A number of studies showed that rock oysters can accumulate higher levels of Cd in tissues, much higher than that in other mussel species collected at the same sites. Despite these higher levels of Cd however, they survive. So, why can rock oysters retain higher levels of Cd in their body and what biological mechanisms can explain that? Thank you.
Many factors influence the accumulation of cadmium in rock oysters, like, their size-weight, sex, sampling season etc. The physical and chemical properties of their habitat also may be a factor. Their capacity for Cd accumulation may change with respect to their age and seasonal variations in their flesh weight.
In general, variability in bioaccumulation among species is a function of their rate of accumulation (e.g. ventilation or passing water over the gills), rate of elimination, and their ability to sequester metals internally (for example metallthionein and other mechanisms of sequestration and compartmentalization). Surprisingly, these parameters can be quite different among species that are expected to exhibit similar results. For those species that are able to sequester metals internally, these high tissue concentrations are not available to cause toxicity because they are “locked up” with other molecules and rendered non-toxic.
Dear Chindu. Thank you. I absolutely agree that many factors influence Cd accumulation in not only oysters but also other mussel species. However the point is why oyster can retain extremely Cd in its tissues without dysfunction or die. I understood that when Cd enter animal' tissues as a signal to induce metallothoinein synthesis to bind Cd and reduce the toxic of Cd or Cd can also be sequestered in specific molecular. However to explain more detail for the case of Cd accumulation in oyster is limit information available or may be I have not found the good references yet.
Dear James. Thank you. You're right, you mentioned what I am looking for the references to explain more detail in my query. I found some papers related to oyster or other mussel studies but they also explained in general. Actually, I want to know more specific mechanism of the different Cd accumulation between oyster and other mussels such as clam or green or blue mussel. Because we may know that Cd level in oyster is extremely high and much higher than that in other mussels at the same sampling site. With such level of Cd retaining in oyster, other species can be died or dysfunction, but oyster may be OK and normally lay eggs.
I am sorry if my query is not clear . Thank you.
i think it depend on the filtering capacity of this mussel and of course the size of those organisms.
I am completely with James. The body (or tissue) concentration of metals depends on accumulation and excretion capability and on the organism's capacity to compartementalize the metals in a bioavailable and bioinavailable fraction. The latter does not cause toxicity in the organism, although it can be released into the bioavailable fraction as a function of time and environment (e.g. Cd in smokers is released to the bioavailable fraction in the kidney after many years). The amount a given species can accumulate can be highly variable among species, even if they are closely related. As far as I know in the vast majority of cases there is no way to predict this. Good measurement starting with accumulation and depletion curves is essential.