الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Tilapias fish belong to the family Cichlidae and are found in freshwater and brackish water in Africa. The Egyptian species members of family Cichlidae are: Oreochromis niloticus, Tilapia zillii, Sarotherodon galilaeus, and Oreochromis aureus. Tilapia are freshwater fish that live mainly in shallow waters, ponds, rivers, and lakes, which less commonly live in saltwater. Tilapia zillii have been shown to be adaptable in most water sources, including high salinity and low temperatures. It is also known for their aggressive behaviour against some other species such as Oreochromis niloticus which are known for their high economic importance. Thus, the study aimed to investigate the population structure, distribution and invasiveness of T. zillii in the Egyptian water bodies.
Samples were randomly collected from seven different locations along the Nile water stream and divided into groups according to the water system (closed, open, semi-closed) and the type of water (fresh, brackish), to: 1) determine population structure and haplotype diversity of T. zillii using the mitochondrial D-loop region as a non-coding region where mutations can be accumulated; 2) study the flow and distribution of genes and genetic differentiation of these population structures; and 3) frame the possible invasive network among sampled locations to understand its invasiveness to Tilapia aquaculture in Egypt.
Through the population genetic approach, sequences were analysed using several bioinformatics programs. A total of 30 variable sites out of 437 bp were detected. The brackish water system showed the highest number of different haplotypes and 12 mutations were detected, while the freshwater system submitted the highest numbers of haplotype diversity and eight mutations were detected.The open water system recorded (e.g. Lake Nasser, El Qanater el Khaireya) five different haplotypes, and six mutations.While the semi-closed water system (e.g. Mariouteya, Edku Lake, Max Bay, Lake Burullus, Siro, Suez Canal) recorded 11 different haplotype and 14 mutations, Closed water (e.g. Ismailia farms, Lake Qaroun) one different haplotype.
According to the MJ haplotype network, Nasser lake was found to be the most diverse location in Egypt and considered to be a water gateway to the rest of the location. The TzHap2 haplotype was found unique to three lakes in northern Egypt on the coast (MX, IL, and BL) and (TzHap6) was a unique haplotype of Qaroun lake which is characterized by the ability to withstand high and toxic salinity levels in this lake. According to the results of AMOVA test, the sampled locations were less differentiated by the water system (open-open, open-close or close-close) than by water type (freshwater or brackish). This reflects the importance of salinity level in the distribution of the fish genotypes and is could be considered as a key factor that affect the fish migration, which gave a low FST value and a high value of gene flow Nm. The result indicated the existence of several genetic structures of these invasive species and their ability to coexist and adapt in areas with high salinity, brackish and freshwater. The invasiveness to this species was not affected by the geographic barriers due to the human impact and its influence on the distribution intentionally or mistakenly to more isolated habitats. In conclusion, the water type naturally influenced the distribution of this invasive species, while the contribution of the water system influence was only significant when the human impact was presented (e.g. O. niloticus hatchery marketing).