A huge colony of Spirogyra
This algal colony of Spirogyra is so long that it extends beyond the screen. Each individual cell in this long chain has helically arranged chloroplasts. This time-lapse video allows us to see particles moving in the cytoplasm, which cannot be observed in real time.
Commentary by Prof. Yuji Tsukii, Hosei University
Spirogyra is identified by various features: cell diameter; the number of ribbon-shaped chloroprasts arranged in a spiral inside each cell; the number of coils formed by each spiral chloroplast; the structure of the septum with or without folded structure; and characteristics of the conjugation process (how they form conjugation tubes, the shape and appearance of the newly formed zygote). A large number of species of Spirogyra have been identified to date.
The Spirogyra in this video is characterized by a diameter of 120μm, smooth septa between two of the cells, and one ribbon-shaped chloroplast which has four coils inside the cells. However, Spirogyra having these characteristics is not listed in the book of Japanese fresh water algae (Uchida Roukakuho, 1977).
Generally, Spirogyra with a diameter greater than 100μm have more than one chloroplasts, and in many cases more than four chloroplasts. However the Spirogyra in this video has only one chloroplast. Is the scale of this video correct? If the cell diameter of this organism is actually less than 100μm, there are many organisms having the same features as this organism. Please refer to the following link for examples of such smaller organisms in a series of photographs from my personal library.
Sampling Date : 28 May 2009
Sampling Site : Hirose River B Google Map