ABSTRACT
Spathopsis rubens is freshwater bivalves distributed in the Nile River and its main canals all over Egypt.Four populations of S. rubens on Al-Mahmoudia irrigation canal at Damnhour, Egypt were collected andinvestigated for morphometric characters and genetic diversity by using inter simple sequence repeats (ISSR).The results declared that both the length and height measurements of the collected samples from the differentlocations showed slight significant differences; however, no significant differences between the total weightand the width of the samples have found. High degree of correlation between temperature and total weight,height and length was reported in samples collected from the third location. Genomic DNA from the selectedsamples of each population was extracted and amplified using 10 ISSR primers. The primers (M2, M3, M8,M12, M17, F2, F4, and F9) showed 100% polymorphism. Unweighted pair group method with arithmetic meandendrogram characterized the samples of S. rubens into two main definite clusters. The cluster of genotypes2 and 3 recorded the highest similarity and distance indices at a distance of 0.60859, while genotypes 1 and 3recorded the lowest similarity and distance indices at a distance of 0.1716.