Chromosomal polymorphism and molecular variability in the pearly razorfish Xyrichtys novacula (Labriformes, Labridae): taxonomic and biogeographic implications.

The pearly razorfish Xyrichtys novacula (Linnaeus, 1758) is a sedentary benthic species distributed in both sides of the Atlantic Ocean and in the Mediterranean Sea. Previous cytogenetic analysis reported different diploid numbers in samples from Italy, Venezuela and Brazil. This research aims to test the hypothesis that samples from American Atlantic coast and Mediterranean Sea belong to the same single evolutionary lineage, characterized by intra-specific chromosome polymorphism. To this purpose a cytogenetic and molecular (mitochondrial COI sequences) survey was undertaken. Results revealed the existence of three different pearly razorfish molecular lineages: one present in Mediterranean Sea and two in the central and south American area, which are characterized by different karyotypes. One of these lineages shows substantial intra-population chromosomal polymorphism (2n = 45-48) determined by Robertsonian fusions that produce large metacentric chromosomes. On the whole data suggest that specimens morphologically identified as X. novacula correspond to three cryptic species.

The Mugil curema species complex (Pisces, Mugilidae): a new karyotype for the Pacific white mullet mitochondrial lineage.

Recent molecular phylogenetic analyses have shown that the Mugil curema Valenciennes, 1836 species complex includes M. incilis Hancock, 1830, M. thoburni (Jordan & Starks, 1896) and at least four "M. curema" mitochondrial lineages, considered as cryptic species. The cytogenetic data on some representatives of the species complex have shown a high cytogenetic diversity. This research reports the results of cytogenetic and molecular analyses of white mullet collected in Ecuador. The analyzed specimens were molecularly assigned to the Mugil sp. O, the putative cryptic species present in the Pacific Ocean and showed a 2n = 46 karyotype, which is composed of 2 metacentric and 44 subtelocentric/acrocentric chromosomes. This karyotype is different from the one described for M. incilis (2n = 48) and from those of the two western Atlantic lineages Mugil curema (2n = 28), and Mugil margaritae (2n = 24). Data suggest the need for a morphological analysis to assign a species name to this Pacific lineage.