Life cycles of the freshwater,planktonic copepod Cyclops scutifer Sars on a north-south gradient in North America

摘要

A seasonal cycle longer than one year is exceptional both among marine and freshwater zooplankton,but occurs widely in the freshwater cyclopoid Cyclops scutifer Sars.This paper presents the life cycle of this species in eight North American populations in lakes from 42° to 69° N.Five of the populations had life cycles showing a combination of a one and two year cycle.Two populations had a 1-year cycle,and the southernmost had a combination of a 0.5-year and a 1-year cycle.Lengths of cycles increased with latitude and thus inversely with the temperature.Populations in all lakes were divided into a direct and a delayed line of development.Diapause was not documented in any of the lakes.