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Gametogenesis of intergroup hybrids of hemiclonal frogs

Published online by Cambridge University Press:  22 May 2007

Matilde Ragghianti
Affiliation:
Laboratori di Biologia cellulare e dello sviluppo, Dipartimento di Biologia, Università di Pisa, Via Carducci 13, 56010 Ghezzano, Pisa, Italy
Stefania Marracci
Affiliation:
Laboratori di Biologia cellulare e dello sviluppo, Dipartimento di Biologia, Università di Pisa, Via Carducci 13, 56010 Ghezzano, Pisa, Italy
Silvia Marracci
Affiliation:
Laboratori di Biologia cellulare e dello sviluppo, Dipartimento di Biologia, Università di Pisa, Via Carducci 13, 56010 Ghezzano, Pisa, Italy
Claudio Casola
Affiliation:
Laboratori di Biologia cellulare e dello sviluppo, Dipartimento di Biologia, Università di Pisa, Via Carducci 13, 56010 Ghezzano, Pisa, Italy
Hansjürg Hotz*
Affiliation:
Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland Institut für Systematische Zoologie, Humboldt-Universität, Invalidenstraße 43, 10115 Berlin, Germany
Gaston-Denis Guex
Affiliation:
Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
Jörg Plötner
Affiliation:
Institut für Systematische Zoologie, Humboldt-Universität, Invalidenstraße 43, 10115 Berlin, Germany
Thomas Uzzell
Affiliation:
Center for Systematic Biology and Evolution, Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103, USA
*
*Corresponding author. Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
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Summary

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European water frog hybrids Rana esculenta (R. ridibunda×R. lessonae) reproduce hemiclonally, by hybridogenesis: in the germ line they exclude the genome of one parental species and produce haploid gametes with an unrecombined genome of the other parental species. In the widespread L-E population system, both sexes of hybrids (E) coexist with R. lessonae (L). They exclude the lessonae genome and produce ridibunda gametes. In the R-E system, hybrid males coexist with R. ridibunda (R); they exclude either their ridibunda or their lessonae genome and produce sperm with a lessonae or with a ridibunda genome or a mixture of both kinds of sperm. We examined 13 male offspring, 12 of which were from crosses between L-E system and R-E system frogs. All were somatically hybrid. With one exception, they excluded the lessonae genome in the germ line and subsequently endoreduplicated the ridibunda genome. Spermatogonial metaphases contained a haploid or a diploid number of ridibunda chromosomes, identified through in situ hybridization to a satellite DNA marker, and by spermatocyte I metaphases containing a haploid number of ridibunda bivalents. The exception, an F1 hybrid between L-E system R. lessonae and R-E system R. ridibunda, was not hybridogenetic, showed no genome exclusion, and evidenced a disturbed gametogenesis resulting from the combination of two heterospecific genomes. None of the hybridogenetic hybrids showed any cell lines excluding the ridibunda genome, the pattern most frequent in hybrids of the R-E system, unique to that system, and essential for its persistence. A particular combination of R-E system lessonae and R-E system ridibunda genomes seems necessary to induce the R-E system type of hemiclonal gametogenesis.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2007