A PRELIMINARY PLOIDY ANALYSIS OF DIPLOID AND TRIPLOID SALMONIDS

The findings indicate that mosaicism does occur in triploids and espec ially in triploid hybrids. Immature diploid and triploid salmon were o btained from the University of Alaska - National Marine Fisheries Serv ice. These were fixed in 10% buffered formalin and blocks taken from V arious tissues including kidney, liver, spleen, and gonads. The paraff in blocks were sectioned at 4 mu m and stained with hematoxylin and eo sin for histologic evaluation and to quantitate nuclear DNA. The slide s for DNA evaluation were stained using the Cell Analysis Systems, Inc . (GAS, Elmhurst, IL) kit following Feulgen hydrolysis. The Cell Analy sis Systems, inc. (Model 200) computer-assisted image analyzer was use d for DNA quantitation. An attempt was made to evaluate the frequency of mosaicism, ploidy variation in somatic and gonadal tissues of tripl oids and hybrids as compared with normal diploids. Hepatic ploidy vari ation, normal in adult animals, was not present in these specimens. Ho wever, in gonads there was evidence of increased mosaicism among the t riploids. Because of mosaicism in gonadal tissue, sterility of triploi ds cannot be presumed with certainty at this stage. Further studies ar e planned to examine this and other questions raised by these results.