Increased prostaglandin e2 has a positive correlation with plasma calcium during goldfish reproduction

We recently demonstrated that prostaglandin E2 PG¿ increases osteoclastic activity and induces bone resorption in both in vitro and in vivo experiments using goldfish. In the fish reproductive period, the plasma calcium (Ca) level in female teleosts increases remarkably to make vitellogenin, which is a major component of egg protein and a Ca-binding protein. In this period, however, there is no reported relationship between PGE2 and Ca metabolism in fish. To clarify the Ca metabolism in fish reproduction, we examined plasma PGE2 and Ca levels and measured tartrate-resistant acid phosphatase (TRAP) activities as an indicator of osteoclastic activity in goldfish. Plasma PGE2 levels in the reproductive stage significantly increased as compared with those in non-reproductive stages. Also, both plasma Ca and TRAP increased in the reproductive stage. Significant positive correlations were recognized between plasma Ca and the gonad somatic index (r=0.81, p<0.001), plasma Ca and plasma PGE2 levels (r=0.635, p<0.05), and plasma Ca and plasma TRAP activities (r=0.584, p<0.05) from the analysis using samples of both reproductive and nonreproductive stages. Taking these data into consideration, we suggested that PGE, acts on osteoclasts and increases plasma Ca as a result of osteoclastic bone resorption, and we concluded that PGE, is an important hormone in Ca metabolism during fish reproduction

Recent Progress in the Study of Peroxiredoxin in the Harmful Algal Bloom Species <i>Chattonella marina</i>

Peroxiredoxin (Prx) is a relatively recently discovered antioxidant enzyme family that scavenges peroxides and is known to be present in organisms from biological taxa ranging from bacteria to multicellular eukaryotes, including photosynthetic organisms. Although there have been many studies of the Prx family in higher plants, green algae, and cyanobacteria, few studies have concerned raphidophytes and dinoflagellates, which are among the eukaryotic algae that cause harmful algal blooms (HABs). In our proteomic study using 2-D electrophoresis, we found a highly expressed 2-Cys peroxiredoxin (2-CysPrx) in the raphidophyte Chattonella marina var. antiqua, a species that induces mass mortality of aquacultured fish. The abundance of the C. marina 2-CysPrx enzyme was highest in the exponential growth phase, during which photosynthetic activity was high, and it then decreased by about a factor of two during the late stationary growth phase. This pattern suggested that 2-CysPrx is a key enzyme involved in the maintenance of high photosynthesis activity. In addition, the fact that the depression of photosynthesis by excessively high irradiance was more severe in the 2-CysPrx low-expression strain (wild type) than in the normal-expression strain (wild type) of C. marina suggested that 2-CysPrx played a critical role in protecting the cell from oxidative stress caused by exposure to excessively high irradiance. In the field of HAB research, estimates of growth potential have been desired to predict the population dynamics of HABs for mitigating damage to fisheries. Therefore, omics approaches have recently begun to be applied to elucidate the physiology of the growth of HAB species. In this review, we describe the progress we have made using a molecular physiological approach to identify the roles of 2-CysPrx and other antioxidant enzymes in mitigating environmental stress associated with strong light and high temperatures and resultant oxidative stress. We also describe results of a survey of expressed Prx genes and their growth-phase-dependent behavior in C. marina using RNA-seq analysis. Finally, we speculate about the function of these genes and the ecological significance of 2-CysPrx, such as its involvement in circadian rhythms and the toxicity of C. marina to fish

Change in Marine Environment after Artificial Reef Deployment in the South Sea of Korea

In order to study the change of marine environment after artificial reef deployment in the South Sea of Korea, water temperature, currents and nutrients distributions were investigated during the strongly stratified summer season. Before the deployment of artificial reef, the maximum thermocline of water column (MTWC) formed at depths of 30~40m in almost all of the studied area. However, after the deployment of the artificial reef, depending on tide time, variations in MTWC were observed about 10~17m shallower in areas within 1km in radius of the artificial reef due to uplifting of isotherms. In waters surrounding the artificial reef, vertical currents alternate between local downwelling flow (LDF) and local upwelling flow (LUF), and this type of phenomenon is dependent on tide time and takes on various patterns of spatial distribution. In addition, the degree of vertical mixing, which can be deduced from areas with strong current shears, especially in the surrounding area of the artificial reef from which the LUF originates, was found to be distributed in a similar manner. Although there are tide time–dependent differences in the Richardson number (Ri), in depths of 30~40m or deeper, where the Ri is less than 0.25, the water column was destabilized by vertical mixing. In addition, differences in nutrient distribution were noted before and after the artificial reef deployment. Highly stratified nutrients rose to the upper layer after passing the artificial reef, and the accumulation of nutrients can be attributed to the LUF developingat the artificial reef. Thus, in periods of strong stratification during the summer, the upward movement of nutrients from the aphotic to the euphotic layer increases the primary production levels, triggering the formation of a marine food chain in those areas

Effect of Repeated Exposure to Low Oxygen on Respiratory Metabolism and Vertical Movements in the Pen Shell Atrina lischkeana

We exposed pen shells (Atrina lischkeana) to repeated periods of low–oxygen for 30 d and measured their survival, behavior, glycogen content, and organic acid concentration. Exposure to low–oxygen had no effect on survival. Animals moved upward above the sediment under low–oxygen conditions and downward under aerobic conditions, repeating these movements for 19 d. The difference in shell height above the sediment before and after low–oxygen exposure gradually decreased; after 20 d there was no significant difference. Low–oxygen exposure also resulted in a significant decrease in glycogen content and in concentrations of malate and fumarate. Thus, repeated exposure of pen shells to low–oxygen conditions reduces glycogen content, alters metabolism, and affects vertical movements, all of which may cause ecological dysfunction. We suggest that hypoxia might be one factor contributing to the collapse of pen shell resources

Diurnal-Rhythmic Relationships between Physiological Parameters and Photosynthesis- and Antioxidant-Enzyme Genes Expression in the Raphidophyte <i>Chattonella marina</i> Complex

Diurnal rhythms in physiological functions contribute to homeostasis in many organisms. Although relationships between molecular biology and diurnal rhythms have been well studied in model organisms like higher plants, those in harmful algal bloom species are poorly understood. Here we measured several physiological parameters and the expression patterns of photosynthesis-related and antioxidant-enzyme genes in the Chattonella marina complex to understand the biological meaning of diurnal rhythm. Under a light–dark cycle, Fv/Fm and expression of psbA, psbD, and 2-Cys prx showed significant increases in the light and decreases during the dark. These rhythms remained even under continuous dark conditions. DCMU suppressed the induction of psbA, psbD, and 2-Cys prx expression under both light regimes. Oxidative stress levels and H2O2 scavenging activities were relatively stable, and there was no significant correlation between H2O2 scavenging activities and antioxidant-enzyme gene expression. These results indicate that the Chattonella marina complex has developed mechanisms for efficient photosynthetic energy production in the light. Our results showed that this species has a diurnal rhythm and a biological clock. These phenomena are thought to contribute to the efficiency of physiological activities centered on photosynthesis and cell growth related to the diurnal vertical movement of this species