Population genetics of Artemia

• Main Author: Abreu-Grobois, F. A.
• Published: Swansea University 1983
• Subjects: 576.58
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635843

Genetic variation and genetic differentiation in the genus Artemia has been studied using starch gel electrophoresis of 22-23 loci (coding 16 enzymes) and cytological methods. Samples, derived from cysts, included all bisexual species (A. franciscana, A. nnnica, A. persimilis, A. salina,and A. urmiana) and various parthenogenetic forms. In bisexuals, heterozygosity values (H =0.09-0.19) were consistent with other studies of invertebrates. Among the parthenogenetics, numbers of genotypes were generally higher in diploid (autanictic) than in polyploid (apanictic) populations, and heterozygosity increased considerably and significantly with ploidy level. In some localities mixtures of reproductive systems or of different ploidies and/or clones were found. Results are discussed in relation to reproductive modes and current theories. Exceptional parthenogenetically derived males contained genotypes (and had levels of heterozygosity) similar to their asexual "sisters". Chromosome numbers for the bisexuals were 2n=42 (franciscana, monica, salina and urmiana) or 44 (persimilis). Chranaoentres were found only in American species. Ebploid meters of 42, 63, 84,and 105 were found among the parthenogenetic forms, although aneuploid polyploids were also observed. This work generally confirms recent views of geneticists about the taxonomy of the genus but distinguishes several further points. Genetic distances indicate exceptionally high degree of differentiation (mean conspecific D=0.11; mean congeneric 114.5). Phenetic and phylogenetic analysis suggests (1) parthenogenetic Anemia have a monophyletic origin, (2) the ancestral form for this line was derived from a bon on ancestor with A. urmiana, (3) pentaploids were derived from tetraploids, (4) triploids have arisen in several independent events from diploids, (5) no electrophoretic or cytological differentiation exists between A. monica and A. franciscana. Formal genetic studies demonstrate (1) normal Mendelian inheritance of the loci assayed, (2) a disanic control of the unlinked duplicated Pgi loci in A. persimilis, and (3) lack of recombination in asexual forms tested. Evolution and speciation in the genus are discussed in the light of contemporary theories.