Colonial Protists: Definition & Examples

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Protists are a unique group of organisms because they don't quite fit the mold. And while some protists prefer to live as individuals, other prefers to work together for the greatest benefit. These colonial protists are the topic of this lesson.

What are Protists?

When we classify living things we tend to group them together based on evolutionary relationships. In other words, animals, plants, and other organisms are grouped together because they share common ancestors. For example, mammals are more closely related to each other than they are to birds or fish.

But one group of organisms doesn't really follow this convention. In fact, they are grouped together because they simply don't fall into other categories. And that's what makes the protists so special! These eukaryotes don't fit into one of the other kingdoms, such as plant, animal, or fungi, so they get put into their own kingdom called Protista. But this is about the only commonality they have.

Most do not share any evolutionary relationships, and they often don't even look the same. They come in all shapes and sizes, ranging from the microscopic to the very large, living in all different kinds of environments, and offering a multitude of different functions to life on Earth.

Kelp is a multicellular protist.
kelp forest

You're likely already familiar with some well-known protists. Yeasts, algae (such as kelp and seaweed), and amoebas are just a few examples. Most protists are unicellular, but some like kelp are multicellular organisms. Some, known as the plant-like protists photosynthesize, while others that do not photosynthesize are called animal-like protists. Others still are called fungi-like or slime molds because they somewhat resemble fungi, though again there is no evolutionary relationship.

Colonial Protists Live Together

Just like people, some protists prefer to live individually while others prefer to live in large groups. Colonial protists are individual protists that form a colony and act as a larger, multicellular organism. This colony may consist of many individual protists of the same species, but what's really cool about them is that instead of acting as individuals they work together to function as one large group, benefiting from each other.

But be careful, because this is not the same as symbiosis which is when two or more organisms of different species live together and mutually benefit from one another.

Colonial protists aggregate together to form a larger group.
colonial protists

Colonial protists are often capable of living independently but they choose not to because the benefits of living in a group outweigh living alone. And because they work so well together it can sometimes be difficult to distinguish between these colonies and a single multicellular organism.


We can find lots of different examples of colonial protists in nature.

  • Golden algae (from the phylum Chrysophyta) are one such example. These guys live in freshwater environments and get their name from their yellow and brown coloration.
  • Some green algae may also be colonial protists, such as those in the genus Volvox. Also known as 'globe algae' these guys can create very large colonies (tens of thousands of individuals!) and are incredibly beautiful to behold under the microscope. Algae are examples of plant-like protists.

Volvox aureus is a colonial protist that is also quite beautiful.

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