Effect of salinity changes on haemocyte of pearl oyster Pinctada martensii

Objective:To evaluate the impact of salinity changes in the rearing environment on the haemocyte activities of pearl oyster Pinctada martensii(P.martensii).Methods:Three salinity treatments including 12‰,22‰,and 32‰were tested.Haemocyte mortality rate and neutral red retention(NRR)assay were used to investigate the impact of rearing salinity on the haemocyte activities of pearl oyster.Results:Results from the present study indicated that salinity significantly affected the haemocyte mortality rate of P.martensii.The highest haemocytes mortality rate was observed in the 12‰treatment,and the lowest mortality rate was observed in the 32‰treatment.NRR time was also significantly affected by the salinity.The highest NRR time was observed in the 32‰treatment,and the lowest NRR time was observed in the 12‰treatment.Conclusions:Results from the present study indicated that salinity<22‰had significant impact on the haemocyte mortality rate and NRR time.Reducing the environmental salinity will pose an additional stress and may also reduce the defense capacities of P.martensii and make them more susceptible to parasites and bacteria.

Comparative transcriptome analysis on the alteration of gene expression in ayu （Plecoglossus altivelis）larvae associated with salinity change

Ayu （Plecoglossus altivelis） fish, which are an amphidromous species distributed in East Asia, live in brackish water （BW） during their larval stage and in fresh water （FW） during their adult stage. In this study, we found that FW-acclimated ayu larvae exhibited a slower growth ratio compared with that of BW-acclimated larvae. However, the mechanism underlying FW acclimation on growth suppression is poorly known. We employed transcriptome analysis to investigate the differential gene expression of FW acclimation by RNA sequencing. We identified 158 upregulated and 139 downregulated transcripts in FW-acclimated ayu larvae compared with that in BW-acclimated larvae. As determined by Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway mapping, functional annotation of the genes covered diverse biological functions and processes, and included neuroendo- crinology, osmotic regulation, energy metabolism, and the cytoskeleton. Transcriptional expression of several differentially expressed genes in response to FW acclimation was further confirmed by real-time quantitative PCR. In accordance with transcriptome analysis, iodothyronine deiodinase （ID）, pro-opiom- elanocortin （POMC）, betaine-homocysteine S-meth- yltransferase 1 （BHMT）, fructose-bisphosphate aldolase B （aldolase B）, tyrosine aminotransferase （TAT）, and Na＋-K＋ ATPase （NKA） were upregulated after FW acclimation. Furthermore, the mRNA expressions of b-type natriurefic peptide （BNP） and transgelin were downregulated after FW acclimation. Our data indicate that FW acclimation reduced the growth rate of ayu larvae, which might result from the expression alteration of genes related to endocrine hormones, energy metabolism, and direct osmoregulation.

Effects of osmotic stress on the expression profiling of aquaporin genes in the roughskin sculpin(Trachidermus fasciatus)

Aquaporins(AQPs)are a family of integral membrane proteins that have been shown to be important for osmoregulation in many vertebrates.To identify potential stress resistance-related aqp genes in salinity adaptation of the roughskin sculpin Trachidermus fasciatus,we investigated the time-course expression dynamics of seven aquaporin genes(aqp1,4,7,8,10,11 and 12)in three osmoregulatory tissues(kidney,gill and intestine)and one metabolic tissue(liver).The fish were subjected to two different acute osmotic treatments(seawater-tofreshwater transfer respectively achieved in 1 h and 24 h,namely,E-acute and acute group).The expression profiling of the seven aqp genes were performed using quantitative real-time PCR(qRT-PCR).At the time of all sampling time points(0 h,12 h,24 h and 48 h),no expression of aqp4 was found in the gill,liver and intestine;no expression of aqp7 was found in the gill and liver.Significant differences of aqp expression were determined in the four target tissues,and the mRNA levels were largely variable among gene members and tissues.Similar patterns of the time-course expression were detected in most of the aqp genes in T.fasciatus between the two acute groups,except that only one gene(aqp12)in the kidney and three genes(aqp7,aqp8 and aqp10)in the intestine revealed different expression patterns.These results suggest that the expression response of aqp genes was similar under osmotic changes with different rates.

Groundwater contributions in water-salt balances of the lakes in the Badain Jaran Desert,China

Groundwater-fed lakes are essential for the ecology in arid and semiarid regions.As a typical arid region,the Badain Jaran Desert （BJD） is famous in the world for the presence of a large number of groundwater-fed saline lakes among the mega dunes.Based on the up to date geological surveys and observations,this study analyzed the groundwater contributions in water-salt balances of the lakes in the desert.We found different types of springs,including the sublacustrine springs that indicate an upward flow of groundwater under the lakebed.A simplified water balance model was developed to analyze the seasonal variations of water level in the Sumu Barun Jaran Lake,which revealed an approximately steady groundwater discharge in the lake and explained why the amplitude of seasonal changes in lake level is less than 0.5 m.In addition,a salt balance model was developed to evaluate the salt accumulations in the groundwater-fed lakes.The relative salt accumulation time is 800–7,000 years in typical saline lakes,which were estimated from the concentration of Cl-,indicating a long history evolution for the lakes in the BJD.Further researches are recommended to provide comprehensive investigations on the interactions between the lakes and groundwater in the BJD.

Research on soil salt transfer under freeze-thawing condition

Soil salt transformation plays an important role in the freeze-thawing process,which is also one of basic problems of cryopedology. The very special law is made up of the two time salt-moisture transfer under freeze-thawing condition. Based on the latest research at home and abroad,through the investigation of soil moisture-salt change in the freeze-thawing process,the conclusion is made that the soil water potential gradient is the main driving force of soil salt movement and the factors are of quantities. The research shows that,when freezing,temperature drops,salt and moisture move towards frozen layer. All make the salinity content of the frozen layer increase significantly. In the thawing process,salinity and moisture in the soil move up again with evaporation and makes the salt second migration.