渗透压、温度和饲养密度对桃花水母生存与有性繁殖的影响
Effects of osmotic pressure, temperature and stocking density on survival and sexual reproduction of Craspedacusta sowerbii
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摘要: 本文研究了渗透压、温度和饲养密度对桃花水母生存与繁殖的影响。结果表明:桃花水母对渗透压变化十分敏感,在34 mOsm/L条件下存活时间低于90 h并随渗透压的升高而快速降低。仅在6×10-4 M的氯化钙溶液中,最长存活时间才能超过200 h。相比于较高温度(27.0℃和32.0℃),低温环境处理下(23.0℃),水母体平均活力较低但具有更长存活时间。此外,饲养密度与存活时间之间不具有线性关系,低密度饲养产生更大个体。饲养22 d后,有性生殖出现,但仅发生在高密度饲养条件下(10 ind./L, 14 ind./L和18 ind./L),并且相继产生水螅体和新水母。水螅体和新水母的数量与饲养密度存在极强相关性:饲养密度越高,产生的数量越多。最后,新生成水母在30 d内全部死亡并且伞径不超过5.0 mm。Abstract: The effects of osmotic pressure, temperature and stocking density on medusae survival of Craspedacusta sowerbii were examined. The medusae were shown to be sensitive to the variations of osmotic pressure. And the survival time was <90 h at 34 mOsm/L and it declined rapidly with rising osmotic pressure. The peak survival time of >200 h was recorded at 0.2 mOsm/L. Comparing with 27℃ and 32℃ treatments, 23℃ treatment yielded lower activities at a range of 8-13/min. However, there was a longer survival time. A non-linear relationship existed between survival time and stocking density. Lower density resulted in larger body size. And sexual reproduction resumed after breeding for >22 days. Newly-formed polyps and medusae appeared subsequently but only in the higher-density groups of 10, 14 and 18 ind./L. It suggested that the number of newly-formed polyps and medusae was highly dependent on stocking density. That is, a higher stocking density produced more organisms. However, newly-formed medusae died within one month and none grew a diameter of >5 mm.