February 15-18, 2009 Washington State Convention Center Seattle ...

ADULT RED SWAMP CRAYFISH (PROCAMBARUS CLARKII): EFFECTS OF SELENIUM
ENRICHED DIET
Maria Cesarina Abete*, Antonia Concetta Elia, Ilaria Giorgi, A.J. Martin Dörr, Stefania Squadrone, Renata Tarasco,
Maria I. Taticchi and Marino Prearo
State Veterinary Institute
Via Bologna
148 - 10154 Turin –Italy
Selenium (Se) as selenocysteine, is a component of selenoproteins, it has an important enzymatic function in animals because
essential for the proper functioning of the antioxidant enzyme glutathione peroxidase. Many studies on selenium have been
conducted in order to investigate dietary requirements, elimination and uptake rates from water and diet sources in organisms
and toxic levels in water. To our knowledge few data are reported for P. clarkii fed with diets enriched in selenium (Elia
et al., 2007; Dörr et al., 2008). The aim of the present study was to evaluate the effect of selenium on the enzymatic activities
of catalase (CAT), glutathione peroxidase (Se-GPx), and glutathione S-transferase (GST) in hepatopancreas of adult P. clarkii
for both sexes, when treated for 15 days with different diets and the Se accumulation in this tissue.
P. clarkii were fed ad libitum with two diets (0.30 and 1.21 mg/kg Se). After 15 days treatment at specific Se concentrations, 10
specimens from each experimental and control tank were transferred immediately live to the laboratory. For the whole sample
hepatopancreas were removed and immediately stored at –80 °C. The determination of selenium was carried out by atomic
absorption spectrometry. The quantification limit (LOQ) is 0.01 ppm (mg/kg). The same samples (0.5 g) were analyzed for
enzyme activities (CAT, Se-GPx and GST) as reported in the literature.
The concentration of selenium in hepatopancreas was 0.47 ppm in treated females and 0.31 ppm in the control, while in treated
males selenium was 0.55 ppm versus 0.37 ppm in control. Crayfish showed a depletion of CAT activity in females and was
about 70% lower compared to the respective untreated samples. An apposite trend was displayed by Se-GPx, lowered only
in treated males (about 40%), compared to the untreated ones. The Se-GPx and CAT are the two enzymes responsible for the
detoxification of hydrogen peroxide (H 2 O 2 ) in biological systems. The results obtained in the present research indicate that both
sexes of P. clarkii responded differently under a high selenium treatment.
Therefore, the marked low activities of CAT in females and GPx in males might be the result of a compromised oxidative
stress status with a consequent decline of the protection toward the prooxidant effect of Se in both sexes. Most probably the
reduction of these activities could be correlated with the different regulation of enzymes expression between sexes under Se
treatment. GST enzyme, which has the role to detoxify from electrophylic compounds, was not affected by the high selenium
diet treatment. Even if higher activity was recorded in both treated sexes, it was not statistically different compared to their
own controls. Therefore, GST activity was not a sensible marker to detect the Se-prooxidant effect at this experimental condition.
The antioxidant response under selenium exposure might be largely variable depending on species, experimental times,
selenium species and concentrations. In conclusion, these preliminary results indicate that males and females of adult P. clarkii
show a different susceptibility to Se-dietary treatment. More data will be necessary to make more clear the effect of selenium
on these antioxidant enzymes in crayfish.