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Mycology > Phylum Oomycota > Flashcards

Phylum Oomycota Flashcards

1
Q

What superphylum do Oomycota belong to?

A

Stramenopiles (heterokonta)

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2
Q

What is the common term for the organisms in the Oomycota phyla?

A

water moulds

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3
Q

What is the major characteristic of Oomycetes?

A

they have 2 flagella

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4
Q

What are the other phyla in the Heterokonta superphylum?

A

Hyphochytriomycota (a very small group of single flagellum organisms)

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5
Q

What type of environments are Ooymcetes found in?

A

they are water moulds so aquatic - both fresh water, marine and damp soil

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6
Q

What type of life cycles do they exhibit?

A

saprophytes
parasite
pathogens (many economically important ones)

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7
Q

T or F: Oomycetes have known symbionts

A

false

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8
Q

What is the major characteristic that distinguishes Oomycetes from true fungi?

A

they have motile zoospores with 2 flagella

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9
Q

What types of flagella do their zoospores have?

A

one tinsel and one whiplash

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10
Q

Where on the zoospore cell do the flagella arise?

A

from the side of the cell (as opposed to the front or back)

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11
Q

Describe tinsel flagellum

A

Oomycetes have motile zoospores with 2 flagella - one is tinsel:

tinsel flagellum point forwards and have lateral branches (mastigonemes) that PULL the zoospore through water

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12
Q

describe whiplash flagellum

A

Oomycetes have motile zoospores with 2 flagella - one is whiplash:

whiplash flagellum point backward and have no ornamentation but they PUSH the cell through water

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13
Q

Describe the filamentous growth of Oomycetes

A

they have highly branched, non-septate vegetative (coenocytic) DIPLOID hyphae that colonize OM or a host

they form mycelia with cellulose and glucans in the cell walls

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14
Q

Describe Oomycete asexual reproduction

A

asexual reproduction occurs via sporangia, resting spores and/or zoosporangia that produce zoospores with 2 flagella

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15
Q

Describe Oomycete sexual reproduction

A

Sexual reproduction can occur via the fusion of NON-MOTILE female gametes (oogonia) and male antheridia (much smaller gametes) either on the same mycelium or a different mycelium depending on species to form a zygote

zygote = thick-walled oospore that can persist until conditions are ideal

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16
Q

What are oogonia?

A

the very large, non-motile female gametes of Oomycetes

17
Q

What are antheridia?

A

the smaller male gametes of Oomycetes

18
Q

What does homothallic mean?

A

sexual reproduction occurs on the same mycelium - ie., a single mycelium produces both male antheridia and female oogonia

19
Q

What does heterothallic mean?

A

compatible gametes for sexual reproduction (male antheridia and female oogonia) are produced on different mycelium

20
Q

What are the structures involved in asexual reproduction for Oomycetes?

A

either:
sporangia
resting spores
zoosporangia that produce zoospores

21
Q

what is an oospore?

A

the thick-walled persistent (can overwinter or wait until ideal conditions) product (zygote) of sexual reproduction in Oomycetes

22
Q

What are two major orders of Oomycetes?

A

Saprolegniales (water molds)
Peronosporales (downy mildew)

23
Q

Describe saprolegniosis of fish and an example of species that causes it

A

caused by species of the Saprolegniales (water mold) order, example: Saprolegnia parasitica

an opportunistic parasite or pathogen of freshwater fish such as salmon or trout and amphibians

infects host around mouth, gills and fins or eggs

usually infects unhealthy hosts or hosts with other stressors like aquaculture or hatcheries; life stage and living conditions also affect susceptibility

24
Q

What conditions are prone to saprolegniales break outs? how is this related to the method of dispersal for Saprolegnia parasitica?

A

fisheries/hatcheries or aquaculture where fish are under other stressors and more vulnerable to infection

Saprolegnia parasitica disperses by its motile zoospores that swim in water = easily infects multiple individuals and spreads

25
Q

How can the infection and spread of Saprolegnia parasitica be reduced?

A

proper sanitation and chemical treatment and keeping healthy conditions for fish to prevent breakouts

26
Q

What are the symptoms of saprolegniosis in fish?

A

tufts on exterior of fish body around gills, mouth or fins or on eggs

these progress into larger cuts

fatigue and loss of equilibrium

osmoregulation becomes unbalanced and eventually causes death if not treated

27
Q

What does it mean that water molds are opportunistic pathogens or parasites?

A

they only infect unhealthy hosts or hosts under other stressors

28
Q

What stressors can cause fish to be more susceptible to saprolegniosis?

A

high pop density
water temperature too high or low
smolt stage for salmon
spawning season
vaccinations in fish farms
contamination exposure
pollutant exposure

29
Q

Why is identifying water molds to the species level difficult when just using morphology?

A

they do not have a lot of identifying characteristics

30
Q

what is karyogamy?

A

the fusion of 2 haploid nuclei into one diploid nucleus

the process produces the zygote

31
Q

What is plasmogamy?

A

the fusion of 2 cells, each carrying a haploid nucleus

this occurs before karyogamy

32
Q

What happens when the conditions are optimal for the Saprolegniales oospore?

A

it can germinate and become a new DIPLOID mycelium

33
Q

Is the sexual or asexual life stage more commonly observed in Saprolegniales?

A

asexual

34
Q

Why is understanding the spread of water mold infections in fish important?

A

water mold infections in fish can cause fatalities and are easily spread within a population due to their motile zoospores

this can be a major risk for natural populations such as in Northern Alaska - this may have implications on regular fishing that can affect small communities and their food sources

35
Q
A

Mycology (10 decks)

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