Chromosomal nucleolar organizer region (NOR) phenotypes in nine species of the genus Ophryotrocha (Polychaeta: Dorvilleidae) |
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Authors: | G. Sella R. Vitturi L. Ramella M. S. Colomba |
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Affiliation: | (1) Department of Animal Biology, University of Turin, Via Accademia Albertina 17, I-10123 Torino, Italy;(2) Institute of Zoology, Giuseppe Reverberi, University of Palermo, Via Archirafi 18, I-90123 Palermo, Italy |
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Abstract: | Chromosomal nucleolar organizer region (NOR) phenotypes have been characterized in nine species of the genus Ophryotrocha (Polychaeta: Dorvilleidae), namely O. notoglandulata, O. sp. macrovifera, O. sp. labronica pacifica, O. labronica labronica, O. puerilis puerilis, O. diadema, O. sp. robusta, O. gracills and O. hartmanni. Irrespective of chromosome number and morphology, Ag positive regions were terminally located in all but one species, O. diadema, where the NORs were pericentromerical in a metacentric pair. The presence of a single chromosome pair bearing NOR in invertebrates is considered an ancestral trait. According to this assumption, O. sp. robusta, O. dialema, and perhaps O. p. puerilis appear to be more ancestral than the other species. On the contrary, O. notoglandulaia, O. sp. macrovifera, O. sp. labronica oacifica, with two chromosomal pairs bearing NOR sites, seem to represent examples of further evolution within the genus Ophryotrocha. |
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