Myxomycota

Question 1

Myxonycetes meaning

Dictosteliomycetes meaning

Protosetliomycetes meaning

Answer 1

True Slime molds

Cellular slime molds

Protoselid plasmodial slime mold

Question 2

How do slime molds differ from Eumycota?

Answer 2

1. Vegetative state is multinuclear plasmodium in plasmodial slime molds and individual amoeba in the dictyosteliomycetes
2. Motile stage bears two anterior whiplash-like flagella may be present in plasmodial slime molds
3. Amobea or plasmodia feed by the ingestion (phagocytosis) and Intracellular Digestion in vacuoles of bacteria

Question 3

Largest group of slime molds and there habitat

Answer 3

Mycomycetes-true plasmodial slime molds

-moist, decaying wood and other organic substrates
-abundant in soil and may fulfill many ecological functions which are poorly understood

Question 4

Movement of true plasmodium

Answer 4

1. Margin of extending plasmodium. The protoplasm is particularly dense at the advancing stage. Further behind, protoplasm is concentrated in large veins which show rhythmic pulsation
2. Fusion between compatible plasmodia. Note complete fusion of veins.
3. Lethal reaction following fusion between incompatible (genetically distinct) plasmodia

Question 5

Life cycle of Physarum Polycephalum

Answer 5

-low moisture and nutrition= plasmodium changes into dormant sclerotium
-numerous walled compartments, each containing several nuclei, each enveloped by a cell wall
-upon resumption of growth, the protoplast emerge from their spherules and fuse to reestablish the plasmodium

-when food supply is nearly exhausted, the plasmodium forms fruiting bodies or fruitifications: sporangia, aethalia, plasmodiocarps

Question 6

Sporangia of myxomycetes

Answer 6

Simple fruiting bodies, stalked or sessile

-sporangia enclosed by a wall (peridium) within which the spores are contained

Question 7

Aethelium life cycle

Answer 7

Entire plasmodium converts into hemispherical or cushion-shaped structure

Comprises several sporangia -> lost structural identity and surrounded by shared peridium

Question 8

Plasmodiocarps

Answer 8

-sessile, irregular in shape, varying from ovoid to elongated and even branched or netlike

Formed by secreting a peridium around the veins or parts of the veins of a plasmodium just after it stops streaming and prepares to sporulate

Question 9

Life cycle of myxomycetes

__________ spores germinate and release an Amoeboid cell the _______ or flagellate ______ cell

Answer 9

Wind-dispersed
Myxamoeba
Swarmer

Question 10

Swarmer safe equipped with

Answer 10

Two anterior, whiplash flagella-> may behave as gametes, fusing by their posterior ends to form flagellates zygotes, which eventually withdraw their flagella

Question 11

Where in the world can you find slime molds?

Where are they most common?

Answer 11

Anywhere!-all continents
Cultivated or native soils

Most abundant in upper layers of humus in well-established deciduous forests

Question 12

Cellular slime molds crawl in ______ soil as _______ cells (________): feed on bacteria by_______ and reproduce by ______

Answer 12

Moist
Individual
Myxamoba

Phagocytosis
Cell division

Question 13

During unfavourable conditions, what do myxamoeba do?

Answer 13

Encyst (Microcysts)

Microcysts germinate liberating myxamoebas that resume their normal feeding activities

Question 14

Asexual sporulation of cellular slime molds

Answer 14

When the food supply is exhausted, the myxamoebas aggregate
-starving amoebae emit pulses of a hormone chemoattractant, cyclic adenosine mono phosphate (cAMP), that induce surrounding cells to move in their direction and to secrete cAMP pulse themselves

Question 15

Pseudoplasmodium

Answer 15

Aggregate then transforms into a finger shaped structure
(Cellular slime molds)
-also called slug -c
-slug is comprised of individual amoeba cells

Question 16

What does the slug stage enable

Answer 16

Enables cellular slime molds to migrate towards the surface of the litter stratum thus to have a better chance for spore dispersal

Question 17

About ____% of the cells express genes that will ultimately cause them to transform into spores (cellular slime molds)

The remaining _____% will…..

Answer 17

75

25
Express genes that will finally cause their transformation into the stalk cells, that are doomed to die

Question 18

Prestalk cells move where

Perspire cells move where

Answer 18

Forward to front of slug

Perspires stay back

Question 19

Upon initiation of the fruiting body formation, the migrating slug ______

Answer 19

Contracts and points it’s tip upwards

Prestalk cells at the front first synthesize a central cellulose tube and differentiate into stalk cells

Perspore cells follow Prestalk cells up the stalk to mature into spores by loosing water and constructing spore coats

Question 20

Altruism

Answer 20

Differentiation in the cellular slime molds poses an evolutionary problem. Because, the amoebae that contribute to the stalk die, they can not pass genes to next generations. That being the case, why do they aggregate when the other cells do?

Although a cell joins an aggregate that has a finite chance dying, it may do better than it would by remaining alone

Question 21

Cheaters? In slime molds

Answer 21

Cells that move to the rear of the slug have an advantage -> cheater strains are known

Question 22

Dictyostelium discoideum in cell bio research

Answer 22

Advantages to studying cytokinesis, motility, phagocytosis, chemotaxis, signal transduction and aspects of development such as cell sorting , pattern formation, and cell-type determination