Aquatic Fungi Flashcards
Are aquatic fungi eukaryotic or prokaryotic?
Eukaryotic
Do aquatic fungi have chlorophyll?
They are transparent, no chlorophyll present
What part do aquatic fungi play in the foodweb?
Decomposers- important nutrient recyclers
Feed on dead organic matter
What are types of feeding strategies do aquatic fungi employ?
Saprobes- feed on dead matter
Symbionts- live in co-oporation with other organisms
Parasitic- prey on hosts
What are fungi cell walls composed of?
Chitin
What product do they store in their cells?
glycogen
What are hyphae
Filamentous branching threads- how growth occurs
- White/colourless
- (0.5 - 100 um thick)
List the key characteristics of aquatic fungi
- Apical Growth
- Asexual reproduction (budding/spores)
- Sexual reproduction (Biphasic alternation of generation)
What are fungi with no septa called?
Aseptate
Describe the characteristics of the hyphal tip
-Structurally weak and the area behind it
What are phylum chytridiomycota?
Chytrids- Flagellated Moulds
Characteristics of chytridiomycota.
- Thallus
- Single celled organisms
- No true mycelium
- Cell wall contain cellulose instead of chitin
- Parasitic and saprophytic species
- Some develop aseptate multi-nucelate mycelia
What is a thallus?
Colourless, spherical cell with branching threads called rhizoids
-Function is to penetrate a host or non-living substratum
What role can parasites play in a food web?
- Allow energy transfer between trophic levels
- Predators can easily target infected prey
- Predators prey on free-living stages of parasites
What does the chytrid parasite Zygorhizidium planktonicum prey on?
Asterionella formosa (araphid diatom)
What is the haplontic life cycle?
It involves both asexual and sexual phases within the life cycle
List the steps of the asexual life cycle of Zygorhizidium planktonicum.
- Step 1- Attachment
- Step 2- Encystment
- Step 3- Germ tub formation
How does Zygorhizidium planktonicum carryout asexual reproduction?
Uni-flagellated zoospores
Describe Step 1 in the Zygorhizidium planktonicum asexual reproduction?
Zoospores attach to the cell wall of Asterionella formosa
Describe Step 2 in the Zygorhizidium planktonicum asexual reproduction?
- A thickened wall is formed around the zoospore forming a cyst
- If infection is successful, the cyst develops into a mature sporangium
Describe Step 3 in the Zygorhizidium planktonicum asexual reproduction?
- Germ tube develops and enters host algal cell, totally dependant on the host cell for nourishment
- New uni-flagellated zoospores are released
- During dispersal, zoospores depend on internal energy storage
- Capable of infecting a new host diatom
What triggers Zygorhizidium planktonicum to reproduce sexually?
Adverse environmental conditions
How does Zygorhizidium carry out sexual reproduction?
Via gametangial copulation
What is the process of sexual reproduction in Zygorhizidium?
- Female thalli are large and develop from a zoospore
- Male thalli are small
- Zoospores empty their contents into the female thallus via conjugation tubes
What happens after fertilisation in Zygorhizidum?
Female thallus is fertilised
Develops in thick-walled resting spore (2n)
Germination and meiosis form haploid zoospores
List the challenges Zygorhizidium face in the wild?
- Rapid change in diatom population size
- Small moving targets (prey)
- Resistance to infection of host
- Hypersenstivity response
- Host rapidly dies and not enough time for life cycle of parasite to finish
List the adaptations of Z. planktonicum to survive
- Gains nutrient from diatom quickly
- Faster growth rate than diatom
- Large number of motile spores to increase change of infection
- Resting stages- can survive adverse conditions
- Rapid population growth in good conditions
