Induced polyploidy in sturgeons: back to the problem in Russia

Arefjev VA. Nikolaev AI.

Experiments on the polyploidy induction in sturgeons were conducted in Russia in the mid-1960s and yielded practically negative results: the subjects of those investigations were pure species, mainly the Russian sturgeon, Acipenser gueldenstaedti. In 1990-91 we made an attempt to return to this problem dealing with a hybrid between the great sturgeon, Huso huso, and the sterlet, Acipenser ruthenus. The experiment included four variants and two controls: 1) thermal shock (31°C) for 10 min., 20 min. after fertilization; 2) thermal shock for 15 min., 15 min. after fertilization; 3) chemical shock (colchicines, 0,01%) for 15 min., 15 min. after fertilization; 4) chemical shock for 40 min., 1.5 hours after fertilization. The viability in all six variants did not differ significantly both during embryogenesis and after hatching. Ploidy control was made by conventional cytogenetic methods when the fish attained the age of about 1.5 months. The proportions of triploids in Variants 1, 2 & 3 were 30%, 45.7% and 28%, respectively; no tetraploids were observed in variant 4. The proportions of mosaic specimens (mainly mixoploids) were 3.3%, 20%, 6.7% and 10%, respectively. The modal chromosome numbers were 2n=116-118 in diploids and 3n=168-176 in triploids. Interestingly, viable colchiploid fish were obtained for the first time. It thus appears that induction of triploidy is possible in principle, at least in sturgeon hybrids, possibly due to higher flexibility of their genomes in comparison with “pure” species, though elaboration of a method for 100% triploidization is doubtful.