Prof. Ramy R. Avtalion

Theoretical Research

1) Effect of environmental temperature on the immune system of fish, with emphasis on regulatory effects of helper and suppressor functions and the involved cell subsets. This model is currently used to study the mechanism of action of these functions, their kinetics, antagonism, cells subsets and production of specific and non-specific factors.

2) Influence of stress on the immune system. By using fish (tilapia and striped bass) as animal model where stress can be easily induced and defined, the influence of stress on different functions of the immune system (e.g., antibody, phagocytosis, lymphocyte proliferation, natural killer cells) and on resistance to diseases are currently investigated.

3) Sex determination mechanism in tilapias and the crucial role of lethal genes in its regulation. This study is carried out with the BIU-O. aureus gynogenetic line using selected UNH-microsatellite markers.

Applied research

4) Induced immunity and vaccination against agents of 2 important fish diseases: 1) goldfish ulcerative disease (GUD). An efficient vaccine is under development and will be available in the near future; 2) viral encephalitis of tilapia larvae.

5) Chromosome set manipulations in tilapias for the creation of meiotic and mitotic clone. During the last decade, our laboratory has investigated these subjects and different gynogenetic lines and clones were developed. Growth performance and sex ratios of some of these clones were performed in tilapia progenies of interspecific
(O. niloticus female X 0. aureus male) and intraspecific crosses using the communal-test model. Results showed: (1) in all interspecific spawns, whereby male parent was gynogenetic O. aureus, all male progenies were consistently obtained; (2) growth performances highest by 34% in comparison to normal strains. This genetic potential was suggested to be the result of (1) massive removal of defective genes which have been accumulated during the generations, by gynogenetic selection; (2) improvement of this line during many generations at the Laboratory of Fish Immunology and Genetics at Bar-Ilan University.

6) Regeneration of tissues and organs (caudal fins, cardiomyocytes, and spinal cord).