THE COMPLETE MITOCHONDRIAL-DNA SEQUENCE OF THE CRUSTACEAN ARTEMIA-FRANCISCANA

The complete mitochondrial DNA (mtDNA) sequence of the brine shrimp Ar temia franciscana has been determined. It extends the present knowledg e of mitochondrial genomes to the crustacean class and supplies molecu lar markers for future comparative studies in this large branch of the arthropod phylum. Artemia mtDNA is 15,822 nucleotides long, and when compared with its Drosophila counterpart, it shows very few gene rearr angements, merely affecting two tRNAs placed 3' downstream of the ND 2 gene. In this position a stem-loop secondary structure with character istics similar to the vertebrate mtDNA L-strand origin of replication is found. This suggests that, associated with tRNA changes, the divers ification of the mitochondrial genome from an ancestor common to crust acea and insects could be explained by errors in the mtDNA replication process. Although the gene content is the same as in most animal mtDN As, the sizes of the protein coding genes are in some cases considerab ly smaller. Artemia mtDNA uses the same genetic code as found in insec ts, ATN and GTG are used as initiation codons, and several genes end i n incomplete T or TA codons.