Understanding the processes that enable adaptation of organisms to time-varying environments is critically relevant in evolutionary ecology. A way to cope with environmental fluctuations where predictable conditions affect several generations of individuals is through non-genetic transgenerational effects. The phenotype of ancestors affects the phenotype of their descendants matching it with the expected environment of the latter. Facultatively sexual rotifers inhabiting water bodies that cover a wide gradient of environmental predictability in Eastern Spain are a good study model for this topic. In their life cycle sex is linked to diapausing-egg production that enables survival between growing seasons. In several rotifer species, sexual reproduction is inhibited in several generations after diapausing-egg hatching. We hypothesized that in ponds where the growing season length is more predictable, rotifer clones proliferate asexually longer, hence allowing a fuller exploitation of the growing season and therefore maximize diapausing-egg production by the end of the season. We tested this prediction by estimating the proportion of sexual females produced by eight clones of the rotifer Brachionus plicatilis inhabiting eight ponds (8x8= 64 clones) from our study system. Here, we present the raw data gathered from the experiment.