Gargantuan Gastropods

All summer long, the tabloids and gossip columns are full of Malibu celebrity sightings, but here's a really big celebrity (or possibly a sea-lebrity) that's been overlooked: Aplysia vaccaria, the California black sea hare, a mild-mannered sea slug that has the distinction of being the world's largest gastropod. Eat your heart out, Orlando Bloom. Unless otherwise noted, all photos are © 2016 S. Guldimann.

Were you aware, dear reader, that the Malibu coast is currently playing host to large numbers of the world’s largest gastropod? While that sounds alarming like the plot of a 1950s B movie, this celebrity among slugs is a peaceful vegetarian, despite a passing resemblance to that movie monster favorite, The Blob.

Although it bears a distinct resemblance to Hollywood's favorite invertebrate horror,  A. vaccaria is mostly harmless. Image: Wikipedia

While the California brown sea hare, Aplysia Californica, is a regular tidepool resident in Malibu, this year, its much larger relative, Aplysia vaccaria—the black sea hare—is turning up in large numbers. No one at the Malibu Post can remember seeing more than one or two black sea hares. It's unclear if the vast number showing up this year is related to the unusually warm water or if other factors are in play.

Brown sea hares are smaller and usually a lighter color than their giant relative. Both species graze on kelp, which they chew up with a rasp-like tongue called a radula. Sea hares get their name from their rabbit ear-like appendages—actually scent organs called rhinophores.

Brown sea hares can grow to be impressively large for a slug, often measuring more than 15 inches from nose to tail.  A. vaccaria, however, can grow to be more than three feet long and weigh as much as 30 pounds. That’s one big slug. The largest specimens rarely turn up in the intertidal zone, but this year’s Malibu crop of A. vaccaria is still impressive, resembling a football in size and shape.

This unfortunate slug was left high and dry by the receding tide. However, sea slugs have adapted to the extreme conditions of the intertidal zone and can survive several hours out of water even in bright sunlight during low tide. The holes in the rock near this slug's head measure about an inch across, giving an idea of the creature's size.

Sea hare eggs look exactly like noodles, but probably would not be pleasant to eat. Both California species contain toxins from their algae diet that make them inedible to almost everything except lobsters—the garbage crew of the sea—and green anemones, which appear to be immune. There's a type of Australian sea hare that is so toxic that dogs have died after coming into contact with it. California sea hare species are much less potent, but it's a good idea not to handle them and to keep dogs away from them. Brown sea hares can release a purple dye that is a skin irritant. Black sea hares appear to depend on their terrible toxic taste for defense.

Sea hares are usually observed grazing on seaweed in tidepools during low tide, like this California brown sea hare, or waiting for the tide to rise while stranded, blob-like, on the beach, but they can also "fly" through the water with their wing-like parapodia—literally "foot wings."

There's actually a third giant gastropod on the loose in Malibu: the giant limpet, which is really another type of sea snail and not a true limpet at all. This species, Megathura crenulata, is the only known member of its genus, making it a monotypic genus. 

M. crenulata can grow to be nearly a foot in length. It may not be much to look at, but compounds in the blood of this primitive snail apparently hold promise as a cancer treatment. According to a 2011 article in the Journal of Immunology Research, "Keyhole limpet haemocyanin (KLH) appears to be a promising protein carrier for tumor antigens in numerous cancer vaccine candidates." 

After a sort of gastropod goldrush in the early 2000s that ran the risk of pushing this rare animal to the edge of extinction, M. crenulata is now being raised via aquaculture techniques.

Megathura crenulata, the only known member of its genus, lives only off the coast of California. The blood of this primitive snail species has become a key ingredient in vaccine research, but the burgeoning demand for the giant limpet blood could push this poorly understood and increasingly rare species to extinction. 

Here's a side view of M. crenulata, suggesting a very old person shuffling along under a large umbrella, and revealing the creature's true snail nature. Sea hares also have a shell, but it is internal and vestigial.

Sea hares are also important for medical research. According to the Aquarium of the Pacific's sea hare page, the California brown sea hare may not have a lot of brain wattage, but it has "the largest neurons in the animal kingdom, making it possible to identify individual nerve cells that are responsible for specific behaviors. They have been and are being used extensively in studying memory, behavior, and learning."

Humans may not find sea hares or giant limpets lovely to behold, but there's more to Malibu's giant gastropods than meets the eye. 

A football-sized specimen of A. vaccaria waits for the incoming tide on the beach at Little Dume.

Winter Tides

The Pacific rocky intertidal zone is one of the most punishing and extreme environments on earth but it contains amazing diversity and beauty, and this week offers one of the best opportunities of the year to explore this strange world. Above, a starburst anemone, Anthopleura sola, lives up to its name, displaying a dazzling array of tentacles that resemble the petals of a flower. All photos © 2014 S. Guldimann

... All things are one thing and that one thing is all things—plankton, a shimmering phosphorescence on the sea and the spinning planets and the expanding universe, all bound together by the elastic string of time. It is advisable to look from the tide pool to the stars and then back to the tidepool again.

—John Steinbeck, The Log from the Sea of Cortez

Winter brings spectacular daytime low tides to the Malibu coast, offering earthbound mortals a glimpse of the bizarre and wonderful microcosm that exist between the ocean and the shore.

This year, some of the lowest tides of the year will arrive just in time for Christmas. This "king tide" occurs during the new moon and peaks from December 21-23, but there will be low tides in the afternoon all week, starting on Wednesday, December 17, with a .65-foot low tide at 12:45 p.m. The lowest tide—minus 1.24—will arrive on December 23 at 4:30 p.m.

It can be hard to make time for anything extra—even mundane necessities like laundry—during the holidays, but an hour at the beach is a wonderful thing for restoring equilibrium.

Park visitors explore the rocky landscape revealed during a minus tide in November. December's new moon low tides should be even more revealing. This was a minus .44 tide. On December 23, the tide will be minus 1.24.

Visitors, and even locals, often fall into the comfortable pattern of picking a beach and sticking with it. The winter low tides are an invitation to step out of that habit and explore.

Leo Carrillo, El Matador, Point Dume and Surfrider all offer good opportunities for tidepooling. These are all State Park beaches,  and while there are parking fees for the official lots there's always plenty of free parking near by on PCH or, in the case of Point Dume, along Westward Beach Road, where a half-mile walk along Westward Beach and up and over the Point Dume Headlands to reach the access stairs down to Pirate's Cove provides an opportunity to watch for dolphins and the first winter whales.

The most accessible tidepools in the Malibu area are at Leo Carrillo, where the intertidal zone starts just a few hundred feet from PCH. They are also some of the best. Despite its proximity to the road, this area is still home to an amazing array of marine life.

The starburst anemone at the top of the page is open, active, and waiting for prey to come its way. This one is exposed during the low tide. It's pulled its tentacles in while it waits for the water to rise again and is attempting to avoid becoming prey itself with a camouflage of broken shells and urchin spines that it glues to its outer layer with a tough, waterproof cement.

The California sea hare, Aplysia californica, can move fairly rapidly in the water, where it grazes on algae, but it's entirely helpless out of the water.  Just like the anemone, the sea hare has a strategy to wait out the low tide. Like its distant garden slug relatives, this sea slug conserves moisture behind its thick, slimy skin. It can survive for several hours this way, even in full sun,  until the tide returns. This sea hare is just a couple of inches long. If it survives, it can grow to be 16 inches long and weigh up to five pounds. 

Most encounters with the sea hare are on the shore, where this unfortunate animal, unable to move and armed only with purple ink to discourage predators, resembles a black blob. In the tidepool, they're actually rather spectacular, with a pattern of gold and red spots, and a graceful undulating motion when they swim.

Empty California cone shells often wash up on the beach, or turn up in tidepools as the home of hermit crabs, but it's rare to get a glimpse of the live mollusk. This small sea snail is a veracious predator that feeds on a wide range of species, including purple olive shells and, believe it or not, fish, which the snail paralyses with a fast-acting venom. There are a number of tropical species of cone shell that are deadly to humans. This little snail is only a threat to other snails, worms, and tiny fish. However, cone venom shows promise as a pain medication for humans.

The tidepool sculpin, Oligocottus maculosus, is one of the species the cone shell preys on. In fact, it's one of the species all kinds of things prey on, which is why it, too, has a weapon: sharp spines on its fins. Some sculpin are also equipped with venom but I've never heard of anyone getting stung by a tidepool sculpin. It may look fierce and somewhat dragon-like, but it seems to depend on being fast moving and hard to see for survival. This remarkable small fish can breath air if it finds itself trapped out of water or in a pool with low oxygen levels during low tide. It's the most commonly observed fish in our local intertidal zone. 

Here's someone who isn't impressed by cone shells, except as a source for housing material. This is the blue-band hermit crab, Pagurus samuelis. This one has taken up residence in a somewhat battered Acanthina shell. Blue-bands are one of the most common Southern California intertidal hermit crabs, and always fun to watch—they're fast moving and usually very active.

If you are fortunate, you might see one of these. This is a live California  cowrie, also known as a chestnut cowrie or Neobernaya spadicea. Although it's hard to see here, this mollusk has, arguably, one of the most beautiful shells found in Southern California waters, and it has been collected to the brink of disappearing along the local coast, although their numbers appear to be increasing recently. I've seen more chestnut cowries at Point Dume this year than I have in the past 10 years. I don't know what that means, but hopefully it's good news.

Humans aren't the only ones taking advantage of the winter minus tides. This great egret has just snagged a fish—probably a sculpin—in a bed of surf grass and is in the process of turning it right-way-round to swallow it.

The shorebirds also take advantage of the low tide. Godwits have specialized bills that have evolved to enable them to probe the sand for sandcrabs and other tasty morsels. This bird is sometimes mistaken for the curlew, another shore species with a long bill. An old birdwatcher told me long ago that the way to tell the difference is to remember that the curlew's beak curves down, while the godwit's beak curves slightly upward—towards God. 

I am extraordinarily blessed to have had the opportunity to grow up by the ocean and to still spend many hours there. I've seen many tides—high and low—but I still see things that amaze and astonish me. The curious object in the photo above is called a mermaid's purse. It's actually the egg case of a dogfish shark or a stingray. I've read about them all my life, but this is the first one I've ever seen. I found it among the tide wrack at Surfrider Beach last week. The Christmas season brings many gifts, literal and figurative, but sometimes one of the best gifts is finding the time to step away from everything. There's no reason why a day at the beach, or even just an hour, shouldn't be part of holiday tradition. The king tide offers a perfect incentive. However, there's another chance to catch a spectacularly low afternoon minus tide during the first king tide of the new year, the week of January 20, 2015.

It's important to remember that the reverse side of this week's minus tides are formidable 8-foot-plus high king tides. Beachgoers should double-check the local tide tables and plan to leave when the tide begins to come in. This is especially critical at beaches like Leo Carrillo, El Matador, and Point Dume, where the low tides provide access to sea caves or otherwise inaccessible rock formations that are rapidly reclaimed by the returning tide and can trap unwary visitors. That sounds preposterously melodramatic, but serious injuries—and the need for rescue—result more often than one would think. 

It's a good idea to keep an eye on the surf report as well as the tide chart. Waves like this one at Point Dume on Sunday are great for surfers but less than ideal for tidepool explorers.

Winter storms bring joy to the surf community but they can complicate the tidepooling experience, generating big surf and "sneaker" waves even when the tide is at its lowest. The warnings about staying off piers and breakwaters during high surf events also applies to reefs and rocks, and it's good to remember that old advice about never turning your back on the waves. 

The website for NOAA tide predictions offers an easy to access, accurate online source for tides. Surfline is a good basic surf report site. This is their page for Point Dume. There are also dozens of tide and surf report apps.

See you at the beach!

Suzanne Guldimann
15 December 2014

Looking for the perfect Christmas gift? A selection of cards and photographic prints from the Malibu Post is now available at Fine Art America.