5 Facts On Contractile Vacuole In Fungi(Formation, Function)

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Through evolution, the contractile vacuole is lost in most multicellular organism but is still found in fungi and sponges. Let us discuss the role of this organelle in fungi.

A contractile vacuole is an osmoregulatory organelle that maintains the water balance inside the cells by periodic expansion and contraction. It is mainly a waste-removing apparatus in these organisms.

The contractile vacuole in fungi is a specialized structure with semi-permeable membrane that can transport water via osmosis. Through this article, let us now learn some important facts related to the structure, position and function of this organelle in fungi.

Which fungi have contractile vacuoles?

Contractile vacuoles are a common feature found in cells of protists, marine protozoans and metazoans like sponges and hydra. Now let us learn about its presence in fungi.

Contractile vacuoles are found in single-celled fungus, commonly known as yeasts, but are absent in multicellular fungi.

Yeasts are unicellular chemo-organotrophs belonging to the fungus family. Example of unicellular yeasts such as Saccharomyces cerevisiae, Schizosaccharomyces pombe, Cryptococcs neoformans possess contractile vacuoles.

Where are contractile vacuoles found in fungi?

Contractile vacuoles have been lost in multicellular animals but are specifically found in only eukaryotic cells. So let us see where they are found in fungus.

Contractile vacuoles are present inside the cytoplasm of the unicellular fungi. The location of vacuoles in the cytoplasm is not permanent and they are distributed randomly without causing interference with movement.

contractile vacuole
Image Credits: Presence of contractile vacuole in unicellular organism by Ali Zifan is licensed under (CC BY-SA-4.0)

How are contractile vacuoles formed in fungi?

Contractile vacuoles in fungi are of various size and shapes as the other types of intracellular vacuoles. Let us learn the process of how a vacuole develops in fungi.

Contractile vacuoles in fungi are formed by the fusion of vesicles released from endoplasmic reticulum and Golgi apparatus. From dark-field illumination staining studies it is found that vacuoles are formed by the merge of several minute droplet-like structures.

The membrane of the vacuoles is not rigid structure and they are formed randomly. They even change their size depending upon the conductivity of water inside them.

Contractile vacuole functions in fungi

Vacuoles perform a range of functions inside the cell and vary in their numbers depending upon the function they perform. Let us see the function of contractile vacuoles in fungi.

  • Through relaxation in the Diastole phase, the excess water and solutes inside the cytoplasm enters the vacuole in fungi and it expands.
  • In the systole phase, the vacuoles contracts and expels the waste outside the cells and then again return into its diastole phase.
  • The amount of water being expelled from the cells and the contraction rate depends upon the osmotic pressure of the cells.
  • Contractile vacuoles maintain the osmolarity in the cells, thus preventing the fungi cells from being ruptured through excessive water accumulation.

Thus contractile vacuoles are an important osmoregulatory cell organelle in fungi.

Contractile vacuole structure in fungi

Contractile vacuoles have a very flexible structure that helps in functioning. Now let us learn about the structure of a contractile vacuole in fungi.

  • Contractile vacuoles do not have a specific shape and are usually spherical or tubular ranging from 1.5µm to about 45µm in diameter.
  • Contractile vacuoles have a single semi permeable membrane which is highly extensible and flexible.
  • The vacuoles in fungi have membrane folding and sometimes have tubular canals and small vesicles connected to them which help in expelling water. These features are together termed as contractile vacuole complex.
  • Contractile vacuoles are well equipped to hold high amount of water and solutes during their diastolic phase.

Conclusion

In this article, we learnt that contractile vacuoles in fungi are an important excretory cell organelle that is crucial to maintain the osmotic regulation inside the cells.