A tasty orange

Last week's storms had tossed up many sponges with the torn seaweeds. Some were shredded, dead, sun-bleached, white, as I usually find them after a windstorm. But this week, most were still bright orange.

Orange finger sponge, Isodictya rigida, as found. On a bed of shredded rockweed, sea lettuce, turkish towel, and eelgrass.

I brought home a couple of pieces, one white, one still orange, and put them in the aquarium to see what my critters thought of them.

Orange (and white) finger sponge. With crab hiding underneath, hermit climbing in back.

The hermits climbed the white specimen, taking a few nibbles, then went back to eating the kelp stipe I'd brought them.

The larger crab (seen beneath the orange sponge) ripped big chunks off the orange sponge and ate them; an orange powder floated off into the water as he ate. That was in the first hour; after that, he and the other crabs went back to eating kelp. They've ignored both pieces of sponge ever since, and the orange piece is retaining its colour. I wonder if it's still alive; how can you tell, with sponges?

Central Coast Biodiversity says that dorid nudibranchs and blood stars eat this sponge. It looks like crabs are not so inclined. My little sea urchin has not made a move in its direction, either.

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Las olas y el viento habían aventado muchas esponjas, despegadas de su sitio en el fondo, hacia la playa, donde, arrastradas por el viento, terminaron en la parte superior de la playa, entre montones de hierbas y algas marinas hechas trozos. Algunas de las esponjas eran como las encuentro comunmente, rotas, blancas, blandas, muertas. Pero muchas eran nuevas, con su color fuerte anaranjado sin disminuir.

Me traje dos pedazos, uno anaranjado, el otro blanco, a casa para ver que hacían mis animales con ellos, y los coloqué en el acuario.

Allí, los ermitaños se treparon al pedazo blanco, tomando una u otra mordida, después regresando al kelp que también les había traído; allí se han quedado, comiendo kelp.

El cangrejo grande (que en la foto se ve escondido debajo de la esponja) arrancó grandes pedazos de la esponja grande, y se los comió; la esponja emitió un polvo amarillo mientras el cangrejo comía. Esto al principio, pero pronto perdió interés y se fue con los otros cangrejos a comer kelp. Desde entonces, los dos pedazos de esponja se mantienen sin cambio. (¿Estará viva la esponja amarilla? ¿Cómo se puede saber, con las esponjas, que son enteramente pasivas?

Central Coast Biodiversity dice que los nudibranquios y algunas estrellas de mar, (las estrellas sangrientas) comen estas esponjas. Parece que los cangrejos y ermitaños no cuentan entre sus predadores. Y mi pequeño erizo de mar no se ha acercado, tampoco.

People food

In midwinter, the seaweed harvest on the shore is limited; here, it's mostly shreds of red algae, much battered, and mostly rotting. Occasionally, then, I supplement my critters' diet with a bit of people food, from the supermarket. Dried nori seaweed, made for sushi wraps. The brand I buy contains nothing but seaweed; no flavourings or additives. And all my critters love it! (Even the mud snails.)

Here's a green shore crab, hogging a section for himself, keeping an eye out for marauding hermits.

"Mine, mine, mine, all mine!"

I gave them enough for a small plate of sushi last night. This morning, there wasn't a shred left.

Corn-fed shrimp

The label on the shrimp's favourite food says, "Crab Cuisine". It is intended for a variety of underwater scavengers, from crabs to hemits, lobsters and even crawfish. I read the fine print on the label tonight; the first ingredient is fish meal, but from there it goes on to corn, rice, wheat, and soybeans, and only then, krill and fish oil. Next, there's garlic (just in case I might want to eat my hermits?), yeast, and a long list of vitamins and minerals.

It must be good for them; they're healthy and happy. But - corn? And garlic?

Shrimp with a corn and fish pellet. Yum!

I also have dried shrimp, and when I can find them, frozen raw shrimp; everybody loves those, but they disintegrate and pollute the water, so I feed them sparingly. And there are "shrimp pellets"; the primary ingredient in these is ... wheat.

At least there's no high fructose corn syrup in there. And I'm glad that I supplement their diet with seaweeds and, in season, hydroids.

The lettuce eaters

Winter in the intertidal zone is difficult, even here where it barely gets cold. The water is often turbulent, the nights are long, the daylight dim. The plants and algae, the seaweeds and eelgrasses, die back, leaving no shelter from the flocking thousands of sandpipers foraging in the shallows.

We see little more than worm tubes and holes, snails, those everlasting invasive Asian mud snails mostly, and the hermit crabs that use their abandoned shells, fewer hermits than we would see in warmer weather. Many don't make it through to spring.

My tank residents have it easy. The temperature stays the same year-round. The current rarely changes, except when I'm cleaning the pump. There is daylight 16 hours a day, always bright, never clouded over. And there are no birds. No birds!

The one small bump in this easy road is the intermittent supply of greens. Often, on a trip to the beach, I manage to bring back only a few handfuls of skimpy eelgrass and a bit of half-dead kelp. It's rare that I find sea lettuce for them in the winter, or Turkish towel that isn't all torn and rotting. Sometimes their tank is almost empty of vegetation; when I then bring the hermits a mess of hydroid-covered eelgrass, they climb on it and never leave until it's bare.

This winter has been exceptionally hard for them; they have been getting a small taste of what their cousins on the beach go through every year. What with one thing and another, the weather, and the state of our health, and other time constraints, we haven't been down to the beach since mid-February. I did bring back a couple of pieces of fresh sea lettuce then, and I found a big leaf of fresh Turkish towel, which lasts well in the tank. But there was little eelgrass to go with it, and no replacements since then. The tank is bare; an underwater desert, decorated with small shreds of fading Turkish towel, stripped of any food value.

One of the smaller hermits, on a barnacle-covered stick.

I read somewhere that hermits will eat ordinary people-food lettuce. Worth a try; I tore off a bite-sized piece and anchored it in the sand. Within a minute, the largest hermit and the crab were having a tug-of-war over it, yanking and pulling and at the same time tearing off pieces and shoving them into their mouths. (It's handy having so many grabbing mouth parts.)

I added a few more pieces of lettuce for the rest of the crew. That was a couple of hours ago. They have eaten it all, leaving only a few floating shreds, as thin as soggy tissue paper.

Hermit on lettuce leaf, all stretched out to grab as much as possible before the rest get there.

Hermit on the far side of a scrap of lettuce. His shell is showing through the hole someone has already torn.

As far as I can tell, all the hermits got a chance at the lettuce. The largest one stuffed himself so much, finishing off one piece and going to the next, and the next, that I wonder how he fits into his shell now.

I saved a leaf for them tomorrow; I ate the rest.

Hurry, hurry! Dinner is served!

I wonder if they like cilantro? I've got a big, fresh bunch.