Data for: INFLUENCE OF MATERNAL AGE ON THE EFFECTS OF SELENO-L-METHIONINE IN THE MODEL ORGANISM DAPHNIA PULEX UNDER STANDARD AND HEAT STRESS CONDITIONS
We evaluated the influence of maternal age on the effects of seleno-methionine (SeMet) for lifespan, reproduction, and heat-stress resistance in D. pulex. Populations of animals were maintained under previously established laboratory culture protocol conditions. All D. pulex cultures were maintained in COMBO media at a density of 20 animals per 1 L media. COMBO media and Animate stock solutions were prepared as described by Kilham, Kreeger, Lynn, Goulden, & Herrera, 1998. For dose-finding study a total of five SeMet treatment concentrations were analyzed: 0-g SeMet/L, 1-g SeMet/L, 2-g SeMet/L, 4-g SeMet/L, and 8-g SeMet/L. The highest treatment (8-g SeMet/L) is the concentration of SeMet at which 50% of the population were dead (LD 50) in adult Daphnia magna after a 48-hour exposure48. A 50% dilution was applied to obtain the remaining treatments. In the control group (0-g SeMet/L) no additional Se was added. Each SeMet treatment was assessed using a population of n=20 individuals, that were followed as populations throughout their lifespan. Mortality and presence of offspring were recorded throughout the lifespan of each population. Daphnia pulex maternal populations were established from the third brood of our laboratory maintenance D. pulex culture (maternal age ~ 12 days). Neonates ( 24 hours of age; n=80) were obtained from the maintenance population and randomized into four maternal populations. These maternal populations each consisted of n=20 individuals that were housed in 1 L beakers containing 1,000 ml COMBO media and allowed to age under standard laboratory maintenance conditions. All experimental animals exposed to SeMet were obtained from these maternal populations when the mothers were 8-days of age (early life (2nd-3rd) brood) and when the mothers were 32-days of age (late life (12th-14th) brood). For the lifespan analysis, offspring from maternal populations were combined into a single pool from which offspring were randomized into three SeMet treatment groups [(1 maternal population x 3 SeMet treatments) x 25 replicates per SeMet treatment]. This was conducted once when the maternal populations produced an early life brood and repeated when the maternal populations produced a late life brood. For the heat induced stress analysis, offspring were tracked by maternal population. Within the maternal population tracks, offspring were randomized into the three SeMet treatments and housed as populations, creating one experimental group for each maternal population. This was repeated for replicate groups to ensure that each SeMet treatment is assessed in 8 populations for each maternal age group; giving a total of n=24 exposure groups per maternal age [(4 maternal populations x 3 SeMet treatments) x 2 replicates]. Daphnia were submitted to the Virginia-Maryland College of Veterinary Medicine Toxicology Lab for quantification of Se content by atomic absorption spectrometry.