Forgotten beasties

From the "hold" folder, a few beach critters:

Wosnesenski's isopod. I think I held this photo because I wanted to id the tentacly bit near the isopod's rear. I still don't know what it is.

Three snails. Shell road beach, September, 2018. Half the snails I see turn out to be hermit crabs; I think the one on the left may have a hermit in residence; see the tips of her toes.

Three crabs; red rock, green shore, and a hermit. I like the pie-crust look of the red rock crab's carapace. April, 2018

Unidentified polychaete, stretching out of its tube.

A thin slab of wood, riddled with teredo clam burrows. The white bits are remains of the clam's burrow lining.

Textures on the shore

Wind, rain, and waves rearrange objects on the shore, sometimes in surprising ways. And provide me with contrasting textures to look at.

Teredo-drilled log, sponge, ice. As found, well above the high tide line.

Also well above the usual high tide line; a small collection of rocks in a hollow near the root end of a log. As found.

On a lonely, icy stretch of Miracle Beach.

More hole than wood

I often pick up chunks of teredo*-tunnelled wood on the beach. Sometimes I find an entire log riddled from end to end.

Each tunnel is coated with a layer of white calcareous material. The big hole is man-made.

Angular cut, showing the tunnel walls.

I measured the holes in a piece of tunnelled wood that sits on my desk (approx. 10 x 5 x 5 cm.). The holes are circular, and most measure 1 cm. across. Of 24 tunnels in this piece, 20 go straight through; two are slightly curved. On the log above, a few of the tunnels look curved.

When the wood dries completely, the white coating usually crumbles and falls off. It is only a couple of millimetres or less thick.

The tunnel of one teredo can be up to 2 feet long. In the log below there are thousands of tunnels.

The log. It looks like someone has cut a slab off, realized that the wood is unusable, and discarded the log. The outside looks normal.

*Teredos are usually called shipworms, but they are a species of clam, not a worm at all. The tiny bivalve shell is used as a file or scraper to burrow through the wood, which is their diet. Underwater termites!

Teredo navalis is a very destructive pest of submerged timber. In the Baltic Sea, pine trees can become riddled with tunnels within 16 weeks of being in the water and oaks within 32 weeks, with whole trees 30 centimetres (12 in) in diameter being completely warped within a year. (Wikipedia)

Tide-wrack; October collection

Each stretch of shore, and each season, even each weather pattern, has its own assortment of toss-ups. Towards the end of October, after several days of wind and wild waves, the northern section of Oyster Bay had refreshed its collection, substituting kelps for the usual eelgrass fragments and sea lettuce salad.

Possibly a broad-rib kelp, Pleurophycus gardneri

The various kelps look as if they should be easy to identify by asking a few questions: do they have a stipe, and what's it like? Are they smooth, winged, frilled, or blistered? What is the holdfast like? Do they carry floats?

Once they land up on the beach, in fragments, they become confusing.

Blistered, with a stipe-like centre. Similar to seersucker kelp, but missing the 5 ribs.

Nice holdfast, with two stipes, one bearing a blistered and ribbed blade, one with a smooth blade.

Alien invader

I took the photo of that mess with the frog (I think that's what it's supposed to be), because I was annoyed at the intrusion. I carried the critter out, dumped it in the garbage. One less bit of plastic left on the beach.

But before I deleted the photo, I blew it up and looked at it closely, wondering what else was there in that hodge-podge of land-based and wave-tossed vegetation. See the little fly on the blade of kelp just above the neat, round leaf?

But there's more: I noticed first one, then another and another ... transparent segmented tubes, small and smaller, scattered here and there. I chopped them out of the larger photo:

What are they? Plant stems? Leftover worm tubes? Plastic trash? Now I'll have to go back and look for more.

Clamshell. At least this is easy to identify.

A small branch, riddled with shipworm tunnels.

The shipworm (Teredinidae) is a clam, disguised as a worm. It has a long, worm-like body, up to about a metre long, depending on the species. But it wears two hard, ridged clam shells on its head, and uses them to carve out its burrow in the wood, lining some of the burrows with a calcareous coating.

When shipworms bore into submerged wood, bacteria ... digest the cellulose exposed in the fine particles created by the excavation. (Wikipedia)

This one was a larger, fatter clam than most I see on these beaches, and the wood is fresh, (most Teredos eat rotting wood), exposing the beautiful grain of the wood. (Click to look at it full-size.)

Group sculpture project

I've been sorting photos all afternoon and evening, cleaning and organizing the hard drive and storage, (working my way through 2010 today). And for a break, Laurie and I are sorting his paper photos, starting last week with the first ones from his disposable cameras, some 20 years ago.

What's that about "All things in moderation"? Never heard of such a concept!

I came across a photo that I loved, and thought I hadn't posted here. Looked it up in the archive, and I was wrong; it's here, in a post about shipworm. (Not a worm.)

Never mind; I still love the photo.

Carving by teredo clams, probably Bankia setacea, finishing by wind and waves.

Tomorrow, if the sun comes out again, I'm taking a break, attaching my new lens to the camera, and going out to load up on new photos. I've made space for them already.

When is a worm not a worm?

Answer #1: When it's a clam.

I grew up hearing about shipworms, the dreaded teredo worms that ate the logs that supported our wharves and float houses, and made our boats leaky. I'd seen their long holes in driftwood, and their white tubes cemented into the holes; long, snaking tubes for a tubeworm. Not until tonight did I learn that I had been completely mistaken about them all these years.

A teredo is a clam. An odd clam, to be sure; it's long (up to 2 feet) and snaky, like a worm, and the body's only protection is the calcareous tube it coats the tunnel with. But it does have the clam shell. On it's "head", or at least, the leading end. And it uses the double shell as teeth, to chew its way through the wood.

Its two shells, enclosing only the front end of the body, function as a tool, rather than a protective covering; their ridged and roughened surfaces are used for boring. (From bruceruiz.net)

Like other clams, it has two siphons. They are at the "tail" end. And the leading end is the foot. (It's a bivalve monopod.)

Drawing from bruceruiz.net

I was looking teredos up because Laurie took an interesting photo of shipworm-eaten wood today. I wanted to check my spelling, and ended up wandering around shipworm pages. Fascinating!

Like other clams, the teredo is a filter feeder, straining plankton from the water. But it also eats some of the wood it burrows in, with the aid of the bacteria it houses in special structures called "bacteriocytes". These bacteria produce enzymes that digest the cellulose of the wood. (Nobanis) They also "fix" nitrogen, and produce necessary amino acids.

(In this way, they are similar to termites, which also rely on protozoans and bacteria to digest the cellulose in wood. And similar, also, to us humans, whose intestines are home to many bacteria that work with us to digest our food. Not wood, though. Our bacteria can't handle cellulose.)

Laurie's photo. A rain- and wave-worn section of shipwormy log. Our local teredo is Bankia setacea.

Or there is Answer #2: When it's a crustacean.

The gribble, or gribble worm, as it is often called, also drills through wood found underwater,  like pilings, float logs, and boats. It is not a worm, but a crustacean, a marine isopod.

Limnoriidae are second only to theTeredinidae in the amount of destruction caused to marine timber structures such as jetties and piers. ... Gribbles bore the surface layers of wood, unlike the Teredinidae which attack more deeply. Their burrows are 1–2 mm diameter, may be several centimetres long, and have the burrow’s roof punctured with a series of smaller ventilation holes. Attacked wood can become spongy and friable. (From Wikipedia)

These critters seem to make their own enzymes to digest cellulose, but at least one species does find a use for symbionts:

L. tripunctata is unusually tolerant ofcreosote, a preservative often used to protect timber piles, due to symbiosis with creosote-degrading bacteria. 

Log showing gribble damage, and a teredo tube. Oyster Bay.

Come to think of it; I've never seen a live gribble or teredo; just their holes. I must remedy that.