Transmission et expression des caractères ‘ovaire’ et ‘testicule’ dans des clones de Némertes allophéniques produits par multiplication végétative de chimères bipartites mâle/femelle et femelle/mâle chez Lineus sanguineus

Summary

Two stable strains of bilaterally allophenic nemertines were obtained 15 years ago by vegetative multiplication of two bipartite chimeras constructed from symmetrical worm halves of opposite sexes.

From year 1 to 3 of the organismal cloning, the ‘testis’ and ‘ovary’ characteristics differentiated at the onset of the sexual development in respectively male and female sides of allophenic nemertines. Subsequently, unilateral sex reversal by substitution of ovaries for testes regularly occurred as a secondary process.

The 4th year, transient ovotestes were the only type of gonad showing features of masculinity in clones. ‘Pure’ testes did not differentiate.

From year 5 to 9, the ‘ovary' characteristic alone expressed in the two sides of the allophenic worms’ body. Such a transmission of the primary feminization phenotype by organismal cloning showed that the genetic determinant of the testicular differentiation either had been eliminated or was permanently repressed.

From year 10 up to date, the differentiation of the single ‘ovary’ characteristic was again the usual pattern of the gonadogenesis. However, some worms from a sub-clone differentiated a few transient testes in year 10. Although this male-gonad-phenotype reminiscence was discreet, it showed that the testicular determinant had not been eliminated.

The present data support the hypothesis that allophenic worms derived from vegetative multiplication of male-female chimeras retain genetically male and female cells but that interactions between cells of two genetic sexes eventually result in complete repression of the testicular determinant.