july 08
Sex Ratio Manipulation
– For aquaculture or stocking, it may be desirable to use only one sex due to differences in growth rate or characteristics concerned with maturity and reproduction,
– Sex ratio can be manipulated either directly (using steroid hormones to alter the sex ratio in fry during sexual differentiation) or indirectly (manipulating the sex determination system of broodstock so that selected fish produce monosex offspring).
Chromosome Manipulation: Polyploidy
– Nearly all species of fish are diploid (2n),
– Triploidy (3n) fish exhibit good growth and condition over the spawning period comparing with 2n fish,
– Tetraploidy (4n) fish produce eggs and sperm which are 2n, thus a cross between a 4n fish and a 2n fish will produce 3n offspring without the need to use shocks to induce triploidy.
Gynogenesis and Androgenesis
– Gynogenesis is a tool for producing all-females where females are homogamety, has been used in the study of sex determination and gene recombination and as a tool for inbreeding and the production of clonal lines,
– Androgenesis is a tool for producing all-males where males are homogamety.
recapped from N. Pongthana