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RESEARCH PRODUCT

Effects of low mercury concentration exposure on hatching, growth and survival in the Artemia strain La Mata parthenogenetic diploid

subject

description

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 hatching and emergence. We studied mercury effects on the growth of viviparous nauplii obtained from mothers that had been acclimatised to 25 nM of mercury for all their lives. Measurements of the length of Artemia individuals were carried out using video recordings in order to reduce the stress experienced by the test animals. The mean body length of the mercury-treated group (25 nM) was higher than that of the control animals 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 increased growth rate, or both, a mathematical model was used. This model showed that both initial size (size at birth) and growth rate were higher in the mercury-exposed subpopulation than in the control subpopulation. However, at this mercury concentration, lifespan is reduced in the metal-treated group in comparison with the controls. These effects may be related to the phenomenon of hormesis and to an increased reproductive allocation.