Study on the biological function of tropical minute rotifers and its application for mass preservation of live food.

1.SS型轮虫的遗传特性利用印度尼西亚、泰国和西班牙的3个轮虫品系进行了杂交育种试验。轮虫的交配行为包括雄性在雌性冠上接触，雄性围绕雌性落叶松旋转并交配，然后受精。通过在5毫升的培养皿中共培养100只雌性和50只雄性，监测交配频率并获得受精率。SS品系间杂交的交配率和受精率分别为5.0-16.6%和7.7-34.7%。在本试验中，S品系与SS品系之间未观察到交配受精现象，而与其他S品系和SS品系均有此现象。S品系和SS品系可能都存在较大的遗传变异。2.繁殖和大量保存SS轮虫在10和12℃可保存14天。在25℃时，添加50微克/毫升的γ-氨基丁酸可促进种群增长。当培养温度在30~25℃之间变化时，休眠产卵量显著高于30℃时。在500L水箱的大规模试验中，轮虫在9天的实验中产生2.6×10~(-6)休眠卵，是不变温轮虫数量的1.6倍。3.用SS轮虫培育石斑鱼幼体，将SS型轮虫密度维持在3、10和30个/ml时，石斑鱼幼体的摄食率在第6天和第7天减少，第7天的幼体总长也最小。然而，在第8天后，不同处理之间没有发现差异。提供的SS轮虫的洛里卡大小为80-156微米(平均洛里卡长度为114微米)，而幼虫摄食的洛里卡长度为75-138微米(平均104微米)。因此，石斑鱼幼体在这一阶段只能摄食体型较小的SS轮虫。

1.Genetic characteristics of SS type rotifersCrossbreeding experiments were conducted using three rotifer strains from Indonesia, Thai and Spain strains. Rotifer mating behavior involves male contact on female corona, male circling around female lorica and copulation, followed by fertilization. The frequency of mating was monitored and percent fertilization was obtained, by co-culturing 100 females and 50 males in a 5 ml petri dish. In the crossing between SS strains, percent copulation and fertilization were 5.0-16.6% and 7.7-34.7%, respectively. No copulation and fertilization was observed between S and SS strains in this experiment, whereas such cases were reported with other S and SS strains. A large genetic variation probably exists both in S and SS strain groups.2.Reproduction and mass preservationSS rotifers could be preserved for 14 days at 10 and 12℃. The addition of gamma-aminobutyric acid at 50 ug/mL increased population growth at 25℃. Significantly higher resting egg production was observed when the culture temperature was changed from 30 to 25℃, than when temperature was kept at 30℃. In the large-scale trial using 500L tanks, rotifers produced 2.6x10^6 resting eggs during a 9-day experiment, which was 1.6 times more than the number of rotifers without temperature change.3.Larval rearing of grouper using SS rotifersBy maintaining the SS type rotifer density at 3, 10 and 30 ind./ml, ingestion rate of grouper larvae was reduced on day 6 and 7, and total length of larvae on day 7 was also the smallest. After day 8 however, no difference was found among treatments. The lorica size of supplied SS rotifers ranged from 80-156um (average lorica length=114um), while larvae ingested rotifers whose lorica length was from 75 to 138 um (104 um in average). Thus, grouper larvae at this stage could ingest only smaller size class of SS rotifers.