Hitchikers and their kin.

My little home aquarium is a self-sustaining habitat. (Well, with a lot of work on my part, but that's just maintenance, making up for the lack of the tides which keep their home clean on the shore.) It's always full of life. Because over the years critters keep appearing, sometimes coming in on seaweed brought in, groceries for the current residents, sometimes sandwiched between barnacles I bring home to keep the snails happy. And sometimes they just sort of appear, whether brought in as eggs or floating in the clean water I collected at the shore. I'm cleaning the tank, scraping off brown algae, getting rid of leftover crumbs, and I see a tiny shape, sometimes just a hint of movement, a crab-like walk, or a waving tentacle. Something new living in the tank.

And I have to keep up the maintenance because I can't abandon my tiny friends, not without carrying every single one down to the proper level of the intertidal zone and releasing it safely. 

Green isopods arrive clinging so tightly to rockweed that I don't see them, even while I'm rinsing it off before I anchor it in the tank.

Rockweed isopod, Idotea wosnesenskii. Showing up on a piece of red alga. About 4 cm. long.

A fourteen-legger. Notice the hooks at the tip of each leg. They cling tightly to the algae, so that even with strong wave action (or me harvesting it) they are not dislodged.

And growing up in the tank is a large community of tiny isopods.

Isopods on an oyster shell. The largest are about 5 mm long. 

A large one, captured on its own.

Whenever I take a shell out of the tank, I find it covered in these critters, all running about, always in a hurry. I don't know what species they are.

A mussel shell, holding two isopods, and a couple of amphipods (the curly ones). The isopods always lay flat.

And this: I first noticed it a month or so ago. It was stuck to the glass below the sand level, only the size of one of the isopods, and looked like a baby limpet from that point of view. But the shape was wrong; it looked oval, not circular. Even with a lens, that was all I could see, but I thought it might be a chiton.

Two weeks ago, it turned up, now recognizable, on an oyster shell. And today it was on a small rock, which I took out, still keeping it underwater, to get a photo.

Woody chiton, Mopalia lignosa. With two orange-striped green anemones.

As far as I can tell, he's a woody chiton. If so, he will grow up to 8 cm. long. Today, he 1.7 cm.

He was not pleased with the trip. As soon as I replaced him in the tank, he hurried back to the oyster shell. These are shy beasties, hiding on the underside of rocks and shells. There, he barely moves from one day to the next, just peacefully eating algae and diatoms; he especially likes green sea lettuce, Ulva spp.. Tomorrow is a low-tide day; if the weather holds, I'll go find a handful of the lettuce for "Woody". And some eel-grass for the hermits, kelp for the crabs, barnacles for the carnivore snails, and ...

And no telling what else will hitchhike in.

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Mi acuario casero es un habitat que se sostiene vivo solo. (Bueno, aparte de mucho trabajo de mi parte, pero eso es mantenimiento solamente, debido a la falta de la marea, que en el mar les mantiene su casa limpia.)  Siempre sigue llena de vida. Porque año tras año siguen apareciendo criaturas nuevas. A veces llegan escondidos entre las algas que traigo a casa para la comida de los residentes ya presentes; a veces se cuelan entre los bálanos que mantienen felices a los caracoles marinos. Y muchas veces aparecen como por magia, tal vez habiendo llegado como huevos o como el plancton que flota en el agua que traje desde el muelle.Estoy limpiando el tanque, raspando algas invasivas, aspirando restos de comida, y veo algo que se mueve, apenas el movimiento ya que el animal es tan pequeño; el movimiento lateral típico de un cangrejo, o el ondeo de un tentáculo miniaturo. Algo nuevo que ahora vive en el acuario.

Y tengo que seguir con el mantenimiento, pues no puedo abandonar a mis amiguitos, no sin llevarlos uno por uno al sitio adecuado de su zona intramareal.

Isópodos verdes llegan cogidos tan fuertemente al alga parda, Fucus spp., tan apegados que no los veo, ni cuando estoy enjuagando las algas antes de instalarlas en el tanque.

Foto: # 1, 2: Isópodo de Fucus, Idotea wosnesenskii. Visible sobre un alga roja. Nótense los ganchitos en cada una de las catorce patas; estos se agarran tan fuerte al alga que ni las olas ni yo al trasportarla logran despegar el animal.

Y han crecido en el acuario una generación de isópodos muy pequeños.

Fotos # 3, 4: Isópodos en una concha de ostión. Los más grandes miden aproximadamente 5 mm. de largo. Siempre que saco una concha cualquiera del tanque, la encuentro cubierta de un gran número de esto, todos corriendo de acá para allá, siempre con mucha prisa.

Foto # 5: en una concha de mejillón hay dos de estos isópodos miniaturos y dos amfípodos; estos son los que se doblan, haciendo medio círculo.

Y esto: lo vi por primera vez hace un mes o más, apegado al vidrio debajo del nivel de la arena. Desde ese punto de vista se parecía a una lapa chica, pero la forma era diferente. Con una lente de aumento lo examiné y pensé que tal vez sería un quitón juvenil.

Hace quince dias estaba, ya más grande, en una concha de ostión y si era un quitón. Y hoy lo encontré en una piedrita. Lo saqué del tanque, manteniéndolo siempre en el agua, y le saqué una foto.

Foto # 6: Un quitón "de madera", Mopalia lignosa, creo. Con dos anémonas.

Parece que si es un quitón de madera. Si es así, puede crecer hasta los 8 cm.; por ahora mide 1.7 cm.

No estaba contento con su viaje. En cuanto lo regresé al tanque se fue a esconder bajo la concha de ostión de nuevo. Estos son animales tímidos que se esconden en la parte inferior de las piedras y las conchas de mar. Allí, no se mueve mucho; se mantiene allí tranquilamente comiendo algas y diátomos. Le gusta la lechuga de mar, Ulva spp.; mañana, que va a ser un dia con marea muy baja, si el tiempo lo permite, voy a la playa a buscarle un poco de lechuga marina para "Woody", y algo de hierba Zostera para los ermitaños, kelp para los cangrejos, y unos bálanos para los caracoles carnívoros. Y ...

Y quien sabe que otra criatura se subirá de pilón.

Chiton lips

"Woody", the green and blue chiton in my aquarium, spends most of his time plastered to a shell, a slow-moving, flattish, 2-inch-long mound blending into the background. If he has a "face", it's hidden. But for a moment, the other day, I caught him lifting the edge of his girdle, tasting the water.

Underside of the girdle, and the mouth, open. Also present: an amphipod, a mud snail, and a pink-tipped green anemone.

Woody does not have a head, as we understand the term. He has no eyes, tentacles, or brain here, just the mouth. (His shell does include light-sensitive spots, but around his mouth, there is no need, since it is usually clamped tight against the substrate.)

Like many other molluscs, chitons feed with a thin strap bearing rows of teeth known as the radula. The anterior rows are used up and discarded or swallowed and replaced by new rows moving forward like a conveyor belt. ... The chiton radula is noteworthy because one pair of cusps in each row is hardened with magnetite, which provides these teeth with a coating harder than stainless steel. They are the only molluscs that have magnetite-coated teeth. In fact, they are the only organisms known to manufacture such vast quantities of magnetite. (http://biology.fullerton.edu/deernisse/pubs/Eernisse_07_chitons_Tidepools.pdf)

Before I start to take photos through the glass, I scrub the inside walls; overnight, they develop a coating of green algae. A soft cloth removes most of it, but underneath that, there's always a more tenacious growth of yellowish-brown algae; for that, I use a green kitchen scouring pad, scrubbing and wiping with the cloth alternately. With a fingernail, I pry off harder lumps.

And even then, once I give up, the glass is still covered with these tiny pink dots, visible against the yellow flesh of the chiton. Pacific rose seaweed, trying to establish itself on every surface in the aquarium. When it grows on a shell, I can't rip or scrape it all off; it's tremendously tenacious. I tear off and discard double handfuls every time I clean the tank, but the glued-on "roots" are always left behind, ready to leap into action.

So fragile-looking, so delicate! And so strong!

No lights, please!

Last February, among the barnacles I brought home for my intertidal snails, a small chiton was hiding. He joined the other beasties in the aquarium, and trundled about happily for some time, cleaning algae off the glass walls and the stones. Then he disappeared.

Much later, cleaning the aquarium, I found him, inside an old moon snail shell. He'd grown some, was obviously thriving.

Since then, I've seen him often, on the outside of the moon snail shell, sometimes deep inside, sometimes on the bottom. But always on the snail shell; he never explores the glass walls any more, nor the sandy floor, nor even other shells. The moon snail shell is home.

Woody chiton, Mopalia lignosa , on algae-encrusted moon snail shell, fleeing the camera.

Chitons are slow animals, as slow, almost, as limpets. (Although a limpet on a mission can trot right along.) And on the beach, the chitons don't seem to mind being partially out of the water at low tide. I thought that maybe I could get some clear photos of "Woody", and maybe get a close look at his spines with the microscope, if I took his shell out of the tank. I put him in a tray with a half-inch of water, and set up the lights and camera.

But Woody didn't approve. As I rolled the shell around to get him within reach, he kept turning, heading down, towards the bottom of the shell, under the water. There are light-sensitive spots on his plates; he saw those bright LED lights, and hated them. Every photo I took was of him hurrying away. I didn't even try to aim the microscope at him.

He never left the moon snail shell. It's his safe place.

Side view.

The small, soft spines on his girdle arise from light freckles. The girdle is quite flexible; at one point, he galloped up and over the limpet, lifting the edge of the girdle to fit.

I gave up and replaced his home in the tank. He stopped racing around; he must have been pretty tired. He's still on the moon snail shell.

Rust, sea lettuce, and a baby chiton

The tide was as low as I've seen it at Oyster Bay, and I was wading around the remains of old ships left decades ago as a breakwater.

Clammers, and remains of an old ship, draped heavily in sea lettuce.

A long ship, reduced to spikes and sea lettuce holders.

In a few inches of water between rusty girders, I noticed a little chiton, upside-down. Unusual; they're normally stuck tightly to the substrate, but maybe his perch had gotten too hot and dry for his taste.

I picked him up, and he immediately rolled himself into a tight ball. I didn't know they did that.

I think this the woody chiton, Mopalia lignosa; his hairy girdle is lighter, softer, and has shorter hairs than the common hairy chiton.

After a brief wait, since I wasn't moving, he started to unroll himself again.

Orange underside. Like a limpet's, his foot includes a mouth (not visible on the right) and is separated from the girdle by a space which includes the gills.

When I moved, he rolled up again, so I gently replaced him back in the water, foot down.

These chitons grow to about 3 inches long; this was a youngster. They live in the middle to low intertidal zone, mostly on the sides and bottoms of rocks. There are no rocks in the area where I found him, so he had to make do with rusty metal.

They eat mainly sea lettuce; he'd picked a good place for that; these old ships are loaded with the stuff.