INSIGHTS ON THE DIVERSITY WITHIN A SPECIES OF THALASSICOLLA (SPUMELLARIDA) BASED ON 16S-LIKE RIBOSOMAL-RNA GENE SEQUENCING

We compared 16S-like ribosomal RNA (rRNA) coding regions of samples of the solitary spumellarian radiolarian Thalassicolla nucleata collecte d from the Sargasso Sea and the Pacific Ocean. Sequences derived from these locations showed variability in both length and base-pair compos ition. This level of sequence variability is similar to the degree of variability reported in the literature for species- or even genus-leve l distinctions. Explanations for our results include multiple alleles for the rRNA gene, or the existence of multiple species of Thalassicol la that are morphologically indistinguishable. The seven existing desc riptions of Thalassicolla species, including T. nucleata, are discusse d in view of these molecular findings and with reference to our curren t understanding of the physiology and life cycle of the spumellarian r adiolaria.