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Abstract
Nowadays, it is well established that sources of drainage (municipal, industrial and agriculture) cause bad alterations (physical and chemical) to waters of seas, lakes and rivers leading to variable degrees of pollution. Such alteration in water quality may influence most aquatic living organisms, especially the sensitive species. The pollution impacts of water may act either by weakening these species gradually, leading finally to their disappearance or/and by pushing them to escape to the less polluted zones hence they display a limited distribution. from the sensitive fish species are Lates niloticus, Bagrus bayad, Chrysichthys rueppelli, Sarotherodon galilaeus, Cyprinus carpio and Tilapia zillii.
At the same time, there are some freshwater fish species which can live in such polluted zones, where they have a high ability to tolerate the serious conditions of pollution (ex., Clarias gariepinus, Oreochromis niloticus and O. aureus).
The aim of the present study was to change one of the sensitive fish species to tolerate pollution conditions. This goal accomplished via two directions; firstly, the mass selection by selecting the powerful members that could live in a serious environmental conditions amongst a lot numbers of this species. Secondly, by using a high advanced technique methods of gene transfer from species of high ability to live in serious conditions to another sensitive one.
The gene tolerated system may be transferred from the pituitary glands of high tolerant species C. gariepinus which can lives in a high degrees of pollution into S. galilaeus of the present study, then the following generations were checked in the same polluted zone (El-Genka zone, Lake Manzala).
However, the whole work may be summarized in the following:
1- Analysis of the water of locations (I, II, III, IV and V) of El-Genka zone and the reference area (El-Salam Canal - loc. VI) including some physical and chemical parameters (temperature, turbidity, pH, DO, NH3, NO2.N and H2S).
2- Estimation of some heavy metals contents (lead, cadmium, copper and zinc) in waters of El-Genka zone and El-Salam Canal (as reference area), as well as determining the accumulation of these elements in some organs (muscle, gills, brain, kidney and liver) of three freshwater fish species present in El-Genka zone (Clarias gariepinus, Oreochromis aureus and O. niloticus).
3- Determination whether the following freshwater fish species (Lates niloticus, Bagrus bayad, Chrysichthys rueppelli, Sarotherodon galilaeus, Cyprinus carpio, Tilapia zillii, Oreochromis aureus, O. niloticus and C. gariepinus) were influenced with the pollution or not. The nine fish species were arranged them in an order according to their tolerance in high polluted zones depending on the duration period as living, throughout two experiment (Exp. 1 & Exp. 2) in the three trips.
4- Choosing one sensitive fish species to pollution (S. galilaeus) and trying to strength it and introducing it again in the polluted zones by means of two ways:
a) The classic mass selection, that had been achieved throughout the two experiments (Exp. 2 and Exp. 3).
b) Gene transfer, by trying of transferring some genes concerned with the protection of the fishes against pollution via injecting genome (DNA fragments) of pituitary glands of C. gariepinus inside the peritoneal cavity of S. galilaeus throughout experiment (Exp. 4).