Cleuvers Michael, Goser Brigitte, Ratte Hans-Toni
Department of Biology V (Ecology, Ecotoxicology, Ecochemistry), Aachen University of Technology, Worringerweg 1, D-52056 Aachen, Germany, , , , , , DE.
Oecologia. 1997 Apr;110(3):337-345. doi: 10.1007/s004420050167.
In Daphnia magna, high animal density causes a mutual intraspecific influence, called life-strategy shift by intraspecific interaction (LiSSII). We investigated mothers (F), living singly or in groups of four per 50 ml, and their F offspring. Clutch sizes of F daphnids living in groups were smaller than those of singly living ones. However, the F neonates were bigger in size, had higher dry weights and contained more lipids. They were also able to survive longer starvation periods. If these F␣daphnids were again kept in groups of four, the effects of LiSSII on some life-history parameters were stronger. As compared to group-living F daphnids, juvenile development time was prolonged from 7.5 to 10.0 days. In contrast, body size was reduced and the further reduction in offspring number was slight. The F␣neonates exhibited the same change towards bigger size and higher dry weight as observed in the F. In contrast F daphnids, that were the offspring of daphnids living in groups but were kept singly were bigger and produced more offspring than single daphnids that were the offspring of daphnids kept singly. The neonates of the former were bigger in size and heavier. It is suggested that for the F generation the ecological significance of the LiSSII effects is an increase in both the parent and offspring survival probability when food is limited. LiSSII acts before food conditions deteriorate seriously. Daphnids affected by LiSSII invest less of their biomass into offspring. Offspring release is well-timed and quality is better, at the expense of quantity. Under favourable environmental conditions, F daphnids that are the offspring of mothers affected by LiSSII appeared well adapted to fast recolonisation when living at low density.
在大型溞中，高动物密度会导致一种种内相互影响，即种内相互作用引起的生活策略转变（LiSSII）。我们研究了单独生活或每50毫升四只一组生活的母溞（F）及其F代后代。群居的F代溞的产卵量比单独生活的要小。然而，F代幼溞体型更大、干重更高且含有更多脂质。它们也能在更长的饥饿期内存活。如果将这些F代溞再次以四只一组饲养，LiSSII对一些生活史参数的影响会更强。与群居的F代溞相比，幼体发育时间从7.5天延长至10.0天。相比之下，体型减小，后代数量的进一步减少则不明显。F代幼溞表现出与F代相同的向更大体型和更高干重的变化。相比之下，作为群居溞后代但单独饲养的F代溞比作为单独饲养溞后代的单独饲养溞体型更大且产生更多后代。前者的幼溞体型更大且更重。研究表明，对于F代而言，LiSSII效应的生态意义在于当食物有限时，亲代和后代的生存概率都会增加。LiSSII在食物条件严重恶化之前起作用。受LiSSII影响的溞将较少的生物量投入到后代中。后代释放时机适宜且质量更好，但数量有所牺牲。在有利的环境条件下，受LiSSII影响的母溞的F代溞在低密度生活时似乎很适应快速重新定殖。
