4. Zygomycetes

Question 1

Main orders of zygomycetes

Answer 1

Mucorales- e.g Rhizopus and Mucor

Entomophthorales- Associated mainly with insects

Zoopagales - associated mainly with small animals;

Glomales- Mycorrhizal species

Question 2

Mucorales- e.g

Answer 2

Rhizopus and Mucor

Many Saprophytes

Few animal infectious agents

some plant pathogens mainly post harvest

Question 3

Entomophthorales- Associated mainly with

Answer 3

Associated mainly with insects

Question 4

Zoopagales - associated mainly with

Answer 4

Associated mainly with small animals

Question 5

Glomales-

Answer 5

Mycorrhizal species

Question 6

Zygomycetes produce

Answer 6

thick walled resting spores called zygospores

Question 7

Zygomycetes have a range of nutritional types found within class including

Answer 7

saprophytes and parasites (facultative, obligate and few mycorrhizal species)

Question 8

Zygomycetes hyphae are normally

Answer 8

coenocytic (lacking septa), although few species may have septate hyphae

Question 9

Zygomycetes Asexual reproduction - Mucorales

Answer 9

normally via sporangiospores

sporangia usually have columellae of different shapes

sporangium divides by cytoplasmic cleavage into uninucleate segments that secrete walls around them and develop into spores;

sporangium may contain 50 to 100,000 spores.

Some small sporangia called sporangiola (3-30 spores)

Question 10

Diagram of Rhizopus sporangia

Question 11

Zygomycetes Sexual reproduction - Mucorales such as RHIZOPUS (rhizopus)

Answer 11

Both homothallic and heterothallic species can be found;

Zygospore production takes place by fusion of multinucleate gametangia

normally sexually undifferentiated but may vary in size;

Gametangia may arise from somatic hyphae or from specialized hyphal structures called zygophores;

Question 12

Zygomycetes Sexual reproduction - Mucorales such as RHIZOPUS (rhizopus) - in heterothallic species zygophore may be

Answer 12

chemically induced (by pheromones) when two compatible mating types are present

Pheromones –> Trisporic acid –> Caretonoids —-> more trisporic acid (high levels) —> Supression of asexual reproduction

Question 13

Zygomycetes Sexual reproduction - Mucorales such as RHIZOPUS (rhizopus) -zygophore may also be positively zygotrophic in that they

Answer 13

may grow towards each other (up to several mm)

Question 14

Karyogamy normally occurs in the zygospore just before

Answer 14

germination

Question 15

Zygomycetes Sexual reproduction - Mucorales such as RHIZOPUS (rhizopus) -some may produce spores with the appearance of zygospores but are actually

Answer 15

asexual spores called azygospores which derive parthenogenetically

Question 16

Diagram life cycle of Rhizopus

example of a zygospore production

Question 17

Diagram labelled of zygospore