LAUSR

Mitotic chromosomal aberrations and DNA polymorphism (RAPD-marker) was conducted on the same population of Nile tilapia Oreochromis niloticus populations collected from five sites in Minia governorate- Egypt as in Abu Shnaf et al., (2021) to test the applicability of them as biomonitors for heavy metals water contaminants. The diploid chromosome number of O. niloticus population was 2n= 44. Different types of chromosomal aberrations were recorded such as (Deletion, ring, centromeric attenuation, end-to - end association, dicentric chromosome, stickiness chromosome, endomitosis, fragments and chromatid gap). The chromosomal aberrations varied between O. niloticus population collected from five sites and the most common type was ring (R) chromosomes. Samples obtained from Bahr Yousef and Irrigation drain exhibited the highest aberration frequency. The frequency of chromosomal aberration was positively correlated with the concentration of heavy metals where heavy metals concentration in surface water of Irrigation drain and Bahr Yousef exceeded the limits defined by WHO as well as the concentration of (Pb) in muscles (Abu Shnaf et al., 2021). The RAPD marker was also used to identify genetic variation among Nile tilapia samples collected from five different water sources. It created polymorphic and unique bands that can be used as genetic markers to track DNA variations. The dendrogram also reveals that exposure to heavy metal pollution causes gradual accumulation of variance, whereas areas subjected to environmental stress showed higher genetic variation and clustered together. This article is protected by copyright. All rights reserved.