Effect of temperature on demography of Ophryotrocha labronica (Polychaeta, Dorvilleidae)

A laboratory experiment was performed to evaluate the temperature-induced variation in the life history traits of Ophryotrocha labronica (Polychaeta). In this species age and size at maturity, survival and fecundity are affected by temperature. In particular in O. labronica, low temperatures cause a considerable delay in the attainment of sexual maturity, a reduced number of spawnings and longer intervals between one spawning and the next; fecundity is therefore lower and the animals generally live longer. At high temperatures, the animals mature rapidly, spawn very frequently and at shorter intervals; fecundity is high, even though the animals have a much shorter life span. Temperature determines the age-specific fecundity and survival patterns and hence the demographic characteristics of O. labronica; both the net reproductive rate R-0 and the population growth rate X vary in accordance with the temperature, thus demonstrating the importance of environmental factors in determining not only the reproductive characteristics of the individual animal but also the fitness of the populations as a whole.