Physical mapping of rDNA genes, (TTAGGG)(n) telomeric sequence and other karyological features in two earthworms of the family Lumbricidae (Annelida : Oligochaeta)

A cytogenetical study was carried out on the chromosomes and nuclear DNA am ounts of the terrestrial earthworms Octodrilus complanatus and Eisenia foet ida (Annelida: Oligochaeta: Lumbricidae). Chromosomes were studied using Gi emsa staining, banding methods and fluorescent in situ hybridization (FISH) with two repetitive DNA probes [rDNA and (TTAGGG)(n)]. rDNA FISH and silve r staining consistently identified one chromosome pair per spread in both s pecies. The telomeric sequence (TTAGGG)(n) hybridized with termini of all t he chromosomes in both earthworms. Flow cytometry DNA assays showed that O. complanatus and E. foetida had different nuclear DNA contents (2C value = 1.72 and = 1.40 pg, respectively) but very similar base composition in thei r genomes.