The complete mitochondrial genome (mitogenome) of Mythimna separata (Lepidoptera: Noctuidae) was determined to be 15,329 bp, including 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes and an A+T-rich region. The AT skew of this mitogenome was slightly negative and the nucleotide composition was also biased toward A+T nucleotides (81.00%). All PCGs were initiated by ATN codons, except for cytochrome c oxidase subunit 1 (cox1) gene, which was initiated by CGA. Five of the 13 PCGs have the incomplete termination codon, T or TA. All the tRNA genes displayed a typical clover-leaf structure of mitochondrial tRNA. The A+T-rich region of the mitogenome was 372 bp in length and consisted of several features common to the Noctuidae. Phylogenetic analysis confirmed the placement of M. separata within the Noctuidae.

Bombyx mori, a key lepidopteran model with economic importance, is highly susceptible to environmental heavy metal pollution. This study investigated the mechanisms of Pb toxicity and the associated detoxification and metabolic defense responses in silkworms, employing transcriptome sequencing, enzyme activity assays, and histopathological analysis. Pb exposure caused significant histopathological changes and apoptosis in the fat body, marked by structural disorganization, swollen adipocytes, and degraded extracellular matrix. Molecular analysis showed activation of antioxidant defenses, with superoxide dismutase (SOD) and catalase (CAT) activities significantly elevated (p < 0.05), while peroxidase (POD) activity declined (p < 0.05). Levels of malondialdehyde (MDA) and glutathione (GSH) also decreased. In detoxification responses, carboxylesterase (CarE) activity was reduced, whereas cytochrome P450 (P450) and glutathione S-transferase (GST) activities increased (p < 0.05). Transcriptome sequencing revealed 1,418 differentially expressed genes (DEGs), with notable upregulation of key detoxification genes (p < 0.05), including six cytochrome P450s (CYPs), five uridine diphosphate-glycosyltransferases (UGTs), three glutathione S-transferases (GSTs), and six ATP-binding cassette transporters (ABCs). KEGG enrichment analysis highlighted the involvement of these DEGs in drug metabolism, glutathione metabolism, and ABC transporter pathways (p < 0.05). Functional validation showed that knocking down Cap ‘n’ Collar C (CncC) significantly suppressed key detoxification genes (CYP18A1, CYP332A1, GSTd3, GSTt1, UGT33D8; p < 0.05). qRT-PCR and Western blot analyses confirmed that the Caspase-3 pathway mediates Pb-induced apoptosis, with increased cleaved Caspase-3 and Caspase-4 levels following CncC silencing. Overall, our findings elucidate the mechanisms of Pb toxicity in silkworms and identify CncC as a critical regulator of detoxification and defense against heavy metal stress in lepidopteran insects.

Acute heat stress frequently causes mass mortality in farmed red swamp crayfish (Procambarus clarkii), yet the mechanisms underlying immune collapse remain poorly understood. We established an acute heat stress model (37 °C, 6 h) and performed an integrative analysis combining hemocyte profiling, redox and immune assays, RNA-seq, and qRT-PCR. Heat stress significantly increased mortality and disrupted the hemocyte system, with a ~25% reduction in total hemocyte count and a selective decline in granular cells. This was associated with severe redox imbalance, evidenced by ROS/H₂O₂ accumulation, suppressed SOD and CAT activities, and lipid peroxidation damage. Transcriptomic analysis revealed 1446 differentially expressed genes, indicating concurrent activation of ER stress and autophagy alongside suppression of energy metabolism. Key gene validation confirmed upregulation of pro-apoptotic factors (CASP3, P53) and ER stress markers (GRP78, XBP1), consistent with hemocyte depletion. These findings provide multi-level evidence that acute heat stress triggers a redox crisis (“oxidative burst–defense suppression”), which in turn activates ER stress and apoptosis, leading to selective loss of granular cells and systemic immune compromise. This study establishes a mechanistic framework for understanding heat-induced mortality in crustaceans and offers a theoretical basis for developing targeted interventions to enhance thermal resilience in crayfish aquaculture.

Salinity fluctuation is a common environmental stressor threatening coastal crustaceans. Abrupt salinity drop can disrupt osmotic balance, trigger oxidative damage, and impair tissue homeostasis, yet the underlying molecular mechanism in Portunus trituberculatus remains insufficiently understood. In this study, we integrated histopathology, biochemical assays, transcriptomics, RNA interference (RNAi) and western blotting to explore the toxic effects and molecular responses of P. trituberculatus under acute low-salinity stress. The results revealed that the activities of antioxidant enzymes (SOD, CAT) and immune-related enzymes (ACP, AKP) in both anterior and posterior gills presented a notable trend of rising first and then falling. Throughout the experiment, the activity of Na⁺/K⁺-ATPase was consistently higher in posterior gills, indicating their dominant role in osmoregulation. In addition, acute low-salinity exposure triggered detachment of some epithelial cells and formation of large vacuoles, along with a marked increase in cell apoptosis in posterior gills. Transcriptomic analysis demonstrated that the JNK-JUN/MAPK axis was specifically activated in posterior gills to mediate stress responses. Western blotting verified that RNAi-mediated JNK knockdown significantly down-regulated the expression of JNK and JUN. Moreover, JNK inhibition exacerbated epithelial detachment, vacuolization and apoptosis in posterior gill tissues, further confirming the regulatory function of the JNK-JUN/MAPK axis in stress adaptation. Collectively, these findings uncover the core mechanisms by which the JNK-JUN/MAPK axis modulates gill injury, apoptosis and antioxidant responses upon acute low-salinity stress and provide potential molecular biomarkers for environmental risk assessment of coastal crustaceans.

The taxonomy of the genus Metopograpsus is still a matter of debate because its species have limited morphological differences. Mitochondrial genomes, which are highly informative and easily accessible genetic markers, have been widely used to study molecular evolution and clarify relationships among species. This study aims to investigate the mitochondrial genome of Metopograpsus quadridentatus, a species with unique ecological and evolutionary significance. By analyzing the mitochondrial genome, we seek to address taxonomic uncertainties and provide insights into the evolutionary history of this species. In this study, we sequenced and analyzed the mitochondrial genome of M. quadridentatus to investigate its gene rearrangement patterns and its place within Brachyura. We compared the gene order of M. quadridentatus with that of 40 other Brachyuran species and created phylogenetic trees based on the nucleotide and amino acid sequences of 13 protein-coding genes (PCGs). We found that the mitochondrial gene arrangement of M. quadridentatus is mostly unchanged, similar to the original crustacean pattern, except for the movement of the trnH gene. Notably, the gene orders of several families, such as Eriphiidae, Grapsidae, Camptandriidae, Dotillidae, Plagusiidae, Ocypodidae, and Gecarcinidae, are the same. Phylogenetic analyses consistently placed M. quadridentatus within the genus Metopograpsus and the family Grapsidae, confirming its current taxonomic classification. These results offer important insights into evolutionary relationships and gene order conservation within Brachyura. Our study highlights the significance of mitochondrial genomes in resolving taxonomic uncertainties within the genus Metopograpsus.