Quantitative observations on asexual reproduction of Aeolosoma viride (Annelida, Aphanoneura)

Agametic reproductive activity (via paratomy) of Aeolosoma viride was analyzed throughout the life cycle in individually reared specimens. Aeolosoma viride is organized in linear chains of 3–4 zooids; the main zooid is anterior, and the secondary zooids are posi- tioned posterior to the main zooid in inverse order with respect to their degree of growth, the most advanced being at the posterior end, and those less advanced nearer the main zooid. On average, worms lived 66?10 d and produced 57?6 offspring. A budding area located in the sub-terminal part of the main zooid produced chaetigers that formed the ori- gin of the secondary zooids. A growth zone was located in the posterior end of each sec- ondary zooids. Fission occurred between the penultimate and the last zooid of the chain. Just before fission, the growth zone of each secondary zooid became a budding area. Aga- metic reproduction was via multiple paratomy with linear succession of the secondary zooid and terminal fission. The structure of the chain was therefore modulated by the interaction of the processes of budding, growth, cephalic differentiation, and fission, which occurred continuously and on different timescales. Values of parameters describing paratomic activity (interval between origin of the zooids, time to produce a chaetiger, growth time of the zooids, and interval between the fission of the filial chains) are low early in an individual’s life, but increase during senescence. Due to its relatively rapid lifecycle and high reproduc- tive activity, A. viride is a convenient experimental organism for the study of agametic reproduction.