| Pacific abalone (Haliotis discus hannai Ino) is one of the most commerciallyimportant cultured shellfishes, which naturally inhabit in Liaodong and Jiaodongpeninsula. Currently, H. discus hannai was cultivated in large-scale in Liaoning,Qingdao, Fujian and Guangdong coast areas in our country. H. discus hannai isstenohaline.While the exact experimental data on the salinity effects was quite limited.So, this study was aimed to exploit the effects of salinity on H. discus hannai and theregulatory mechanism of juvenile abalones adjusting to the different salinities,including the abalone’s tolerance to salinity, especially low salinity and a piecewisefunction was fitted out according to our experimental data to fully evaluate the salinityeffects on abalone survive; the influence of low salinity on the abalone’s growth; thechange of some physiological indexes by the stimulation of low salinity in short term.Main results were listed as follows:1salinity-survival curve of juvenile abalones, Haliotis discus hannai InoSalinity gradient:16,20,24,26,28,29,30,32,34,36,40,44. Ninety individualswere used in each gradient (3×30). After six weeks’ cultivation, the survival rates areas follows: the survival rates of26,29,30,32and34groups were100%; the survivalrates of28,24,20and16were97.8%,85.6%,10%and0respectively; the survivalrates of36,40,44were94.4%,88.9%,27.8%. So it could be concluded that juvenileswere more sensitive to low salinity and the salinity lower than24or higher than40were not suitable for abalones. At the same time, a piecewise function was fitted outaccording to the above results to better describe the relationship between the survivalrate of juvenile abalones and different salinities. It could be calculated that theminimum salinity was19and maximum salinity was51for abalone. More survivalrates of juvenile abalones at different salinities could be calculated to help us studythe effects of salinity on abalones more comprehensively. 2dynamic death curve of juvenile abalones in different salinitiesIn salinity16, the mortality of juvenile abalones reached53.0%after48h and allindividuals died after11d; in salinity20, the mortality of juvenile abalones was15.6%after48h and reached25.6%,51.1%and90.0%respectively after10d,20d, and40d;in salinity44, the mortality were7.8%,44.4%and71.1%respectively after10d,20d,and40d. The first dead individual was observed after four weeks when transferred theabalones to24,28and36respectively.3the adaptive capacity of juvenile abalones to low salinityWhen the salinity of sea water gradually decreased1every5d, the juvenileabalones may adjust to low salinity20. The first dead individual was found after15d.The mortality rates were only8.9%and24.4%after40d and100d. While the controlgroups, being transferred directly from32to20suddenly, nearly died totally (90.0%).4the growth rate of juvenile abalones in different salinities for long periodSalinity gradient:26,28,29,30,32.120individuals (3×40) were used in eachtreatment. The length of shells were controlled in the range of40.4~43.0mm. After65d, length and width of shells, and wet weight of abalones were measured. The survivalrates of all groups were more than97%. It was showed that individuals grew best atsalinity28to30. However, the feeding rate and shell growth rate of the individuals atsalinity26decreased significantly.5change of total soluble protein and hemocyanin in hemolymph ofjuvenile abalones when salinity decreasedThe change of total soluble protein and hemocyanin in hemolymph wereevaluated when the abalones were transferred directly to different low salinities. Threetest groups were set (salinity from30to26,30to20h,26to20). It showed that totalsoluble protein and hemocyanin in hemolymph maximized at21h when abalonestransferred from salinity30to26. Other abalones of the rest groups maximized at24h.The more decreasing of the salinity, the smaller change appearing of the total solubleprotein and hemocyanin in hemolymph. It suggested that the extent of the regulatorymechanism of abalone was limited. |
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