Weekend Science Fun: Sea Slug Color

Have you ever thought about sea slugs and why they are different colors? It turns out color can be pretty important in sea slugs.

One sea slug, (Elysia chlorotica), is green. Recently scientists investigated the color and found out that the sea slug makes its own food with chlorophyll! Chlorophyll, as you probably know, is the pigment plants use to make their food via photosynthesis. This sea slug not only borrows chloroplasts from the algae it eats, but also can make its own chlorophyll. It is the first animal to be shown to have that ability. Cool! ( Wired Science has a copy of the original article from ScienceNews. Both sites have ads, but the Wired site is less busy.)

Here’s a video that shows the sea slug eating algae. (The video is silent.)

This video from National Geographic shows other, more colorful sea slugs (nudibranchs). (You’ll have to close a pop-up ad.)

Why are these sea slugs so bright? The colors are to warn predators that they aren’t good to eat.


1. Draw and color your own sea slug.View images of sea slugs by searching images online, or look for photos in books to help you. Research a particular sea slug. Find out where it lives, what its habitat is like and what it eats.

Tidepool Coloring Book has a drawing of a nudibranch you could use, as well as images of other tidepool creatures.

2. Writing Prompt:

Imagine what our world would be like if more animals could make their own food from sunlight. Imagine green cows or elephants. Now, write a story about it.

Related Activities:
Fieldwork has extensive lesson plans for a high school level marine biology/oceanography class. For example, here’s the lesson on Mollusca/beaches. The author recommends that you have access to a body of salt water to be able to do the hands on activities. Check out the “busy fieldworkers.” Now, that’s my idea of learning.

Tide Pool Invertebrates post from last summer

Thanks to Carl for the heads up about the green sea slug and Susan for leading me to the Fieldwork site.


  1. Kate Kosman

    I probably don’t need to tell you just how much I love sea slugs! My screen name is “Dorid”!

  2. Roberta

    Yes, that reminds me that you have a cool photo up of a lion nudibranch at the Life Photo Meme.

    Maybe you can help me sort out whether the sea slug with the chlorophyll is a nudibranch? Because not all sea slugs are, right?

  3. Sarah N.

    Very cool! We had a great time studying tidepool creatures last summer before and during our trip to the beach. We got to see a few species of sea slugs and my daughters found them fascinating. Thanks for the resources.

  4. Roberta

    You got to see living sea slugs? That’s wonderful!

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