lecture 24 slime molds

Plasmodial Slime Plasmodial Slime MoldsMolds

http://www.ucmp.berkeley.edu/chromista/chromistasy.html

Ribosomal RNA phylogenies place slime molds as unrelated, early branching eurkaryote lineages

Actin, elongation factor, and β-tubulin phylogenies place the plasmodial and cellular slime molds as a monophyletic group close to Animal + FungI

Baldauf and Doolittle, 1997. PNAS 94 (22): 12007-12012

ClassificationClassification

Mycetozoa = cellular, plasmodial slime Mycetozoa = cellular, plasmodial slime molds plus protostelidsmolds plus protostelids

Cellular slime molds and protostelids now Cellular slime molds and protostelids now placed in phylum Myxomycotaplaced in phylum Myxomycota

Names imply a fungal-like affinityNames imply a fungal-like affinity

MyxomycotaMyxomycota

Myxomycetes--5 orders, 13 families, 62 Myxomycetes--5 orders, 13 families, 62 genera, 800 speciesgenera, 800 species

Characterized by Characterized by plasmodiumplasmodium Engulfs bacteria, fungal spores, small pieces Engulfs bacteria, fungal spores, small pieces

of organic matterof organic matter

PhysarumPhysarum life cycle life cycle

macrocyst

karyogamy

meiosis

microcyst

Synchronous mitotic divisions

Stages in Life CycleStages in Life Cycle

Spores (2nSpores (2nn)n) 4-20 4-20 µmµm, pigmented , pigmented

ornamented; meiosis ornamented; meiosis in spore = 4 nuclei; 3 in spore = 4 nuclei; 3 degeneratedegenerate

Stages in Life CycleStages in Life Cycle

Myxamoebae (n)Myxamoebae (n) feed, divide, convert to feed, divide, convert to

swarm cells, function swarm cells, function as gametes; form as gametes; form microcysts under microcysts under adverse conditionsadverse conditions

www.uoguelph.ca/~gbarron/ MISCE2002/myxamo2.jpg

Stages in Life CycleStages in Life Cycle

Swarm cells (n)Swarm cells (n) 1-4 anterior whiplash 1-4 anterior whiplash

flagella, amoeboid flagella, amoeboid posterior; feed posterior; feed (absorption and (absorption and engulfment), function engulfment), function as gametesas gametes

can’t undergo cell can’t undergo cell divisiondivision

http://www.botany.hawaii.edu/faculty/wong/Bot201/Myxomycota/Swarm_Cells2.jpg

Stages in Life CycleStages in Life Cycle Zygote (2n)Zygote (2n)

Formed by fusion of myxamoebae or swarm Formed by fusion of myxamoebae or swarm cells; enlarges through synchronous nuclear cells; enlarges through synchronous nuclear divisiondivision

Plasmodium (2n)Plasmodium (2n) Multinucleate, wall-less protoplasmMultinucleate, wall-less protoplasm

Photo by Stephen Sharnoff

http://www.plant.uga.edu/mycology-herbarium/myxogal/Physros3.jpg

Stages in Life CycleStages in Life Cycle

Sporophore (2n)Sporophore (2n) Entire plasmodium is Entire plasmodium is

converted into converted into sporophore(s)sporophore(s)

Sclerotium or Sclerotium or macrocyst (2n)macrocyst (2n) Resistant stage Resistant stage

formed by plasmodiumformed by plasmodium

Types of plasmodiaTypes of plasmodia

PhaneroplasmodiumPhaneroplasmodium Conspicuous, often colored, with protoplasm Conspicuous, often colored, with protoplasm

forming veins with reversible streamingforming veins with reversible streaming AphanoplasmodiumAphanoplasmodium

With a network of fine, transparent threads With a network of fine, transparent threads and homogenous protoplasmand homogenous protoplasm

ProtoplasmodiumProtoplasmodium Microscopic, with homogenous protoplasm, Microscopic, with homogenous protoplasm,

giving rise to one sporophore giving rise to one sporophore

SporophoresSporophores

Mass of spores formed inside peridium, spores Mass of spores formed inside peridium, spores intermingled with:intermingled with: CapillitiumCapillitium

• threadlike, often ornamentedthreadlike, often ornamented ElatersElaters

• Threadlike, ornamented, not connected at endsThreadlike, ornamented, not connected at ends PseudocapillitiumPseudocapillitium

• Threads, bristles, membrane or platelike networkThreads, bristles, membrane or platelike network

Lime may be present on peridium, stalk, Lime may be present on peridium, stalk, columella or capillitium, or nodes of columella or capillitium, or nodes of pseudocapillitumpseudocapillitum

www.botany.hawaii.edu/.../Bot201/ Myxomycota/elaters.jpg

Capillitium (top left; photo by David Geiser)

Pseudocapillium (top right; photo from Fifth Kingdom)

Elaters (bottom left)

Sporocarp—stalked or sessileSporocarp—stalked or sessile

May have columella

AethaliumAethalium

Large, cushion-shaped Large, cushion-shaped sporophore, one per sporophore, one per plasmodiumplasmodium

PseudoaethaliumPseudoaethalium

Cluster of sporophores Cluster of sporophores grouped tightly grouped tightly togethertogether

Photo by David Geiser

PlasmodiocarpPlasmodiocarp

Sporophore developing Sporophore developing along veins of along veins of phaneroplasmodium; phaneroplasmodium; takes on reticulate takes on reticulate shape of veinsshape of veins

Photo by Stephen Sharnoff

Liceales-- Pale or brown spores, capillitium and lime absent, Liceales-- Pale or brown spores, capillitium and lime absent, pseudocapillitium may be presentpseudocapillitium may be present

Dictydium

Lycogala Photo by Stephen Sharnoff

Trichiales--Pale spores (yellow, orange or red) and abundant, Trichiales--Pale spores (yellow, orange or red) and abundant, conspicuous capillitium conspicuous capillitium

Trichia

Arcyria

Physarales--Purplish-brown spores, usually with abundant Physarales--Purplish-brown spores, usually with abundant and conspicuous lime on or in sporophoreand conspicuous lime on or in sporophore

Badhamia

FuligoLeocarpus

Stemonitales--Violet-brown spores, lime absentStemonitales--Violet-brown spores, lime absent

Diachea

Lamproderma

Stemonitis

Photo by Stephen Sharnoff

Ceratiomyxales--Exosporous sporophores; probably Ceratiomyxales--Exosporous sporophores; probably belongs in protostelids (one genus, belongs in protostelids (one genus, CeratiomyxaCeratiomyxa))

Photo by Stephen Sharnoff Photo by David Geiser

ProtostelidsProtostelids

Simplest known slime moldsSimplest known slime molds Discovered in 1970Discovered in 1970

Easily mistaken for mucoraceous fungi or Easily mistaken for mucoraceous fungi or deuteromycetesdeuteromycetes

In dead, attached plant parts, herbivore In dead, attached plant parts, herbivore dung or soil; feed on bacteria, yeast and dung or soil; feed on bacteria, yeast and fungal sporesfungal spores

14 genera and 32 species14 genera and 32 species

Protostelid Life CycleProtostelid Life Cycle

Amoeboid cells (filose pseudopodia) Amoeboid cells (filose pseudopodia) become one or more prespore cells that become one or more prespore cells that rise on stalk and encyst to form one to four rise on stalk and encyst to form one to four spores spores

Plasmodium and flagellated cells present Plasmodium and flagellated cells present in “complex” life cyclesin “complex” life cycles

Sexual reproduction not knownSexual reproduction not known

http://comp.uark.edu/~fspiegel/protist.html#sporocarp%20morphology

Life cycle of simple protostelid

http://comp.uark.edu/~fspiegel/protist.html#sporocarp%20morphology

Life cycle of complex protostelid

Images courtesy of Fred Spiegal, Univ. of Arkansas