Dr. Rebecca Johnson is a systematic biologist and studies the evolution of color in sea slugs at the California Academy of Sciences.

In the slow paced world of marine sea slugs, a sedentary defense can be the difference between eating and being eaten. With shelled armor, stealthy camouflage or chemical warfare, defense strategies are not only fascinating, but are a potential source of novel cancer and cardiac therapies. Of the 3,000 species of nudibranchs, or “naked-gilled” slugs, many display beautiful, vivid color patterns. These colors warn predators that the slugs are toxic.

Post-doctoral researcher at the California Academy of Sciences, Dr. Rebecca Johnson studies the evolution of color patterning in these brazen beauties. Her specialty lies within a family of 300 species called the chromodorid nudibranchs, which mainly live in shallow tropic waters worldwide.

Chromodorid nudibranch (Risbecia tyroni) Photo credit: Stephen Childs

Most nudibranchs take something from their prey to use as their own chemical defense. For example, the chromodorid nudibranchs selectively feed on sponges and steal toxic chemicals from the sponge originally intended to keep animals from living and growing on the sponge. The slugs redistribute those chemicals throughout their tissues to use for defense.

Species that eat sea anemones and other cnidarians can capture the stinging cells from their prey and store them in their tissues. The aeolid nudibranchs store these stinging cells in cerata, which are long finger-like projections that line the body.

A group of slugs that are closely related to nudibranchs, called sacoglossans, steal chloroplasts from algae prey. Instead of stealing for defense, these slugs steal for energy. They redistribute the chloroplasts throughout their tissues and can actually keep the chloroplasts photosynthesizing. These animals are essentially crawling plants.

Dr. Johnson has been named one of the 16 Rubenstein Fellows by the Encyclopedia of Life (EOL). “I am honored and excited to be a Rubenstein Fellow,” says Johnson. “With this award, I will use the Encyclopedia of Life as a platform with which to consolidate and organize historical data, new research findings, and information on chromodorid nudibranchs that is only found in the scientific literature, libraries, natural history museums, and scattered across the web.  As a fellow, I look forward to sharing the beauty of these animals with a larger audience and to making scientific information about them more widely available.”

In addition to working as postdoctoral researcher at the Academy, Johnson also works with the Gulf of the Farallones National Marine Sanctuary to train tide pool naturalists at Duxbury Reef—a marine protected area in Marin County—and contributes to the Academy’s exhibits and education programs, including a recent display on the Farallon Islands.

37.7699 -122.467174

  • Martin Meiss

    An interesting article, but I object to use of the value-laden term “stealing” to describe what preditors do with materials they sequester from their prey. If they are stealing, shouldn’t they face trial, fines, and prison sentences? There are good reasons why biologists have developed specialized vocabulary to describe their observations of the natural world, and one of those reasons is to avoid useless anthropomorphism.

    Martin M. Meiss

  • Rebecca Johnson

    Hi Martin,
    Thanks for your comment. You are correct when you point out that biologists have specialized vocabulary with which to describe the natural world. I think if you listen to the audio portion of this contribution (push play on the nudibranch photo) you will hear that I, as a biologist interested in making science accessible to those not familiar with the technical jargon, use the appropriate terms and then explain them in terms everyone can understand. I actually feel that by using the appropriate terms and then explaining them, I can reach the most people. Interestingly, to your point on ‘stealing’ the ‘specialized term’ is kleptoplasty. Kleptoplasty literally means the ‘stealing of plastids’. So, in this case, Kim Vincent (the writer who interviewed me and wrote the text) used ‘stealing’ as a direct translation of the specialized term. I think we can agree that most readers can separate the values associated with theft and the fact that a slug maintains the plastids from its prey after ingestion. Thanks for reading (and listening, I hope).

  • Bruce Bowser

    As one you instructed and helped become a Marine Sanctuary / Cal Academy Rocky Shore Naturalist, I can see from this video that we indeed were just scratching the surface on so many subjects and most certainly your colorful friends nudibranchs. I am sure I speak for all my classmates who have yet to see the Quest video that your selection as a Rubenstein Fellow is richly deserved and will help further your research. Way to go, Rebecca
    See you on the reef. Bruce Bowser

  • Anmunguia

    Hi Dr. Johnson,

    I am curious, are there any organisms that have shown coevolution with certain species of nudibranchs. I have searched online and it seems that some nudibranchs have coevolved the amount of nematocyst they take from their prey, but no article really talks about the nudibranchs predators becoming more resistant etc. Just something that popped in my head and left me curious. Thanks

    Angelica Munguia

  • Doven Cardenas

    Good Day!

    I am Doven P. Cardenas, a B.S. Biology student of the University of Southeastern Philippines (Main Campus here in Davao City, Philippines), designing a research study about the distribution and identification of sea hare here in our location.Impart of my study assignments/tasks is to look for a peer-reviewed journal article (about 16 published research) related to my study. Looking and finding some alternative or relevant topics is a kind of hard one especially that is only few had done and published their articles on the internet.
    In this regard ma’am, I would like to ask a support and help from your concerned. Maybe a link or an attachment of a known sources or informations that will probably help my manuscript particularly about “Identification of Sea Hare”. Moreover, if you have a connection(s) to other known experts about my study, It’s my pleasure to have a linkage from them. It is an honor in my part to acknowledge your support ma’am.
    Thank you for your positive response ma’am. More power and God bless!

    Sincerely yours,

    Doven P. Cardenas


Kim Vincent


Sponsored by

Become a KQED sponsor