General characteristics
• Hyphae are coenocytic
• Flagellated spores are absent
• Most reproduce asexually by producing
sporangiospores within a special sac
called the sporangium.
• Sexual spores are called zygospores
contained within a zygosporangium
formed following gametangial fusion /
copulation
Classification
• Two classes:
•
Zygomycetes and
Trichomycetes.
• Zygomycetes
• 870 species in 124 genera, 32 families and 10
orders.
• Trichomycetes
• 218 species in 55 genera, 6 families and 3 orders.
Class: zygomycete.
order
mucorales
Family
Family
Mucoraceae
Mortierellaceae
Family
Family
Thamnidiaceae
Chaenophoraceae
Family
Cephalidaceae
Family
Pilobolaceae
Asexual reproduction
• Reproduce asexually by sporangiospores in most
orders of the Zygomycetes, conidia in the
Entomophthorales and arthrospores in some
Trichomycetes
• Sporangium types (4 types)
• True sporangium
• Sporangioles - much smaller than true sporangia. No
columella produced and few spores (1-50)
• Monosporous sporangium (one-spored sporangium)
• Merosporangium - sac containing 10 -15 sporangiospores
that occur in a linear sequence
columella
sporangium
sporangiophore
rhizoids
Rhizopus
Sexual Reproduction
• Gametangial copulation
• Homo- & heterothallic species
• Heterothallism the condition of being self-sterile,
requiring a partner for sexual reproduction
• Homothallism the condition of being self fertile;
able to reproduce sexually without a
partner exhibited among species in this phylum
• zygos (Gr.) - yoke, joining
• Refers to the fusion of gametangia to form a unique
structure called the zygosporangium
•Zygosporangium
•gametangium
Sexual Reproduction
+
Mycelium
Progametangia
karyogamy
Suspensors
Gametangia
Zygote
Zygospore
Zygomycota Life Cycle
Order Mucorales
• 30% of known zygomycetes (~300 spp.)
• Well developed, typically coenocytic mycelium
• Wall composition of chitosan, chitin and
polyglucoronic acid
• Asexual reproduction by formation of
sporangiospores cleaved out from the cytoplasm of
sporangia
• Chlamydospores may be formed
• Called mucoralean or mucoraceous fungi
Mucorales
• Members of this group are the "weeds" of the fungal
world
• Common genera include Mucor, Absidia, Rhizopus,
and Pilobolus.
• Grow and invade quickly on easily digestible
substrates, such as those containing starches,
sugars, and hemicelluloses
• Can act as parasites and/or cause diseases in
plants, animals and some insects and humans
• In humans, such diseases are opportunistic and
occur in an immunocompromised person (e.g.,
uncontrolled diabetes, AIDS)
Order Mucorales: Body plan
• rhizoids: root-like hyphae that adhere reproductive
structures to substrate
• stolon: connect two groups of rhizoids
Classification of mucorales
Mucorales is divided into the following
families:
1- Mucoraceae: sporangia always present, columellae
present, zygospor usually naked;
wall of the sporangium homogenous, not cuticularized,
usually diffluent, sporangia of one sort.
2- Thamnidiaceae: sporangia of two – sorts, primary and
secondary. e.g. Thamnidium sp.
3- Pilobolaceae: wall cuticularized and persistent
above,thin and diffluent below. E.g. pilobolus sp.
4- Mortierellaceae: columella absent; zygospore
enveloped in a dense hyphal covering. E.g.
mortierelle sp.