Investigating the relative importance of parentage versus environmental factors on heterochrony in basommatophoran freshwater snail radix balthica

The importance of genetics in inter-specific heterochrony is long known, however intra-specific heterochrony was believed to be driven by environmental variation. Recent studies on Radix balthica showed higher similarity in developmental timing across generations in genetically similar embryos then distantly related ones. This study compared the relative importance of parentage and egg-mass origin and the environment in generating heterochrony in Radix balthica. Six developmental events were recorded daily. The analysis showed that parentage influence in developmental timing to be more important than environmental conditions. When comparing the sequence of developmental events, a strong link was found between treatment showing sequence variation and nil mortality in that treatment. This was found between parents and between same parent egg-masses. This study shows that parentage influences timing of developmental events whereas the sequence of developmental events is influenced by treatment. These findings indicate that both genetics and environmental plasticity influences intra-specific heterochrony.