Difference Between Zoospore and Conidia

Main Difference – Zoospore vs Conidia

A spore is a minute, single-celled, reproductive cell that gives rise to a new individual without fusion. Lower plants, fungi, and protozoans produce spores. Zygospores, oospores, ascospores, and basidiospores are sexual spores produced by meiosis. Sporangiospores, zoospores, and conidia are asexual spores produced by mitosis. Zoospores are produced inside a sporangium. Thus, they are endogenous spores. Conidia are produced at the tip of the conidiophores. Thus, they are exogenous spores. The main difference between zoospore and conidia is that zoospores are flagellated and mainly found in algae whereas conidia are non-flagellated and mainly found in fungi.

Key Areas Covered

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

Key Terms: Asexual Spores, Blastic Conidiogenesis, Conidia, Conidiophore, Endogenous, Exogenous, Fungi, Thallic Conidiogenesis, Zoospore

What is a Zoospore

A zoospore refers to an asexual spore of certain algae, capable of swimming by means of a flagellum. Zoospores are produced in a sac called sporangium at the end of the aerial hyphae. As they are produced internally by the division of protoplasm, they are called endogenous spores. Zoospores are unicellular and hyaline. Since they lack cell walls, zoospores are not resistant to unfavorable conditions. However, they are capable of rapid multiplication. A zoospore of Saprolegnia with two flagella is shown in figure 1.

Figure 1: A Zoospore

Zoospores use their endogenous food reserves for locomotion. They are capable of responding to environmental signals in order to decide where to locate and where to encyst. Aplanospores are the non-motile, endogenous, asexual spores.

What are Conidia

Conidia (singular: conidium) refer to asexual spores produced by various fungi at the tip of the specialized hypha. The specialized hyphae are called conidiophore. These spores are not covered by a sac. Thus, conidia are a type of exogenous spores. The production of conidia is a primary method of reproduction in fungi. Conidia of Penicillium is shown in figure 2.

Figure 2: Conidia of Penicillium

The size, shape, color, septation, and branching of the conidiophore may differ with the species. Some conidia are unicellular while others are multicellular. Two types of conidia developments can be identified in fungi: blastic conidiogenesis and thallic conidiogenesis. In blastic conidiogenesis, the conidia are evident before its separation from the conidiogenous hyphae. In thallic conidiogenesis, a conidium separates with the production of a cross-wall.

Similarities Between Zoospore and Conidia

• Both zoospore and conidia are two types of asexual spores.
• Both zoospore and conidia are produced at the end of the aerial hypha.
• Both zoospore and conidia are produced by mitosis.
• Both zoospore and conidia are haploid.
• Both zoospore and conidia are single-celled structures that can develop into a new individual.

Difference Between Zoospore and Conidia

Definition

Zoospore: A zoospore refers to an asexual spore of certain algae, capable of swimming by means of a flagellum.

Conidia: Conidia refer to asexual spores produced by various fungi at the tip of the specialized hypha.

Endogenous/Exogenous

Zoospore: Zoospores are endogenous spores produced inside a sporangium.

Conidia: Conidia are exogenous spores produced at the tip of the conidiophores.

Mainly produced in

Zoospore: Zoospores are mainly produced in algae.

Conidia: Conidia are mainly produced in fungi.

Unicellular/Multicellular

Zoospore: Zoospores are always unicellular.

Conidia: Conidia are either unicellular or multicellular.

Size

Zoospore: Zoospores are small.

Conidia: Conidia are larger than a zoospore.

Cell Wall

Zoospore: Zoospores lack a true cell wall.

Conidia: Conidia possess a cell wall.

Environmental Conditions

Zoospore: Zoospores are incapable of enduring harsh environmental conditions.

Conidia: Conidia are capable of enduring harsh environmental conditions due to a presence of a cell wall.

Flagella

Zoospore: Zoospores may have one, two or more flagella.

Conidia: Conidia lack flagella.

Mobility

Zoospore: Zoospores are motile.

Conidia: Conidia are non-motile.

Dispersion

Zoospore: Zoospores are dispersed through the water.

Conidia: Conidia are dispersed through the wind.

Examples

Zoospore: Oomycota such as Phytophthora, Chytridiomycota, Myxomycota and Plasmodiophoromycota as well as Opisthokonts and heterokonts produce zoospores.

Conidia: The phylum Ascomycota produces conidia.

Conclusion

Zoospore and conidia are two types of asexual spores in algae and fungi respectively. Zoospores are endogenous spores while conidia are exogenous spores. Zoospores have flagella for locomotion while conidia lack flagella. The main difference between zoospore and conidia is the structure of the two types of asexual spores.

Reference:

1.“The Microbial World: Fungal zoospores.” Zoospores, Available here.
2.“FUNGI REPRODUCING ASEXUALLY BY MEANS OF CONIDIA.” Natural History of Fungi, Available here.

Image Courtesy:

1. “Zoosporo saprolegnia” By desegno de user:Pancrat ŝanĝo de Bildoj – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Penicillium” by AJC1 (CC BY-SA 2.0) via Flickr 

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