTGS2 pathway. The study focused on investigating the action mechanism of cinnamaldehyde on IIF through combining pharmacology and experimental verification in vivo, which provided a fresh perspective on the promoting effect of cinnamaldehyde on IIF in fish.

The nearshore marine fish known as black rockfish (Sebastes schlegelii) is found in the Yellow Sea, Bohai Sea, and East China Sea. The population structure and genetic diversity of S. schlegelii are vulnerable to the effects of artificial stocking, environmental pollution, overfishing, and climate change, so relevant studies are urgently needed. This study used comparative mtDNA loop (D-loop) analysis to examine the genetic diversity and natural population structure of 98 individuals from the northern Chinese cities of Qingdao, Jinzhou, and Dalian. A total of 22 haplotypes were identified in the three groups of samples, with the most common haplotypes being Hap-2, Hap-3, Hap-4, Hap-5, and Hap-6. The results of genetic diversity based on the D-LOOP sequence showed that the genetic diversity of S. schlegelii in the study area showed high Hd and low π type, indicating that the genetic diversity of S. schlegelii was low. Analyses of molecular variance (AMOVA) showed that the percentage of among population variation was − 0.29%, and the percentage of within population variation was 100.29%, indicating that the genetic variation was mainly from within the population. Between the three locations, the genetic differentiation index (Fst) was − 0.0113 ~ 0.0061, and there was no genetic differentiation among the populations. The results of gene flow (Nm) coefficients showed that the average Nm among the three populations was infinite (Nm = inf > > 4) and the three populations formed a stochastic unit. The results of the neutrality test (Tajima’s D, Fu’s Fs) and the frequency of nucleotide mismatch distribution demonstrated that the three geographic populations of S. schlegelii did not undergo a large population expansion in recent history. Based on the above conclusions, the S. schlegelii as a whole should be protected in situ.