There are very many creatures, amphibians, insects, microbes, water-weed and algae, in the common rice field in Japan. Do you know any other very similar to water-weed? The species name is Chara buraunii, and they are called “Charophyte” in English. Commonly algae shapes are a leaf like kelp, intertwined with a thin thread, single cells and so on, but the charophyte has an organ-like stems and leaves, so they are similar to water-weed. The form is that the stem that is 1 mm diameter and about 10 to 50 cm length and has nodes at which grow 8 to 11 twigs like leaves or stalks with whorled phyllotaxis. In Japan, the charophyte is called “Shyazikumo” meant “axle algae” the name of which comes from the stem and whorled phyllotaxis which are like a spindle and wheels.
C. buraunii is kind of Chara species, and also belong to Chara and Characeae. Basically Chara has cortex, but C. buraunii is an exception in that it doesn’t have cortex. In Chara, there are many algae described in the red data book in Miyazaki prefecture or Fukui prefecture on one of Ministry of the Environment classified C. buraunii into “an endangered species Ⅱ” which means “species in danger of extinction is increasing”.
Charales species often live in shallow fresh water area like rice fields, but it can grow in relatively faint light areas like the bottom of lakes and marshes or a little dirty water. So, they make pure colony, “Charophyte area” in the bottom where other algae and water-weed can’t live. But the hardship to live in the area isn’t only for other algae and water-weed, but it’s also hard for the charophyte to live. If the water gets cloudy by water pollution, the sun light will not be able to reach the charophytes living in the area will die out. For that reason, there are some species that have already died out, hakonesyazikumo (Chara globularis var. hakonensis) etc. We can’t save the species that have already become extinct, but may be able to bring back the species that had briefly disappeared by water improvement, provided that the lake once they had lived, because sometimes the spore remained in the bottom of the lake.
Charophyte’s appearance is like water-weed that is seed plants, but its ecology is near to algae. Charophyte is kind of multi cellular algae that do not have vascular bundles and the regeneration used the spore, and has photosynthesis pigment which is chlorophyll a and b, so classify Chlorophyceae. The regeneration doesn’t use seed, but use spore that made from the gamete of male and female. Charophyte’s the antheridium and the archegonium has feature that are reddish.
Certainly, there are some endangered species in charales, but many species can be often seen in rice fields of Kochi prefecture. Particularly, we can see charales in the spring when fields are filled with water, about May in Kochi, to the end of summer. But the appearance is only water-weed that we often see, so I think that you probably aren’t interested to see it.