Combined effects of salinity and temperature on survival and reproduction of five species of Artemia

Survival and reproductive performance were measured at nine temperature-salinity (T-S) combinations (15 degrees C, 24 degrees C and 30 degrees C/60 ppt, 120 ppt and 180 ppt) for four sexual (Artemia franciscana, A. salina, A. sinica and A. persimilis) and one parthenogenetic (A. parthenogenetica) species of brine shrimp. There was significant interaction between temperature and salinity for survival and reproductive traits. For most species there was disconcordance among seven performance estimators (LT50, 21-day survival, r, and four female reproductive traits) for the optimal T-S combination. We propose that the best ecological estimator of reproductive success is cohort reproductive output because it incorporates both survival (I,) and reproductive (rn,) functions. All species had maximum reproduction at 24 degrees C; at 120 ppt for A. parthenogenetica, A. sinica and A. franciscana, and at 180 ppt for A. salina and A. persimilis. There was only one T-S combination (24 degrees C/120 ppt) where all species completed their life cycle. While at least one Artemia species reproduced at eight of the nine possible T-S combinations, sustainable reproduction (where R-o greater than or equal to 1) occurred at only five T-S combinations. A. parthenogenetica had the narrowest tolerance range of T-S combinations, contradicting the general purpose genotype hypothesis advanced for obligately parthenogenetic species. (C) 2000 Elsevier Science B.V. All rights reserved.