Morphometry and cyclomorphosis in Daphnia middendorffiana from a fishless pond of the Southern Andes

The morphology of a population of D. middendorffiana collected during sprin g and autumn in a fishless pond of the Southern Andes was examined to ident ify seasonal variations in growth patterns. Body size, tail spine length, w idth, thickness and biomass were analyzed, and growth was characterized by correlating various morphological dimensions with biomass. A pattern of thr ee growth stages was identified: a juvenile stage characterized by body gro wth without variation of the tail spine length, a transition stage during w hich the tail spine experienced a sudden length reduction, and an adult sta ge with growth patterns similar to the first stage. Specific cyclomorphic g rowth patterns were found. The dimensions displaying most apparent seasonal differences were tail spine length and body flatness.