Fungal Biology Lecture 2B (F09)

Lecture: Fungal Diversity, Part B BIOL 4848/6948 - Fall 2009

Biology of Fungi The Kingdom Fungi

 Kingdom Fungi (Mycota)  Phylum: Chytridiomycota The Diversity of Fungi and  Phylum: Zygomycota  Phylum: Glomeromycota Fungus-Like Organisms  Phylum: Ascomycota  Phylum: Basidiomycota  Form-Phylum: Deuteromycota (Fungi Imperfecti)

The Chytridiomycota The Chytridiomycota (cont.)

 ‘Chytrids’ are considered the earliest  Zoospore branch of the true fungi (Eumycota) ultrastructure is  Cell walls contain chitin and glucan taxonomically important within  Only true fungi that produce motile, flagellated zoospores this phylum  Usually single, posterior whiplash type Ultrastructure of chytrid zoospores.  Some rumen species have multiple flagella Source: Kendrick, 2003

The Chytridiomycota (cont.) The Chytridiomycota (cont.)

 Commonly found in soils or aquatic  A few are obligate intracellular parasites environments, chytrids have a of plants, algae, and small animals significant role in degrading organics (e.g., frogs)  Exhibit many of the same thallus structure types and arrangements as hyphochytrids (e.g., eucarpic; rhizoidal; endobiotic; etc.)

Unstained specimen showing a number of oval-shaped chytrids (arrow) infecting the skin of a frog. Source: www.jcu.edu.au/school/phtm/PHTM/frogs/anzcarrt.htm

1 Lecture: Fungal Diversity, Part B BIOL 4848/6948 - Fall 2009

The Chytridiomycota (cont.) The Chytridiomycota (cont.)

 Very few economically  Isolation of chytrids is not easy important species  Requires ‘baiting’ techniques (Synchytrium  Appears to be species-substrate specificity/ endobioticum causes preference presumably due to specific potato wart disease) receptor molecules on the zoospore Gametophyte stage of Allomyces. Source:  More important (and www.bsu.edu/classes/ruch/msa/blackwell.html surface membrane fascinating) as biological models (e.g, Allomyces)

The Chytridiomycota (cont.) The Chytridiomycota (cont.)

 Five orders within the chytrids, based  Blastocladiales largely on zoospore ultrastructure  Produces true hyphae and narrow rhizoids  Some species (e.g., Allomyces) exhibit  Chytridiales and Spizellomycetales alternation of generations (i.e., rotating from  Similar to one another haploid and diploid phases)  Haploid thalli of Allomyces produce gametes in  Spizellomycetales live in soil specialized gametangia  Chytridiales live in aquatic environments  Diploid thalli of Allomyces produce flagellated  These Orders do not produce hyphae zoospores and resting sporangia  Allomyces also exhibits anisiogamy - two different  Unique to the chytrids, Spizellomycetales sizes of gametes (small, highly mobile [‘male’] and zoospores exhibit amoeboid movement larger, less mobile [‘female’])

Life cycle of Allomyces. Source: The Chytridiomycota (cont.) www.bio.utexas.edu/faculty/laclaire/ bot321/handouts/AllomyLH.jpg

Gametophyte stage of Allomyces (right) and the sporophyte stage (left). Source: www2.una.edu/pdavis/kingdom_fungi.htm

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The Chytridiomycota (cont.) The Chytridiomycota (cont.)

 Monoblepharidales  Neocallimastigales

 Unique among the  Obligate anaerobes true fungi for its  No mitochondria, but means of sexual instead produce energy reproduction via via a hydrogenosome oogamy  Often found in animal rumens; highly cellulytic  Not of economic  Multiflagellated DAPI-stained nuclei (left) from the mature importance thallus with spherical zoosporangium of the rumen fungus, Neocallimastix. Source: Thallus of a Monoblepharella sp. with antheridia zoospores www.bsu.edu/classes/ruch/msa/wubah.html and oogonia (the globose bodies (arrow) are probably mature oospores). Source: www.bsu.edu/classes/ruch/msa/barr.html

The Zygomycota The Zygomycota

 Five features of Phylum Zygomycota  Cell walls contain chitin, chitosan, and polyglucuronic acid  Some members typically bear multinucleate, coenocytic hyphae, i.e., without cross walls (septa; sing., septum)  When present, septa are simple partitions

 Some Orders have regular septations that are Diagrammatic comparison of a coenocytic hypha (arrow) with a septated form [left figure] and a photomicroscopic image of coenocytic hyphae from a zygomycetous fungus [right figure]. flared having a centrally plugged pore Sources: www.apsnet.org/education/IllustratedGlossary/PhotosA-D/coenocytic.htm and www-micro.msb.le.ac.uk/MBChB/6a.htm

The Zygomycota (cont.) The Zygomycota (cont.)

 Produce zygospores (meiospore) via  Importance of the zygomycetous fungi sexual reproduction (gametangial fusion)  Organic degraders/recyclers  Asexual spores (mitospores), termed  Useful in foodstuffs/fermentations sporangiospores, form through cytoplasmic  Pathogens of insects/other animals cleavage within a sac-like structure termed a sporangium  Haploid genome

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The Zygomycota (cont.) The Zygomycota (cont.)

 Generalized life cycle  Asexual stage (cont.)  Asexual stage  A thin-walled sac (anamorphic; imperfect) (sporangium) is walled off at the tip and fills with  Hyphae develop erect cytoplasm containing branches termed multiple nuclei (with sporangiophores collumella underneath Mature sporangia (left image) and a visible collumella (right image). Source: Kendrick, 2003 Development of erect sporangiophores. Source: Kendrick, 2003 sac)

The Zygomycota (cont.) The Zygomycota (cont.)

 Asexual stage (cont.)  Asexual stage (cont.)

 Cytoplasmic cleavage  Cytoplasmic cleavage and separation of and separation of nuclei into walled nuclei into walled units produces units produces sporangiospores sporangiospores  Thin sporangial wall  Thin sporangial wall Ruptured peridium and underlying sporangiospores (left (peridium) breaks image) and remaining collumella following complete (peridium) breaks spore dispersal (right image). Source: Kendrick, 2003 releasing releasing Diagrammatic representation of sporangiospore development and release. Source: www.unex.es/ sporangiospores sporangiospores botanica/LHB/anima/mucor2.htm

The Zygomycota (cont.) The Zygomycota (cont.)

 Asexual stage (cont.)  The zygospore represents the  Sporangiospores teleomorphic phase (sexual; perfect germinate to repeat the asexual life cycle form) of this phylum

Mating of Phycomyces in culture (left image) forming a line of darkly- pigmented zygospores at the point of contact. The zygospores are highly ornate (left image). Source: Generalized life cycle of a zygomycetous Kendrick, 2003 fungus. Source: Deacon, 2006

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The Zygomycota (cont.) The Zygomycota (cont.)

 The zygospore represents the  Mating process  Hyphae make physical contact and exchange teleomorphic phase (sexual; perfect chemical signals to establish that each is of a form) of this phylum different mating type  Results from the fusion of gametangia of  Hyphal tips (isogamous zygophores - not distinguished from one another) grow, loop heterothallic (two different mating types; back towards one another, swell (becoming designated “+” and “-”) or homothallic (self progametangia at this point) then fuse fertile) strains (anastomose)  Nuclei mix/fused and immediate region walled  Acts as a thick-walled resting spore off from rest of hyphae (gametangium or zygosporangium) BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr. BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.

The Zygomycota (cont.) Generalized life cycle of a zygomycetous fungus. Source: Deacon, 2006  Zygosporangium becomes thick walled to form the zygospore

 Hyphae to the sides become empty appendages (suspensor cells)

 Zygospore often forms ornate appendages

 Zygospore and suspensor cells of Zygospore is constitutively dormant Rhizopus. Source: Deacon, 2006 for a time, but then germinates to

Diagrammatic representation of zygospore development. produce a sporangium containing Source: www.unex.es/botanica/LHB/anima/mucor3.htm haploid sporangiospores

The Zygomycota (cont.) The Zygomycota (cont.)

 Phylum Zygomycota - two Classes  Class Zygomycetes (cont.)  Order Entomophthorales - insect pathogens  Class Zygomycetes - six orders  Order Kickxellales - atypical zygomycete  Order Mucorales having regularly septate hyphae  Typical globose mitosporangium containing  Order Zoopagales - mycoparasites hundreds of non-motile asexual spores   Contains saprobes and the common ‘black bread Class Trichomycetes - four Orders molds’ - Mucor, Rhizopus, Absidia  Live nearly exclusively in the guts of arthropods  Contains the corpophilous (dung-fungus) Pilobolus,  Does not produce sporangiospores, but instead which can ‘shoot’ its single spored sporangium trichospores almost 6 feet in the direction of light  Unusual zygospore structure

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The Glomeromycota The Glomeromycota (cont.)

 These fungi were originally placed  Produce large, within the Phlyum Zygomycota thick-walled  Do not produce zygospores spores in soils  Live as obligate, mutualisitic symbionts in that germinate in >90% of all higher plants - known at the presence of arbusular mycorrhizas (AM; a plant root endomycorrrhiza) Spores of the endomycorrhizal fungus Glomus (top image) and an intracellular endomycorrhizal fungus that  has developed vesicles (V) and arbuscules (A) (bottom Will not grow axenically image). Sources: Kendrick, 2003 and Deacon, 2006

The Glomeromycota (cont.) The Glomeromycota (cont.)

Develop non-septate hyphae that invade the root, then form a branch, tree-like arbuscules within the root  Help plants thrive in nutrient poor soils, especially phosphorous

Fossil hyphae and spores (A and B) compared with a spore (C) of a present-day Glomus species (an arbuscular mycorrhizal fungus). Sources: Deacon, 2006

Source: Schusler et al., 2001 The Glomeromycota (cont.)

 Phylogenetics of the Glomeromycota  Based upon rRNA sequences, this phylum is monophyletic

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The Glomeromycota (cont.) The Ascomycota

 Phlyogenetics of the Glomeromycota  This phylum contains 75% of all fungi  Based upon rRNA sequences, this phlyum described to date is monophyletic  Most diverse phylum being significant:  Morphologically distinct from other fungi  Decomposers  Probably had same ancestor as the phyla  Agricultural pests (e.g., Dutch elm disease, Ascomycota and Basidiomycota powdery mildews of crops)  Pathogens of humans and animals

The Ascomycota (cont.) The Ascomycota (cont.)

 Asexual spores  Key feature is the ascus (pl., asci) - (mitospores) sexual reproductive cell containing  Variety of types meiotic products termed ascospores  Usually not used for taxonomic purposes Mitospores (conidia) of Penicillium.  Generally referred Source: Kendrick, 2003 to as conidia  Tend to be haploid Asci and ascospores of Tuber (left image) and Sordaria (right image). Note the thin sac layers (blue arrows) and the ring-like structure (red and dormant arrow) in the inoperculate ascus. Source: Kendrick, 2003

The Ascomycota (cont.) The Ascomycota (cont.)

 Another significant structural feature - a simple septum with a central pore surrounded by Woronin bodies

These two images show Woronin bodies (WB) and vesicles (V) Septate hyphae (left image) and the central pore of a adjacent to the central pore of a simple septum. Source: simple septum (right image). Source: Kendrick, 2003 www.deemy.de/Descriptors/CharacterDefinition.cfm?CID=366

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The Ascomycota (cont.) The Ascomycota (cont.)

 The fruiting body of these fungi, termed  Cup-shaped - apothecium an ascocarp, takes on diverse forms  Flasked shaped - perithecium

Perithecium (left image) and asci with ascospores (right image) of Sordaria. Source: Deacon, 2006

Diagram of an apothecium showing asci/ascospores (left image) and ascomata (apothecia) of Ascobolus (right image). Source: Kendrick, 2003

The Ascomycota (cont.) The Ascomycota (cont.)

 Closed structure - cleistothecium  Embedded structure - pseudothecium  Some ascospores are borne singly or not enclosed in a fruiting structure

Diagram (left image) and a photomicrograph (right image) of a pseudothecium showing asci/ascospores. Source: Kendrick, 2003

Diagram (left image) and a photomicrograph (right image) of a cleistothecium showing asci/ascospores. Source: Kendrick, 2003

The Ascomycota (cont.) The Ascomycota (cont.)

 Asci also vary in  Unituicate-inoperculate - structure: operculum replaced with an elastic ring; found in  Unitunicate-operculate - perithecial and some single wall with lid/opening apothecial (operculum); found only in apothecial ascomata

(fruiting body tissue) Electron micrograph of an unitunicate (single wall) and inoperculate ascus depicting the apical elastic ring (arrow). Source: Kendrick, 2003 Unitunicate (single wall) and operculate (lid) asci. Source: Kendrick, 2003

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The Ascomycota (cont.) The Ascomycota (cont.)

 Protunicate - no active spore shooting  Bitunicate - double-walled ascus in which mechanism; ascus dissolves to release outer wall breaks down, inner wall swells spores; characteristically produced by fungi through water uptake, then expels spores that form cleistothecia

Electron micrograph of a protunicate ascus. Source: Kendrick, 2003 Diagram (left image) and a photomicrograph (right image) of a bitunicate ascus with ascospores. Source: Kendrick, 2003

The Ascomycota (cont.) The Ascomycota (cont.)

 Ascomycetes differ from zygomycetes  Teleomorph - in zygomycetes, the in both their basic anamorphic and anamorph and teleomorph often occur teleomorphic characteristics: together and share the same nomenclature; in ascomycetes, anamorphs  Anamorph - mitospores (conidia) of can be completely separated from the ascomyetes are typically derived from teleopmorph and are often given different modified bits of hyphae, whereas binomials zygospores result from the cleavage of a multinucleated cytoplasm within a  For the Ascomycota, anamorph + sporangium teleomorph = holomorph

The Ascomycota (cont.)

 Life cycle of most ascomycetes typified by Neurospora  Conidia/ascospores give rise to hyphae  Hyphae may continue to grow and produce conidia  Sexual reproduction begins with the differentiation of female hyphae into a trichogyne Diagrammatic overview of the life cycle of Neurospora. Source: Deacon, 2006

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The Ascomycota (cont.)

 Trichogyne is fertilized by a conidium or by an antheridium (male reproductive structure)  Plasmogamy occurs without karyogamy, i.e., cytoplasmic fusion without nuclear fusion, producing heterokaryotic hyphae (presence of two different nuclei in the same cytoplasm)

 The heterokaryotic hyphae undergo crozier Ascus production. Source: Deacon, 2006 formation

The Ascomycota (cont.) The Ascomycota (cont.)

 Nuclear division continues followed by  Karyogamy occurs to form septation of the crozier to produce an a diploid nucleus that then ascus initial cell that contains one nucleus undergoes meiosis of each mating type, i.e., a dikaryotic state  Haploid nuclei are then walled off to form ascospores - typically there are 4-8 meiotic products

Ascus production. Source: Kendrick, 2003

The Basidiomycota The Basidiomycota (cont.)

 Very important for  Oldest confirmed their ecological and basidiomycete fossil agricultural impact is about 290 millions  Majority are years old terrestrial, although  Some are molds, some can be found in some are yeasts, and

The mushroom Russula emetica. marine or freshwater some are dimorphic Mushroom cap in amber. Source: Source: Kendrick, 2003 www.uky.edu/AS/Geology/ webdogs/amber/plants/mushroom- environments b.jpg

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The Basidiomycota (cont.) The Basidiomycota (cont.)

 Features similar to those of the  Key differences Ascomycota  Cell wall  Haploid somatic hyphae  Ascomycetes - two layered  Septate hyphae  Basidiomycetes - multilayered  Potential for hyphal anastomosis  Septa  Ascomycetes  Production of complex fruiting structures  Hyphal forms - simple with central pore surrounded  Presence of a dikaryotic life cycle phase by Woronin bodies  Yeast forms - simple with micropores  Production of a conidial anamorph

The Basidiomycota (cont.) The Basidiomycota (cont.)

 Septa  Basidiomycetes  Dolipore type septum  Ascomycetes surrounded by a  Hyphal forms - parenthosome simple with central  Central pore blocked by a pore surrounded by pulleywheel occlusion Woronin bodies  Dolipore-like, but  Yeast forms - simple parenthosome is absent with micropores

The Basidiomycota (cont.) Dolipore septum in the hypha of the basidiomycetous fungus Coprinus psychromorbidus.

Ascomyceteous septum (left image) showing Woronin bodies (W) and a basidiomycetous dolipore-type septum (right image) depicting the parenthosome. Sources: forages.oregonstate.edu/is/tfis/enmain.cfm?PageID=69 and Kendrick, 2003

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The Basidiomycota (cont.) The Basidiomycota (cont.)

 Dikaryophase  Basidiomycetes  Heterokaryotic nuclei (2 per cell)  Ascomycetes  Not restricted to a tissue phase and may continue  Restricted to indefinitely ascogenous tissue  Perpetuated by the formation of a clamp connection  Nuclear fusion and at each septum of a dikaryotic hypha subsequent meiosis involve the formation of a crozier

Diagrammatic representation of ascosporogenesis. Source: www.unex.es/botanica/LHB/an/asca2.gif

The Basidiomycota (cont.) The Basidiomycota (cont.)

 Basidiomycetes  Heterokaryotic nuclei (2 per cell)  Not restricted to a tissue phase and may continue indefinitely  Perpetuated by the formation of a clamp connection at each septum of a dikaryotic hypha

Clamp connection (left image) and the its dolipore-type septum (right image). Sources: www.apsnet.org/education/IllustratedGlossary/PhotosS-V/septum.jpg and Kendrick, 2003

Diagrammatic representation of clamp cell formation in a basidiomyceteous fungus. Source: www.unex.es/botanica/LHB/an/fibula0.gif

The Basidiomycota (cont.) The Basidiomycota (cont.)

 Meiospore production - meiosis occurs  Very complex life cycles that vary within a specialized cell termed a basidium among the different classes/species (pl., basidia), but the spores are borne exogenously on tapering outgrowths  Generalized life cycle: termed sterigmata (sing., sterigma)  Haploid basidiospores germinate to form hyphae with a single nucleus per cell (monokaryotic phase)  Monokaryons can produce oidia (= conidia)

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Diagrammatic representation of The Basidiomycota (cont.) the generalized life cycle of a basidiomyceteous fungus. Source: Deacon, 2006  Monokaryons of different mating types fuse or an odium attracts monokaryon of compatible mating type, then fuses  Fusion (plasmogamy) results in dikaryotic hyphae (two nuclei per cell; heterokaryotic)  Fruiting body forms containing dikaryotic basidia  Nuclear (karyogamy) fusion occurs followed by meiosis

The Basidiomycota (cont.) Basidiosporogenesis. Source: Kendrick, 2003

 Sterigmata form on the surface of the basidium  Haploid nuclei migrate into the sterigmata as the basidiospore Transmission electron micrograph of a basidium with develops the accompanying sterigma and basidiospores. Source: www.bsu.edu/classes/ruch/msa/mims/1-39.jpg

The Basidiomycota (cont.) The Basidiomycota (cont.)

Diagrammatic representation of basidiospore  Mature basidiospore in  Mature basidiospore in release involving a hilar drop. Source: many fungi released many fungi released www.unex.es/botanica/LHB/an/basid0.gif through a ballistic-like through a ballistic-like method involving a hylar method involving a hylar (or hilar) drop (see (or hilar) drop (see Chapter 1 in Money’s Chapter 1 in Money’s book for historical and book for historical and Scanning electron micrograph of a basidium with the accompanying sterigma, descriptive details about basidiospore, and hilar droplet. Source: descriptive details about from McLaughlin et al. (1985) as depicted at this mechanism) tolweb.org/tree?group=Basidiomycota this mechanism)

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The Basidiomycota (cont.) The Basidiomycota (cont.)

 Phylogenetics  Taxonomy  rDNA analysis has separated the Phylum  Urediniomycetes Basidiomycota into three separate sub-  Agriculturally significant “rusts” groups (clades)  Example Puccinia graminis - causes black stem  Hymenomycetes - typical mushroom, of wheat toadstools, and “jelly fungi”  Urediniomycetes - “rusts”  Ustilaginomycetes  Ustilaginomycetes - “smuts”  Agriculturally significant “smuts”  Phylogenetic relationships between and  Example Ustilago maydis - corn smut fungus within the sub-groups remains unclear

The Basidiomycota (cont.) The Basidiomycota (cont.)

 Selected differences between ‘rusts’ and  Hymenomycetes - four clades

‘smuts’ (adapted from Table 5.1 in  Homobasidiomycetes - mushrooms, toadstools, Kendrick): bracket fungi, puffballs, earthstars  Jelly fungi Urediniomycetes Ustilaginomycetes  Tremellomycetidae Terminal teliospores Intercalary teliospores  Dacrymycetales No clamp connections Clamp connections present  Auriculariales Requires 2 hosts Does not require 2 hosts Infections are localized Infections are systemic Obligate biotroph Facultative biotroph

The Mitosporic Fungi The Mitosporic Fungi (cont.)

 Many ascomycetous fungi produce  Due to the absence of a teleomorph, asexual (mitotic) spores (anamorphic these fungi are often given a provisional phase), but their teleomorph phase name termed a “form” genus/species (sexual reproduction) is absent  If the teleomorph is discovered, the  Taxonomically, such fungi are placed in fungus renamed an artificial category variously termed Deuteromycota (or Deuteromycotina) or Fungi Imperfecti

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The Mitosporic Fungi (cont.) The Mitosporic Fungi (cont.)

 Example of  Teleomorph - teleomorph/anamorph Emerciella nidulans - dichotomy of names: forms a cleistothecium containing ascospores,  Anamorph - Aspergillus therefore classified nidulans - forms within the Phylum mitosporically-derived Ascomycota conidia, therefore Scanning electron micrograph of conidia and classified within the phialides of Aspergillus nidulans. Source: Cleistothecium of Aspergillus. Source: www.gettysburg.edu/~rcavalie/em/sem_pics.html www.angelfire.com/wizard/kimbrough/Textbook/ form-phylum CommonGroupsZygoAsco_blue.htm Deuteromycota

The Mitosporic Fungi (cont.) Thallic vs. Blastic

 Conidia are produced in a variety of ways, but never by cytoplasmic cleavage as in the Zygomycota  Two main types of conidium development are the basis for the production for all types of conidia  Thallic - fragmentation process  Blastic - swelling process Thallic vs. blastic conidiogenesis. Source: Kendrick, 2003

Thallic vs. Blastic The Mitosporic Fungi (cont.)

 Most conidia are blastic in origin and are borne in various ways:  Budding

Geotrichum candidum. Source: Phialophora verrucosa. Source: www.doctorfungus.com pathmicro.med.sc.edu/mycology/ mycology-5.htm

Thallic vs. blastic conidiogenesis. Source: Kendrick, 2003

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The Mitosporic Fungi (cont.) The Mitosporic Fungi (cont.)

 Extrusion of flask  Aggregation of shaped cells condiophores in stalks termed phialides termed synnema or coremium

Fungal synnema Source: bios.sakura.ne.jp/ gf/2003/synnema.html

Conidiophore of Aspergillus of phialide (long arrow) and metulae (arrow head). Source: abmed.ucsf.edu/Education/fung_morph/fungal_site/subpages/aspergillusvesiclemetulasp.html

The Mitosporic Fungi (cont.) The Mitosporic Fungi (cont.)

 On a pad-like surface  Taxonomic divisions of the Fungi (acervulus) Imperfecti - truly an artificial  Within a flask-shaped classification scheme based solely on structure (pycnidium) conidial structures  Hyphomycetes - conidia borne on conidiophores  Coelomycetes - conidia borne on an acervulus or within a pycnidium Fungal acervulus (left) and pycnidium (above) Source: Kendrick, 2003  Agonomycetes - “Mycelia Sterilia” - no conidia; sometimes sclerotia BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr. BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.