Abstract

When copepod Acartia tonsa is isolated from tropical populations, the produced eggs exhibit low hatching after long-term storage, a critical aspect that makes their use difficult in aquaculture. In three experiments, this study spawned adults of A. tonsa cultured at different salinities and temperatures. The eggs were collected to determine hatching success of fresh and cold-stored eggs (HS-C). Experiment 1: Adults spawned under four combinations of two temperatures (18 and 28 degrees C) and two salinities (18 and 30 PSU) to determine the HS-C from 0 (fresh eggs) to 4 weeks of storage. Experiment 2: Adults spawned under three combinations of temperatures (18, 23, and 29 degrees C) and 30 PSU to determine the HS-C (from 0 to 4 weeks of storage). Experiment 3: Adults spawned under 18 degrees C and 30 PSU to determine the HS-C (from 0 to 8 weeks of storage). All adults were distributed in triplicate in 2 L containers at 0.5 individual mL(-1) and fed with the Rhodomonas sauna microalgae at 2000 mu g C L-1. In every experimental unit, the eggs were collected and stored at 3 +/- 1 degrees C. In fresh eggs (0 weeks of storage), most of the treatments showed great hatching ( > 90%). However, low salinity and high temperature resulted in a significantly (p .05) lower hatch (81%) of the fresh eggs. The combination of 18 degrees C and 30 PSU produced better hatching (p .05) in eggs stored for 2 and 4 weeks (85% and 73%, respectively), followed by 18 degrees C and 18 PSU (65% and 41%), 28 degrees C and 30 PSU (50% and 17%) and 28 degrees C and 18 PSU (11% and 2%). Stored quiescent eggs were strongly affected by the temperature and salinity of the culture environment. On the other hand, fresh (subitaneous) eggs do not depend so much of these variables. Therefore, the criteria to select what salinity and temperature combination is best to raise adults for egg production will depend on whether the eggs will be used for immediate-use (fresh) or storage.