Cytogenetic Studies on Metaphase Chromosomes of Six Bivalve Species of Families Mytilidae and Veneridae (Nucinelloidea, Mollusca)

Chromosomes of 6 bivalve species were studied from mitotic metaphases using cell suspension techniques. Among Family Mytilidae, Modiolus barbatus (Linnaeus 1758) has a diploid chromosome number of 2n=32 with 5 metacentric, 2 submetacentric, 5 subtelocentric and 4 telocentric chromosome pairs, Septifer excisus (Wiegmann 1837) has 2n=26 with 9 metacentric, 2 submetacentric, and 2 telocentric chromosome pairs and Septifer bilocularis (Linnaeus 1758) also has 2n=26 with 8 metacentric, 2 submetacentric and 3 subtelocentric chromosome pairs. Among Family Veneridae, Ruditapes decussatus (Linnaeus 1758) has 2n=38 with 6 metacentric, 5 submetacentric, 3 subtelocentric and 5 telocentric chromosome pairs, Circe scripta (Linnaeus 1758) has 2n=38 with 6 metacentric, 6 submetacentric, 4 subtelocentric and 3 telocentric chromosome pairs and Venus verrucosa (Linnaeus 1758) has also 2n=38 with 7 metacentric, 4 submetacentric, 4 subtelocentric and 4 telocentric chromosome pairs. These results are reported for the first time in Egypt.