| For the purpose of palaeoenvironment and palaeoclimate research, over thirty living samples of Ostracods were collected during three scientific mineral and biological resources surveys of saline lake in Qinghai-Tibet Plateau from 2007 to 2009. Eucypris elliptica (Baird), collected from Rongma Hot spring in Nyima County, Nagqu District, Tibet, were selected for biological tests, for its fossils were widely distributed in the Quaternary of Qinghai-Tibet Plateau salt lake district and its modern species are still live in modern lakes.According to experimental needs, E.elliptica from Guogenco Hot spring (GGH) in ShuangHu Special District and Xiaochi Salt-lake (XCS) were considered as experimental samples.During the inspection of ecological parameters of temperature factor, six gradients of temperature were set between 6.0℃and 34.0℃, and six gradients of salinity were set between 0.40 g/L and 25.00 g/L (NaCl). The method of life table was used for the designing of experiment and the calculation of parameters. The ecological parameters to be calculated included population net reproduction rate(R0), mean generation time(T), intrinsic rate of natural increase (rm), finite rate of increase(λ) and doubling population time(t).The semi-lethal method in 24 hours was used to test high temperature and survival limit of high salinity.The determination results of ecological parameters of RMH temperature factor showed that R0 was above zero between 6 and 34℃,R0 increased along with temperature increasing between 6 and 10℃,R0 maintained high level in 27.89-28.2ind./♀on the whole between 10 and 22℃, R0 decreased along with temperature increasing when it was beyond 22℃.The temperature had the most significant impact on the mean generation time. Tvalue showed linear decrease between 10 and 34℃. T value was 427d at 6℃, that meant that it took more than one year to complete a generation. T value was 138d at 10℃,23d at 34℃.The change trends of rm andλis in line with Ro on the whole. The maximum of rm andλwere 0.13/d and 1.12/d both at 17.2℃. In the temperature range of biological significance, t value was 188.77d at low temperature (6℃),t value dropped to 18.6d at 10℃,t value dropped to minimum,10.4d,at 22℃. Then t value increased slightly along with temperature increasing.The determination results of ecological parameters of RMH salinity factor showed that R0 increased along with salinity increasing when salinity was between 0.4 and 5g/L,R0 decreased along with salinity increasing when salinity was between 5 and 20g/L,the maximum of R0 was 25.6ind./♀,R0 was near zero when salinity was 20g/L.The change trends of rm andλwas in line with R0 on the whole, the maximum of rmis 0.0673/d at 9.22g/L, and he maximum ofλis 1.076/d at 10.19g/L. In the experiment salinity range, T value have no obvious change and this showed that salinity had slightly impact on mean generation time. The impact of salinity on t value had no obvious biological significance.The determination results of the heat demand of RMH individual development showed that the development threshold temperature of RMH was 4.48±1.14℃, and the thermal constant for finishing one generation was 609.23±31.98℃d. According to this results, to complete one generation development, there should be at least 100 days maintaining above 10℃in one year.The determination results of three geographic strains of E.elliptica showed great discrepancy in survival limit of high temperature and survival limit of high salinity. Regarding 24h-TL50 as standard, the survival limit of high temperature of RMH and GGH were 37.60℃and 32.62℃, respectively. There were some errors during the survival limit experiment of high temperature of XCS and it was necessary to reconstruct laboratory population for another determination. The threshold temperature of producing adverse reaction of RMH, GGH and XCS were 30℃,26℃and 26℃, respectively. The temperature zone of death rate rising rapidly of RMH, GGH and XCS were 38-42℃,30-34℃and 26-30℃, respectively. Regarding 24h-LC50 as standard, the survival limit of high salinity of RMH and XCS were 25.66g/L and 22.57g/L, respectively. The death rate of GGH was below 25% at 30 g/L and the survival limit of high salinity needed further inspection. The threshold salinity of producing adverse reaction of RMH, GGH and XCS were 12g/L,20g/L and 17g/L, respectively. The salinity zone of death rate rising rapidly of RMH and XCS were 24-28g/L and 17-22g/L. The death rate of GGH was below 25% at 30 g/L and the salinity zone of death rate rising rapidly needed further inspection.According to the experimental results, three geographical strains had obvious difference in survival limit high temperature and survival limit high salinity. It was understandable that this kind of difference between three geographic strains, for their habitats were different.The geoecological significance of these ecological parameters were that (1) the paleosalinity of stratum containing E.elliptica fossils was below 20g/L in the process of deposit, and the extreme salinity did not exceed 22.56g/L in short period. (2)the paleotemperature of stratum having few E.elliptica fossils could be above 4.48℃in the most part time of one year, and it could not be over 1/3 which temperature was above 10℃.The paleotemperature of stratum which had many E.elliptica fossils could be between 10℃and 30℃in the most part of one year,and the extreme temperature did not exceed 37.6℃in short time.The experimental results showed that, E.elliptica belong to eurythermal and eurysaline species, having a wider indicating range of environment.
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