Morphological variation of Keratella cochlearis in the presence of cyclopoid copepods in Meimoa Reservoir

Species succession and succession of different morphs of the same species throughout the year are frequently reported. Environmental factors have been considered uneffective to justify such variations while the role of biotic relationships has received increasing attention. During this study the importance of biotic factors on body and spine lengths variation of Keratella cochlearis (Rotifera) during 1995 in Meimoa Reservoir was investigated. The predation impact on K. cochlearis morphology was evidenced as a general increase of body and spine lengths in the presence of potential cyclopoid preda-tors. The importance of predator species composition and abundance on morphological variation of K. cochlearis was emphasised by direct correlation of both spine and body lengths to Acanthocyclops robustus density and not to the whole cyclopoid population