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Karyotypic characterization and genomic organization of the 5S rDNA in Erpetoichthys calabaricus (Osteichthyes, Polypteridae)
No full textPolypterids are a group of Osteichthyan fish whose evolutionary relationships with closer basal ray-finned and lobe-finned fish have been disputed since their discovery. Very little is known about the evolutive karyology in the whole Polypteriformes group. In order to fill this gap, a cytogenetic analysis of Erpetoichthys calabaricus species was performed, using both classical and molecular techniques. Karyotype structure (2n = 36; FN = 72), chromosome location of telomeric sequences (TTAGGG)n and ribosomal 5S and 18S rRNA genes were examined in twenty specimens of E. calabaricus by using Ag-NOR, classical C-banding, sequential CMA3/4′,6- diaminidino-2-phenylindole (DAPI) staining and fluorescent in situ hybridization (FISH). CMA3 marked all centromerical and some (n°1 and n°15) telomeric regions. Staining with Ag-NOR and CMA3 showed the presence of two NORs on the p arm of the chromosome pair n°1. Hybridization with telomeric probes (TTAGGG)n showed signals at the end of all chromosomes. 5S rDNA was cloned and sequenced. After the alignment, the 5S rRNA sequences revealed an organization made up of two different classes of tandem arrays (type I and type II). FISH with 5S rDNA marked the telomeric regions of the small chromosome pair n°15, while FISH with 18S rDNA marked the telomeric region of the pair n°1. The results obtained were compared with cariological data on closer species now available in literature. © 2006 Springer Science+Business Media, Inc
A molecular approach to systematics of polypteriformes among osteichthyes
No full textThe Sarcopterygii are considered to be the living species most closely related to the ancestors of the tetrapods: they include the extinct rhipidistians, the coelacanths and the dipnoans. Furthermore, many Authors debate whether the Polypteriformes should be assigned a very peculiar place in the phylogeny of the bony fishes. To investigate the group of Polypteriformes and the Dipnoans and to provide new support for the classic morphological and molecular data and previous karyological evidence, we examined the DNA sequences of the mitochondrial genes 16S, 12S and cyt-b in two polypterids (Polypterus palmas and Erpetoichthys calabaricus) and two lungfish (Protopterus annectens and P. aethiopicus). In all the trees, Polypteriformes and Dipnoi are grouped together, while coelacanths remain as a sister group of these two. This molecular evidence supports the earliest hypotheses in which Polypteriformes were grouped in the same subclass together with the coelacanths and Dipnoi. © 2004 Taylor & Francis Group, LLC
Struttura del cariotipo e localizzazione dei geni ribosomiali in Polypterus ornatipinnis (Cladistia, Polypteridae)
No full text
Analisi molecolare e cariologica di un retrotrasposone non LTR (Rex3) in alcuni Osteitti primitivi
No full textIdentificazione e localizzazione cromosomica di una famiglia LINE nel genoma degli Elasmobranchi
No full textKaryotype and genome size of zoarcids and Notothenioids (Teleostei, perciformes) from the Ross Sea: Cytotaxonomic implications
No full textIn the absence of fossils, the origin of Notothenioidei, a perciform suborder dominating the fish fauna of the Southern Ocean, remains conjectural; some morphoecological evidence suggests relationships to zoarcoids. To test this point we have compared the karyotype morphology and genome size of two species of zoarcids from the Ross Sea to those of one species each of the notothenioid families. Artedidraconidae, Bathydraconidae, Channichthyidae and Nototheniidae from the same region. A karyotype of 48, mostly acrocentric, chromosomes, localization of nucleolar organizers on a pair of small dibrachial chromosomes, a genome size of about 3 pg of DNA, characterize both zoarcids; similar features can be found in the karyology of the notothenioids (especially the Nototheniidae). However, all shared characters appear as plesiomorphic in teleost karyology, which does not help in producing new data on the problem of notothenioid relationships
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