Spirogyra sp. (Green Algae)

Spirogyra is a filamentous green algae that can often form flimsy green aggregates in freshwater ponds. It is distinguished by having unbranched filaments and with chloroplasts forming a spiral ribbon just under the cell surface. This gives a coiled or twisted texture to the cells, and it is from this appearance that the organism gets its name (Greek speira, "coil" + gyros, "twisted") The cell wall is characteristically straight and parallel-sided. The single chloroplast usually almost fills the length of the cell. There are several pyrenoids which are starch-containing bodies and can be revealed by staining with Lugol's iodine. Sexual reproduction involves neighboring filaments that send out processes which fuse into tubes. The contents of one cell pass through the conjugation tube into a partner cell and go through process that lead to the formation of a reasonably resistant zygospore. In many species, adjoining cells in the two filaments form conjugation tubes at the same time, giving the appearance of a ladder.