Life cycle of Boeckella poppei Mrazek and Branchinecta gaini Daday (King George Island, South Shetlands)
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In Lake Wujka, a shallow, polymictic Antarctic lake situated at 15 m from the seashore, several yearly cohorts occur of the copepod Boeckella poppei and one of the fairy shrimp Branchinecta gaini. There is circumstantial evidence that the two species compete for food, and perhaps adult fairy shrimp feed on the nauplii of the copepod. Both species are positively influenced by a measure of salinity. However, when autumn storms massively sweep seawater into the lake, all fairy shrimp are wiped out; no hatching occurs until next spring. In B. poppei, some nauplii and copepodites survive or hatch after the salt flows out of the lake. This is an advantage to the copepod that may balance its coexistence with the shrimp. Its cycle is, however, aborted by the freezing of the lake. In contrast to many other Antarctic lakes, the life cycle of the crustaceans is therefore controlled by salinity rather than freezing.
KeywordsBoeckella poppei Branchinecta gaini Environmental factors Freshwater lake Antarctica Life cycles
The first author is deeply grateful to Dr. P. Olejniczak for statistical analysis and would like to thank Prof. S. Rakusa-Suszczewski for enabling her to participate in the 28th Polish Antarctic Expedition to the H. Arctowski Station. This study was supported by the State Committee for Scientific Research based in Warsaw, grant PBZ-KBN-108/PO4/2004.
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