Evolution du tractus uro-génital chez les Pleurodèles chimères à corps double. Effet de position dans les interactions entre glandes génitales de sexe différent

Abstract

Chimeric grafts of the embryos of the urodele amphibian (Pleurodeles waltlii Michah.) produced viable, double-bodied animals having two pairs of genital glands of the same sex [homosexual chimeras: anterior testes--posterior testes (male----male) and anterior ovaries--posterior ovaries (female----female)] or of different sex [(heterosexual chimeras: anterior ovaries--posterior testes (female----male) and anterior testes--posterior ovaries (male----female)]. 115 chimeras aged 5 months to 15 years were analysed. Gonadal development in a same animal was observed at different times by exploratory laparotomy. The testes of heterosexual chimeras were removed in order to prevent their inhibitory effect on the ovaries (freemartin effect). The 115 experimental animals were classified according to gonadal development as follows: 47 male----male chimeras (41%), 26 female----female chimeras (23%), 13 female----male chimeras (11%), 29 male----female chimeras (25%). As a rule, male----male chimeras only developed three normal testes. The fourth testis, always situated in the anterior part of the chimera, remained vestigial; nevertheless, it could attain a normal size if the other three testes were removed. female----female chimeras usually had four ovaries; the times of vitellogenesis and of sexual maturity were synchronous in all four ovaries. The anterior ovaries of female----male chimeras were always inhibited and the posterior testes were always normal. male----female chimeras always had normal anterior testes but their posterior ovaries were often weakly inhibited. The high number of male----male chimeras and the low number of female----female ones could be due to a phenotypic reversal of the anterior ovaries in some of the female----male chimeras. The number of male----female chimeras (corresponding to the theoretical number) suggests that the phenotypic sex of the posterior ovaries was not reversed. The freemartin effect in double-bodied heterosexual chimeras depended on the location of the ovaries in relation to the testes. The effect was more significant on the anterior ovaries when posterior testes were present. No or weak freemartin effect was observed when the posterior ovaries developed facing the anterior testes; in about 60% of cases, a reciprocal inhibition or an equilibrium between gonads of different sex occurred.(ABSTRACT TRUNCATED AT 400 WORDS)