The effect of temperature on the development and hatching of resting eggs of non-indigenous predatory cladoceran Cercopagis pengoi in the Gulf of Finland, Baltic Sea

The effect of temperature on the development and hatching of resting eggs of the Ponto-Caspian Cercopagis pengoi was studied experimentally in the Gulf of Finland, Baltic Sea. Morphological changes were monitored as the development of the resting eggs proceeded. Sexual reproduction of the C. pengoi population in the Gulf of Finland was evaluated by combining the data from hatching experiments and resting egg abundances in the sediment. Development time of resting eggs was dependent on temperature: increase in the temperature shortened the time needed until hatching. Hatching success was also dependent on incubation temperature. Almost sixfold increase in hatching success was detected when temperature increased two degrees above the storage temperature. Average resting egg abundances varied between 0.16 and 0.49 eggs cm(-3) in the 0-6 cm sediment layer.