What is the Difference Between Zoospore and Zygospore

The main difference between zoospore and zygospore is that zoospore is an asexual, naked spore produced within a sporangium, whereas zygospore is a sexual spore with a thick wall. Furthermore, zoospore is haploid while zygospore is diploid. Also, Phycomycetes fungi and green and brown algae produce zoospores, while fungi, including Phycomycetes and Zygomycetes and green algae, produce zygospores.  

Zoospores and zygospores are two types of spores produced by fungi and algae. Generally, spores are reproductive structures of lower organisms, including protists, fungi, and algae. 

Key Areas Covered 

1. What is Zoospore
     – Definition, Structure, Importance
2. What is Zygospore
     – Definition, Structure, Importance
3. What are the Similarities Between Zoospore and Zygospore
     – Outline of Common Features
4. What is the Difference Between Zoospore and Zygospore
     – Comparison of Key Differences

Key Terms 

Algae, Asexual, Fungi, Phycomycetes, Sexual, Spores, Zoospore, Zygomycetes, Zygospore

What is Zoospore 

Zoospore is the motile, asexual spore of many algae, fungi, and protists. It is also called the swarm spore. Generally, the production of zoospores occurs inside sporangia, which are the sacs at the end of the aerial hyphae. Moreover, the rapid internal division of the protoplasm of sporangia gives rise to zoospores. Thus, zoospores are a type of endospores, which are unicellular and hyaline. However, they lack a thick wall surrounding the spore and are less resistant to unfavorable conditions. 

Figure 1: Different Types of Zoospores

Furthermore, the two types of flagella in zoospores are tinsellated flagella and whiplash flagella. Based on the different combinations of these flagella, there are four types of zoospores. Opisthokont is the type of zoospores that occurs in Chytridiomycota containing posterior whiplash flagella. Moreover, anisokont is a type of zoospores in some Myxomycota and Plasmodiophoromycota, containing two whiplash flagella with unequal lengths. On the other hand, Hyphochytriomycetes fungi contain single anterior tinsellated flagellum. In contrast, heterokont is a type of zoospores oomycota and other Heterokonts containing a single whiplash and a single tinsellated type flagella. 

What is Zygospore 

Zygospore is a type of chlamydospore producing by the sexual conjugation of two fungal hyphae. Generally, zygospores are dark in color an contain a thick wall, allowing to resist unfavorable conditions. Moreover, the wall of the zygospores contains many spines and ridges. Since it is a result of sexual reproduction, zygospore is diploid. Basically, nuclear fusion of haploid cells results in zygospores.

Figure 2: Zygospores

Furthermore, zygospores remain dormant until they get favorable conditions such as light, moisture, heat, or chemicals secreted by plants. After that, they undergo germination in which the diploid cell undergoes meiosis to produce the haploid gametophyte.  

Similarities Between Zoospore and Zygospore 

• Zoospore and zygospore are two types of spores produced mainly by fungi and algae. 
• They are units of reproduction produced inside sporangia. 
• They are adapted for survival and dispersal for extended periods of time in unfavorable conditions. 
• Moreover, they are unicellular. 
• However, they undergo mitosis under favorable conditions to produce a multicellular gametophyte. 

Difference Between Zoospore and Zygospore 

Definition 

Zoospore refers to a spore of certain algae, fungi, and protozoans, capable of swimming by means of flagella while zygospore refers to a thick-walled resting cell of certain fungi and algae, arising from the fusion of two similar gametes. 

Type of Spore 

While zoospore is an asexual spore, zygospore is a sexual spore. 

Ploidy 

Zoospores are haploid while zygospores are diploid. 

Structure 

Moreover, zoospores are naked while zygospores contain a thick wall. 

Color 

Zoospores are hyaline while zygospores are dark in color. 

Motility 

Furthermore, zoospores are motile and contain one or several flagella while zygospores are non-motile. 

Resistance 

While zoospores are less resistant to unfavorable conditions, zygospores are more resistant to unfavorable conditions.  

Germination Process 

Zoospores undergo mitosis to produce the next haploid generation while zygospores undergo meiosis to produce the next haploid generation. 

Occurrence 

Also, zoospores occur in protists, fungi, and bacteria while zygospores occur in fungi, protists, and algae. 

Conclusion 

Zoospore is an asexual spore that mainly occurs in fungi and algae. Generally, it is naked and contains flagella for motility. Moreover, it is a haploid spore. On the other hand, zygospore is a sexual spore that mainly occurs in fungi. However, it contains a thick wall and can resist unfavorable conditions. Moreover, it is a diploid spore. Therefore, the main difference between zoospore and zygospore is their structure.  

References:

1. Deacon, Jim. “The Microbial World: Fungal Zoospores.” Zoospores, Available Here.
2. “Spore.” Zygospore, Available Here.

Image Courtesy:

1. “Zoospores types” By Pancrat – Own work (CC BY-SA 3.0) via Commons Wikimedia   
2. “Rhizopus zygospores” By Curtis Clark – Own work (CC BY-SA 3.0) via Commons Wikimedia