Peptidoglycan recognition proteins (PGRPs) are a family of pattern recognition receptors (PRRs) involved in host antibacterial responses, and their functions have been characterized in most invertebrate and vertebrate animals. However, little information is available regarding the potential function of PGRPs in the giant triton snail Charonia tritonis. In this study, a short-type PGRP gene (termed Ct-PGRP-S1) was identified in C. tritonis. Ct-PGRP-S1 was predicted to contain several structural features known in PGRPs, including a typical PGRP domain (Amidase_2) and Src homology-3 (SH3) domain. The Ct-PGRP-S1 gene was constitutively expressed in all tissues examined except in proboscis, with the highest expression level observed in the liver. As a typical PRR, Ct-PGRP-S1 has an ability to degrade peptidoglycan (PGN) and was proven to have non-Zn²⁺-dependent amidase activity and antibacterial activity against Vibrioalginolyticus and Staphylococcus aureus. It is the first report to reveal the peptidoglycan recognition protein in C. tritonis, and these results suggest that peptidoglycan recognition protein Ct-PGRP-S1 is an important effector of C. tritonis that modulates bacterial infection resistance of V. alginolyticus and S. aureus, and this study may provide crucial basic data for the understanding of an innate immunity system of C. tritonis.

It has been reported that the giant triton snail (Charonia tritonis) inserts its large proboscis and then injects venom or acid saliva from its salivary gland into its prey, the crown-of-thorns starfish Acanthaster planci (COTS), paralyzing it. A full-length cDNA sequence of the C. tritonis Ct-kunitzin gene was obtained by RACE PCR based on a transcriptomic database constructed by our laboratory (data not published), which contains an open reading frame (ORF) sequence with a length of 384 bp including a 1–32aa Kunitz domain. The Ct-kunitzin peptide was synthesized by solid-phase polypeptide methods according to its conserved amino acid sequence, with a molecular weight of 3746.0 as well as two disulfide bonds. Renatured Ct-kunitzin was injected into mice ventricles to evaluate its potential function. Compared with the normal control group (physiological saline), the spontaneous locomotor activity of the Ct-kunitzin group decreased significantly. There was a significant effect on Ct-kunitzin on mice grip strength in the grip strength test. In addition, Ct-kunitzin exhibited remarkable biological activity in suppressing pain in the pain thresholds test. There were no significant differences between the Ct-kunitzin group and the normal control group in terms of various hematological indexes and histopathological observations. When tested in COTS, the most significant histological change was the destruction, disorganization, and significant reduction in the amount of COTS tube feet tissues. Altogether, the potential paralyzing effect on mice suggests that Ct-kunitzin is a possible agent for novel drug development.

Macrophage-expressed gene 1 proteins (Mpeg1/Perforin-2 (PRF2)) are a family of pore-forming proteins (PFPs) which can form pores and destroy the cell membrane of invading pathogens. However, little information is available regarding the function of Mpeg1 in the giant triton snail Charonia tritonis. In this study, a homolog of Mpeg1 (Ct-Mpeg1) was identified in C. tritonis. The predicted protein of Ct-Mpeg1 contains several structural features known in Mpegs, including a membrane attack complex/perforin (MACPF) domain and single transmembrane region. The Ct-Mpeg1 gene was constitutively expressed in almost all tissues examined except in the proboscis, with the highest expression level observed in the mantle. As a typical pore-forming protein, Ct-Mpeg1 has antibacterial activities against Vibrio (including Vibrio alginolyticus and Vibrio parahaemolyticus). In addition, rCt-Mpeg1 challenge to V. alginolyticus represses the expression of most outer membrane protein synthesis-related genes and genes involved in the TCA cycle pathway, which will lead to reduced outer membrane protein synthesis and less energy capacity. This is the first report to characterize the macrophage-expressed gene 1 protein in C. tritonis, and these results suggest that macrophage-expressed gene 1 protein Ct-Mpeg1 is an important immune molecule of C. tritonis that is involved in the bacterial infection resistance of Vibrio, and this study may provide crucial basic data for the understanding of the innate immunity system of C. tritonis.

Cladophora-dominated filamentous algal blooms constitute a growing threat to aquatic ecosystem stability and aquaculture operations. This study systematically evaluated the algicidal efficacy of sodium hypochlorite (NaClO), both individually and in combination with an organosilicone adjuvant, against Cladophora sp., with particular focus on induced oxidative damage mechanisms. Results demonstrated that NaClO exhibited a dose- and time-dependent inhibitory effect, achieving ≥90% inhibition at 1.20 mmol L⁻¹ within 48 h and >99% by 120 h, significantly surpassing the efficacy of lower concentrations (0.40 mmol L⁻¹) (p < 0.05). Physiological assessment revealed that 1.20 mmol L⁻¹ NaClO significantly suppressed total antioxidant capacity (T-AOC) after 96 h (p < 0.05). Notably, synergistic enhancement was observed with adjuvant co-application: at 0.40 mmol L⁻¹ NaClO, superoxide dismutase (SOD) activity reached its minimum with 0.33 ppm organosilicone adjuvant, showing significant reduction compared to higher adjuvant concentrations (p < 0.05). Furthermore, combinations of 0.80 and 1.20 mmol L⁻¹ with organosilicone adjuvant consistently maintained inhibition rates ≥ 94% across all sampling intervals, achieving control efficacy equivalent to 2.00 and 2.40 mmol L⁻¹ NaClO alone within 48 h. These findings demonstrate that NaClO supplemented with low-dose organosilicone adjuvant constitutes a promising and efficient strategy for mitigating Cladophora blooms.

Argopecten irradians concentricus (Say), one of four geographic subspecies of the bay scallop, has become the major cultured species in southern China since its introduction in 1995. However, its population has been significantly reduced due to high mortality.Also, poor growth rate has been observed following decades of culture.Therefore, the introduction or creation of new varieties is an urgent need. This study describes the first introduction of the new strain, Bohai Red, from the north to southern China. Hybridization trials were conducted between the recently introduced new strain and the local specie, A. irradians concentricus (Say). The success of hybridization was confirmed by SSR maker.The adult and juvenile Bohai Red cannot tolerate high temperatures compared to A. irradians concentricus (Say), whether in natural waters or under laboratory conditions. Fertilization rate for A. irradians concentricus (Say) × Bohai Red exceeded 80%, and hatching rate was 70%. The hybrids exhibit heterosis in survival rate, growth rate, and high-temperature tolerance, demonstrating substantial potential to replace A. irradians concentricus (Say) in southern China.

While chemosymbiosis offers deep-sea bathymodioline mussels a critical metabolic advantage, this dependence makes them vulnerable when removed from their native environment, and their early post-recovery dynamics remain poorly resolved. We maintained adult Gigantidas haimaensis collected from the Haima cold seep at atmospheric pressure and sampled gill tissues at 0, 3 and 9 h after collection. Coupled 16S rRNA amplicon sequencing and RNA-Seq were used to follow changes in the gill microbiota, host transcription and descriptive temporal covariation. Methyloprofundus remained the dominant bacterial genus throughout the experiment, whereas Ca. Vesicomyosocius, the SUP05 cluster, and operational taxonomic units (OTUs) assigned to Vibrio and Pseudoalteromonas had higher relative abundances at 9 h in the descriptive analysis and exhibited positive temporal covariation. RNA-Seq showed a stronger transcriptional shift at 3 h than at 9 h. Stress-related genes, including HSP70, HSP105, Toll-like receptors, fibrinogen-related proteins, dual oxidase, thioredoxin-system genes, ferritin, taurine transporter and sulfide:quinone oxidoreductase, changed markedly, while energy-consuming ribosome biogenesis was suppressed to conserve energy under combined physical and nutritional stressors. The temporal patterns of Ca. Vesicomyosocius and other low-abundance bacterial signals coincided with broad host stress and immune and metabolic transcriptional changes; gene-level microbiome–transcriptome associations were exploratory and did not survive false-discovery-rate (FDR) correction. These results document rapid short-term transcriptional and microbiome changes after recovery, while their causal drivers and consequences require controlled validation.