الفهرس 
ACKNOWLEDGMENT
Clastogenic effect of genotoxic agents on aquatic organismsOnly 14 pages are availabe for public view
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Abstract
The mosquitofish (Garnbusia affinis) was introduced into Egypt to control mosquito. This fish has a karyotype with 2n=48 chromosomes, a high initotic activity, a small size which requires only limited space and equipments, in addition to being inexpensive to obtain and care for in the laboratory. Therefore, the present investigation was carried out to explore the possibility of using this fish as a simple cytogenetic system in screening for genetically active water-borne substances that may be mutagenic and or carcinogenic.
The normal karyotype of G.affinis hoolbrooki was studied. It consists of 23 pairs of acrocentric chromosomes along with a small submetacentric pair of chromosomes. No evidence of a heteromorphic sex chromosome pair was noticed in this population of Gambusia collected from El Harafsha canal, Sohag, Egypt.
The LC50 for ametryn was determined to be 12.2 ppm. Fish were exposed to two sublethal concentrations (3.05 and 6.10 ppm) of the herbicide. Exposing the fish to both concentrations of the chemical resulted in a highly significant increase (P<0.001) in the frequency of ch”omosomal aberrations compared with the control. The incidence of chromosomal anomalies tend to increase with the increasing dopage of the herbicide.