General Characteristics of Phycomycetes: An Overview
Kavita Rambal
FYBSC -BOTANY
Fungi Classes
•
Fungi are usually classified according to biological taxonomy based
upon the type of hypha, spore, and reproduction. There are four
classes of fungi, whose characteristics are
•
a.
Class Phycomycetes
. The algal fungi: bread molds and leaf molds
•
•
b.
Class Ascomycetes
. The sac fungi: yeasts, mildews, and cheese
molds.
•
c.
Class Basidiomycetes
. Mushrooms, toadstools, rusts, and smuts.
•
d.
Class Deuteromyceters
. Fungi imperfecti: a heterogeneous
collection of fungi without sexual reproduction. Most of the
pathogens encountered in medical mycology belong to this class.
PHYCOMYCETES
•
Phycomycetes is derived from two Greek
words viz; “Phykos” : ALGA and
“Mycetae”:Mushroom (Fungi).Primitive
phycomycetes are predominantly
aquatic,higher forms show dependence on
moisture and are either saprophytic or
parasitic.
PHYCOMYCETES
•
A large, important class of parasitic or
saprophytic fungi, alga like fungi.
•
The plant body ranges from an undifferentiated
mass of protoplasm to a well-developed and
much-branched mycelium.
•
Reproduction is mainly sexual, asexual by the
formation of conidia or sporangia; but the group
shows every form of transition from this method
through simple conjugation to perfect sexual
reproduction.
Phycomycetes
Thallus Structure
•
In very primitive forms the thallus is one celled with
or without cell wall. In Olpidium cell wall is absent.
•
Advanced unicellular types show branched hair like
rhizoidal system (anchorage).Chytridium.
•
Unicellular forms are holocarpic.Majority have
coenocytic,branched and aseptate hyphae.Vegetative
& reproductive parts are well differentiated.Hyphae
together form a mycelllium.
•
Hyphae give out haustoria.
Phycomycetes
Reproduction
Phcoymycetes reproduce
:
1)
Asexually
2)
Sexually
3)
Vegetatively (Fragmentation)
Asexual Reproduction
•
Asexual reproduction takes place by means of
a) Spores (within sporangia on sporangiophores).
b)Conidia .
c) Chlamydospores.
Asexual reproduction occurs by sporangia which
contain spores. Depending
on
the
habitat
sporangia produce different
spores. In terrestrial they produce conidia and in
aquatic conditions it produces zoospores. They
have two flagella. One of the flagella is smooth
and the other one is tinsel type.
Asexual Reproduction
•
The sporangia are developed at the end of the
hyphae and are cut off by the formation of
septa.The sporangia are of different
shapes.(flask,cylindrical,irregularly lobed or
rounded.
•
The spores are single celled or
aflagellate.Flagellate spores are called zoospores
while aflagellate spores are known as
aplanospores or sporangiospores.
•
Other aflagellate spores are conidia and
chlamydospores.
Asexual Reproduction
•
Zoospores:
Zoospores are formed in aquatic
Phycomycetes.The zoospores are uniflagellate or
biflagellate and naked.
•
The uniflagillate zoospore has one ,whiplash
type of flagellum attached at the anterior narrow
end.
•
Biflagellate zoospore has two types of flagella
one tinsel and the other of whiplash type.
•
Monoplanetism as well as diplanetism is found.
Asexual Reproduction
Sporangiospores or aplanospores
Formed generally by the terrestrial
Phycomycetes e.g,Rhizopus.
1.
The spores are thin, nonmotile ,rounded ,
wind dispersed formed within sporangia.
2.
The sporangia are borne on the tips of the
erect hyphae called sporangiophores.
3.
The sporangiophores may be branched or
unbranched.
Asexual Reproduction
Conidia
•
These are one celled formed on hyphae called
conidiphores.These can be branched or
unbranched.
•
On germination in wet conditions produce
zoospores but in dry conditions they
germinate to form germ tube which develops
into mycelium.
Asexual Reproduction
Chlamydospores
•
Formed in unfavorable conditions
•
Also called resting spores
•
Intercalary in position
•
Eg: Mucor
Oidia
•
These are rounded or oval shaped, thin walled
spores
•
They germinate to produce new mycelium
Sexual Reproduction
It ranges from Isogamy to Oogamy.
Types include:
1.
Gametangial Union or Planogametic
copulation.
2.
Gametangial Contact
3.
Gametangial Copulation
Sexual Reproduction
Gametangial Union or Planogametic copulation.
•
It is the fusion of two gametes,where one or both aremotile.
They may be uniflagellate or biflagellate.
•
The gametes may be similar (isoplanogametic) e.g,Olpidium.
•
The gametes may be dissimilar (anisoplanogametic)
e.g, Allomyces
•
One of the gametes is motile (male) called spermatozoid while
the female gamete is non-motile and is call egg. Eg:
Monoblepharis
Sexual Reproduction
Gametangial Contact
•
Gametes are non-motile (aplanogametes).
•
They are never released.
•
The gametangia are highly differentiated.
•
Male Gametangian is called anthredium and
female oogonium.
•
Anthredium at the time of fertilization develops
fertilization tube which connects oogonium.
Through this tube the male gamete passes and
unites with egg to form a zygote.
Eg: Pythium, Albugo.
Sexual Reproduction
Gametangial Copulation
•
The two gametangia unite without the
formation of fertilization tube.
•
The walls in between dissolve.
•
The cytoplasm and nuclei merge/unite to form
zygospore
Eg: Rhizopus
Phycomycetes constitute an important class of parasitic or saprophytic fungi, exhibiting characteristics ranging from undifferentiated masses to well-developed mycelium. They reproduce sexually and asexually, utilizing spores, conidia, and chlamydospores. The thallus structure varies, with some having a one-celled thallus with a cell wall, while others show branched hair-like rhizoidal systems. Understanding their reproductive mechanisms and thallus structure is crucial in studying these alga-like fungi.
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Presentation Transcript
General Characters of Phycomycetes Kavita Rambal FYBSC -BOTANY
Fungi Classes Fungi are usually classified according to biological taxonomy based upon the type of hypha, spore, and reproduction. There are four classes of fungi, whose characteristics are a. Class Phycomycetes. The algal fungi: bread molds and leaf molds b. Class Ascomycetes. The sac fungi: yeasts, mildews, and cheese molds. c. Class Basidiomycetes. Mushrooms, toadstools, rusts, and smuts. d. Class Deuteromyceters. Fungi imperfecti: a heterogeneous collection of fungi without sexual reproduction. Most of the pathogens encountered in medical mycology belong to this class.
PHYCOMYCETES Phycomycetes is derived from two Greek words viz; Phykos : ALGA and Mycetae :Mushroom (Fungi).Primitive phycomycetes are predominantly aquatic,higher forms show dependence on moisture and are either saprophytic or parasitic.
PHYCOMYCETES A large, important class of parasitic or saprophytic fungi, alga like fungi. The plant body ranges from an undifferentiated mass of protoplasm to a well-developed and much-branched mycelium. Reproduction is mainly sexual, asexual by the formation of conidia or sporangia; but the group shows every form of transition from this method through simple conjugation to perfect sexual reproduction.
Phycomycetes Thallus Structure In very primitive forms the thallus is one celled with or without cell wall. In Olpidium cell wall is absent. Advanced unicellular types show branched hair like rhizoidal system (anchorage).Chytridium. Unicellular forms are holocarpic.Majority have coenocytic,branched and aseptate hyphae.Vegetative & reproductive parts are well differentiated.Hyphae together form a mycelllium. Hyphae give out haustoria.
Phycomycetes Reproduction Phcoymycetes reproduce : 1) Asexually 2) Sexually 3) Vegetatively (Fragmentation)
Asexual Reproduction Asexual reproduction takes place by means of a) Spores (within sporangia on sporangiophores). b)Conidia . c) Chlamydospores. Asexual reproduction occurs by sporangia which contain spores. Depending on the habitat sporangia produce different spores. In terrestrial they produce conidia and in aquatic conditions it produces zoospores. They have two flagella. One of the flagella is smooth and the other one is tinsel type.
Asexual Reproduction The sporangia are developed at the end of the hyphae and are cut off by the formation of septa.The sporangia are of different shapes.(flask,cylindrical,irregularly lobed or rounded. The spores are single celled or aflagellate.Flagellate spores are called zoospores while aflagellate spores are known as aplanospores or sporangiospores. Other aflagellate spores are conidia and chlamydospores.
Asexual Reproduction Zoospores: Zoospores are formed in aquatic Phycomycetes.The zoospores are uniflagellate or biflagellate and naked. The uniflagillate zoospore has one ,whiplash type of flagellum attached at the anterior narrow end. Biflagellate zoospore has two types of flagella one tinsel and the other of whiplash type. Monoplanetism as well as diplanetism is found.
Asexual Reproduction Sporangiospores or aplanospores Formed generally by the terrestrial Phycomycetes e.g,Rhizopus. 1. The spores are thin, nonmotile ,rounded , wind dispersed formed within sporangia. 2. The sporangia are borne on the tips of the erect hyphae called sporangiophores. 3. The sporangiophores may be branched or unbranched.
Asexual Reproduction Conidia These are one celled formed on hyphae called conidiphores.These can be branched or unbranched. On germination in wet conditions produce zoospores but in dry conditions they germinate to form germ tube which develops into mycelium.
Asexual Reproduction Chlamydospores Formed in unfavorable conditions Also called resting spores Intercalary in position Eg: Mucor Oidia These are rounded or oval shaped, thin walled spores They germinate to produce new mycelium
Sexual Reproduction It ranges from Isogamy to Oogamy. Types include: 1. Gametangial Union or Planogametic copulation. 2. Gametangial Contact 3. Gametangial Copulation
Sexual Reproduction Gametangial Union or Planogametic copulation. It is the fusion of two gametes,where one or both aremotile. They may be uniflagellate or biflagellate. The gametes may be similar (isoplanogametic) e.g,Olpidium. The gametes may be dissimilar (anisoplanogametic) e.g, Allomyces One of the gametes is motile (male) called spermatozoid while the female gamete is non-motile and is call egg. Eg: Monoblepharis
Sexual Reproduction Gametangial Contact Gametes are non-motile (aplanogametes). They are never released. The gametangia are highly differentiated. Male Gametangian is called anthredium and female oogonium. Anthredium at the time of fertilization develops fertilization tube which connects oogonium. Through this tube the male gamete passes and unites with egg to form a zygote. Eg: Pythium, Albugo.
Sexual Reproduction Gametangial Copulation The two gametangia unite without the formation of fertilization tube. The walls in between dissolve. The cytoplasm and nuclei merge/unite to form zygospore Eg: Rhizopus
