Evidence against self-fertilization in the hermaphroditic flatworm Dugesia gonocephala (Tricladida, Paludicola)
Vreys, C.; Michiels, N.K.; Schockaert, E. (1994). Evidence against self-fertilization in the hermaphroditic flatworm Dugesia gonocephala (Tricladida, Paludicola). Neth. J. Zool. 44(1-2): 55-64
In: Netherlands Journal of Zoology. E.J. Brill: Leiden. ISSN 0028-2960; e-ISSN 1568-542X, more
The individual cocoon production of 50 specimens of the simultaneous hermaphroditic flatworm Dugesia gonocephala was followed in the laboratory for nine months. (I) Though cocoons were produced continuously, the number of fertilized cocoons decreased to zero in six months; (II) Twenty-one worms produced no cocoons, 16 produced only unfertilized cocoons and the remaining 13 produced at least one fertilized cocoon. (III) In the latter the proportion of fertilized cocoons relative to the total number produced, decreased with time. This was not compensated for by an increase in the number of hatched young. (IV) In sections of worms that produced either only fertilized cocoons, or only unfertilized cocoons or a combination of first fertilized, then unfertilized and finally no cocoons at all, sperm was only found in the seminal receptacles (near the ovaries) of a worm that produced only fertilized cocoons. All individuals had many sperm in the seminal visicles of their male reproductive system. These results strongly suggest that self-fertilization does not occur in D. gonocephala.
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