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.