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The California Sea Hare

Updated on January 14, 2015

The Sea Slug or Sea Hare: A Laguna Beach Local

This is probably the world's first fan page devoted to the California sea hare. No, seriously. When I looked up A. californica online after finding a tidepool full of them, I discovered some fascinating facts about this unassuming animal. Not only does it switch sexes every other day during at least part of its life cycle; it's played an important role in Nobel Prize-winning research in neuroscience!

Not bad for a critter that doesn't even have a spinal cord.

On this page I'll share photos, videos, and basic information about the California Sea Hare, a large sluglike mollusk found snuffling about the tidepools off the coast of California. For beachcombers, tidepoolers and nature lovers, I hope I can give you some appreciation for an animal that doesn't have quite the star power of a clownfish (of Finding Nemo fame) or humpbacked whale. For marine biology students looking for more in-depth scientific information than my Sea Hare factsheet covers, check my links section below: I may not have the level of expertise you're looking for, but I've found a few sites that do!

Video: California Sea Hares - Tidepools at Laguna Beach in Orange County, CA

Sea hare video clips taken by me and my mother (Ann Brundige), 02.27.09.

They're oddly cute, aren't they? Although the hermit crab caught in the slow-motion hit-and-run in the first clip might dispute me, if it had higher brain functions.

All About California Sea Hares - Scientific Name: Aplysia californica

There's dozens of species of sea hares, sluglike marine animals found around the world. The California Sea Hare is a brown or reddish spotted species found all along the coast of California down into Baja.

  • Names: California Sea Hare, California Sea Slug, Aplysia californica

  • Size: Varies. A foot (30 cm) is typical for full-sized adults when stretched out. Those pictured here were closer to 5 to 8 inches.

  • Weight: According to this Aplysia Californica size chart, foot-long California Sea Hares are typically around 100 grams; the ones I saw were closer to 20 grams.

  • Diet: Unlike some sea hare species, Califonia Sea Hares are vegetarians! They eat Coralline Algae (brown or red algae), soft frilly stuff found in rocky tidepools during low tides. In other words, they fill the same role as aquarium fish used to clean up algae and keep tanks scum-free.

  • Color: Dark brown to reddish-brown, sometimes with a yellowish or pink cast, depending on the color of their food. Adults are mottled and well-camouflaged. Young juveniles are pinkish-orange and don't show mottling.

  • Anatomy: They're gastropods, from the Greek for "stomach-foot," which describes most of their body. They have a small bit of leathery shell inside, protecting some of their organs. They have a sucker-like mouth and a pair of small black eyes on the top of their head. But they do most of their tasting/smelling/sensing using their "rabbit ears," the pair of short tentacles behind their eyes that gives sea hares their common name. These tentacles are called "rhinophores." Sea hares use them not only to detect food but also enemies, their surroundings, and other sea hares. (They also have two more tentacle-like "toes" at the leading edge of their foot, on either side of the mouth, which can look like rabbit ears from above).

  • Lifespan: Usually a year. Here's a diagram with videos showing you the life cycle of sea hares at different ages.

  • Reproduction: California Sea Hares are hermaphrodites, meaning they have both male and female parts -- in fact they alternate being male or female on different days! Eggs hatch after 8 or 9 days into microscopic larva, which gradually grow into full-sized slugs, dining on other kinds of red algae as juveniles.

  • Habitat: Shallow tidepools with red algae in the "Low Tide Zone," only exposed during the lowest tides each month. In Orange County, I've noticed bright purple sea urchins during these especially low tides, so if you can see them, start hunting for sea hares in shallow pools with pinkish red algae. You'll also see blue mussels, hermit crabs, and sea anemones in the area (although these also live higher up, so they are not reliable indicators of sea slug habitat).

  • Fun Facts: This kind of animal has been called "sea hare" since antiquity, since some European species are markedly rabbit-shaped. The purple ink of one species was used by ancient scholars in Jerusalem to write sacred texts-- maybe even the Old Testament!

Going Tidepooling? Keep This in Mind...

Be gentle, if you come across a sea hare. They have no bones and tear easily. You can pet them lightly, but don't prod, stab, squash, or pull on them. (They're quite soft to the touch, like wet velvet). They're not poisonous, and they won't do anything worse than squirt ink if alarmed.

California Sea Hares: Nobel Prize Winners!

Helping Neuroscientists for Over Fifty Years

The nervous system is the "wiring" that makes our bodies work. It includes our brains. It just so happens that California Sea Hares have very simple nervous systems and very large neurons (nerve cells), making them perfect subjects for studying neurobiology!

A lot of what scientists now know about the human nervous system, neurons, reflexes, memory, and even complicated behavior like learning grew out of studies of Aplysia californica.

"In 2000, Dr. Eric Kandel won the Nobel Prize in Physiology or Medicine for his research in how neurons are able to form and store memories. For this award-winning research, he used Aplysia from Rosenstiel School's National Resource for Aplysia along with neurons from mice. Other studies of Aplysia have led to drugs now in clinical trial aimed at reversing memory loss in patients with degenerative mental diseases."

~ Source: Aplysia Center Website

In other words, drugs currently being tested to reverse Parkinson's Disease and Alzheimer's have been developed thanks to the humble California Sea Hare!

California Sea Hare Links - My Bibliography For This Page

I'm not a marine biologist. In fact, when I saw these animals in tidepools at Laguna Beach, I didn't know anything about them except that they were sea hares! I Googled "sea hare" and studied a lot of photographs and descriptions on expert websites until I was sure I'd identified my slug. (A pity there's not much of a market for a Roger Tory Peterson Guide to Marine Invertebrates.)

Here's the websites where I found all my information.

California Sea Hare, Laguna Beach

California Sea Hare, Laguna Beach
California Sea Hare, Laguna Beach

More Sea Hare Videos

Here's a couple more videos of sea hares by people with better cameras than mine!

© 2009 Ellen Brundige

Sea Hare Fan Mail

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    • jimmielanley profile image

      Jimmie Lanley 8 years ago from Memphis, TN, USA

      Quite a fascinating creature. You've dug out so many neat tidbits about this fellow. I like him!

      The sea hare deserves a blessing as well. So, voila, there it is!

    • religions7 profile image

      religions7 8 years ago

      A leathery shell? Must be an ancient type of snail then :)

    • mythphile profile image
      Author

      Ellen Brundige 8 years ago from California

      [in reply to spirituality] Yep! Sea hares seem to have evolved from a primitive form of snail; the bit of shell that's left inside of them is vestigial, like an appendix.

    • Dianne Loomos profile image

      Dianne Loomos 8 years ago

      I enjoyed reading about the sea hare. Lensrolled to my snail lens.

    • Kiwisoutback profile image

      Kiwisoutback 8 years ago from Massachusetts

      Strange! I've never seen of these. I'm headed to Long Beach in May, I'll see if I can spot one. Thanks for the education!

    • profile image

      anonymous 7 years ago

      I went to malibu today and I saw a bunch lying on the sand. Not sure if they were alive or dead but I ended up taking 4 of those back to the water. One was releasing a purple ink...

      I hope I was able to save them.

    • mythphile profile image
      Author

      Ellen Brundige 7 years ago from California

      [in reply to Joe] As long as you handled them gently, you probably saved them! They can't live out of the water too long. Don't worry about the ink -- the animal does that to say "put me down!" but it's not a sign of injury, just alarm. Good job!

    • KathyMcGraw2 profile image

      Kathy McGraw 7 years ago from California

      I enjoy the tidepools at Swamis in Encinitas. There is so much to see, and your tips on using caution when handling are good. *Blessed* by an Angel

    • LabKittyDesign profile image

      LabKittyDesign 7 years ago

      Cool lens! But is spinal "chord" a typo (or a Brit spelling)? Or is this a Nudibranchia thing?

    • mythphile profile image
      Author

      Ellen Brundige 7 years ago from California

      @LabKittyDesign: Ack! No, that was Greekgeek's brain on the fritz. Thanks for catching it!

    • nebby profile image

      nebby 6 years ago from USA

      This lens is fascinating - I had never heard of California Sea Hares before.

    • mythphile profile image
      Author

      Ellen Brundige 6 years ago from California

      @nebby: Thanks for visiting! It just goes to show you that there may be unusual things right in our own back yards -- or right offshore.

    • profile image

      makeamill 6 years ago

      you have a pretty neat article you should check out mine when you get a chance

    • profile image

      anonymous 6 years ago

      Can sea hares be taken out of the water for short periods of time, no more than 3-4 minutes? I run a sailing camp and there are a bunch of sea hares on the rocks by the dock, I pulled one out of the water, very carefully not to harm it or squash it, to show the kids, and someone mentioned that I had just killed it taking it out of the water for such a short period of time. Is this true?

    • mythphile profile image
      Author

      Ellen Brundige 6 years ago from California

      @anonymous: I'm not a marine biologist, so I don't know for certain. But that marine biologist in video #5 did take a sea hare out for a while to show a class he was teaching.

      I've been hunting around on the net trying to find an expert to ask, but unfortunately the sea slug forum is closed right now!

      I would err on the side of caution -- hold them in shallow water to demonstrate, only take them out for a very brief time -- just to make sure. I'm not sure if they can breathe out of the water.

      But I doubt they die instantly. Most marine animals can handle being out of the water for a short time, just as we can get by without breathing for a short time.

    • NanLT profile image

      Nan 6 years ago from London, UK

      These are fascinating little creatures. I could sit here and look at the photos over and over.

      And is it a coincidence that the captcha is lookpod?

      Blessed

    • GonnaFly profile image

      Jeanette 6 years ago from Australia

      The ocean is so full of amazing creatures. We haven't gone scuba diving for a while now but it's like a completely different world under the water. These are certainly fascinating creatures.

    • profile image

      eridqua 6 years ago

      Haha. I'm delighted to know there's another person out there that knows what a sea hare is! I grew up here in SoCal and my dad is a major ocean/beach nut. From the time I was a baby he's been teaching me ocean terminology. We love to go explore the tide pools and enjoy the marine life there. Thanks for making this lens. Go sea hares!

    • percula lm profile image

      percula lm 6 years ago

      I was just looking at one of your lenses and noticed you had a link to a sea hare lens, and here I am. I have been fascinated with marine life and marine biology since before I can remember. When I was around 20 years old I started in the reef tank world. I had reef tanks for about 8 years. I wanted to mention that sea hares are more and more common in the reef aquarium community. In fact I have had 1 in the past and some friends of mine have owned them too. They are interesting critters to watch, and very easy to keep as pets (as long as you keep the water quality up).

    • profile image

      ShamanicShift 6 years ago

      Thanks for introducing me to a new, wondrous critter to consider! I have added this to my featured California lenses on my California_ lens.

    • mythphile profile image
      Author

      Ellen Brundige 6 years ago from California

      @percula lm: That's great! They're like living lava lamps, aren't they?

    • mythphile profile image
      Author

      Ellen Brundige 6 years ago from California

      @eridqua: I really need to stop Squidooing and get out to the beach more. We're very lucky to live here. And sadly, the mess in the Gulf reminds me that something could happen -- you just never know.

    • joanhall profile image

      Joan Hall 6 years ago from Los Angeles

      Hi! I'm adding this to my Animal Instruction Lenses lensography.

    • profile image

      anonymous 6 years ago

      Interesting creates, I hadn't heard of the California Sea Hare before. I like to go on site that show pictures of newly discovered living things. There are so many strange but wonderful creatures, I'm just in awe of them all. Creation is inspiring!

    • profile image

      VideoGameFanatic 6 years ago

      Never knew there was something called a sea hare. Thanks for creating this lens and letting us know.

    • ChemKnitsBlog2 profile image

      ChemKnitsBlog2 6 years ago

      Thanks for identifying the unicornfish! I have featured this lens on my fish page.

    • mythphile profile image
      Author

      Ellen Brundige 6 years ago from California

      @ChemKnitsBlog2: Oh, wow, thanks! That was a fun page.

    • EdTecher profile image

      Heidi Reina 6 years ago from USA

      I've seen them in tidal pools but never knew they were "sea hares". Great info, pics and videos. Blessed by a SquidAngel ~

    • profile image

      ShamanicShift 6 years ago

      This was a new critter for me -- and I'm circling back today to bestow a SquidAngel blessing!

    • BLouw profile image

      Barbara Walton 6 years ago from France

      What interesting photos, but anything less like a hare I can't imagine! Fascinating subject.

    • profile image

      anonymous 6 years ago

      WOW I SURE APPRECIATE YOUR SITE AND WILL SHARE IT AT THE CHANNEL ISLANDS NATIONAL PARK VISITOR CENTER WHERE I AM A VOLUNTEER. WE HAVE ONE CALIFORNIA SEA HARE IN OUR TIDEPOOL AND IT LOVES THE RED ALGAE !

    • MokaChocolate profile image

      MokaChocolate 5 years ago

      How cool! Thanks for introducing me to a new sea critter.

    • mythphile profile image
      Author

      Ellen Brundige 5 years ago from California

      @anonymous: Oh, I will have to look up that visitor center!

    • GonnaFly profile image

      Jeanette 5 years ago from Australia

      They look so sweet! Just returning to add a little angel blessing and to let you know that this lens has been added to my animal alphabet lens.

    • profile image

      anonymous 5 years ago

      Useful for my homework project. Thanks.

    • profile image

      anonymous 5 years ago

      Really great, thanks! Helped me heaps while researching Sea hares.

    • profile image

      anonymous 5 years ago

      Students in my Chemical Ecology class created scientific music videos and these premiered this morning at our 2nd Annual Chemical Ecology Filmfest. Three of the videos focus on A. californica research. Here are the links...

      http://www.youtube.com/watch?v=bPZQ7ZUEn8Y

      http://www.youtube.com/watch?v=c_5WPJB-1O4

      http://www.youtube.com/watch?v=2OGu-bzkEg8

      Enjoy.

    • Gypzeerose profile image

      Rose Jones 5 years ago

      Really fun lens. And BTW - I visited the three youtube videos (mentioned in the comment below) created by the graduate students about A.californica - very funny. I wish my biology teachers had been like that. I pinned your lens to a new board I created "Cool Critters"

    • mythphile profile image
      Author

      Ellen Brundige 5 years ago from California

      @anonymous: Good heavens. I usually delete random links dropped on my pages, but those are very creative and funny! Good job, all of you!

    • profile image

      RuralFloridaLiving 4 years ago

      Nice lens!

    • profile image

      anonymous 4 years ago

      Please know that you can not handle or touch any tidepool animals in Laguna Beach. You can observe all of them, but do not handle them. You will see large signs with the "Tidepool Rules" at the entrance to every beach.

    • profile image

      mouse1996 lm 4 years ago

      Great information. I've never heard of a sea hare before. They look so interesting. I'd like to see one in person some day.

    • profile image

      anonymous 4 years ago

      You can come to the Newport Nautical Museum and touch a Sea Hare!

    • profile image

      terri-daskalakis 3 years ago

      They taste great with garlic

    • profile image

      JohnGauman 2 years ago

      @terri-daskalakis: Yikes! These invertebrate animals are protected---and are ILLEGAL TO TAKE WITHOUT A PERMIT!

    • profile image

      JohnGauman 2 years ago

      @anonymous: Also, in California (and other places, as well), marine invertebrates (and vertebrates!) are protected! You may not even remove them without a permit!

    • mythphile profile image
      Author

      Ellen Brundige 2 years ago from California

      @JohnGauman: EEK. Sorry, I didn't realize my guestbook was unmoderated. I will leave that comment up, along with yours. Folks, this page is about admiring and photographing wildlife, not harming it!

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