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Dive Dry with Dr. Bill

#553: Hunting Lions in the Hood

When I first arrived on Catalina 44 years ago, I wanted to introduce my students not just to the subject of science but get them involved in doing science. I was very fortunate that Dr. H. Barraclough Fell, my mentor during my Harvard years, was interested in working with us under his National Science Foundation grant to study the dispersal of marine invertebrates. Barry was interested in how drifting rafts of giant kelp could serve as "vehicles" for marine critters in southern California, especially those which either lacked the ability to crawl or swim all the way to Catalina or which had no planktonic dispersal stage. Barry, my students and I worked together for 7 1/2 years on this research project and only stopped when his research interests turned to the "dispersal" of humans to North America well before Columbus arrived and "discovered" the New World..

While collecting the drifting rafts (or paddies for you anglers) off the island, we found one sample off the East End that had hundreds if not a thousand or more of a strange creature that I couldn't identify. Remember, this was back in the days when we had relatively few field guides and my Harvard classmate Al Gore had just recently "invented" the Internet (tee hee). My correspondence with Dr. Fell was via snail mail (appropriate for two marine biologists!) in the days before e-mail, and back when first class postage stamps were just a few pennies (which is about all I earned as a teacher).

Out of the water this critter looked like a blob of green jelly. I wrote Barry and described the find as a "Hoover vacuum cleaner with wings" and drew a crude picture of it when spread out in the water. He wrote back two weeks later saying it was the nudibranch Melibe leonina, commonly known as the lion, lion's mane or hooded nudibranch. I kept several of them alive in my laboratory tanks at Toyon and used ancient 35mm technology to photograph them through the glass walls. We didn't have the instant gratification of digital cameras back then. Oh, and I had to walk to and from school two miles uphill in both directions with tons of snow falling on me back in Chicago!

The lion nudibranch is known from Kodiak Island, Alaska, to the Gulf of California (Sea of Cortez) and is most commonly seen in the warmer months, although nudibranch biologist Dave Behrens states they may peak in spring and fall. I hadn't seen one of these nudis in years here in Catalina waters, although I had filmed a few on scrawny kelp plants at La Jolla Shores a few years ago. Then a few weeks ago I was on another night dive when I noticed something unusual on a kelp blade swirling around with the surge. It took me a while to relocate it among the profusion of kelp, but when I did, I was pleasantly surprised. It was a small lion nudibranch crawling around on the kelp looking for its own variety of munchies! The next night I found a second one.

I've mentioned before that nudibranchs are snails without a shell. Most of them don't need such protection because they either taste terrible (chemical defense) or incorporate stinging cells from their prey (including sea anemones and hydroids). Often they are very colorful and many underwater photographers focus on taking images of them around the world. The lion nudibranch relies on camouflage since its body is a translucent green that blends in well with the kelp blades on which it is often found. If that doesn't work, it can autotomize (shed) some of its 4-6 pairs of "wings" or gills in the hopes a would be attacker (including some crabs, starfish and fish) will be distracted and gobble them up instead. Other critters including starfish and brittle stars often do the same when confronted with a potentially life ending dilemma. The Melibe can also lift off from the kelp and use its body in a flapping fashion to swim away.

Most people think of snails as mostly herbivorous, feeding on your garden plants or seaweed in the ocean. Nudibranchs are carnivores, vicious predators if you are potential food for them. The lion nudibranch is no different than its namesake, although it focuses on much smaller prey than the gazelles or antelope of the African savannah. It lacks the scraping radula of many snails and instead uses a large oral hood to capture small invertebrates such as crustaceans (copepods, amphipods, mysid shrimp), the larvae of invertebrates and other zooplankton, small jellyfish and occasionally even small fish. Upon contact, the hood closes over the prey and it is forced down the snail's oral opening. Behrens says he has observed these nudis with their hoods wide open waiting to catch food like an outfielder awaits a fly ball (go Cubbies!).

Lion nudibranchs have a fruity smell when taken out of the water or when a group of them is kept captive. The Monterey Bay Aquarium states it is like watermelon and may be used to repel predators (although kelp crabs appear to be immune to it). Now my sense of smell is very poor (how else could I eat my own cooking), so I can't confirm this (nor did I take the recent one I sighted out of the water since it was in a marine reserve). One source states that groups of these snails are known as a bouquet. However, I doubt I'd consider giving them to any lovely lady that comes my way, even if she is a mermaid.

Like most nudis and their relatives, this lion is a hermaphrodite and has both male and female organs making mating a snap when one encounters another of its own species. It takes no "pride" like its namesake (get it?). Fertilization is internal and the eggs are laid in ribbons of as many as 30,000 attached to giant kelp or eelgrass. Sadly these interesting critters apparently live but a year and often die after laying their eggs. I'm so glad I'm human!

© 2013 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Image of small lion nudibranch filmed at night and overview from the 1970s;
two images of the lion nudibranch in San Diego courtesy of Steve Murvine.

This document maintained by Dr. Bill Bushing.
Material and images © 2013 Star Thrower Educational Multimedia