Secondary structure of some elements of 18S rRNA suggests that strongylid and a part of rhabditid nematodes are monophyletic

Abstract

Analysis of the secondary structure of 18S rRNA molecules in nematodes revealed some new traits in the secondary structure peculiar to their hairpin 17. Some of them are characteristics of all the nematodes, whereas others are characteristics exclusively of the order Rhabditida. The loss of a nucleotide pair in the highly conservative region of hairpin 17 distinguishes of 18S rRNA of the Strongylida and some species of the Rhabditida from other nematodes and, moreover, from all other organisms. Hence, it is possible to regard the Strongylida and a part of the Rhabditida including Caenorhabditis elegans as a new monophyletic taxon.