On temporal variation in the rotifer Keratella cochlearis (Gosse): the question of “Lauterborn-cycles”

The existence of separated forms within the population of Keratella cochlearis (Gosse) from Lake Plußsee was demonstrated on the basis of a biometric analysis. The morphs cochlearis, hispida and tecta were definitely not connected by transitional forms. Micracantha and tecta were not links of a macracantha-micracantha-tecta-series. Hence, the general validity of Lauterborn-cycles is questioned. In this connection, the taxonomy of this species is also involved, because it is derived from the idea of phenotypic cycles in the sense of Lauterborn.