non-billiards fun at the tide pools


another day at the tide pools
more marine fun

We made another trip to the tide pools (one of my favorite places to go)… Along the hike, we saw these pieces of brick and concrete by the water. They looked to have dropped from the cliffs above, but we couldn’t figure out what they were.


One of the big rocks on the beach.

big ass rock

This elegant grey seal stayed around and observed us, even as we observed him. He’d pop up on the rocks now and then and seemed completely unafraid of humans.

insert clapping sound here


hermit crabs
seashell squatters

Hermit crabs (Pagarus sp.) are crustaceans who have soft, unshelled abdomens. To protect their abdomens, they find the empty shells of snails and occupy them. This hermit crab pictured below does not have a shell. Oftentimes, the shell home of a hermit crab can get wedged into a rock crevice and become immobile. As a result, the hermit crab usually abandons the shell to seek another one (or be stuck in the same rock crevice forever).

They are very vulnerable when they do not have their shells. Some of their biggest enemies are other hermit crabs who won’t hesitate to engage in a little cannibalism… The other non-predatory danger is drying out from the hot sun. We put this little dude in a small pool of water to help him stay cool…

As for finding him another home, he’s on his own for that one. We can’t afford another mortgage.

bank foreclosed on his house poor homeless hermit crab

Here are two hermit crabs fighting over the yummy carcass of an isopod with the warm and fuzzy name of Beach Cockroach or Rock Louse (Ligia occidentalis). Ugh.

fighting over food... I might have to get in on that

Meanwhile, back at the pool…

We were surprised by the amount of aggression displayed by thise lil critters, both towards other species and their own kind. Hermit crabs seems constantly engaged in some sort of battle. Here, one hermit crab drags another one along by the shell and makes repeated attempts to pull the occupant out of the shell.

This is probably because Hermit Crab #1 wants to upgrade to Hermit Crab #2’s shell home. The shells look about the same, but maybe Hermit Crab #2’s has new interior renovations such as hardwood floors and granite countertops. Regardless, Hermit Crab #1 spent a long time and a lot of effort to get that shell — we watched him struggle dragging Hermit Crab #2 for at least half-hour before they both fell off the rock back into the water.

well what do we have here...

to the left... to the left... everything you own in the box to the left...


regular crabs
alas, too small to eat

There were other crabs hiding in the crevices of the rocks. One of the most common species in west coast tide pool is the Striped Shore Crab (Pachygrapsus crassipes), pictured below.

big red

These crabs vary in color from green to red to purple, and they have distinctive black horizontal stripes on their shells. Although they are considered native to the western coast of North America, they are also found in parts of Asia. This is a result of the merchant ships of the 1800s using ocean water for ballast — the ships may have carried the crab larvae all the way across the ocean and then released them when they emptied the ballas water from their hulls.

This small green crab has a Beach Cockroach in its claws for lunch.

yo gimme some o' dat

These Striped Shore Crabs were just as cannibalistic as their hermit crab cousins. Here, one of them drags around the carcass of a neighbor, which is impressively the same size — maybe even a little bigger — than himself.

This crab was quite bold and when we tugged on his lunch, he tugged back mightly and even attempted to fight us off with his free claw.

cannibalistic lil critter! go eat yo' own kind, biatch!


clingy invertebrates
I don’t mean your last significant other

There was a nifty grotto at the bottom of the big rock. I wasn’t able to explore it as the tide was coming in and I preferred not to drown on this fine day.

window to the world

Although the rock was large, it was relatively soft and evidence of erosion was everywhere. Here, a tiny pool formed by erosion or perhaps a long-dead piddock (we’ll get to those later) is now home to tiny snails known as Eroded Periwinkles (Littorina keenae).

come on in, the water's fine!

Here is a cluster of Eroded Periwinkles. Note the delicate checkered patterns on the shell! The largest snail in this photograph measured in at a hefty 1/4″. I should go to the tide pools more often — I feel taller there.

itty bitty works of nature's art

Finger or Ribbed Limpets (Lottia digitalis) are also another common inhabitant of the rocks. They stay on the rock through the surf and tide by virtue of the powerful suction of their muscular foot.

little ass limpets

I surprised a limpet while he was crawling and flipped him over. After I was done photographing him, I righted him and sent him on his way.

Limpets have a homing instinct. They each carve out a specific groove in the soft rock over time with their shells. When the water rises, they’ll roam around the rock foraging for food and when the tide recedes, they’ll make a beeline for their particular address on the rock.


Here we have one of the Giant Owl Limpets (Lottia gigantea). This limpet measured a whopping 4″+ long. By comparison, the small limpets above averaged about 1″ in length. Giant Owl Limpets are male when they are young and small, and turn into females as they grow older and larger. These animals are in danger because… [drum roll, please] … they taste good.


Apparently, people collect them illegally for gourmet purposes and the Giant Owl Limpet is now facing the same problems abalones did a while back, where their numbers declined due to overfishing. Limpets are a delicacy in Hawaii and Portugal, and it’s a possibility that Asians like to eat them as well — because Asians will eat anything remotely edible.

big ass limpet

This colorful dude is a Hairy Chiton (Mopalia ciliata). Chitons behave a lot like limpets and abalone but are not considered snails. Their main defense is composed of eight shell plates held together by a very tough, muscular girdle. They are quite flexible in one direction and they can roll into a tight ball to protect their undersides from predators.

armored car of the ocean

A lone Black Turban Snail (Chlorostoma funebralis), plodding along patiently to whatever tea party he’s late for…

whither thou wilt


bits of calcium carbonate fascinate me…

On the left is a colony of Scaled Worm Shells or Wormsnails (Serpulorbis squamigerus). Although the shells look “wormy”, the inhabitant (and producer of the shell) is a snail. The shells are not neatly coiled, and usually cemented permanently to a surface. If a part of the shell is damaged, the snail can seal it off with a wall and build another addition.

On the right is a Volcano Limpet (Fissurella volcano), so named because it resembles a miniature volcano. The white shell at the top left is a Murex shell with some of its outer whorls worn away to expose the interior structure. At the bottom is an Eroded Periwinkle.

And now… a few blurbs about Piddocks.

Piddocks are a bivalve species who shell is textured at the rear, making it especially suitable for digging and wearing away at rock. The piddock makes its burrow by moving in a circular motion, the same way a drill bit would work to drill a hole.

These are California Piddocks (Parapholas californica), deeply burrowed into the soft rock. You can see just the top opening of the shells where their siphons poke out to filter water for food. Click here for a photograph of the whole clam. Click here for a (somewhat grotesque) top view of the piddock’s large siphon, flared out for feeding. And yet another fascinating picture of a live piddock’s colorful siphon.

A crab had taken up residence in one of the empty piddock shells.

squatter in an abandoned house...

in parting
yet another fun trip

One of the last things I saw was this name carved into the rock. The periwinkles had already colonized the grooves for their own purposes. 🙂


I hope you have found this post interesting and informative. Until next time… Watch out for sharks. 😉

One Reply to “non-billiards fun at the tide pools”

  1. thanks a lot for the info! i just found a rock at solana beach w/ holes either from angelwings or purple sea urchins…i saw the photo of the crab
    inhabiting one of the holes. now i feel a bit guilty for taking the rock…maybe i’ll return it this week. p.s. im still looking out for those sharks!!

Comments are closed.