Age Dynamics of Telomere Length of Baikal Gastropods is Sex-Specific and Multidirectional

The age dynamics of telomeres are affected by various internal and external factors. We examined the age dynamics of relative telomere length (RTL) and telomerase activity in freshwater dioecious gastropod species from Lake Baikal (Benedictia fragilis, B. baicalensis and Kobeltocochlea martensiana). They differ in habitats, growth rate, size of mature specimens, reproductive strategy and degree of phylogenetic relatedness, but do not possess sexual dimorphism and, irrespective of sex, they have a similar lifespan (∼8 years) and time to maturity (∼4 years). Sex specificity in changes of telomere with age was observed in each species of benedectiids. Immature specimens do not differ in telomere size irrespective of sex. However, when they become mature, we recorded differences and similarities in telomere length between females and males. Telomeres are longer in 4-6 year-old adult females than in males. At the age of 7-8 years, sex differences in telomere sizes are leveled in B. fragilis and K. martensiana, while in B. baicalensis the difference remains. Sex differences in the telomere age dynamics of B. baicalensis have also been revealed between the embryonic and mature stages of development. Telomeres in mature males are shorter than in embryos and mature females. In females after the embryonic stage, telomeres shorten rapidly, and then at the age of 4-8 years telomere length is restored up to the embryonic level. Active telomerase was revealed in all species irrespective of sex and developmental stage. The multidirectionality of sex-dependent age dynamics of telomere size may be attributed to the combined effect of internal and external factors on telomeres during ontogenesis.