Population stagnant growth caused by cryptic species of Brachionus plicatilis species complex

褶皱臂尾轮虫自20世纪60年代以来一直是水产养殖中不可缺少的活食浮游动物。根据体型分为L、S和SS三种类型，但最近的研究表明褶皱假单胞菌是由遗传隔离的种/株组成的，称为种复合体。根据COI基因座的替换，本研究中检测的标本被归类为5个遗传分离株。随后，进一步研究了L型的两个株系，Amami株和Obama株，以比较它们的生活史参数。Amami品系表现出相对较快的生长和成熟，但抗震荡能力低于Obama品系。他们生活史上的这些差异表明，Amami和Obama可以分别被认为是R型和K型策略师。这两个品系之间的这种不同的适应行为会导致大众文化中的竞争，并导致种群的停滞增长甚至崩溃。

Rotifer Brachionus plicatilis has been an indispensable zooplankton as a live-food in aquaculture since 1960s. Three types of L, S and SS have been recognized based on their body size, but recent studies revealed that B. plicatilis consists of genetically-isolated species/strains, called species complex. Based on substitutions in the COI locus, the specimens examined in this study were classified into 5 genetically-isolated strains. Subsequently, the two strains of the L-type, Amami and Obama strain, were further investigated to compare their life-history parameters. The Amami strain showed relatively faster growth and maturation, but had lower stavation resistance than the Obama strain. These differences in their life-history suggested that the Amami and Obama strains could be considered to be r-and K-strategists, respectively. Such different adaptive behaviors between the two strains can cause the competition in the mass-culture, and resulted in the stagnant growth or even collapse of the population.