Genetic characterization of Argentinean Artemia species with different fatty acid profiles

Abstract

The Anostracan genus Artemia is composed by several sibling species reproductively isolated, but identical or very similar in outward appearance. The genus shows also an underlying striking variability from the biochemical point of view, regarding especially the fatty acid profile of the cysts and nauplii. In Argentina, Artemia is represented by two bisexual species: A. franciscana and A. persimilis. Former studies have shown that A. franciscana is present in northern of 36º and that A. persimilis is constrained southwards of 37° S. In general, there is good agreement between morphological and cytogenetic comparisons of Argentinean populations with respect to species discrimination. However, new Argentinean Artemia populations are being analyzed morphologically and it becomes necessary to further investigate if the genetic adscription of these populations is congruent with the results obtained from the current morphological analyses. Restriction fragment length polymorphism (RFLP) analysis of a fragment of the 16S rRNA mitochondrial gene was used to investigate the genetic diversity and population structure of 10 new Artemia populations from Argentina. The mitochondrial DNA (mtDNA) results showed a similar pattern to that of previous cytogenetic and morphological analyses with the two Argentinean species appearing as highly divergent. The presence of A. persimilis in southern Argentina and the southernmost Chilean population was confirmed unveiling a novel picture of species distribution in the country. A. franciscana showed a unique haplotype. Populations of A. persimilis appeared highly structured, although their clustering did not follow a clear geographic pattern. The different Argentinean Artemia populations analyzed were characterized by high variability in their fatty acids, showing both marine- and freshwater-type profiles. For the first time, the investigation of the relatedness between the fatty acid composition in Artemia and genetic markers was attempted. The study aimed at the putative association of molecular markers with marine versus freshwater-type populations. A lack of correlation between RFLP patterns at mtDNA and the fatty acid (FA) profiles was found in the A. persimilis populations which was discussed from the point of view of two main genetic hypotheses and/or phenotypic plasticity.