温度和饵料对双刺纺锤水蚤产卵率和孵化率的影响

THE EFFECTS OF TEMPERATURE AND DIET ON EGG PRODUCTION AND HATCHING SUCCESS OF ACARTIA BIFILOSA(COPEPODA:CALANOIDA):A LABORATORY INVESTIGATION

桡足类在海洋生态系统的物质循环和能量流动中起着关键作用,其种群变动影响着初级生产及以浮游生物为食的鱼类的变动。同时,由于部分桡足类的卵及无节幼体是多种经济鱼类仔稚鱼的开口饵料,因此其作为养殖饵料的开发在国内外也引起了关注。纺锤水蚤(Acartia sp.)分布于世界各地的近岸海域,适应力强,很多种都有根据环境条件的改变而产休眠卵的机制。纺锤水蚤作为仔鱼饵料已经受到了广泛关注并在澳大利亚、日本等地区进行了应用性研究(Ikeda,1973;Schipp et al.,1999;McKinnon et al.,2003)。

Acartia bifilosa(Copepoda:Calanoida)is a common species of global waters and it often becomes dominant species in some estuaries.This species develops different strategies according to the variation of environment.Despite its ecological role,Acartia bifilosa also has been concerned as live feeds in aquaculture,but study on egg production rate of this species in saturated diet in different temperature and different diet is so far not available.In order to interpret the importance of temperature and diet on natural population variation and also on aquaculture as foods of larval fish,the functional response of reproductive success of Acartia bifilosa was quantiffed in the laboratory under different temperatures and diets. Acartia bifilosa was captured in Jiaozhou Bay and acclimated to corresponding temperature for 3～4 days.In order to reduce the effect of large extent temperature range on organism,we captured Acartia bifilosa from March to June and acclimated them to temperature which is adjacent to natural temperature.Daily egg production rate(EPR,eggs female ^(-1) day^(-1)) was detected for 11～15 days at 5 different temperatures ranging from 8.0 to 23℃and all the females were fed on saturated diet all through the experiments.EPR on first day was not calculated in the mean EPR to eliminate the effect of different diets.This result showed that Acartia bifilosa spawned continuously during the experiment days and no obvious regulation was found.EPR was positively correlated with temperature from 8.0 to 23℃.The highest mean EPR was observed at 23℃(7.3 eggs female^(-1)day^(-1)),and the lowest value was found at 8℃(3.8 eggs female^(-1) day^(-1)).The effect of diets on EPR was evaluated at two different temperatures(8.0℃and 12.5℃).Same trends were found at the two temperatures:mean EPR fed on Chaetoceros sp.was higher than that fed on Skeletonema costatum,and during the 14-day experiments, EPR was higher for females fed on Skeletonema costatum than Chaetoceros sp.in the first few days(3～5 days),but it changed reversely in the subsequent days until the end of the experiments. Hatched eggs were observed in the two experiments at temperature 8℃and 12.5℃and no diapause eggs were found.The hatching success rate was low at 8℃but reached 93.2%at 12.5℃. According to the results in this paper,we detected the favorable temperature range for EPR,and evaluated the effect of Skeletonema costatum which often blooms in natural waters. These results are beneficial to ecological research for explaining population variation and population recruitment of this species.These data also can be used in Acartia bifilosa aquaculture.