Induction of all-female triploids in grass carp (Ctenopharyngodon idella) by integration of hormonal sex inversion and ploidy manipulation

The herbivorous grass carp (Ctenopharyngodon idella V. & C.) is an importan t species for controlling nuisance aquatic vegetation. In the present study , chromosome-set manipulation and hormonal sex inversion were integrated to produce monosex females and males and sterile female triploids. The albino grass carp (AGC) served as a recessive genetic marker for induction of gyn ogenesis and androgenesis. Sperm of common carp (Cyprinus carpio L.) or gol den tench (Tinca tinca L.) were examined as activators of albino eggs for g ynogenesis. Eggs of common carp and wild-type colored grass carp were teste d for androgenesis of AGC. Early shocks (0.15-0.2 tau (O)) were applied to obtain the desired ploidy level in meiotic gynogenesis and triploidy and la te shocks (1.6-2.2 tau (O)) in mitotic gynogenesis, androgenesis and tetrap loidy. Pressure, heat, and cold shocks at several intensities were examined . Meiotic gynogenotes were obtained (200-600 individuals) in all experiment s using UV-irradiated (800 J/m(2)) sperm of common carp. The highest surviv al of gynogenotes was obtained from eggs shocked by heat (40 +/-1 degreesC/ 2 min). In 1994, a group of fish was hormonally sex-inversed with androgen implants. Sex-inversed females (neomales) served as donors of X-bearing spe rmatozoa for the production of female monosex populations. The timing of la te shock, required for induction of androgenesis and tetraploidy, was defin ed through induction of mitotic gynogenesis. Mitotic gynogenotes were produ ced by exposing activated AGC eggs to cold shock for different durations (1 0, 20 and 30 min). The survival and hatching of mitogynotes were inversely related to the duration of the shock. Androgenesis was induced in UV-treate d eggs of common carp and wild-type colored grass carp, fertilized with int act AGC sperm. Only two diploid albino androgenetic fish survived more than one year. Female (XXX) triploids were produced by fertilizing AGC eggs wit h sperm of AGC neomales, then shocking them early to retain the second meio tic polar body. The use of neomales provided a mechanism for commercial-sca le production of sterile (XXX) all-female AGC. So far, trials to induce tet raploid AGC using cold shocks have failed. Fluorocytometric examination was applied to assess the DNA contents in samples of pioidy-manipulated larvae and fish. Due to the highly applicative importance of tetraploid broodstoc k, we intend to continue our study on tetraploidy.