|Oedogonium sp., showing an oogonium (swollen cell) and antheridia (short stacked cells)|
(Hirn, 1900) Link
Oedogonium is a genus of filamentous green algae, with unbranched filaments that are one cell thick. Oedogonium can be free-floating, though it is usually attached to aquatic plants by a holdfast. It appears greenish and inhabits calm, fresh water.
Oedogonium can reproduce asexually by fragmentation of the filaments, through some other types of non-motile spores, and also through zoospores, which have many flagella. These develop in a zoosporangium cell, one zoospore per zoosporangium. After settling and losing its flagella, a zoospore grows into a filament.
The life cycle of Oedogonium is haplontic, i.e., meiosis is zygotic. Antheridia which produce sperm, and oogonia which produce an egg, release the sperm and egg. The egg and sperm then fuse and form a zygote which is diploid (2n). The zygote then produces the filamentous green alga which is haploid (1n).
Species of Oedogonium are divided into two major groups on the basis of the distribution of the sex organs:
- Macrandous Species – In these species, antheridia are borne on filaments of normal size. This group is further subdivided into:
- Macrandous Monoecious – In these species, antheridia and oogonia are found on the same filament. E.g.: O. nodulosum and O. fragile
- Macrandous Dioecious – In these species, antheridia and oogonia are borne on different filaments. Although filaments bearing antheridia and oogonia are morphologically similar, they differ physiologically. E.g.: O. crassum and O. aquaticum
- Nannandrous Species – In nannandrous species, filaments bearing antheridia and oogonia show morphological distinction. The male filament, which are much smaller than the female filament, is called a dwarf male or nannandrium. Nannandrous species are always dioecious, i.e., antheridia and oogonia are borne on different filaments. The small male filaments are likely to be attached to a female filament, near an oogonium.
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