A snail’s pace

As we speed towards the summer solstice the days continue to get longer. The early morning low tides are much easier to get up for, as the sky is lightening by 05:30. Even so, when traveling an hour to get to the site, it’s nice when the low is later than that. This past Saturday the low wasn’t until 08:00. My parents were in Monterey for the weekend, so I decided it would be a good day to work the tide at the southern end of Monterey Bay, and then visit my parents. The Monterey Peninsula has some of the most spectacular tidepooling terrain in the region, and if I lived closer you can bet I’d know those sites better. Not that there is anything at all wrong with the sites on my end of the Bay and up the coast. But sometimes it’s good to get out of one’s comfort zone and explore the less well known.

So explore we did. It was cold and windy. The tide wasn’t all that low and the swell was up, so we didn’t get beyond the mid-tidal zone. My hip boots have deteriorated to the point that I have pinprick leaks at the seam where the boot part meets the leg part. Usually the tiny leaks don’t bother me, but when the water is cold I definitely feel the trickles. What all this means is that I didn’t get down into the low zone, which is fine. Biodiversity is highest in the mid zone anyway. The mediocrity of the low tide meant that I had to keep an eye out for sneaker swells, so less heads-down poking around and more scanning from above and then zooming in on individual items of interest.

One thing we noticed right away is that groups of Tegula funebralis, the black turban snail, were clumped together above the waterline of the high pools.

I’m trying to decide whether or not this is noteworthy. The pattern did catch my eye, but that might be only because it’s unusual (although not particularly interesting). It was a cold and drizzly morning, so the snails didn’t have to worry about desiccation. Was the clumping together benefiting the snails in any significant way? Hard to say.

The T. funebralis were also clumping together in the water! Here’s a large clump of Tegula shells in a pool.

Almost all of these are snails, but can you see the one that is a hermit crab?

Poor Tegula funebralis. It is so common that it is invisible and vastly underappreciated. I find them quite charming, though. There’s something about a grazing snail’s slow way of life that is very soothing. Not that you might not fall asleep waiting for them to do something interesting, but it is good to slow down to the pace of nature. Anyway, Tegula is one of my favorite animals, precisely because it is so unassuming and ignored. One of delightful things about Tegula funebralis is when it plays host to Crepidula adunca. I’ve written about the biology of C. adunca before and don’t want to rehash that here. I just wanted to show off my favorite photo of this trip to Asilomar:

I don’t know why I like this photo so much. It certainly isn’t the best shot I’ve ever taken. There isn’t any vibrant color at all. The subjects are the same color as the background. But it works for me.

When it comes to a snail’s pace, you can’t find anything slower than Thylacodes. That’s because Thylacodes squamigerus is the snail that lives in a calcareous tube. Much like a barnacle, or the serpulid worms that have similar tubes, Thylacodes makes one decision about where to live and lives there for the rest of its life. I see Thylacodes at places like Pigeon Point up north, but they are much more abundant on the Monterey Peninsula.

And the snail winners in the Most Likely to be Overlooked have got to be the littorines. These little snails (most of which are smaller than 15 mm) live in the highest intertidal, where they get splashed by the ocean just often enough to keep their gill sufficiently moist. They are never entirely submerged, but they do tend to gather in cracks, even the tiniest of which will hold water longer than a flat rock surface.

If you look closely at the photo above, you might see pairs of mating snails. Given where they live, high up in the intertidal where they are rarely covered by water, broadcast spawning isn’t a viable option for the littorines. They have to copulate. There are, I think, eight copulating pairs in this group of ~30 snails.

Because Littorina‘s habitat makes broadcast spawning an unfeasible option, the snails must lay eggs. But the splash zone isn’t a very friendly place for the eggs of marine animals. The littorines lay eggs in gelatinous masses in crevices or depressions where water will remain. After a week or so of development, the egg mass dissolves as it gets splashed, and veliger larvae emerge. They recruit back to the intertidal after spending some period of time in the plankton.

When all is said and done it’s difficult to make the claim that snails live exciting lives. Nonetheless, they are interesting animals. The diversity of morphology and lifestyle we see in the intertidal snails makes them eminently worthy of study and appreciation. I like to think that, as biologists once again “discover” the usefulness of natural history, students will be encouraged to fill in some of the gaps in our understanding of these and other abundant animals.