Morphological responses to the presence of predator info-chemicals have been described for many Daphnia (Cladocera) species, but D. galeata is generally considered to exhibit almost no morphological changes that could increase its fitness under predation. Therefore, the aim of our study was to examine the nature and magnitude of morphological responses of D. galeata to their predators in detail and assess their potential role in decreasing the predation threat. Two clones of Daphnia were exposed to predator info-chemicals (kairomones) from perch, a fish (Perca), and a phantom midge larvae (Chaoborus) an invertebrate, and a kairomone mixture from both these organisms. Laboratory life-table experiments were carried out and five parameters characterising the body shape of the daphnids were measured: helmet length, head- and carapace width, eye diameter and body size. The last-named three parameters did not differ significantly between the clones or the treatments. The differences found between the clones were significant for head width and helmet length, but only in combination with the treatment effects. Our results on genotype-dependent phenotypic plasticity indicated that, although phenotypic plasticity is present, the clonal composition of a Daphnia population can be altered by selection on the morphotype. This potential for a change in clonal frequencies is given by the differences measured between the two clones in head width and helmet length, altering the curvature of the Daphina body in response to kairomone presence. [KEYWORDS: Chaoborus, Info-chemicals, Kairomones, Morphology, Perca, Predation]
Original languageEnglish
JournalAquatic Ecology
Journal publication date2002

ID: 334613