Objective To study the effects of long-term tritiated water exposure on the growth and development of zebrafish offspring.
Methods Embryos produced by wild-type AB strain zebrafish were exposed to 0, 1×102, and 1×105 Bq/L tritiated water for long-term feeding as parents (F0 generation). After their sexual maturity, they reproduced, and the offspring obtained were recorded as F1 generation. The F1 generation zebrafish continued to be raised in tritiated water concentrations corresponding to the F0 generation. We observed the growth and development of F1 generation zebrafish and detected autonomous movement and heart rate during the embryonic stage; hatching rate, body length, and reactive oxygen species (ROS) fluorescence intensity during the seedling stage; total superoxide dismutase (T-SOD), malondialdehyde (MDA), and total tritium contents during the juvenile stage; and egg production during the adult stage. The t-test was used for intergroup comparison of various detection indicators(equal variance).
Results The hatching rates of the three groups of zebrafish in F1 generation were (90.66±0.05)%, (85.63±0.10)%, and (78.06±0.15)%. Compared with the 0 Bq/L tritiated water exposure group, no statistically significant difference was found in the hatching rate of F1 zebrafish between the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.785, 1.370; P=0.462, 0.220). The number of autonomous movement of the three groups of zebrafish in F1 generation at 24 h after fertilization was (12.93±2.70), (11.30±0.78), and (10.50±0.80) times/min. Compared with the 0 Bq/L tritiated water exposure group, we observed no statistically significant difference in the number of autonomous movements of F1 generation zebrafish at 24 h after fertilization in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=1.008, 1.499; P=0.370, 0.208). The number of autonomous movement of the three groups of zebrafish at 36 h after fertilization was (3.63±1.43), (4.50±1.15), and (5.40±3.55) times/min. Compared with the 0 Bq/L tritiated water exposure group, we found no statistically significant difference in the number of autonomous movement of F1 generation zebrafish at 36 h after fertilization in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.817, 0.799; P=0.460, 0.469). The heart rates of the three groups of zebrafish at 48 h after fertilization were (59.43±6.93), (65.00±3.30), and (61.23±4.55) times/20 s. Compared with the 0 Bq/L tritiated water exposure group, we observed no statistically significant difference in the heart rate of F1 generation zebrafish at 48 h after fertilization in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=1.256, 0.376; P=0.278, 0.726). The heart rates of the three groups of zebrafish at 60 h after fertilization were (69.87±2.71), (66.17±6.97), and (69.77±9.08) times/20 s. Compared with the 0 Bq/L tritiated water exposure group, we found no statistically significant difference in the heart rate of F1 generation zebrafish at 60 h after fertilization in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.857, 0.018; P=0.440, 0.986).The body lengths of the three groups of zebrafish at 72 h after fertilization were (3.20±0.22), (3.32±0.08), and (3.29±0.06) mm. Compared with the 0 Bq/L tritiated water exposure group, no statistically significant difference was noted in the body length of F1 generation zebrafish at 72 h after fertilization in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.614, 0.178; P=0.525, 0.868). The body length of the three groups of zebrafish at 84 h after fertilization were (3.42±0.07), (3.46±0.11), and (3.40±0.04) mm. Compared with the 0 Bq/L tritiated water exposure group, no statistically significant difference was observed in the body length of F1 generation zebrafish at 84 h after fertilization in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.527, 0.496; P=0.626, 0.646). The ROS fluorescence intensities of the three groups of zebrafish in F1 generation were (21.07±4.74), (23.71±7.73), and (23.19±5.32), respectively. Compared with the 0 Bq/L tritiated water exposure group, there was no statistically significant difference in ROS fluorescence intensity of F1 generation zebrafish seedlings in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.582, 0.593; P=0.582, 0.575). The T-SOD contents of the three groups of zebrafish in F1 generation at 45 days were (41.84±4.91), (42.30±5.04), and (36.97±5.26) U/mgprot. Compared with the 0 Bq/L tritiated water exposure group, we found no statistically significant difference in the T-SOD content of F1 generation zebrafish at 45 days in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.112, 1.171; P=0.916, 0.307).The T-SOD contents of three groups of zebrafish at 60 days were (36.93±1.91), (34.07±3.02), and (33.54±1.87) U/mgprot. Compared with the 0 Bq/L tritiated water exposure group, there was no statistically significant difference in the T-SOD content of F1 generation zebrafish at 60 days in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=1.397, 2.195; P=0.240, 0.093). The MDA contents of the three groups of zebrafish at 45 days were (3.60±1.56), (3.59±0.44), and (2.95±0.58) nmol/mgprot. Compared with the 0 Bq/L tritiated water exposure group, we found no statistically significant difference in the MDA content of F1 generation zebrafish at 45 days in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.007, 0.677; P=0.995, 0.536). The MDA contents of the three groups of zebrafish at 60 days were (4.00±0.52), (4.19±1.37), and (3.01±0.32) nmol/mgprot. Compared with the 0 Bq/L tritiated water exposure group, there was no statistically significant difference in the MDA content in F1 generation zebrafish at 60 days in the 1×102 Bq/L tritiated water (t=0.229, P=0.830); the difference in the MDA content in F1 generation zebrafish exposed to 1×105 Bq/L tritiated water was statistically significant (t=2.831, P=0.047). The eggs laid by the three groups of zebrafish in F1 generation were 188±88, 204±22, and 220±40. Compared with the 0 Bq/L tritiated water exposure group, we found no statistically significant difference in the egg production of F1 generation zebrafish in the 1×102 Bq/L and 1×105 Bq/L tritiated water exposure groups (t=0.400, 0.757; P=0.700, 0.477). The tritium content in the body of F1 generation zebrafish was (32.23±1.97) Bq/g at 60 days.
Conclusion Long-term exposure to 1×105 Bq/L tritiated water can lead to the accumulation of tritium in F1 generation zebrafish.
DownLoad: