Nan Chen

In the context of global climate change, intensified salinity fluctuations driven by altered precipitation, extreme rainfall events, and typhoons have emerged as a major threat to coastal mollusk aquaculture. In this study, integrated physiological and transcriptomic analyses were performed to investigate the responses of Pacific abalone (DD, Haliotis discus hannai) and its hybrid (DF, H. discus hannai ♀ × H. fulgens ♂) to hypo- and hypersalinity stress. Two salinity breakpoints (BPS1 for hyposalinity, BPS2 for hypersalinity) were identified using heart rate monitoring to indicate the osmotic tolerance thresholds of the abalone. The BPS1 and BPS2 values did not differ significantly between the DD and DF groups. However, a subsequent 30-day culture trial confirmed that exposure to the salinity level corresponding to BPS1 significantly reduced growth and survival of both DD and DF groups. To explore the molecular mechanisms underlying these two salinity breakpoints in abalone, the transcriptomes of hemocytes and gill tissues were profiled under both stress conditions. Both hypo- and hypersalinity stress induced pronounced transcriptomic responses in abalone, accompanied by upregulated differentially expressed genes (DEGs) significantly enriched in pathways like TNF and NF-κB signaling, including genes like piap, diap2, birc7-a, birc2, and birc3. However, abalone exhibited more intense responses to hypersalinity stress, as reflected by a greater number of annotated differentially expressed genes (DEGs) and more complex transcriptional regulation. Overall, this study integrates physiological assessment based on heart rate monitoring, aquaculture trials, and transcriptomic analysis to advance our mechanistic understanding of osmotic stress adaptation in abalone, while laying a scientific foundation for the sustainable development of abalone aquaculture under global climate change.

Copepods are a group of marine plankton that play an essential role in the energy transfer within marine ecosystems. They serve as vital prey for the larvae of numerous economically important fish, shrimp, and crabs species. Bestiolina amoyensis , a copepod species inhabiting nearshore warm waters, possesses numerous commercial advantages for aquaculture due to its small size, rapid reproduction, and strong adaptability, that make it well-suited for use as live prey in aquaculture systems. In this study, a breeding program targeting high fertility was designed and implemented . Fifty pairs of adult B. amoyensis were randomly selected to establish the base population (G0), with the total egg production used as the breeding index. In the selected group, offspring from maternal lines that ranked in the top 30% for total egg production were selected and eggs laid on the 4 ^th day by these selected pairs were used to establish breeding pairs for subsequent generations. In the control group, breeding pairs were established by randomly mating offspring of the G0 population. The selection procedure was repeated for five consecutive generations, with consistent selection criteria maintained only for the selected group. Additionally, the stability of selection effect was investigated by tracking both groups for an another 5, 10, 15 generations after the termination of artificial selection. After five generations of selection, the selected group showed a significant increase in total egg production, whereas no significant change was observed in the control group. By the fifth generation (G5), the selected group exhibited a 23.99% increase in total egg production compared with the control group, with a heritability (h ² ) of 0.46 ± 0.11. At the G5 generation, the population densities of the selected and control groups were 9075.00 ± 193.18 ind/L and 7200.33 ± 249.18 ind/L, respectively. After rearing for another 5, 10, and 15 generations without selection, the total egg production of the selected groups was 167.50 ± 2.47 eggs/female, 164.23 ± 2.46 eggs/female and 158.23 ± 3.14 eggs/female, respectively, indicating a gradual decrease. However, the selected group maintained significantly higher egg production than the control group ( p < 0.05). The results demonstrate that the reproductive capacity of B. amoyensis can be enhanced through continuous selection, providing technical support for the large-scale and high-density cultivation of this copepod species.

Copepods are a group of marine plankton that play an essential role in the energy transfer of marine ecosystems. They serve as vital prey for the larvae of numerous economically important species of fish, shrimp, and crabs. Bestiolina amoyensis , a copepod species inhabiting nearshore warm waters, possesses numerous commercial advantages for fishing, including small size, rapid reproduction, and strong adaptability. These make it an ideal live feed for aquaculture. In this study, a breeding plan for high fertility was conducted with B. amoyensis. The samples were breed five generations using the total egg production as breeding index. A circular mating strategy were applied by randomly selected offspring from the 4th day eggs of different pairs both in selected and control groups. The stability of selection also were investigated for another 5, 10, 15 generations. After multiple generations of selection, there was a gain of 23.99% in total egg production in the fifth generation (G5) with a heritability (h ² ) of 0.46 ± 0.11. The population densities of the selected and control groups were 9075.00 ± 193.18 ind/L and 7200.33 ± 249.18 ind/L, respectively. After the passage of another 5, 10, and 15 generations without selection, there was a decrease in total egg production in the selected group. However, significant differences remained in the total egg production of females and population sizes between the selected and control groups. The results showed that the reproductive capacity of Bestiolina amoyensis has could be improved by continuous selection, which may provide technical support for large-scale and high-density cultivation.