Azolla filiculoides

Location & distribution maps

Phylogeny & links to associated information

Wikipedia links:        Monilophytes > Salviniales > Salviniaceae > Azolla filiculoides

Other links:     http://10000thingsofthepnw.com/2021/09/06/azolla-filiculoides/

Plant  information

Common name:         Pacific Azolla  

• Also, mosquito fern, fairy moss, duckweed fern, red water fern, water velvet and Pacific mosquito fern

Conservation status: ...

Etymology:   

• The common name, Mosquito Fern, is an allusion to the fact that the plants sometimes thoroughly cover the surface of a pond or other body of water, reducing access, to mosquitoes and other insects, to the water to lay eggs

• The genus is from the Greek azo (to dry), and ollyo (to kill), a reference to the fact that plants are killed by drying out

• The specific epithet, filiculoides, is from the Latin for ‘fern like’, which seems slightly disingenuous since it is, actually, a fern

Spores:                            

• Leaves are tiny (.6-2mm), alternate, with two lobes

• The lower lobe hollow for floatation, submerged

• The upper lobe is red or green with hyaline margins

• Dorsal surface of leaves with elongated trichomes (hairs), visible only under > 40 x magnification

Leaves:         

Stem & branches: 

Roots:         

Habit:        

• Plants are floating or laying flat on liquid mud, forming mats which may be very dense and reddish in color (they are green in shadier spots but turn red in direct sunlight or the presence of high nitrogen levels because of the production of anthocyanins, a type of pigment that is responsible for the reds, blues and purples of many fruits

• It is very fast growing, capable of spreading over lake surfaces to give complete coverage of the water in only a few months

• Each individual plant is 1–2 cm across, green tinged pink, orange or red at the edges, branching freely, and breaking into smaller sections as it grows

Habitat:   

• Ponds, sloughs, slow moving streams, up to 1700 m elevation. 

• It is not tolerant of cold temperatures

• In temperate regions it largely dies back in winter, surviving by means of submerged buds 

Distribution:                  

• Temperate regions around the world; region wide in appropriate habitat

• Mostly absent from the coldest and driest parts of the interior

• Native to suitable regions of the Americas (which was introduced to Europe), North and sub-Saharan Africa, China, Japan, New Zealand, Australia, the Caribbean and Hawaii

Additional notes:     

• Reproduction

  • Mostly by pieces breaking off and starting new plants

  • Sporocarps are usually iformed n late spring and summer

• Ecology

  • Eaten by-Geese, swans, herbivorous ducks, larval amphibians, carp, snails, and many other herbivorous aquatic invertebrates feed on this plant

  • When it dies off in the late fall/winter it’s decomposition feeds a multitude of detritus and filter feeding aquatic invertebrates and young fish

• Nirogen fixation

  • All Azolla spp  have an amazing adaptation for meeting their nutritional requirements

  • There is an ovoid space in the bottom of the upper (dorsal) leaf lobe that is filled with their symbiotic partner, the cyanobacteria Anabaena azollae, which acts to fix nitrogen from the air, converting it to ammonia to feed the plant

  • When the plants die back in winter this nitrogen is then released into the environment and acts as fertilizer for other plant life

  • Some consider Azolla spp. to be super-organisms, because this is the only known case of a plant transmitting its symbiotic partner into the next generation via reproduction, in this case as part of the spore

  • Other organisms that utilize symbionts, like Gunnera sp., Cycads, and lichens, must ‘meet up’ with their symbionts after the host has germinated

  • This relationship has been going on for at least 80 million years

• Genome & fossils

  • Azolla filiculoides is one of the first two fern species for which a reference genome has been published

  • Fossil records from as recent as the last interglacials are known from several locations in Europe 

  • Azolla bloom in the Arctic Ocean about 50 million years ago may have sequestered enough carbon to reverse the greenhouse effect on Earth that lead to a warm enough climate that reptiles and palm trees lived at the Poles

• Identification

  • The only sure method of distinguishing this species from Azolla cristata (long incorrectly known as A. caroliniana) is to examine the trichomes on the upper surfaces of the leaves

  • Trichomes are small protuberances that create water resistance

  • They are unicellular in A. filiculoides but septate (two-celled) in A. cristata

• Global spread

  • A. filiculoides was first recorded in Europe in 1870s-1880s, when the species may have been accidentally transported in ballast water, with fry, or directly as an ornamental or aquarium plant

  • It was introduced into Asia from East Germany in 1977 as an alternative to the cold susceptible native strain of A. pinnata, used as a green manure in the rice industry

  • A. filiculoides has also been spread around the world as a research model plant for the study of Azolla-Anabaena symbiosis

• Cultivation

  • Though the mechanism was probably not understood then, Asian rice farmers as far back as 7,700 years ago noticed the positive effect of Azolla on their rice yields, and a separate agriculture of Azolla inoculates was born to meet the demand, since the paddies had to be re-seeded with the stuff each spring after the winter die back

  • Once the mechanics of this relationship between the ‘green manure’ of mosquito ferns and rice production became better known in the early 20th century the practice eventually became almost universal, and in the early 1960s Azolla filiculoides became the Azolla of choice for most rice farmers because of its resistance to cold temperatures. 

  • A. filiculoides is frequently cultivated in aquariums and ponds, where it can become easily dominant over other species

  • Besides fertilizing rice paddies Azolla spp. are now being farmed to provide feed for livestock, and even humans

  • It can double its mass in just a few days under good conditions, and is highly nutritious, with 25-30% protein by dry weight, vitamin B12, beta carotene, amino acids, and calcium, iron, magnesium, and a host of other minerals

  • After harvesting it can also be used to to bulk up compost and fertilise terrestrial crops

• Invasive 

  • It  is capable of rapid growth, especially in eutrophic ecosystems, and outcompetes native aquatic plants

  • In some places it has become a noxious weed which can starve and suffocate the lifeforms below

Sources of information:

• https://en.wikipedia.org/wiki/Azolla_filiculoides (2023)