Coleochaete Morphology & Reproduction

Algae

1. Coleochaete: Morphology & Reproducti on Ganesh Kumar Asst. Professor-Botany MBC Govt. Girls College Barmer

2. Occurance: The genus Coleochaete (Gr. Keleon, sheath; chaetos, hair) is represented by about 10 species, out of which 3 species are found in India. They grow in fresh water either as epiphytes on different angiosperms ( Trapa, Hydrilla, Ipomea, Sagittaria, Typha , etc.) and algae ( Oedogonium , Vaucheria ) or as endophytes ( C . nitellarum ) within the cells of Chara and Nitella (Chlorophyceae).

3. Morphology Plant body is thalloid, multicellular and of two types: (a) Cushioned forms: Cushioned forms, such as Coleochaete pulvinata show clear heterotrichous habit with a prostrate and an erect system. Erect system is very much branched and combine to form cushion. (b) Discoid forms:Discoid forms, such as Coleochaete scutata and C. nitellarum , are represented mainly by prostrate system. Filaments in this system combine and form discin which the cells remain arranged radially.

4. Morphology continued….. Thallus is surrounded by a sheath of mucilage in both the types. All the species are characterized by the presence of some fine hairs called setae. A basal sheath is present at the base of these hairs. These hairs are not permanent structures. Each cell is slightly elongated, uninucleated with parietal chloroplast. In general, cells possess single pyrenoid only.

5. Asexual Reproduction During spring or early summer, asexual reproduction takes place by the formation of zoospores. Any cell of the plant body may function as zoosporangium. Each zoosporangium produces single zoospore. Zoospores are ovoid, unicellular, uninucle­ate and biflagellate structure with a large parietal chloroplast. Eye-spot is absent. The zoospores are liberated from the zoosporangium through a pore on the sporangial wall. It loses flagella within a short time and secretes a wall on the periphery.

6. Sexual Reproduction Sexual Reproduction is of oogamous type. Antheridia are formed in marginal cells and are present intermingled. In each antheridium, single, colorless and biflagellate antherzoid develops. Oogonia also develop in marginal cells. Each oogonium is flask like structure which contains a single egg. After fertilization, some branches develop around the oospore which surrounds it completely known as spermocarp.

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