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A consensus microsatellite-based linkage map of the turbot (Scophthalmus maximus) was constructed from two unrelated families. The mapping panel was derived from a gynogenetic family of 96 haploid embryos and a biparental diploid family of 85 full-sib progeny with known linkage phase. A total of 242 microsatellites were mapped in 26 linkage groups, six markers remaining unlinked. The consensus map length was 1343.2 cM, with an average distance between markers of 6.5 6 0.5 cM. Similar length of female and male maps was evidenced. However, the mean recombination at common intervals throughout the genome revealed significant differences between sexes, $1.6 times higher in the female than in the male. The comparison of turbot microsatellite flanking sequences against the Tetraodon nigroviridis genome revealed 55 significant matches, with a mean length of 102 bp and high sequence similarity (81-100%). The comparative mapping revealed significant syntenic regions among fish species. This study represents the first linkage map in the turbot, one of the most important flatfish in European aquaculture. This map will be suitable for QTL identification of productive traits in this species and for further evolutionary studies in fish and vertebrate species.

The Atlantic Ocean-Mediterranean Sea junction has been proposed as an important phylogeographical area on the basis of concordance in genetic patterns observed at allozyme, mtDNA and microsatellite DNA markers in several marine species. This study presents microsatellite DNA data for a mobile invertebrate species in this area, the cuttlefish Sepia officinalis, allowing comparison of this relatively new class of DNA marker with previous allozyme results, and examination of the relative effects on gene flow of the Strait of Gibraltar and the Almería-Oran oceanographic front. Genetic variation at seven microsatellite loci screened in six samples from NE Atlantic and Mediterranean coasts of the Iberian Peninsula was high (mean Na = 9.6, mean H e = 0.725). Microsatellites detected highly significant subpopul-

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Mytilus edulis L. and M. galloprovincialis Lmk. are 2 forms of mussels that live on the European coasts, and where they coexist, hybridize in varylng proportions. While the Atlantic coast of the Iberian Peninsula is a key area for understanding the distribution of the genus Mytilus in Europe, the available evidence on the distribution from thls area is scarce and contradictory. Five partially diagnostic allozyme loci (aminopeptidase-l, esterase-D, leucine aminopeptidase-l, mannose phosphate isomerase and octopine dehydrogenase) and the best diagnostic morphological characters (length of the anterior adductor muscle scar and internal radius of the hinge plate and shell length and height) between M. edulis and M. galloprovincialis were investigated in 37 and 39 samples respectively taken from the Iberian coasts. Concordance between morphological variation and enzyme polymorphlsms is virtually complete and in&cates that M. galloprovincialis occurs all along the Iberian Peninsula (Mediterranean, Lusitanian, Gahcian Rias and Cantabrian coasts). M. galloprovincialis follows, therefore, a continuous distribution all along the Atlantic coast of Europe, from the Mediterranean Sea to the English Channel and the British Isles. Moreover, M. galloprovincialis exhibits an abrupt discontinuity in allozyme frequencies of about 40% for Odh'100 and 25% for Ap-1'100 in the southeastern Mediterranean Iberian coasts. This strong genetic differentiation appears to be associated with an oceanographic current barrier (the Almeria-Oran front). On the other hand, evidence for the presence of M. edulis and hybrids of M edulis and M. galloprovincialis was obtained only on the Atlant~c coast near the Hispano-French frontier. Therefore, it seems that the meridional h i t of the geographical distribution of M. edulis in Europe, and the concomitant h u t of the hybrid zone, are between the mouths of the Bidasoa and Nervion rivers in Spain. These results clarify some evolutionary aspects of M. edulis and M. galloprovincialis.