Horizon 1 1 17 ACLN : Articles dans des revues avec comité de lecture non répertoriées par l'AERES Molecular Marine Biology and Biotechnology 123-130 INVERTEBRE AQUATIQUE POLYMORPHISME GENETIQUE TAXONOMIE 1997 fdi:010011003 ENG Molecular Marine Biology and Biotechnology 2 https://www.documentation.ird.fr/hor/fdi:010011003 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_6/b_fdi_47-48/010011003.pdf 6 Horizon (IRD) A novel intron-length polymorphism at the actin gene locus mac-1 is here reported and used as a genetic marker for population studies in mussels of the genus #Mytilus$. Two closely related genes subsequently identified as alleles, mac-1a1, and mac-1b1, from a genomic library of #M. galloprovincialis$ were partially cloned and sequenced. They mainly differed from each other by a 65-bp insertion within their first intron. Polymerase chain reaction (PCR) primers were designed outside the insertion. The PCR analysis of 166 individual mussels from #M. galloprovincialis$ and #M. edulis$ populations revealed three size-classes of alleles or allelomorphs, two of which were of the expected sizes for mac-1a1 and mac-1b1. One allelomorph was absent from #M. edulis$ samples, although it was present at substantial frequencies in #M. galloprovincialis$ populations. The frequencies of the two other allelomorphs significantly differed between #M. galloprovincialis$ and #M. edulis$ populations. The comparison of six mac-1 intron sequences over 277 bp showed at once that allelomorphs encompassed alleles differing from one another by substantial numbers of mutations, and that identical alleles were present in both #M. galloprovincialis$ and #M. edulis$ individuals, a probable result of the recent introgression between the two species. (Résumé d'auteur) 034BIOINV03