From morphology and karyology to molecules. New methods for taxonomical identification of asexual populations of freshwater planarians. A tribute to Professor Mario Benazzi

Abstract

Asexual reproduction by fissiparity is a frequent mode of reproduction in freshwater planarians (Turbellaria, Tricladida, Paludico‐la). Asexual populations pose a main taxonomical problem: to assign them to particular sexual species. We review here two case studies of asexual populations of freshwater triclads belonging to the genera Schmidtea and Dugesia. We show that karyotypes and morphology of the reproductive system of rare ex‐fissiparous specimens led to identifing as Schmidtea mediterranea the few asexual populations of this genus. Instead, morphology and karyology were unable to deal with the frequent asexual populations of Dugesia. We used the internal transcribed spacer region (ITS‐1) of ribosomal DNA to study 20 populations, sexual and asexual, of this genus. The pattern of sequence variation enabled the unambiguous assignment of all asexual populations to particular sexual species. The origin of asexual populations is briefly discussed.

Key words:

• Molecular markers
• ITS‐1 Sequences
• Planarians
• Turbellaria
• Fissiparity
• Karyology
• Enzyme polymorphism.

Notes

Department of Zoology, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom.

Department of Invertebrates, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA.

Center for Conservation Research and Training, 3050 Maile Way, Gilmore 409, University of Hawaii, Honolulu, HI 96822, USA.