Genetic analysis of developmental mechanics in hydra. XI. Mechanism of sex reversal by heterosexual parabiosis.

Sex change from female to male occurs at a high rate in hydra when a female polyp is exposed to a male polyp by parabiosis for a limited length of time. The mechanism of this masculinization process was investigated. When a male strain which produces immotile sperm was used to masculinize female strains, the resultant masculinized animals produced only immotile sperm. Evidence was also obtained which indicated that the original female interstitial cells remained in large numbers in the masculinized animals but did not differentiate into gametic cells. These observations suggest that masculinization is achieved not by the hypothetical "masculinizing factor" but by the migration of the male interstitial cells from the male to the female tissue during parabiosis.