Abstract
Periwinkles of the family Littorinidae (Children, 1834) are common members of seashore littoral communities worldwide. Although the family is composed of more than 200 species belonging to 18 genera, chromosome numbers have been described in only eleven of them. A molecular cytogenetic analysis of nine periwinkle species, the rough periwinkles Littorina arcana, L. saxatilis, and L. compressa, the flat periwinkles L. obtusata and L. fabalis, the common periwinkle L. littorea, the mangrove periwinkle Littoraria angulifera, the beaded periwinkle Cenchritis muricatus, and the small periwinkle Melarhaphe neritoides was performed. All species showed diploid chromosome numbers of 2n = 34, and karyotypes were mostly composed of metacentric and submetacentric chromosome pairs. None of the periwinkle species showed chromosomal differences between male and female specimens. The chromosomal mapping of major and minor rDNA and H3 histone gene clusters by fluorescent in situ hybridization demonstrated that the patterns of distribution of these DNA sequences were conserved among closely related species and differed among less related ones. All signals occupied separated loci on different chromosome pairs without any evidence of co-localization in any of the species.
Highlights
The family Littorinidae (Children, 1834) comprises more than 200 species of periwinkles grouped in 18 genera that are common members of marine intertidal communities around the world. the systematics and evolution of the Littorininae have been widely studied [1,2,3,4], there is still some degree of taxonomic confusion due in part to the high phenotypic polymorphism showed by some of the taxa
All male and female specimens of the nine periwinkle species showed diploid chromosome All male and female specimens of the nine periwinkle species showed diploid chromosome numbers of 2n = 34 and karyotypes characterized by a superabundance of meta/submetacentric numbers of 2n = 34 and karyotypes characterized by a superabundance of meta/submetacentric chromosome pairs (15 to 17)
Five of them displayed a single major (45S) rDNA cluster located at subterminal positions on the short arms of submetacentric chromosome pair 8 in the flat periwinkles subterminal positions on the short arms of submetacentric chromosome pair 8 in the flat periwinkles
Summary
The family Littorinidae (Children, 1834) comprises more than 200 species of periwinkles grouped in 18 genera that are common members of marine intertidal communities around the world. Cytogenetic analyses, mostly limited to the description of chromosome numbers, have been published for a total of 11 species of the family Littorinidae (Table 1) [5,6,7,8,9,10,11,12,13,14,15] Five of these species belong to the genus Echinolittorina [E. hawaiiensis (Rosewater & Kadolsky, 1981), E. miliaris (Quoy & Gaimard, 1833), E. punctata (Gmelin, 1791), E. radiata (Souleyet, 1852), and E. subnodosa (Molina, 1782)], four to the genus Littorina [L. brevicula (Philippi, 1844), L. keenae (Rosewater, 1978), L. obtusata, and L. saxatilis], and the remaining two are Littoraria strigata (Philippi, 1846) and Melarhaphe neritoides (Linnaeus, 1758). A fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene was further amplified and sequenced to add independent genetic information for species identification
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