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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3142

Herbert Kiechle and Hans Buchner; [Untersuchungen uber die Variabilitat der Radertiere: V. Dimorphismus und Bisexualitat bei Asplanchna]. Revue Suisse de Zoologie 73:283-300, 1966

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Asplanchna sieboldi occurs in several varieties. Experiments were made to find out if the morphologically different varieties f. leydigii and f. ebbesbornii also differ, as it is often assumed, in biological (number of offspring) and physiological respect (bisexuality rate). Both varieties can be obtained by suitable feeding. Though the females of f. ebbesbornii were mostly larger, no rigid correlation between form and size can be proved. Nor does the number of offspring, dependent on food, show any differences typical of either variety. The bisexuality rate depends in the same way on the kind of food organisms. However, by suitable feeding the number of mictic animals can be increased without any change of variety occuring either at once or later. Given a certain diet, females of f. leydigii have the same bisexuality rate as females of f. ebbesbornii. After dietary changes, which affect the bisexuality rate as well as the variety and body size, the transformations do not occur simultaneously: The size changes immediately, the mixis increases in the following generation, the variety changes only six to eight generations after the diet was changed.