Mi-Jin Choi

In commercial abalone production, sperm quality is a key determinant of fertilization success and, consequently, the long-term sustainability of the industry. However, human activities, such as the release of acidic and alkaline industrial wastes, have altered ocean pH levels, particularly affecting coastal waters, which may reduce abalone sperm quality and prevent fertilization. Currently, most studies regarding the effects of pH have focused on the development of embryos and larvae. Research on Pacific abalone sperm quality responses to pH remains limited. This study investigates the impact of pH on the quality of Pacific abalone sperm and the success of fertilization. Fresh sperm were incubated for 15 min in artificial seawater at pH values ranging from 6 to 10. Sperm quality was then assessed using computer-assisted sperm analysis (CASA), which included measurements of motility, progressive motility, beat cross frequency (BCF), the amplitude of lateral displacement (ALH), curvilinear velocity (VCL), straight-line velocity (VSL), the straightness index (STR), linearity (LIN), and average path velocity (VAP). We also assessed fertilization rates, live/dead sperm viability, acrosome integrity, hydrogen peroxide levels, and DNA damage levels. Compared to the control, decreases in motility and progressive motility were observed at pH levels of 6, 9, and 10. However, other CASA metrics (BCF, ALH, VCL, VSL, STR, LIN, and VAP) were not significantly affected. The percentage of cells exhibiting DNA damage was impacted considerably by pH. Similarly, the proportion of cells with damaged acrosomes rose at pH 10, and the proportion of dead sperm cells increased dramatically at pH 6, 9, and 10. At pH 6, hydrogen peroxide levels increased. Fertilization rates were reduced by exposure to the extreme pH levels tested, pH 6 and pH 10. In conclusion, Pacific abalone sperm quality may be adversely affected in seawater at pH values of 6, 9, and 10. These findings suggest that changes in coastal seawater pH may impact sperm quality, potentially affecting both natural abalone populations and aquaculture yields.

Fisheries and Aquatic Sciences

Fisheries and Aquatic Sciences

Fisheries and Aquatic Sciences

Gas vesicle nanoparticles (GVNPs) are hollow, buoyant prokaryotic organelles used for cell flotation. GVNPs are encoded by a large gas vesicle protein (gvp

Genes that influence the growth of Pacific abalone (Haliotis discus hannai) may improve the productivity of the aquaculture industry. Previous research demonstrated that the differential expression of a gene encoding a C-type lectin domain-containing protein (CTLD) was associated with a faster growth in Pacific abalone. We analyzed this gene and identified an open reading frame that consisted of 145 amino acids. The sequence showed a significant homology to other genes that encode CTLDs in the genus Haliotis. Expression profiling analysis at different developmental stages and from various tissues showed that the gene was first expressed at approximately 50 days after fertilization (shell length of 2.47 ± 0.13 mm). In adult Pacific abalone, the gene was strongly expressed in the epipodium, gill, and mantle. Recombinant Pacific abalone CTLD purified from Escherichia coli exhibited antimicrobial activity against several Gram-positive bacteria (Bacillus subtilis, Streptococcus iniae, and Lactococcus garvieae) and Gram-negative bacteria (Vibrio alginolyticus and Vibrio harveyi). We also performed bacterial agglutination assays in the presence of Ca²⁺, as well as bacterial binding assays in the presence of the detergent dodecyl maltoside. Incubation with E. coli and B. subtilis cells suggested that the CTLD stimulated Ca²⁺-dependent bacterial agglutination. Our results suggest that this novel Pacific abalone CTLD is important for the pathogen recognition in the gastropod host defense mechanism.