Life Cycle of the Copepod Limnocalanus macrurus Sars 1863 (Copepoda, Calaniformes, Centropagidae) in Lake Onego

— Limnocalanus macrurus Sars 1863 (Calaniformes, Centropagidae Giesbrecht 1892) is a glacial marine relict species. In the pelagic zone of Lake Onego, one of the European Great Lakes, this copepod is part of the zooplankton dominant complex all year round. Limnocalanus macrurus is a monocyclic species with one generation and winter reproduction. Based on the analysis of long-term data, the main features of the life cycle of the copepod have been studied in Petrozavodsk Bay and in the central part of Lake Onego. Thus, during the growing season the average values of abundance are two times lower in the bay compared to the central part of the lake (2700 vs. 5500 ind./m 2 , respectively). The same tendency was observed in relation to biomass (0.82 vs. 1.36 g/m 2 , respectively). A comparison of the average long-term maximal values of abundance and biomass in these parts of the lake also shows that the values of abundance are 1.6 times (5600 vs. 9000 ind./m 2 ), while the biomass values are twotimes lower (1.41 vs. 2.83 g/m 2 ) in Petrozavodsk Bay compared to the central part. A shift in the timing of the spring development of L. macrurus in Petrozavodsk Bay has been found; here the development begins 2–3 decades earlier due to the difference in the thermal regimes of the areas compared. Despite the climatic changes observed in recent decades, no significant changes in the abundance of L. macrurus have been detected in the lake.