As an important aquaculture species, the marine snail Babylonia areolata is frequently subjected to fluctuation in dissolved oxygen concentration during farming and transportation processes. In the present study, we investigated the metabolic rates, transcription, and enzyme level responses of juvenile B. areolata exposed to long-term stress (144 h). The results showed that the mortality rate of juvenile B. areolata was higher in the 0.5 mg O₂/L group compared to the 2 mg O₂/L group. During the hypoxic stress period, both oxygen consumption and ammonia excretion rates were observed to be lower in juvenile B. areolata than those in the control group. As hypoxic stress duration prolonged, juvenile B. areolata demonstrated significantly elevated activities of pyruvate kinase (PK) and alkaline phosphatase (AKP), alongside reduced activities of lactic dehydrogenase (LDH), acid phosphatase (ACP), and superoxide dismutase (SOD). Significant changes in the expression levels of PK and LDH genes were observed during the hypoxic stress. The expression levels of ACP and SOD genes were significantly downregulated, while juvenile B. areolata exhibited elevated AKP gene expression levels under 0.5 mg O₂/L. Our findings suggest that under long-term exposure to hypoxia, B. areolata failed to maintain energy homeostasis and suffered biochemical disruptions, leading to a reduction in survival. The mortality rate of B. areolata can be substantially decreased by ensuring that transportation time does not exceed 48 h.

This study explored the physiological responses and gene expression profiles of the Manila clam (Ruditapes philippinarum) and the hard clam (Mercenaria mercenaria) under heat and hyposaline stress. Experimental conditions involved increasing the temperature from 25 °C to 35 °C and decreasing salinity from 25 ppt to 15 ppt over a 6 h acclimation period, followed by 72 h exposure. Key physiological and immune indicators, including filtration rate, oxygen consumption rate, ammonia excretion rate, and the expression of related genes, were measured. Under heat stress, R. philippinarum exhibited higher filtration, oxygen consumption, and ammonia excretion rates than M. mercenaria at most sampling time points. The expression of fatty acid desaturase (Δ6FAD) and heat shock protein (HSP70) genes increased and then decreased for both species, whereas superoxide dismutase (Cu/Zn SOD) gene expression gradually decreased over time. Furthermore, the expression levels of all three genes were generally significantly higher in M. mercenaria compared to R. philippinarum. Under hyposaline stress, R. philippinarum exhibited significantly higher filtration, oxygen consumption, and ammonia excretion rates than M. mercenaria between 24 h and 72 h. Expression levels of the Na⁺-K⁺-ATPase (NKAα), HSP70, and Cu/Zn SOD genes remained higher in M. mercenaria compared to R. philippinarum. Overall, the present study indicates that M. mercenaria maintains relative stability and R. philippinarum exhibits greater physiological fluctuation under both heat and hyposaline stress. This study highlights bivalve species-specific responses to environmental stressors and provides valuable insights for aquaculture planning and ecological management in different environmental regions, particularly in the context of global climate change.

This study employed an artificial greenhouse-based system to enhance gonadal development in the Manila clam, Ruditapes philippinarum. The dynamics of gonadal development and expression patterns of five regulatory genes were analyzed through histological sections and quantitative PCR. Under the controlled conditions (Chlorophyll a: 18.61 ± 1.36 μg/L; temperature: 27.3 ± 2.0 °C), the clams’ gonads reached full maturity within approximately one month, underscoring the critical importance of appropriate food availability and temperature. Gene expression analysis revealed sex- and stage-specific patterns. The gonadotropin-releasing hormone (GnRH) gene was more expressed in males at day 7, reaching a significant peak at day 7. In contrast, females exhibited synchronized expression peaks for both estrogen-related receptor (ERR) and 17β-hydroxysteroid dehydrogenase (17β-HSD) at day 14 (p < 0.05). Cytochrome P450 17 (CYP17) exhibited a dynamic, sex-specific profile, with significantly higher levels in males at day 7 but elevated expression in females at day 14 and day 21. Furthermore, doublesex and mab-3-related transcription factor 4-like (Dmrt4-like) showed clear sex-dependent temporal patterns: it peaked early during maturation in males, while in females, the peak occurred significantly later, at day 21 (p < 0.05). These dynamic changes in gene expression were closely synchronized with histological alterations, providing mechanistic insights into the regulation of gonadal maturation in R. philippinarum.

As an important aquaculture species, the marine snail Babylonia areolate is frequently subjected to fluctuation in dissolved oxygen concentration during farming and transportation processes. In the present study, we measured the oxygen consumption rate, ammonia excretion rate, metabolic enzyme activities, immune enzyme activities, as well as changes in gene expression of these enzymes under long-term stress (144 hours) on B. areolate at two hypoxia levels (2.0 and 0.5 mg O2/L). The findings indicated that the mortality rate of juvenile B. areolate was higher in the 0.5 mg O2/L group compared to the 2 mg O2/L group. During the hypoxic stress period, both oxygen consumption and ammonia excretion rates were observed to be lower in juvenile B. areolate than those in the control group. The group exposed to 0.5 mg O2/L exhibited lower oxygen consumption and ammonia excretion rates compared to the group exposed to 2 mg O2/L at most measurement time points. As stress duration prolonged, juvenile B. areolate demonstrated significantly elevated activities of PK and ACP, alongside reduced activities of LDH, ACP, and SOD. The expression levels of PK and LDH genes in juvenile B. areolate were significantly reduced during the early stages of hypoxic stress; however, a significant increase was observed in the later stages. The expression levels of ACP and AKP genes were significantly downregulated, while juvenile B. areolate exhibited elevated SOD gene expression levels under 0.5 mg O2/L. The results indicated that B. areolate may respond to hypoxic stress by reducing its metabolic rate and modulating the expression of metabolism-related enzymes. Furthermore, hypoxic stress was found to significantly impact the antioxidant capacity and immune function of B. areolate. Notably, the mortality rate of B. areolate can be substantially decreased by ensuring that transportation time does not exceed 48 hours.