African Journal of Biotechnology Vol. 4 (5), pp. 449-459, May 2005          
ISSN 1684–5315 © 2005 Academic Journals

Full Length Research Paper

Application of biotechnology in fish breeding. II: production of highly immune genetically modified  redbelly tilapia, Tilapia zillii

Samira S. Assem¹ and Samy Y. El-Zaeem²

¹National Institute of Oceanography and Fisheries, Kayt Bey, Alexandria, Egypt.

²Animal and Fish Production Department, Faculty of Agriculture, (Saba-Bacha) Alexandria University, Alexandria, Egypt.

*Corresponding author.  E-mail: selzaeem@yahoo.com. Tel: 2-045-3349473; Fax: 2-03-5832008.

Accepted February 18, 2005

The present study aims to produce a highly immune, genetically modified redbelly tilapia, Tilapia zillii with accelerated growth as a result of direct injection of shark (Squalus acanthias L.) DNA into skeletal muscles of fish fingerlings at concentrations of 10, 20, 40 and 80 µg/fish. The results showed that the fish injected with 40 µg/fish had significant (P≤0.05) superiority of growth performance. Also, the body composition of these fish was improved. The fish injected with 20 and 40 µg/fish had significant (P≤0.05) higher means of total antibody activity (total IgM), serum total protein and globulin compared with other injected groups. Cytological examination for all injected fish and their control revealed the same diploid number (2n=44) of chromosomes, and no chromosomal abberations were detected. Moreover, DNA fingerprinting showed high polymorphism among injected fish. Therefore, variable fragments of shark DNA may randomly integrated into T. zillii muscle genomes. The present investigation revealed also that egg diameters of injected females and their control were divided into nine groups, which varied between 0.2 and 1.7 mm. In addition, ovary of T. zillii females injected with 10; 20; 40 and 80 µg/fish of shark DNA showed 10, 38, 65 and 18% normal oocytes, respectively. Also, test of males injected with various amounts of DNA showed large number of abnormalities. Moreover, the comparison between all injected fish revealed that the testes and ovaries of fish injected with 80 µg/fish were more deformed and atretic. This means that the effects of intramuscular direct injection of foreign DNA into T. zillii could be limited to germ cells of fish. Therefore, further studies about the establishment of these effects on the following generations are needed. The result indicates a possible easy and rapid way for improving fish characteristics.

Key words: Genetically modified, highly immune, accelerated growth, Tilapia zillii, shark DNA, molecular alterations, chromosome investigations, oocyte diameter, gonad histological changes.