title: Unusual intraindividual variation of the nuclear 18S rRNA gene is widespread within the Acipenseridae.
abstract: Significant intraindividual variation in the sequence of the 18S rRNA gene is unusual in animal genomes. In a previous study, multiple 18S rRNA gene sequences were observed within individuals of eight species of sturgeon from North America but not in the North American paddlefish, Polyodon spathula, in two species of Polypterus (Polypterus delhezi and Polypterus senegalus), in other primitive fishes (Erpetoichthys calabaricus, Lepisosteus osseus, Amia calva) or in a lungfish (Protopterus sp.). These observations led to the hypothesis that this unusual genetic characteristic arose within the Acipenseriformes after the presumed divergence of the sturgeon and paddlefish families. In the present study, a survey of nearly all Eurasian acipenseriform species was conducted to examine 18S rDNA variation. Intraindividual variation was not found in the polyodontid species, the Chinese paddlefish, Psephurus gladius, but variation was detected in all Eurasian acipenserid species. The comparison of sequences from two major segments of the 18S rRNA gene and identification of sites where insertion/deletion events have occurred are placed in the context of evolutionary relationships within the Acipenseriformes and the evolution of rDNA variation in this group.
authors.affiliation: Department of Ecology and Evolutionary Biology, Brown University, 80 Waterman Street, Providence, RI 02912, USA. jkrieg@frontiernet.net
authors.forename: Jeannette
authors.initials: J
authors.lastname: Krieger
authors.forename: Anne Kathrin
authors.initials: AK
authors.lastname: Hett
authors.forename: Paul A
authors.initials: PA
authors.lastname: Fuerst
authors.forename: Vadim J
authors.initials: VJ
authors.lastname: Birstein
authors.forename: Arne
authors.initials: A
authors.lastname: Ludwig
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics*; D017931:DNA Primers; D005399:Fishes / Q000235:genetics*; D014644:Genetic Variation; D012336:RNA, Ribosomal, 16S / Q000235:genetics*
chemical_list: D017931:DNA Primers; D012336:RNA, Ribosomal, 16S