Induction of embryonic diapause in the calanoid copepod Acartia hudsonica

TL;DRAbstract

The copepod Acartia hudsonica grows and reproduces in Narragansett Bay in winter and spring, spending summers as dormant eggs. I investigated the change in egg types from immediately-hatching eggs to dormant eggs. Temperature and length of day were hypothesized to act as the cues inducing this population to produce dormant eggs, and the variation in the dormant-egg responses of individual females was quantified. A. hudsonica produced some dormant eggs early in the spring, but most of the switch to dormant eggs occurred in June. Experiments showed that temperatures above about 16°C increased the proportion of dormant eggs produced whereas increased length of day did not. In several experiments between 42% and 85% of the variance in the fraction of dormant eggs produced was attributed to variance among individuals. In estuaries in the northern part of its range, A. hudsonica populations are present year-round and may not express diapause. This difference may be genetic or phenotypic. Usi

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