The water net (
genus ''Hydrodictyon'') is a taxon of freshwater
green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
in the
family Hydrodictyaceae
Hydrodictyaceae is a family of green algae in the order Sphaeropleales.
Genera
* '' Euastropsis''
* '' Helierella''
* '' Hydrodictyon''
* '' Lacunastrum''
* '' Monactinus''
* '' Parapediastrum''
* ''Pediastrum
''Pediastrum'' is a genus of ...
. ''Hydrodictyon'' does well in clean,
eutrophic water, and has become a nuisance in
New Zealand, where it has been recently introduced. The name ''water net'' comes from the (usually
pentagon
In geometry, a pentagon (from the Greek πέντε ''pente'' meaning ''five'' and γωνία ''gonia'' meaning ''angle'') is any five-sided polygon or 5-gon. The sum of the internal angles in a simple pentagon is 540°.
A pentagon may be simpl ...
al or
hexagonal) mesh structure of their colonies, which can extend several decimeters.
Reproduction in hydrodictyon
Algae in the genus can reproduce
asexually or
sex
Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes (spermatozoa, sperm, pollen), while females produce larger ones (ova, oft ...
ually. Asexual reproduction takes place by biflagellated (having two
flagella
A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates.
A microorganism may have f ...
)
zoospores formed by the thousands inside a cell. However, the zoospores hardly move, as they are packed very densely. The zoospores form a cell wall, become cylindrical in shape, and arrange themselves in a hexagonal pattern, much like the mature tissue. The mother cell disintegrates, releasing the
microscopic daughter net.
During sexual reproduction, which takes place by iso-
gametes (gametes of the same size) even smaller than the zoospores, the iso-gametes escape through a hole in the cell wall of the mother cell. Two gametes fuse, forming a
zygote, which then develops a thick cell wall and becomes angular in shape. After a rest period, 2-5 zoospores, which are bigger than the ones formed by asexual reproduction, are produced. The zoospores then enlarge into polygonal cells. The
cytoplasm of the cells then divide into new zoospores which lose their flagella and form a new net by lying against each other.
External links
Hydrodictyon on the Protist Information Server
* ttp://www.mic-d.com/gallery/brightfield/hydrodictyon.html Microscopic viewbr>Entry in the Global Compendium of Weeds
{{Taxonbar, from=Q1508605
Sphaeropleales
