rDNA (18S-28S and 5S) colocalization and linkage between ribosomal genes and (TTAGGG)n telomeric sequence in the earthworm, Octodrilus complanatus (Annelida: Oligochaeta: Lumbricidae), revealed by single- and double-color FISH

Abstract

Spermatogonial and metaphase I chromosomes of the lumbricid earthworm Octodrilus complanatus (Annelida: Oligochaeta) were examined using fluorescent in situ hybridization (FISH) with three repetitive DNA probes - 5S rDNA, 18S-26S rDNA, and (TTAGGG)n. Single-color FISH consistently mapped one chromosome pair per spread using either 5S rDNA or 18S-26S rDNA as probes. Simultaneous (18S-26S)-5S and (18S-26S)-(TTAGGG)n FISH demonstrated that repeated units of the two ribosomal families were overlapped and closely associated with telomeric sequences.