A Hypothesis of Ploidy Elevation by Formation of a Female Pronucleus in the Androgenetic Clam Corbicula fluminea in the Tone River Estuary, Japan Komaru, Akira and Kumamoto, Atsuko and Kato, Takeshi and Ishibashi, Ryo and Obata, Mayu and Nemoto, Takao, Zoological Science, 23, 529-532 (2006), DOI:http://dx.doi.org/10.2108/zsj.23.529