Univoltine and Semivoltine Life Histories in Senecella calanoides (Copepoda: Calanoida) and Their Relationship to Body Size

1984 
Most populations of Senecella calanoides Juday in eastern Canada are univoltine. However, in Lake Mazinaw, southern Ontario, and probably in three additional lakes in western Quebec it has a 2-yr life history (semivoltine) with two fractions, different in age by 1 yr, developing together. The additional year of development in Mazinaw is spent almost entirely in the fourth and fifth copepodite instars. Slower development in semivoltine populations is tentatively attributed to colder waters resulting from extensive hypolimnia, with limited food as a possible secondary cause. Later copepodites of semivoltine populations were smaller than their univoltine counterparts, possibly because of poorer nutrition.
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