The following life history traits of D. rotundatus (O. F. Müll.) were established based on field and laboratory observations: fully calcified eggs ca 1 mm in diameter, of a size correlated with the number of parent’s whorls; 1–11 eggs per clutch; 1–178 eggs per lifetime, in 1–36 clutches; incubation period 14–36 days; egg cannibalism with a strong preference for conspecific eggs; quick growth (33–35 days per whorl) prior to maturity and slow growth in mature snails, resulting from energy expenditure for egg-laying; sexual maturity at 5.5 whorls (2nd–3rd year of life); life span 2.5–3.5 years. Isolated individuals produce fewer eggs of lower viability than individuals kept in groups, they lay their eggs later and at a larger size. Most eggs in the laboratory arelaid in June, in thefie ld themaximum of there productivepe riod falls in July/August.