COMPARATIVE RESEARCH ON THE SEXUALIZATION OF FISSIPAROUS PLANARIANS TREATED WITH SUBSTANCES CONTAINED IN SEXUAL PLANARIANS

SUMMARY Previous research had shown that asexual specimens of fissiparous Dugesia gonocephala s.l. stopped fissioning and developed a hermaphroditic genital apparatus if fed for several weeks on the crushed tissues of sexually mature Polycelis nigra Ehr., a non-fissiparous planarian. The present research shows that the sexualizing substance, probably a neurosecretion, is also present in the tissues of sexually mature Dugesia lugubris s.l., Dugesia dorolocephala (Woodworth), Dugesia anceps Kenk and Dendrocoelum lacteum (O. F. Muller), in concentrations which may differ according to the species but without any zoological specificity. There is a clear different in the capacity of each fissiparous species or strain to react to the sexualizing substances: while many asexual strains of Dugesia gonocephala s.l., Dugesia tigrina (Girard) and Dugesia Pdorotocephala (race from Sabino) reacted more-or-less positively to the treatment, agamic Dugesia dorotocephala, Dugesia mediterranea Benazzi et al. (fissiparous rac...