Choanocytes: Definition & Functions

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  • 0:00 What Are Choanocytes?
  • 0:49 Choanocyte Structure
  • 1:38 Functions of Choanocytes
  • 2:45 Lesson Summary
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Lesson Transcript
Instructor: Margaret Cunningham

Margaret has taught many Biology and Environmental Science courses and has Master's degrees in Environmental Science and Education.

In this lesson, you'll explore a unique structure found in sponges. Choanocytes are special cells that are involved in many activities, ranging from water circulation to feeding and even reproduction.

What are Choanocytes?

When you eat a slice of pizza, your hand picks up the slice and delivers it to your mouth. In your mouth, the pizza is chewed and then transported through your body to your stomach and the rest of your digestive system. This is the typical method of eating for humans but what about organisms with no hands, no mouth, and no stomach?

The group of organisms that comprise the phylum Porifera are known as the sponges. Sponges are often bright in color and found along coral reefs. Many people don't even realize that sponges are animals, not plants. Sponges are an example of an organism that doen't have hands, a mouth, or a stomach. Instead, these organisms have specialized cells called choanocytes that help them survive.

Choanocyte Structure

Most sponges have a vaselike shape. The inside walls of the 'vase' or internal cavity of the sponge are covered in specialized cells, including choanocytes. These specialized cells are tightly packed and cover the entire internal surface of the sponge. Choanocytes are also referred to collar cells because of their structure.

Choanocytes have a round cell body that's attached to the inside wall of the sponge and is also the location of the cell's nucleus and food vacuoles. Each choanocyte has a single flagellum, which looks like a whip-like structure. This structure extends from the center of the cell out towards the open cavity of the sponge. Surrounding this single flagellum is a cylindrical collar comprised of many microvilli, which are very tiny finger-like projections on cells.

Functions of Choanocytes

The unique structure of choanocytes makes it possible for them to carry out several important functions within sponges.

The primary function of choanocytes is to assist with circulation. The flagellum on each choanocyte whips back and forth, which creates water movement. This water current helps circulate seawater within and through the sponge. The moving water brings oxygen into the sponge and removes carbon dioxide and waste products from the sponge.

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