|Laforsch, C; Tollrian, R: Extreme helmet formation in Daphnia cucullata induced by small-scale turbulences, , 26(1), 81-87 (2004), doi:10.1093/plankt/fbg114|
Although Daphnia cucullata is used as a textbook example for cyclomorphosis, distinct helmet development, as shown in the field, has not been demonstrated in the laboratory until now. We show for the first time that small-scale turbulence is able to induce the maximum response of morpho- logical plasticity in D. cucullata. Helmet elongation reached magnitudes as extreme as observed in the field. Different modes of generating small-scale turbulence caused different levels of helmet formation. Small-scale turbulence alone may not be responsible for cyclomorphosis in nature because field data show that two nearby lakes with similar morphometry differ in cyclomorphosis patterns, while laboratory experiments show that there is no difference in the ability to form helmets in the clones of each lake. Although helmet formation in D. cucullata is inducible with predator kairomones, helmet elongation is not as strong as that induced by turbulence. We discuss the possible role of helmets under turbulent conditions.