Salinity-induced quiescence in eggs of the calanoid copepod Acartia tonsa (Dana):: a simple method for egg storage

We report the effect of salinity and temperature on the viability of stored culture-based subitaneous eggs of the calanoid copepod Acartia tonsa for use of copepods in fish larvae culture. Quiescence induction was recorded at 17 and 25 degrees C, in salinities from 0 to 30. Quiescence was strongly induced at 0 salinity and partially at 5 in both temperatures. Eggs incubated at 0 salinity for up to 12 days at both temperatures showed a decline in the fraction able to be induced into quiescence by abrupt salinity changes. The hatching success of eggs that were able to enter quiescence stabilized after a 1-day incubation and remained similar to 25% viable for 12 days in 17 degrees C. On the contrary, the 25 degrees C trial showed a gradual decline in viability until stabilizing similar to 10% at day 7 and onwards. Longterm 17 degrees C incubation for 35 days showed that eggs remained quiescent with a viability of similar to 14%. Hence, we recommend salinity storage of A. tonsa subitaneous eggs as a relevant shortterm technique, and a suitable alternative to the recently proposed cold storage of eggs when eggs are to be shipped from the copepod producer to a given fish larvae hatchery.