Environmental Effects ~100 shrimp/1 liter were exposed to the following environmental combinations: Temperatures ( o C): Salinities: ppt (g/ l ) (control) 23 (control) Photoperiod: LD 12:12 (12 hr light/ 12 hr dark) (control) LD 24:0 (24 hr light/0 hr dark) Starvation Experiments Food (frozen alga) Ration: F1: 100% (control) F2: 50% (1/2) F3: 25% (1/4) F1S: 100% every 4 days Replicated twice: 23 o C; 80 ppt; LD 24:0 Brood Size Experiments 2 day-old larvae (N=100) exposed to: -- Temperatures: 18, 23 and 30 o C -- Salinity: 130 ppt -- Photoperiods: LD 12:12 & LD 24:0 Statistical analysis -- % oviparity arcsine √ to normalize -- 3-way ANOVA without replication -- RxC tests of independence G test applied 1) each treatment 2) between each experiments, 3) for pair wise comparisons between proportions of oviparity Environmental Factors Influencing Oviparity in Artemia from the Great Salt Lake Nicole J. Berthelemy-Okazaki 1, Wenbo-Ye 2, and Robert K. Okazaki 1 I. Environmental Effects on Oviparity A. Temperature: Non significant (Fig. 1) Temperature ( o C) Mean (% oviparity) B. Salinity: Non significant among treatments Salinity (ppt)Mean (% Oviparity) C. Photoperiod: Significant (p=0.0) -- LD 24:0: 28% ovoviviparous (Fig. 1) -- LD 12:12: 71% oviparous (Fig. 1) D. Interaction between environmental factors: -- ? Photoperiod modulated by temperature III. Brood Order Effects on Oviparity -- Significant subsequent broods (p<0.001) -- 1 st brood: 14% -- 5 th brood: 90% o ; LD 24:0 II. Starvation Effects on Oviparity -- Non significant between F1 & F2 rations -- Starvation (F3 & F1S)  ovoviparous broods 1 Department of Zoology, Weber State University, Ogden, UT , USA 2 Department of Biology, Shanghai Normal University, Shanghai, PRC Introduction Abiotic factors influencing Artemia reproduction: -- salinity, photoperiod, temperature, influence either cyst or larval reproduction Brine Shrimp Reproduction -- Oviparity: cysted eggs -- Ovoviparous: live larvae Objectives Determine environmental factors influencing cyst production brood size & maturation time Materials & Methods Results IV. Factors Affecting Brood Size A. Temperature & photoperiod effects (Fig. 2) -- Temperature: Significant (p=0) -- LD 24:0; 23 o C: 34 eggs/brood (largest 30 o C: 16 eggs/brood (smallest) 18 o C: 25 eggs per brood B. Starvation: Significant (p=0.002) -- F1 1 st brood: 35 cysts/larvae -- F2 1 st brood: 26 cysts/larvae V. Factors Affecting Maturation Time A. Temperature: Significant (p=0) 18 o C: 46 d 23 o C: 27 d 30 o C: 28 d (Fig. 3) B. Salinity: Significant (p=0) 30 ppt: 41 d 80 ppt: 34 d 130 ppt: 26 d C. Photoperiod: non significant D. Starvation: Significant (p=0) F1: 18 d F2: 29 d F3: 21 d F1S: 32 d Discussion & Conclusions Ecological Considerations -- GSL permanent body of water -- Harsh winter temperatures stress to all life stages except for the cysts -- Cyst formation in GSL may be explained by interaction between photoperiod & temperature -- Larval broods formed predominantly under long photoperiods & cold temperatures -- Long photoperiods & cold temperatures in early months of population cycle (May - June) -- Females switch to oviparity in early fall, shortened photoperiod & cooler temperatures Acknowledgements -- Work & travel for NJB-O funded through Research Scholarship & Professional Growth Committee of Weber State University -- We thank Dr. Samuel Zeveloff for his logistical support & Michael Richardson for his technical assistance Fig. 1 Fig. 2 Fig. 3 RationF1F2F3F1S Brood%n%n%n%n largest producer of brine shrimp cysts Great Salt Lake -- terminal lake; no outlets -- influx of fresh water from several rivers -- evaporation  salinity: : 60 to > 250 ppt km 2 ; 3-9 meters depth 24:0 12: ppt 30 o C23 o C18 o C 30 o C23 o C18 o C % Oviparity # Cysts/Brood o C23 o C30 o C Maturation Time (d)