RESUMEN
The effect of magnetic water on some biological parameters of B. Alexandrina was investigated. The growth rate, egg laying capacity, hatchability of deposited eggs, development of the newly hatched snails and the mortality rate of the treated snails [maintained in magnetic water for 12 weeks] were determined and compared with control ones maintained in normal water. The mean length of the diameter of treated snails after 12 weeks exposure to magnetic water [6.8 +/- 0.93] was slightly greater than the control group [6.4 +/- 0.8]. Also, a highly significant increase in number of eggs and egg-masses of treated snails [8.06 +/- 6.55 and 1.14 +/- 0.8, respectively] as compared with controls [2.5 +/- 1.2 and 0.33 +/- 0.14, respectively]. Hatchability rate of treated eggs in magnetic water for a period of 5 days was higher [63.4%] than the control group which recorded 28.2%. However, a highly significant reduction in the survival rate of newly hatched snails [22.5%] maintained in magnetic water for another 7 days after hatching as compared with the control [61.5%]. Also a highly significant reduction in the survival rate of adults in magnetic water for 12 weeks which recorded 40% in contrast with the control ones, recorded 88%, [P<0.001]. There was slight decrease in the calcium content of the shells of treated snails [25.44% of wt.] as compared to controls [29.58% of wt.]. The haermaphrodite gland acini of snails in magnetic water for 12 weeks were most frequently in final stages of oogensis and spermato-genesis. There were a significant increase in the mean number of 2ry oocytes and mature ova in acini of treated snails comparing with the control group [P<0.05]