Grandmother Age Effects via Sperm Telomere Length and Egg Telomerase Transcripts

The Lansing effect is a transgenerational age effect by which old parents tend to produce less viable descendants. Despite its importance for the evolution of lifespan and parental effects, the transgenerational nature of age effects and the underlying mechanisms are poorly understood. In an experiment using the three-spined stickleback, we test whether the age of mothers (generation P0) at reproduction affects parental traits of the F1 offspring, and whether they subsequently influence the early development and viability of the F2 descendants. Daughters (F1 females) of old (2-year-old) and young (1-year-old) mothers showed comparable body size, spawning rate, clutch size and egg telomere length (TL). However, sons (F1 males) of old mothers had a smaller adult body size and produced sperm with shorter TL than those of younger mothers. Structural equation model analysis revealed that P0 female age influenced embryo TL and hatching success of the F2 descendants through its effect on sperm TL of F1 males. There was also an interacting effect of P0 female age and telomerase reverse transcriptase gene (tert) mRNA level in eggs of the F1 females on the hatching success of the F2 descendants. Our results provide novel evidence that maternal age can have transmissive effects on successive generations through the gamete traits of their offspring, especially sperm TL and egg tert gene transcripts. We conclude that this transmissible age effect on grandoffspring TL and viability can shape the evolution of life histories because TL is related to health, ageing and lifespan.