Enigmatic Sakhalin Sturgeon (Acipenser mikadoi, Hilgendorf, 1892): ploidy, cytogenetics, molecular phylogeny

Zelenina DA. Yegorov JE. Vishnyakova KS. Galina A. Delone GA. Mugue NS. Mikodina EV.

Sakhalin sturgeon (Acipenser mikadoi) is one of the most endangered and the least examined species among sturgeons. Only one river (Tumnin R., Russian Far East) is known as a spawning ground for this species. According to morphology and mtDNA analysis this is a sister species with green sturgeon (A. medirostris) from the Pacific coast of the North America. The time of their divergence is similar to that of another pair of sturgeons from different coasts of Pacifics white sturgeon (A. transmontanus) and Amur sturgeon (A. schrenckii). Until recently, Sakhalin sturgeon considered to be hexadecaploid or octoploid (depending on the diploid genome size) with estimated number of chromosome near 500. We established a long-living cell culture of Sakhalin sturgeon and examined its karyotype. A. mikadoi cells possess a chromosome set quite similar to that in many other sturgeon species and the average number of chromosomes (248) is close to some other sturgeon species that contain about 250 chromosomes (e.g. Russian (A. gueldenstadtii), Siberian (A. baerii) and green sturgeon). Microsatellite analysis of Sakhalin sturgeon revealed that most of the loci studied have up to four alleles per individual, concordant with other high chromosome group of sturgeons (Russian and Siberian sturgeons), while in low chromosome sturgeons species: beluga (Huso huso) and sterlet (A. ruthenus) these loci were diploid. However, DNA content in A. mikadoi erythrocyte nuclei is two-fold higher than in Russian sturgeon, and that corresponds to the earlier cytofluorimetry data (Birstein et al. 1993).