Original paper

Embryonic development time of parthenogenically reproducing Cercopagis pengoi (Cladocera, Onychopoda) in the northern Baltic proper

Svensson, Stefan; Gorokhova, Elena


The embryonic development of parthenogenically reproducing Cercopagis pengoi (Cladocera, Onychopoda), an invasive zooplankton species in the Baltic Sea and the North American Great Lakes, was studied under laboratory and field conditions. Direct observations of the maturity stage of living embryos in the brood pouches of females were made at frequent intervals (3 to 4 hours), and the sequence of morphological changes was analyzed to estimate duration of embryonic development as well as that of the individual stages. Total embryonic development time (EDT) averaged 3.2 d; the duration of the individual stages decreased from early to mature stages. The results were compared with theoretical values obtained from published growth models, which take into account incubation temperature and neonate mass. The model-derived EDTs were up to 30 % longer than observed. Further, the observed EDT was used to predict generation time (14.7 d), which implies that in the Baltic Sea during summer season, depending on temperature conditions, there could be 5-7 parthenogenic generations.


cercopagis pengoicladoceradevelopment timeeggsembryogenesisinvasive speciesparthenogenic reproduction