Note on specimens of Hydrilla verticillata (Hydrocharitaceae) rooted in Aegagropila linnaei (Pithophoraceae).
Recently five specimens of Hydrilla verticillata (Hydrocharitaceae) which rooted in Aegagropila linnaei (Pithophoraceae) were found in the herbarium of the Hokkaido University museum (SAPS). Aegagropila linnaei in Lake Akan is registered as a national special natural treasure in Japan, also known as an endangered alga. Cases of H. verticillata invasion into A. linnaei have not been reported so far. There is a concern that H. verticillata rhizome invasion will adversely affect the growth of A. linnaei. In the future considering the conservation of A. linnaei, it will be necessary to investigate whether there are similar cases in other aquatic plants, and also to remove these aquatic plants.