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.

本研究针对蚤状溞（D. pulex），评估了母体年龄对硒代蛋氨酸（seleno-methionine, SeMet）在其寿命、繁殖能力及耐热胁迫抗性方面所产生效应的影响。所有实验动物种群均按照已确立的实验室培养规程进行饲养。所有蚤状溞培养体系均采用COMBO培养基进行培养，种群密度设置为每1升培养基中饲养20只个体。COMBO培养基与Animate储备液的配制方法参照Kilham等（1998）发表的方案进行。
在剂量探索实验中，共设置了5个硒代蛋氨酸处理浓度：0 μg SeMet/L、1 μg SeMet/L、2 μg SeMet/L、4 μg SeMet/L及8 μg SeMet/L。其中最高处理浓度（8 μg SeMet/L）为大型溞（Daphnia magna）成体经48小时暴露后的硒代蛋氨酸半数致死浓度（LD₅₀），相关数据引自文献48。其余浓度通过对该最高浓度进行50%梯度稀释获得。对照组（0 μg SeMet/L）不额外添加硒元素。每个硒代蛋氨酸处理组均采用n=20只个体组成的种群进行评估，并对该种群的整个生命周期进行追踪观测。在每个种群的整个生命周期中，记录其死亡率及子代产生情况。
本研究的蚤状溞母本品系取自实验室饲养种群的第三胎幼体，此时母体年龄约为12天。从饲养种群中获取日龄≤24小时的新生幼体（n=80），并将其随机分为4个母本品系种群。每个母本品系种群包含20只个体，饲养于盛有1000 mL COMBO培养基的1 L烧杯中，并按照标准实验室饲养规程进行培养直至成熟。所有接受硒代蛋氨酸处理的实验动物均取自上述母本品系种群，分别在母体8日龄（处于生命早期，对应第2-3胎）及32日龄（处于生命晚期，对应第12-14胎）时获取幼体。
在寿命分析实验中，将各母本品系种群产生的幼体合并为一个混合种群，随后将其随机分配至3个硒代蛋氨酸处理组：（1个母本品系种群 × 3个硒代蛋氨酸处理组）× 每个处理组25个重复。该实验分别在母本品系种群产生生命早期幼胎及晚期幼胎时各开展一次。
在热诱导胁迫分析实验中，幼体按照母本品系种群进行分组追踪。在每个母本品系种群的追踪组内，将幼体随机分配至3个硒代蛋氨酸处理组并以种群形式饲养，由此每个母本品系种群对应一个实验组。该实验通过设置重复组进行重复，以确保每个母体年龄组的每个硒代蛋氨酸处理组均有8个种群样本；最终每个母体年龄组共设置n=24个暴露组：（4个母本品系种群 × 3个硒代蛋氨酸处理组）× 2个重复。
所有蚤状溞样本均送至弗吉尼亚-马里兰兽医学院毒理学实验室，采用原子吸收光谱法对其硒元素含量进行定量检测。