| Summary: | The standing crop of the copepod G. b. thomasi Forbes in Marion Lake, B. C, has been recorded during 1966 and 1967. These copepods excysted as stage IV copepodids during April and moulted to adults, which produced eggs in May. The new population developed to the copepodid IV stage by mid-summer, when 85 % of the animals returned to the bottom and encysted. The copepodids of stage IV and V and the adults are predators. In the laboratory, six groups of animals were presented separately to the predator, which preyed most efficiently on cyclopoid nauplii and copepodids, diaptomid nauplii and rotifers; and least efficiently on diaptomid copepodids and cladocera. In the lake, the forms least affected by cyclopoid predation were also the diaptomid copepodids and cladocera. There was a correlation between C. b. thomasi encystment and food shortage, which suggests that food shortage may stimulate encystment of stage IV copepodids. === Science, Faculty of === Zoology, Department of === Graduate
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