EFFECTS OF LOW MERCURY CONCENTRATION EXPOSURE ON HATCHING, GROWTH ANDSURVIVAL IN THE ARTEMIA STRAIN LA-MATA PARTHENOGENETIC DIPLOID

The effects of exposure to low levels of mercury in the developmental events occurring from hatching to adult life in the Artemia strain La Mata parthenogenetic diploid were studied. Mercury (5, 25, 50, 250 and 500 nM) added at the beginning of incubation had no effect on hatchin g and emergence. We studied mercury effects on the growth of viviparou s nauplii obtained from mothers that had been acclimatised to 25 nM of mercury for all their lives. Measurements of the length of Artemia in dividuals were carried out using video recordings in order to reduce t he stress experienced by the test animals. The mean body length of the mercury-treated group (25 nM) was higher than that of the control ani mals for all times studied. For testing whether the larger size of the mercury-exposed shrimps was due to a greater size at birth or to an i ncreased growth rate, or both, a mathematical model was used. This mod el showed that both initial size (size at birth) and growth rate were higher in the mercury-exposed subpopulation than in the control subpop ulation. However, at this mercury concentration, lifespan is reduced i n the metal-treated group in comparison with the controls. These effec ts may be related to the phenomenon of hormesis and to an increased re productive allocation. (C) 1998 Elsevier Science Inc. All rights reser ved.