Fungus-Animal Mutualism Notes

Mutualism Examples

  • Ambrosia beetles and fungi
  • Woodwasps
  • Termite-Termitomyces
  • Ant – Lepiota
  • Ant – aphid – Cladosporium myrmecophilum
  • Septobasidium
  • Rumen symbionts
  • Invertebrate gut symbionts

Basis of Mutualisms

  • Nutritional
  • Habitat/environment

Mutualism: Ambrosia Beetles

  • Mycophagy has evolved many times
  • Fungi: Ophiostoma, Ceratocystis, Entomocorticium
  • Fungi transported in mycangia
  • Larvae and adults feed on fungi lining galleries

Mutualism – Higher Termites with Termitomyces

  • Termitomyces gets:
    • suitable environment
    • grooming
    • supply of resources
  • Termite gets: highly nutritious food
  • Evolved 24 – 34 MYA in Africa
    • Termites: Macrotermtinae
    • Fungi: Termitomyces

Mutualism – Ants and Basidiomycetes

  • Evolved 50 MYA
  • Ants involved – Atta – leaf-cutters
  • Fungi – monoculture Attamyces, Lecoagaricus, Lepiota
  • In central and South America
    • (Grooming and licking, secretions from actinomycetes – Streptomyces; ascomycete mycoparasite Escovopsis)

Mutualism – Jet Black Ant (Lasius fuliginosus)– Aphid – Cladosporium myrmecophilum

  • Ant lives in hollow tree trunks (especially Salix and Populus) or beneath stumps
  • Builds cardboard-like nest from:
    • Wood ‘dust’ mixed with soil particles
    • Aphid honeydew
    • Fungus
  • Ants keep fungus closely cropped; only fruits in absence of ant

Mutualism: Scale Insects - Septobasidium

  • Within lower layers of mycelium insects form a labyrinth of tunnels
  • Young insects feed on plant
  • Juveniles move between plants and transmit fungus
  • Only some insects are infected
  • Fungi protect insects
  • Hyphae form coils within haemocoel
  • Hyphae emanate through natural orifices and interconnect with main mycelial network, but apparently don’t interfere with mobility
  • Infected insects remain in juvenile condition
  • If insects are infected later they are killed eventually, but may survive winter and reproduce
  • Fungus may determine sex: infected eggs become females

Rumen Symbionts

  • Temp 39-40.5 C
  • Headspace gas – 65% CO<em>2CO<em>2, 27% methane, 0.6% O</em>2O</em>2
  • Bulk of microorganisms in rumen are anaerobic bacteria and ciliate protozoa
  • Anaerobic chytrids on plant material: Neocallimastix, Piromonas, Sphaeromonas

Invertebrate Gut Symbionts - Trichomycetes

  • Obligate symbionts
  • Some have a wide host range, others restricted
  • 3 gut regions can be occupied: cuticular lining of foregut and hindgut; in freshwater diptera larvae – chitinous peritrophic membrane of midgut
  • Some show preference for gut region