Metals in Crawfish - Aquaculture and the Environment: A Shared Destiny - page 209

potential for adverse effects in fish, wildlife, and humans and indicate that further
investigation of human health and ecological risks to include additional exposure pathways
and endpoints is warranted.
A translocation of red swamp crawfish to different sites in the River Guadiamar in
southwest Spain was performed to assess the ability of the species as a bio-indicator of
heavy metal and metalloid pollution (Alcorlo et al, 2006). Crawfish were caged and exposed
to a polluted environment for 6-12 days at three sites with different pollutant
concentrations. Tissue (exoskeleton + gills, hepatopancreas, abdominal muscle) were
dissected and analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) to
assess Cd, Cu, Zn, Pb, and As concentrations. Both exposure times resulted in significant
bio-accumulation of some metals in crawfish tissue versus their environmental
concentration. According to overall metal concentration, crawfish tissue ranked as follows:
hepatopancreas/viscera >exoskeleton/ gills >abdominal muscle. Essential metals for
crawfish metabolism (Cu and Zn) always occur in high concentrations independent of their
environmental concentration due to the ability of crawfish to manipulate concentrations for
their metabolic profit. Metals not involved in crawfish metabolism (Cd, Pb, As) tended to
increase with increasing environmental concentrations and with longer exposure times.
Thus, crawfish could be used as bio-indicator of these pollutants because their dose and
time-dependent accumulation may be reflective of concentrations of nonessential metals in
polluted wetlands. Future guidelines for plans to monitor pollution in Mediterranean rivers
and wetlands should account for implementing crawfish incubation for 6 days and their
subsequent metal content analyses as a routine.
In Spain a study completed using crawfish ( Procambarus clarkii , males and females) that were
exposed simultaneously to Cd and Zn during 21 days (Martin-Diaz et al, 2006). Exposure
concentrations were those determined at the Guadiamar River after the Aznalcollar mining
spill (SW, Spain): 10 and 30 mg/L of Cd and 1000 and 3000 mg/L of Zn. Three biomarkers
(MT: metallothioneins like proteins, VTG: vitellogenin/vitellin like proteins and
histopathology) together with heavy metal bio-accumulation were determined in soft tissues
of male and female crawfish. At the concentrations tested, increasing Cd exposure resulted
in increasing Cd bio-accumulation and increasing sublethal effects (induction of MT, VTG,
and histopathology damage in tissues). Nevertheless, although increasing Zn exposure
showed increasing VTG induction and histopathological damages, a positive relationship
was not determined with MT induction. The only differences found between sexes were at
the highest Cd exposure concentration related to bio-accumulation in hepatopancreas
tissues. Biomarkers responses to heavy metal contamination in this crawfish, even VTG
induction not before tested in heavy metal contamination assessment in crustaceans,
resulted in potential tools for the monitoring of heavy metal environmental contamination.
Biomagnification of some essential metals (Fe, Zn, Cu) and toxic metals (Pb, Ni, Cd, Cr, Co,
Mn) was determined in sediment, three types of fish ( Oreochromis niloticus, Synodonthis,
Clarias gariepinus), and crawfish from the Ondo State coastal region, Nigeria (Asaolu and
Olaofe, 2005). Metal biomagnifications in fish and crawfish was many times greater than in
water; in sediment it was several thousand fold greater than in organisms and water.
Among metals in water, Fe was the most abundant, with average concentrations of 146.7
and 74.3 mg/L in wet and dry seasons, respectively; Co was least abundant at
concentrations of 2.4 and 1.6 mg/L. The Fe concentration was found to have an average