1. Phylum - Zygomycota
Kingdom Fungi

2. Zygomycota Vegetative stage – well developed aseptate hyphae
Asexual reproduction by nonmotile sporangiospores
Sexual reproduction – Zygospore produced in a zygosporangium from fusion of two similar gametangia
Ca. 800 spp.

3. Zygomycota Two classes:
Zygomycetes – a polyphyletic class, the largest (665 spp) and best known class
Trichomycetes – smaller (135 spp), less well understood, are commensals on surface and in guts of arthropods

4. Class - Zygomycetes
Zygospore production is generally similar among species, therefore classification is based on characteristics of asexual reproductive structures
Asexual reproduction is typically by production of sporangiospores, but we will see lines of evolution in which the number of spores/sporangium is reduced until there is only 1 spore/sporangium - conidium

5. Class - Zygomycetes Generally divided into 7 orders, we will discuss 3
Mucorales – mainly saprotrophs, many to one sporangiospore/sporangium
Entomophthorales – mainly parasitic on arthropods, limited mycelium, one sporangiospore/sporangium
Glomales – obligate biotrophs, form arbuscuar mycorrhizae

6. Class Zygomycetes Other orders:
Kickxellales – produced septate hyphae and modified one spored sporangia
Dimargaritales – mycoparasites
Zoopagales – parasites of small animals (amoebae, rotifers & nematodes) and fungi including the lethal lollipop, Zoophagus)
Endogonales – saprotrophs

7. Mucorales
Grow saprotrophically on decaying plant and animal remains in soils, dung, etc.
Produce large numbers of asexual spores that are dispersed in the air
Common contaminants in laboratory
Some are important in spoiling food – common bread mold, storage diseases of fruits and vegetables
Some infect humans and animals – opportunistic pathogens

8. Mucorales
Typically form aseptate hyphae, septa formed to delimit reproductive structures
Some species form rhizoids

9. Multispored sporangium
Morphology of sporangia varies, basis for classification
Typical multispored sporangium contains
Sporangium wall
Columella
sporangiophore

10. Development of sporangium
Tip of sporangiophore swells
Swelling increases, contains multinucleate cytoplasm
Cytoplasm is cleaved to form all spores at one time – cell membrane and cell walls laid down around nuclei

11. Development of sporangia
After formation, sporangial wall may break and release spores into the air or
A drop of fluid may envelop the sporangium with spores being dispersed by small animals that touch the sporangium

12. Reduction of sporangium
Several lines of evolution in the reduction of number of spores/sporangium
Examples of modifications of sporangia
Thamnidium – both multispored sporangium and smaller sporangia = sporangiola

13. Reduction of sporangia
Blakeslea – sporangiola with 3 spores/sporangiolum
Cunninghamella – one spore/sporangiolum, spore wall and sporangiolum wall indisdistinguishable except with EM

14. Reduction of sporangia
One group in the Mucorales produce cylindrical sporangia = merosporangia
Also see a reduction in the number of spores/sporangium in this line
Syncephalastrum

15. Other sporangial modifications
Pilobolus – fungal shotgun
Grows on herbivore dung
Sporangiophore contains carotenoids, acts as a lens to focus light and direct the growth of the sporangiophore to point the sporangium at light source

16. Pilobolus
As the sporangium and sporangiophore mature, the sporangiophore builds up a very high turgor pressure
Sporangium as a whole is shot off suddenly, directly at the light – up to 3 m
A drop of fluid on the sporangium causes it to stick to whatever it hits
Phototrophic ability allows sporangium to be shot out of a pile of dung, land on grass, be eaten by herbivores

17. Pilobolus Passage through gut of herbivore activates spore germination
Sporangium is dark in color to prevent damage from UV when attached to grass

18. Sexual reproduction
Involves fusion of two multinucleate gametangia that are similar in structure, may differ in size
Gametangia are produced as terminal swellings of hyphal branches
After plasmogamy – a thick walled zygospore is produced with a zygosporangium
Both homothallic and heterothallic species

19. Life cycle
Vegetative mycelium is haploid, reproduces asexually by producing sporangiospores in sporangia
In a heterothallic species, when two compatible strains come together, hyphal branches form, enlarge to form progametangia

20. Life cycle
Septa form, producing multinucleate gametangia and suspensors

21. Life cycle
Plasmogamy occurs, end walls of gametangia dissolve and cytoplasm of gametangia mixes

22. Formation of zygospore

23. Life cycle Zygospore forms inside zygosporangium
Zygospore develops thick wall, warty appearance, dark in color
Karyogamy occurs at different times in zygospore formation in different species, so zygospore is diploid at some point

24. Life cycle
When zygospore germinates, meiosis occurs to start the haploid portion of the life cycle over again

25. Life cycle

26. Variation in zygospores
Some variation is seen in zygospore formation

27. Entomophthorales Arthropod parasites, 240 spp.
Asexual reproduction by one spored sporangiola (conidia)
Mycelium exhibits limited growth in the body of the host, forms septa and fragments
Entomophthora is a parasite of flies – seen when fly is stuck to window, white halo around it

28. Entomophthora
Mycelium fills up body of fly, forms sporangiophores that extend out of segments of abdomen

29. Entomophthora
Sporangiophore builds up pressure, shoots off sporangiolum when there is air movement (another fly)
If misses, can form another structure that shoots it off, up to 3 times
Sexual reproduction not well understood, form resting spores that are similar to zygospores

30. Entomophthorales

31. Basidiobolus Another fungus that forcibly ejects its sporangiolum
Grows on a variety of substrates including frog and beetle dung
Sporangiola may be eaten by beetles, which may then be eaten by frog and then grows in dung

32. Glomales Obligate biotrophs
Biotrophic in the roots of higher plants, form arbuscular mycorrhizae
Ca 90 spp.
Now placed in a separate phylum by some – the Glomeromycota

33. Glomerales
Form tree-like structures = arbuscules in cells of plant – exchange of nutrients between fungus and plant
Form large spores in soil – zygospores, azygospores, and chlamydospores depending on species

34. Glomales
Azygospores
Chlamydospores

35. Phylogenetic relationships

36. Trichomycetes Second class in Zygomycota
Small class, contains 3 orders
All but a few species are obligate commensals in guts or on exoskeleton of arthropods
Found in freshwater (mayfly, stonefly, midges) and terrestrial (millipedes)

37. Trichomycetes
Thallus is relatively simple – produce a holdfast that anchors them to lining of gut

38. Trichomycetes
Thallus may be unbranched and aseptate or branched and septate
Variety of asexual spores produced (generally 1 spore/sporangium)

39. Trichomycetes
Sexual reproduction involves formation of zygospores (in one order)
Fusion of cells in thallus
Formation of zygosporophore and then zygospore

40. “Lower fungi”
Major groups of lower fungi – Chytridiomycota, Zygomycota, (Oomycota)
Exhibit diversity in vegetative thallus, asexual and sexual reproduction
Mycelium when present is typically aseptate
Used to be placed in one class = “Phycomycetes” – now clear that they do not share a common phylogeny

41. “Lower fungi”
Asexual reproduction – spores produced inside a sporangium – sporangiospores
In Chytridiomycota and Oomycota, zoospores produced
Transition from multispored sporangia to conidia in both the Oomycota and Zygomycota

42. Review Kingdom – Protoctista Kingdom – Stramenopila
Phylum – Dictyosteliomycota - pseudoplasmodium
Phylum – Myxomycota - plasmodium
Kingdom – Stramenopila
Phylum – Oomycota – biflagellate zoospores, oospores
Order – Saprolegniales
Order – Pythiales
Order - Peronosporales

43. Review
Kingdom – Fungi
Phylum – Chytridiomycota – posterior flagellated zoospore
Order – Chytridiales
Order – Blastocladiales
Phylum – Zygomycota - zygospore
Class Zygomycetes
Order – Mucorales - saprotrophs
Order – Entomophthorales – parasites of arthropods
Order – Glomales – arbuscular mycorrhizae
Class Trichomycetes – commensals in arthropods

44. Reproduction
Asexual - Sporangia – produce sporangiospores, in some zoospores
Sexual Life cycles
Haploid life cycles – Zygomycota produce zygospore, isogametangia
Diploid life cycles – Oomycota produce oospore, oogonia and antheridia
Haploid – Diploid life cycles – Allomyces, Myxomycota