[Investigation on polymorphism of mitochondrial genome in Cobia fish Rachycentron canadum in the northern waters of the Persian Gulf and Oman Sea]

Background and Aim: Given the nutritious value of Cobia and its importance in terms of rapid growth in cultural conditions and noticeable commercial value, along with lack of sufficient literature in this regard, this study was run to investigate genomic polymorphism of this species in southern waters of Iran in 2010. The study aimed at enlightening genetic variation and determining its rate inside and between probable populations

Materials and Methods: This cross sectional study was carried out on 120 specimens of Cobia which were randomly obtained from four southern Iranian provinces. Two-gram cuts of fin tissue of each fish were transferred to the laboratory in 2 ml microtubes containing ethanol. DNA was extracted by Phenol-chlorophorm method and genomic polymorphism investigation was carried out by PCR-RFLP method. In this method, PCR product of COI mitochondrial gene were enzymatic digested using 6 Restriction Enzymes

Results: PCR product of mitochondrial gene COI was obtained in length of 1060 base pair and 6 polymoiphic sites were investigated. But electrophoresis patterns of enzymatic digestion products were monomorphous in all samples and no polymorphism was observed

Conclusion: Lack of genetic diversity or its noticeable decrease in regions where fish can freely migrate and move between two regions has been reported. Due to lack of physical and biological obstacles Dobia is able to migrate to all parts of the Persian Gulf and Oman Sea. Therefore, lack of polymorphism in the studied Cobia population seems to be logical. Future studies with larger samples and more enzymes from other genetic regions are recommended

response of plasma glucose, lactate, protein and hematological parameters to osmotic challenge in common carp [cyprinus carpio]

Fluctuations in salinity impose stress on the physiology of the exposed fish population and can modify their structure. It has been noted that changes in blood characteristics and plasma levels serve as the primary link between environmental change and physiological response [McCormick, 2001]. Ninety healthy adult Cyprinuscarpio [C. carpio] were randomly divided into five groups and kept in salinities of 1 [control group], 3, 6, 9, 12 and 15 g/L The salinity was gradually increased by 3 g/L daily to final their concentrations. Fish were kept for 14 days after transference to the final salinity. Subsequently, plasma glucose, lactate, and protein content, as well as hematological parameters, were evaluated. The highest hematocrit [Hct], hemogloblin level [Hb], red blood cell count [RBC], lactate, and glucose values were found fish kept in the highest salinity. The values of the white blood cell count [WBC] showed an initial increase in fish from the control group until a salinity of 9 g/L, but subsequently decreased at higher salinities. The plasma protein levels among the fish in different groups did not show a significant change. The results demonstrate that changes in blood parameters can be used as indices to monitor the effects of salinity on the physiology of C. carpio