Quantitative ultrastructure of metal-sequestering cells reflects intersite and interspecies differences in earthworm metal burdens

Bioaccumulation and biological effects in the earthworm Eisenia fetida exposed to natural and depleted uranium

The accumulations of both natural (U) and depleted (DU) uranium in the earthworms (Eisenia fetida) were studied to evaluate corresponding biological effects. Concentrations of metals in the experimental soil ranged from 1.86 to 600 mg kg(-1). Five biological endpoints: mortality, animals' weight increasing, lysosomal membrane stability by measuring the neutral red retention time (the NRRT), histological changes and genetic effects (Comet assay) were used to evaluate biological effects in the earthworms after 7 and 28 days of exposure. No effects have been observed in terms of mortality or weight reduction. Cytotoxic and genetic effects were identified at quite low U concentrations. For some of these endpoints, in particular for genetic effects, the dose (U concentration)-effect relationships have been found to be non-linear. The results have also shown a statistically significant higher level of impact on the earthworms exposed to natural U compared to depleted U.

Subcellular distribution of cadmium in two aquatic invertebrates: change over time and relationship to Cd assimilation and loss by a predatory insect

We set out to determine if the efficiency of cadmium (Cd) assimilation and loss by a freshwater predator (the alderfly Sialis velata) differs when it is exposed, for various lengths of time, to Cd in either an insect (Chironomus riparius) or a worm (Tubifex tubifex). Prey were exposed to Cd in sediments for up to 28 days and then fractionated to measure Cd distributions in their cells. Cadmium subcellular distributions varied little over time for a given preytype but differed substantially between the two prey species; for example, the cytosol comprised a larger proportion of Cd in the insect (76%) than in the worm (34%). The predator assimilated proportionally more Cd from the insect (72%) than from the worm (46%) and these assimilation efficiencies were similar to the proportion of prey Cd that would theoretically be available to it (cytosolic Cd + organelle Cd). However, measurements of Cd in the predator's feces confirmed that to obtain an exact 1:1 relationship between predator assimilation efficiency and prey subcellular distribution we had to assume that approximately 50% of the Cd associated with the organelle fraction of T. tubifex was unavailable for digestion by the predator. Losses of Cd from the predator also varied depending on the type of prey that were the source of its Cd.

Age-related toxic effects and recovery from okadaic acid treatment in Enchytraeus crypticus (Annelida: Oligochaeta)

The effects of 48 h okadaic acid (OA) treatment and the ability to recover the induced toxicological injuries were examined in Enchytraeus crypticus of different ages (25 days and 3 months). The results demonstrated that the older worms are more sensitive to the toxin and show less capacity to recover. After 48 h OA treatment, the structural organization of the chloragogenous tissue appeared modified and associated with an immune response involving a higher number of circulating coelomocytes immunoreactive to anti-IL-6 antibody. The toxin effects were more evident in 3-month-old animals compared to specimens aged 25 days. Regarding the morpho-functional recovery from the induced modifications, first signs of recuperation were observed in younger worms at 48 h, and recovery was almost complete within 1 week. In older animals, the morphology of the chloragogenous tissue had not been restored, while a reduction in coelomocyte number was found after 1 week.