Effects of temperature on the respiratory metabolism,feeding and expression of three heat shock protein genes in Anadara broughtonii

Anadara broughtonii is one of the main commercially important species of shellfish in northern China.A.broughtonii lives in relatively stable subtidal zone where the clam could re spond to environmental changes with minimum energy.Therefore,slight fluctuations in water environment may have a great impact on physiological processes such as feeding and metabolism.Large-scale mortality often occurs during the intermediate rearing processes,and high temperatures in summer are considered the leading cause of mortality.To understand the physiological and molecular response patterns of A.broughtonii at high temperatures and to estimate the appropriate metabolism temperature for A.broughtonii,the effects of temperature on the respiratory metabolism and food intake at different growth stages were studied.The response patterns of heat shock protein genes to heat stress and post-stress recovery were also explored.Results show that the temperature and growth stage of A.broughtonii were two important factors affecting metabolism and feeding.The optimum temperature for feeding and physiological activities in each shelllength group was 24℃.The temperature at which the peak metabolic rate occurred in each shell-length group increased with the increase in shell length.With the increase in heat stress,the expression of three heat shock protein genes(Abhsp60,Abhsp70,and Abhsp90) in the tissues of two size groups of A.broughtonii increased significantly when temperature was above 24℃ and reached a peak at 30℃.After heat shock at30℃ for 2 h,the expression of the three heat shock protein genes rapidly increased,peaked at 2 h after the heat shock,and then gradually decreased to the level of the control group at 48 h after the heat shock.The three heat shock protein genes respond rapidly to heat stress and can be used as indicators to the cellular stre ss response in A.broughtonii under an environmental stre ss.     

Synchronous Variations in Abundance and Distribution of Ommastrephes bartramii and Dosidicus gigas in the Pacific Ocean

An analysis was performed in this study to investigate synchronous fluctuations in abundance and distribution of Ommastrephes bartramii in the Northwest Pacific Ocean and Dosidicus gigas in the Southeast Pacific Ocean. The impacts of two Ni?o indices and regional water surface temperature on the two squids during 2006–2015 were evaluated, which possibly can explain the observed synchronicity. Catch per unit effort(CPUE) and the latitudinal gravity centers(LATG) of fishing effort were used to indicate squid abundance and distribution, respectively. The results indicated that both the CPUE and LATG showed highly interannual variations and synchronous fluctuation with significant negative associations between the two squid species from September to November. Strong positive cross-correlations with 2-month lag was found between sea surface temperature(SST) anomaly in the Ni?o 3.4 and Ni?o 1+2 regions, which have significant linkage with the SST on the fishing ground of O. bartramii and D. gigas, respectively. Moreover, the proportion of favorable-SST area(PFSST) and the latitudinal location of the optimal SST for O. bartramii and D. gigas were positively correlated with the CPUE and LATG, respectively. Increased O. bartramii PFSST clearly corresponded to decreased D. gigas PFSST in phase as well as the latitudinal location of the optimal SST from September to November over 2006– 2015. Our findings suggest that synchronous changes in abundance and distribution of the two squids were due to simultaneous variations in the PFSST and the latitudinal location of the optimal SST front which were affected by the SSTA changes in the Ni?o 3.4 and Ni?o 1+2 regions.     

Acclimation-dependent expression of heat shock protein 70 in Pacific abalone (Haliotis discus hannai Ino) and its acute response to thermal exposure

Heat shock protein 70 (Hsp70) is one important member of heat shock protein (Hsp) family that is responsible for various stresses, especially thermal stress. Here we examined the response of Hsp70 gene to both chronic and acute thermal exposure in Pacific abalone (Haliotis discus hannai Ino). For the chronic exposure, abalones were maintained at 8, 12, 20, and 30°C for four months and their mRNA levels were measured. The highest mRNA level of Hsp70 gene relative to actin gene was detected in the 30°C-acclimated group, followed by the 8°C-acclimated group and then the 12°C- and 20°C-acclimated groups. After the long-term acclimation, gills from each of the above acclimation groups were dissected and exposed to different temperatures between 8°C and 38°C for 30 min. Hsp70 expression in gills acclimated to different temperatures responded differentially to the same temperature exposure. The incubation temperature that induced maximum Hsp70 mRNA expression was higher in the higher temperature acclimation groups than lower temperature groups. Pacific abalones could alter the expression pattern of Hsp70 gene according to environmental thermal conditions, through which they deal with the stress of thermal variations.     

Spatial and Temporal Variability of Thermal Stress to China’s Coral Reefs in South China Sea

Coral bleaching, caused by elevated sea surface temperature(SST), is occurring more frequently and seriously worldwide. Due to the lack of field observations, we understand little about the large-scale variability of thermal stress in the South China Sea(SCS) and its effect on China’s coral reefs. This paper used 4-km high resolution gap-filled SST(Filled SST) data and thermal stress data related to coral bleaching derived from Coral Reef Temperature Anomaly Database(Co RTAD) to quantify the spatial and temporal characteristics of chronic thermal stress and acute thermal stress to China’s coral reefs in SCS from 1982 to 2009. We analyzed the trend of SST in summer and the thermal stress frequency, intensity and duration during this period. The results indicate that, as a chronic thermal stress, summer mean SST in SCS shows an average upward trend of 0.2℃/decade and the spatial pattern is heterogeneous. Waters of Xisha Islands and Dongsha Islands of the northern SCS are warming faster through time compared to Zhongsha Islands and Nansha Islands sea areas of the southern SCS. High frequency bleaching related thermal stress events for these reefs are seen in the area to the northwest of Luzon Island. Severe anomaly thermal stress events are more likely to occur during the subsequent year of the El Nino year for these coral reefs. Besides, the duration of thermal stress varies considerably by anomaly year and by region.     

Maixi River estuary to the Baihua Reservoir in the Maotiao River catchment: phytoplankton community and environmental factors

Phytoplankton and environmental variables were measured monthly from July 2009 to August 2011 in the Maixi River from the estuary to Baihua Reservoir in the Maotiao River catchment,southwestern China,to understand phytoplankton community structure and environmental factors.The relationship between phytoplankton community structure and environmental factors including hydrological,meteorological,physical,and chemical variables were explored using multivariate analysis.A total of 81 taxa of phytoplankton were identified,which were mainly composed of chlorophyta,bacillariophyta,and cyanobacteria.The phytoplankton community was dominated by Pseudanabaena limnetica during summer and fall and by Cyclotella meneghiniana during winter and spring.The abundance of phytoplankton ranged from 0.24×104 cells/L to 33.45×106 cells/L,with the minimum occurring during February 2010 and the maximum during July 2009.The phytoplankton community was dominated mainly by cyanobacteria from April to September,and by bacillariophyta and pyrrophyta from October to March.Canonical correspondence analysis showed that temperature,pH values,and orthophosphate were the most important driving factors regulating the composition and dynamics of the phytoplankton community in the estuary.Cyanobacteria and euglenophyta abundance and biomass were affected mainly by temperature and pH values,while most chlorophyta and bacillariophyta were influenced by the concentrations of nutrients.     

Cytochemical characterization of yolk granule acid phosphatase during early development of the oyster Crassostrea gigas (Thunberg)

In this study,a cytochemical method and transmission electron microscopy was used to examine acid phosphatase activities of yolk granules throughout the early developmental stages of the Pacific oyster Crassostrea gigas. This study aimed to investigate the dynamic change of yolk granule acid phosphatase,and the mechanisms underlying its involvement in yolk degradation during the early developmental stages of molluscs. Three types of yolk granules(YGI,YGII,and YGIII) that differed in electron density and acid phosphatase reaction were identified in early cleavage,morula,blastula,gastrula,trochophore,and veliger stages. The morphological heterogeneities of the yolk granules were related to acid phosphatase activity and degrees of yolk degradation,indicating the association of acid phosphatase with yolk degradation in embryos and larvae of molluscs. Fusion of yolk granules was observed during embryogenesis and larval development of C. gigas. The fusion of YGI(free of acid phosphatase reaction) with YGII(rich in acid phosphatase reaction) could be the way by which yolk degradation is triggered.     

Pattern dynamics of thermal-environment effect during urbanization: A case study in Shenzhen City, China

The thermal-environment effect exists in the field of rapid urbanization.It has adverse effects on the urban atmosphere,regional climate,energy consumption,and public health.Shenzhen,a representative of rapidly urbanizing cities in China,was selected as a case for pattern dynamics analysis of the thermal environment.The surface temperature was acquired from the thermal infrared data of Landsat TM and ETM+ images in 1986,1995,and 2005 by Jiménez-Mu?oz and Sobrino’s generalized single-channel method,which was used in assessing the distribution and spatial patterns of the thermal environment.The relative thermal environment curve(RTC) was combined with Moran’s I analysis to assess the pattern dynamics of the thermal environment in different urbanization periods.Moran’s I index and the RTC represent a process of aggregation-fragmentation-aggregation,which shows the aggregation pattern of a decrease during the rapid urbanization period and then an increase during the steady urbanization period.High-temperature areas gradually expanded to a uniform and scattered distribution in the rapid urbanization period;while the high thermal-environment effect was gradually transformed into a steady spatial pattern in the stable urbanization period.To characterize the increasing development in this multiple-center city,we chose profiles along an urban-development axis.The results suggest that heat islands have expanded from internal urban to external urban areas.Four profiles were obtained showing differences in shape due to spatial differences in the process of development.     

An efficient method of noroviruses recovery from oysters and clams

Noroviruses (NoVs) are widespread causes of nonbacterial gastroenteritis. Outbreaks of NoVs caused diseases are commonly ascribed to the consumption of contaminated shellfish. The concentration and RNA extraction of NoVs are crucial steps of detecting NoVs in shellfish. This study aimed to select a simple, rapid and highly efficient recovery method of NoVs detection with real-time RT-PCR. Four methods of recovering GI.3 and GII.4 NoVs from spiked digestive tissues of oysters and clams, respectively, were compared, of them, the method involving proteinase K and PEG 8000 was found the most efficient. With this method, 9.3% and 13.1% of GI.3 and GII.4 NoVs were recovered from oysters and 9.6% and 12.3% of GI.3 and GII.4 NoVs were recovered from clams, respectively. This method was further used to detect NoVs in 84 oysters (Crassostrea gigas) and 86 clams (Ruditapes philippinarum) collected from 10 coastal cities in China from Jan. 2011 to Feb. 2012. The NoVs isolation rates were 10.47% of clams (9/86) and 7.14% of oysters (6/84). All the detected NoVs belonged to genotype GII. The NoVs recovery method selected is efficient for NoVs detection in oysters and clams.     

Cloning and expression patterns of two Smad genes during embryonic development and shell formation of the Pacific oyster Crassostrea gigas

Increasing evidence indicates that transforming growth factor β(TGF-P) signaling pathways play many important roles in the early development of mollusks.However,limited information is known concerning their detailed mechanisms.Here,we describe the identification,cloning and characterization of two Smad genes,the key components of TGF-P signaling pathways,from the Pacific oyster Crassostrea gigas.Sequence analysis of the two genes,designated as cgi-smad1/5/8 and cgi-smad4,revealed conserved functional characteristics.The two genes were widely expressed in embryos and larvae,suggesting multiple roles in the early development of C.gigas.The mRNA of the two genes aggregated in the D quadrant and cgi-smad4 was highly expressed on the dorsal side of the gastrula,indicating that TGF-P signaling pathways may be involved in dorsoventral patterning in C.gigas.Furthermore,high expression levels of the two genes in the shell fields of embryos at different stages suggested important roles for TGF-P signaling pathways in particular phases of shell development,including the formation of the initial shell field and the biomineralization of larval shells.The results of this study provide fundamental support for elucidating how TGF-P signaling pathways participate in the early development of bivalve mollusks,and suggest that further work is warranted to this end.     

Stress Responses to Rapid Temperature Changes of the Juvenile Sea Cucumber （Apostichopusjaponicus Selenka）

Activities of hexokinase （HK）, pyruvate kinase （PK）, superoxide dismutase （SOD） and catalase （CAT） and Hsp70 level were measured to evaluate the response of the commercially important sea cucumber （Apostichopus japonicus Selenka） to rapid temperature changes in laboratory. Animals were subjected to a higher temperature （from 10 to 20℃） （Tinc treatment） or to a lower temperature （from 20 to 10℃） （Tddec treatment） for 72 h. At 1, 3, 12, 24, 72 h of exposure, animals were removed and prepared for further analysis. Results showed that the effect of acute temperature changes on enzyme activities was significant. In Tinc treatment, activities of SOD and CAT increased immediately. The significant enhancement of SOD and CAT activities suggested that oxidative stress increases significantly when ambient temperature increasing from 10 to 20℃. The up-regulation of Flsp70 in Tinc and Tdec treatments indicated that Hsp70 was a bioindicator of thermal stress in the sea cucumber, and the expression pattern depended on the thermal treatment.     

Seasonal Variation of the Glycogen Enzyme Activity in Diploid and Triploid Pacific Oyster Gonad During Sexual Maturation

The glycogen content and the activities of two key enzymes in glycogen metabolism, glycogen phosphorylase and gly- cogen synthetase, in the gonad of diploid and triploid Pacific oysters (Crassostrea gigas) were compared during maturation. The glycogen content in the gonad of diploids decreased with gametogenesis (by 85.7%), but the glycogen content in the gonad of trip- loids did not vary significantly. Activity of glycogen phosphorylase (GP) in the gonad of diploids decreased with gametogenesis (by 55.5%), while GP activity of triploids did not vary significantly during maturation. Activity of glycogen synthetase (GS) in the gonad of diploids increased slightly with gametogenesis, reaching a peak in June. Activity of GS declined sharply from June to July, which might be due to gonad spawning. GS activity of triploid oysters in spawning time (July and August) was significantly higher than that in other months, which might be explained with a ‘compensating’ mechanism for the higher glycogen content in triploids.