Maternal transfer of inorganic mercury and methylmercury in aquatic and terrestrial arthropods

The transfer of mercury from females to their offspring plays an important role in mercury accumulation and toxicity during early development. To quantify the transfer of inorganic mercury and methylmercury from female arthropods to their eggs, the authors collected and analyzed brine shrimp (Artemia franciscana), wolf spiders (Alopecosa spp.), and their attached eggs from aquatic and terrestrial ecosystems at the Great Salt Lake, Utah, USA. Essentially all of the mercury in both the female brine shrimp and their eggs was methylmercury (94 ± 17% and 90 ± 21%, respectively). The brine shrimp eggs had methylmercury concentrations that were 84 ± 2% lower than in the females, reflecting the fact that females transferred 45 ± 4% of their total body mass but only 11 ± 3% of their methylmercury burden to their eggs. As a result of this sequestration, the concentration of methylmercury in the female brine shrimp increased by 62 ± 8% during egg formation. The percentage of the total mercury that was methylmercury in female wolf spiders (77 ± 21%) was similar to that in their egg masses (81 ± 19%), indicating similar maternal transfer efficiencies for inorganic mercury and methylmercury in these invertebrates. The concentration of inorganic mercury and methylmercury in the female spiders was the same as in their eggs. These arachnids transferred 48 ± 9% of their total body mass, 55 ± 13% of their inorganic mercury, and 50 ± 9% of their methylmercury to their egg masses. Thus, female wolf spiders do not have the ability to reduce the transfer of methylmercury to their eggs, nor does this process represent an important pathway for the depuration of mercury. The present study demonstrates that although some arthropods have mechanisms to minimize the transfer of methylmercury to their eggs and reduce the potential for mercury toxicity during early development, other arthropods do not.