Azolla rubra (Red azolla)
Class: Polypodiopsida / Pteridopsida (disputed)
Genus: Azolla (7 species)
Species: A. rubra
Binomial name: Azolla rubra
Synonyms: Azolla filiculoides var. rubra, Azolla filiculoides.
Common names: Pacific azolla, Azolla, Red azolla, Mosquito fern.
Azolla rubra is a species of aquatic, floating, dark-red (when exposed) or glaucous-green fern that is indigenous to New Zealand's North Island (Northland, Auckland, Volcanic Plateau, Taranaki, Gisborne and Southern North Island.) and in Western Nelson, Sounds-Nelson, Marlborough, Westland, Canterbury, Otago, Southland, Fiordland in the South Island. It is also found on the Kermadecs Raoul Island, also Australia (all States), and probably Papua New Guinea, Indonesia and Japan.
Azolla rubra is currently the only species that occurs in the South Island, but the southward spread of A. pinnata into the Wellington region suggests that it may soon cross Cook Strait. It grows in coastal to montane habitats ((c. 800 m) frequenting shallow water bodies such as farm ponds, ditches, drains and dams.
Azolla rubra reproduces sexually, and asexually by fragmentation (splitting). Like all ferns, sexual reproduction leads to spore formation, but Azolla sets itself apart from other members of its group by producing two kinds. A male sporocarp producing male spores and a smaller female sporocarps that is much smaller and produces one large functional spore. The clusters of male spores cling to one large female spores, thus facilitating fertilization.
There is a similar introduced taxa, Azolla pinnata which is extremely invasive and has largely replaced A. rubra in Northland and Auckland. Azolla rubra is readily distinguished from A. pinnata by its irregular branching and by its roots that lack fine rootlets.
Azolla rubra in concentration
No fine rootlets