Haplomastigomycotina
Sub-division: Haplomastigomycotina:- Flagellated cells bear only one type of flagella either whiplash type or tinsel type.
It includes 3 classes -
1. Chytridiomycetes (Aquatic):-
> Most of the members are unicellular, but some advanced taxa form short chains of cells which are attached to the substratum with the help of rhizoids. Some forms possess undeveloped mycelium.
> Chitin and glycan are the main constituents of the cell walk
> In unicellular forms the thallus is holocarpic (whole vegetative thallus transforms into one or more reproductive structures), whereas in filamentous forms it is eucarpic (some part of the vegetative thallus transforms into reproductive structure, while the rest remains vegetative).
> The members of the class may be epibiotic (reproductive bodies present on the host’s surface) or endobiotic (live completely within the cells of the host) and monocentric (having only a single reproductive structure) or polycentric (having more than one reproductive structures).
> The thallus is coenocytic but sex organs are separated from vegetative part by a septum.
> Asexual reproduction takes place with the help of zoospores which are posteriorly uniflagellate. The flagellum is of whiplash type. Zoosporangia are spherical or pear-shaped and inoperculate or operculate.
> Planogametes are also posteriorly uniflagellate.
> The zygote is formed by the fusion of planogametes and it is transformed into a resting spore which produces zoospores on germination.
> Classification:-
4 Orders:-
a. Chytridiales:- Eg.- Olpidium, Rozella, Chytridium, Synchytrium, Rhizophydium, Polyphagus, Chytriomyces, Nowakowskiella
b. Harpochytriales:- Eg.- Harpochytrium, Oedogoniomyces
c. Blastocladiaceae:- Eg.- Allomyces, Blastocladia, Blastocladiella, Coelomomyces, Catenaria
d. Monoblepharidales:- Eg.- Monoblepharis, Gonopodya
2. Hyphochytridiomycetes (Aquatic):-
> All members are aquatic which are either fresh aquatic or marine.
> They are parasites on algae and fungi or saprobic on plant and insect debris in the water.
> Thallus:- Unicellular which is either holocarpic or eucarpic.
- In holocarpic species the thallus is endobiotic and is converted into a zoosporangium.
- In eucarpic species the thallus is either monocentric or polycentric.
- Also they have a rhizoidal or hypha-like vegetative system (hence the prefix "Hypho-").
> Asexual reproduction:-
- The zoosporangia are inoperculate.
- The zoosporangia release their zoospores through discharge tubes.
- They are distinguished by an anterior tinsel flagellum on their zoospores.
> Sexual reproduction:- Unknown.
> Classification:-
Order:- Hyphochytriales
2 Familes:-
i. Hyphochytriaceae:- Eg.- Canteriomyces, Cystochytrium, Hyphochytrium
ii. Rhizidiomycetaceae:- Eg.- Latrostium, Reessia, Rhizidiomyces
3. Plasmodiophoromycetes (Endoparasitic):-
> They are obligate endoparasites of the seed plants (Cabbage, Nasturtium), ferns (Azolla), algae (Vaucheria) and Fungi (Achlya, Saprolegnia).
> The somatic phase is a moving, naked, multinucleate mass of protoplasm feeding in an amoeboid fashion. It is known as the Plasmodium.
> Plasmodium grows within the host cells and is holocarpic.
> Two types of plasmodia namely primary or gametangial plasmodia and secondary or cystogenous Plasmodia occur in the life cycle. The former are haploid and the latter diploid.
> The entire protoplasm of the primary Plasmodium divides to give rise to thin-walled gametangia, each of which contains a single motile biflagellate, uninucleate structure which functions as a gamete. It is called a zoospore and the Plasmodium bearing it as zoosporogenous Plasmodium.
> The cystogenous Plasmodium divides by meiosis to form thick- walled resting meiospores. Some scientists call them resting sporangia or cyst.
> On germination each cyst gives rise to a zoospore or cyst zoospore.
> Both the gametes and the cyst zoospore are uninucleate, biflagellate and similar in structure.
> Both the flagella are of whiplash type but of unequal length (heterokont) and inserted anteriorly, the shorter near the longer one. The longer flagellum terminates in an end piece. The shorter flagellum lacks the end piece. It has blunt tip.
> When the swarm cell is in motion, the longer flagellum trails behind and the short blunt flagellum is directed forward.
> The nuclear division occurring during the somatic phase of both gametangial and cystogenous phases is cruciform.
> Sexual reproduction when present is isogamous and takes place by planogametic copulation.
> Classification:-
Order:- Plasmodiophorales
Family:- Plasmodiophoraceae
Eg.- Plasmodiophora, Tetramyxa, Octomyxa, Polymyxa, Spongospora, Ligniera, Woronina, Sorosphaera, Sorodiscus, Membranosorus