Effect of parental ploidy on reproductive system development in sturgeon hybrids in the second year of life

Abstract

The paper presents the data on germ cell development in various sturgeon hybrids with various ploidy levels. The study was performed at experimental industrial sites of the Branch for Freshwater Fisheries of the Russian Federal Research Institute of Fisheries and Oceanography (VNIIPRKH). Histology samples were taken in the winter, summer and autumn. Histology slides were made following the standard procedure. The figures show all stages of germ cell development in males and females of various hybrids, depending on rearing conditions (thermal constant). Two-year-old Russian sturgeon × Kaluga fish hybrids with similar ploidy levels reached gonad maturity stage I at a thermal constant of 8,571 degree-days (547 days). Female Russian sturgeon × beluga hybrids aged 631 days (10,191 degree-days) showed accelerated germ cell development characteristic of stage I to early stage II. Male Russian sturgeon × beluga and Siberian sturgeon × beluga hybrids had sexually indifferent germ cells. These species are expected to be sterile. Male Russian sturgeon × Kaluga fish hybrids aged 374 days had sexually indifferent germ cells with occasional primary spermatogonia; cell division was observed on Day 547. The study found that distant hybrids show better growth than hybrids with similar ploidy levels, where more intensive germ cell development is observed. Further research will elucidate the effect of gonad development during reproductive system formation on the growth of sturgeon hybrids with various ploidy levels.