Two new centromeric satellite DNAs in flatfish (Order Pleuronectiformes) have been characterized. The SacI-family from Hippoglossus hippoglossus, restricted to this species, had a monomeric size of 334 base pair (bp) and was located in most of the centromeres of its karyotype. The PvuII-family, with a monomeric size of 177 bp, was initially isolated from the genome of Solea senegalensis, and fluorescent in situ hybridization (FISH) localized the repeat to centromeres of most of the chromosomes. This family could only be amplified in 2 other species of the genus Solea (Solea solea and Solea lascaris). Molecular features and chromosomal location indicated a possible structural and/or functional role of these sequence repeats. The presence of species-specific satellite-DNA families in the centromeres and their possible role in the speciation processes in this group of fishes is discussed.

To clarify the species status of sturgeon from rivers of the Iberian Peninsula, eight molecular markers (4 nuclear and 4 mitochondrial) have been analysed in different specimens from historical museum samples and prehistoric samples from archaeological sites. These analyses indicate that one of these specimens (UGP captured in the Guadalquivir River in the 19th century) is A. sturio, based on all the eight molecular markers, four of them used from the first time in this study. In previous analyses based on 5 genetic markers, our group assigned two specimens captured in this river in the 1970-80s (EBD8173 and EBD8401) to the species A. naccarii, suggesting the presence of this species in the Iberian Peninsula. In this work, this conclusion is drawn after successfully obtaining a mitochondrial marker in a very old scute from a prehistoric site (Acinipo, about 1500 BC, from the Guadalquivir River basin). On the other hand, in the specimen EBD8174 captured in the Guadalquivir in 1975, we have obtained two new mitochondrial markers confirming that it can be considered A. sturio for all the mitochondrial markers, but nuclear ones identify it as A. naccarii. Finally, two very old samples (Nerja E-VI and Nerja N/62-63) were not successfully characterized by any molecular markers. Some aspects and consequences of our results are discussed, such as the origin of the “mosaic” specimen EBD8174 and, above all, the native status of A. naccarii in historic and prehistoric times in the southern Iberian Peninsula