| As an exclusive valuable and rare freshwater mussel species in China,Solenaia oleivira was once widely distributed in freshwater lakes and rivers,but the natural resources of S.oleivira are in serious decline and endangered state due to destructed habitat ecosystem,climatic changes and human catch and kill at will.In this paper we analyzed the genetic diversity of S.oleivira from four collection sites along Huaihe River to evaluate their genetic level and differentiation.It was intended to provide not only theoretical reference for the scientific protection of national aquatic germplasm resources of S.oleivira in Huaihe River area,but also the basis for the selection of quality parents in artificial breeding.The culture experiments are performed on the samples of juveniles to select and determine the algae and sediment conditions suitable for the growth of S.oleivira.Furthermore,the effects of temperature on the ingestion and metabolic physiology of S.oleivira of different sizes are explored for the purpose of providing technical support for conservation and large-scale artificial cultivation of S.oleivira resources.The study results are as follows:(1)The genetic diversity analysis of S.oleivira from four sampling sites in Huaihe River indicated that a total of 92 loci were amplified by 5 DNA primers,Gushichun River population had the highest Nei’ genetic diversity index and Shannon diversity index(0.3089 and 0.4518),and Bailu River had the lowest ones(0.2346,0.3631),indicated that Gushichun River population has the highest genetic diversity and Bailu River population has the lowest genetic diversity,therefore,Gushichun River population was selected as the parent of the artificial breeding of S.oleivira;Genetic identity(Ht)of S.oleivira groups was 0.3283,coefficient of gene diversity within the group(Hs)was 0.2705,coefficient of gene differentiation(Gst)was 0.1760,it shows that the level of genetic differentiation among populations is moderate;The gene flow(Nm)among populations was 2.3407,which meaned that there exists certain gene flow in 4 groups;The closest genetic distance between Bailu River population and Caoji population was 0.0398,so it could judged that they had close genetic relationship:The genetic distance between Bailu River population and Gushichun River population was large(0.2031),meaning that the two populations had distant genetic relationship.According to the clustering analysis result,Bailu River population and Wangjiaba population were clustered into one group with Caoji population first and then with Gushichun River population.(2)The study of juvenile S.oleivira cultivation technique manifested that:the algae type and sediment type has significant impact on survival and growth of young S.oleivira.The survival rate and shell length of juveniles in the group of fed with wall-broken Nannochloropsis oceanica were both remarkably higher than those in the group of fed with non-wall-broken N.oceanica(P<0.05).Two algae densities(3.4×105cells/mL and 6.8×105cells/mL)were designed to investigate the influence of algae density on S.oleivira growth.The experimental results showed that the two densities were not statistically different in influencing survival rate and shell length of juvenile S.oleivira(P>0.05).Four types of sediments were selected to probe requirements of S.oleivira for bottom sediment,and the results indicated that the survival rate of juveniles in yellow mud was highest,and in garden mud was lowest;Shell lengths under hard yellow mud and garden mud were slightly higher than those under rust mud and yellow mud,but the four groups had no significant differences(P>0.05).The survival and growth of S.oleivira can be significantly enhanced by optimizing their cultivation conditions,which is expected to offer scientific basis for the large-scale cultivation of S.oleivira.(3)In the study of temperature effects on the ingestion and metabolic physiology of S.oleivira,it was found that oxygen consumption rate,ammonia excretion rate,ingestion rate,assimilation rate and defecation rate of 2-month-old,1-year-old and 2-year-old S.oleivira all increased with the temperature,where oxygen consumption rate,ingestion rate and defecation rate reached maximum values under 30℃ and then remarkably declined again under 35℃.Ammonia excretion rate and assimilation rate reached maximum values under 25℃ and then dropped again under 30℃.The assimilation rate ranged from 51.26%to 92.11%,which varied with temperature,where it reached the maximum value under 25℃.It can be seen from the energy budget equation of S.oleivira,breathing energy accounted for the largest proportion,followed by defecation energy and excretion energy.The percentage(20.23%-53.85%)of breathing energy of adult S.oleivira was lower than those of 2-month-old juvenile and 1-year-old juveniles S.oleivira(32.47%-97.75%and 47.19%-70.15%,respectively),and the percentage(0.99%-2.01%)of excretion energy of adult was also lower than those of 2-month-old juvenile and 1-year-old juveniles S.oleivira(0.37%-20.08%and 0.84%-17.53%,respectively),indicating that the percentages of breathing energy and excretion energy declined with the increase of dry weight in soft body.The percentage of growth energy of S.oleivira reached the maximum value under 20-25℃,which was the most suitable temperature range for S.oleivira growth.This provides an important theoretical basis for the optimization of artificial breeding conditions of S.oleivira. |
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