Notizie preliminari sulla costituzione cariologica dell'ibrido intergenerico Salmo gairdneri X Salvelinus fontinalis (Pisces,Salmoniformes)

Cataudella, Stefano ; Civitelli, Maria Vittoria ; Martinelli, Nora ; Capanna, Ernesto

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 58 (1975) no. 2, pp. 258-262

Résumé

The chromosome complement of an experimental hybrid Salmo gairdneri X Salvelinus fontinalis has been investigated in 21 specimens. The chromosomes number has been demonstrated to vary both intrerindividually as well as within the different tissues of the same subject. The chromosome number ranges from 92 to 106 and the Fundamental numbers vary from 133 to 159. The morphological analysis of the hybrid karyotypes evidences that each complement is made up by one haploid set of Salvelinus fontinalis plus a variable quasidiploid number of Salmo gairdneri chromosomes. This karyological peculiarity has been hypothized to be the consequence of a former allotriploid complement of a hybrid syncarion resulting from the fusion of a non-reduced female Salmo gairdneri pronucleus with the haploid spermatozoon of Salvelinus fontinalis. This allotriploid complement has been supposed to be transformed throughout Robertsonian changes following the peculiar character of the Salmo gairdneri chromosomal pattern. Nevertheless the chromosome variability of Salmo gairdneri differs from that of the hybrids since in Salmo gairdneri Robertsonian changes produce balanced genoma only, whereas in the hybrids the genome portion related to Salmo gairdneri is affected by large losses of genetic material. New experimental approaches are planned in order to explain the problem of the karyological constitution of the Salmonidae intergeneric hybrids.