Feathery orange quill; the sea pen

For those of us humans restricted to dry land, or at least anywhere above the low-tide zone, there are creatures, close neighbours, that we rarely see except in aquariums. Like the orange sea pen; even though it likes relatively shallow water (down to 135 m.), it still remains stubbornly sub-tidal. "Try gently stroking one ..." suggests the Encyclopedia, but adds, "... on your next night dive".

I found an orange sea pen on the shore at high tide. Dead, of course; tossed up by winter storms, but still almost intact.

Orange sea pen, Ptilosarcus gurneyi. About 18 cm. long.

Back side. Restored to water, just in case it still clung to life.

"It", I say, but my pronouns are wrong; I should be saying, "they". It's not an animal; they're a whole community, or colony, of animals, each one joined to his or her neighbour (they come in both sexes) and performing his or her own function in the community. Some fish for planktonic food, some pump water in and out of the central stalk, some attend to respiration, some start the next generation. And one becomes the main support; it loses its tentacles and forms itself into a calcium carbonate stalk ending in a bulbous peduncle which serves as a root, anchoring the colony in the sea floor. The other members of the colony branch off the upper stalk.

They're Cnidarians, members of the phylum that includes sea anemones and corals; each animal is a polyp, a hollow column with eight tentacles, like a miniature sea anemone. They arrange themselves in rows with the tiny tentacles along the outer rims. (For more detail, WallaWalla.edu has photos. Scroll down.)

They can live up to 100 years. If a sea star doesn't eat them. Or a nudibranch; the opalescent nudibranch, Hermissenda crassicornis, common on our shores, is one of its main predators. Scientists estimated the age reading the growth rings in the stalk, like the growth rings on a tree, one ring assumed to represent one year. 

Oh, and stroking them? Like a cat purring, the sea pens glow green when they're petted. Gently, now!

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Para nosotros los humanos, los que estemos limitados a explorar en tierra firma, o por lo menos, si estamos cerca del mar, en la zona intramareal cuando la marea la deja expuesta, hay criaturas vecinas que raramente vemos si no están en el acuario. Entre ellas, la pluma de mar anaranjada; aunque vive en aguas cercanas a la costa (de 10 a 135m. de profundidad) se mantiene sumergida aun en las mareas más bajas. "Acaricie una suavemente," sugiere mi Enciclopedia, pero añade, "en su próximo buceo nocturno."

Encontré una pluma de mar anaranjada en la playa a marea alta. Muerta, claro está, arrancada de su sitio por las tempestades de invierno, pero casi entera.

Fotos: la pluma de mar anaranjada, Ptilosarcus gurneyi, primero fuera del agua, luego en agua, y volteado "boca abajo".

La pluma — pero mejor debo decir, las plumas, porque no es un individuo sino una comunidad, una colonia de animalitos, cada uno (o una; los hay en ambos sexos en la misma comunidad) con su tarea específica; unos (o unas) pescan entre el plancton para alimentar la colonia, unos llenan de agua el soporte, unos se encargan de la respiración, otros llevan a cabo la reproducción. Y uno forma la columna que sostiene erguida la colonia. Perdiendo sus tentáculos, se transforma en un tallo de carbonato de calcio, con el extremo inferior abultado para formar el pedúnculo, que se introduce al fondo marino. Todos los otros miembros de la colonia forman ramas de este tallo.

Son miembros del Filo Cnidaria, animales que incluyen las anémonas de mar y los corales; cada animalito es un pólipo, una columna hueca con ocho tentáculos. Se acomodan en hileras con los tentáculos en el borde exterior. (Para más detalle, vean las fotos de WallaWalla.edu.)

Pueden vivir hasta los 100 años, si no las come una estrella de mar. O un nudibranquio; el nudibranquio opalescente, Hermissenda crassicornis, que se encuentra comunmente en nuestras playas, es una de sus principales depredadores. La edad la estimaron los scientíficos leyendo los anillos de crecimiento en el tallo, parecidos a los anillos de crecimiento que se hallan en el tronco de los árboles, estimando que se forma un anillo cada año.

¿Y eso de acariciarlas? Como cuando lo acaricias, el gato ronronea, la pluma de mar produce un brillo verde, bioluminiscencia. 

Obelia and the Very Messy Limpet

When we go to the beach, I pick up a bag of veggies for the animals in my aquarium. The crabs love green sea lettuce; I often see them grab a floating leaf, tear it into chunks and gobble it down. They're fond of a side salad of red Turkish towel, too. The big brown anemone seems to do better when there is a bit of rotting kelp nearby. Hermit crabs like the red stuff; thin red algae and Turkish towel. Some hang out on the sea lettuce, picking at the surface.

Snails and limpets feed on fresh eelgrass, but the hermits like it best a bit aged, covered with weedy growths. They browse knee-deep in the "pasture", whether eating the weeds or searching for bits of detritus, I don't know.

Eelgrass blade, with fuzz and a couple of limpets.

The last batch of fuzzy eelgrass brought along a small limpet, as fuzzy as the grass itself.

Limpet, bubbles, and a city on a hill.

The limpet is about 1/2 cm. lengthwise, less than 1/4 inch. I looked at it through a magnifying glass, to see if the tiny spiral worms were alive, and found a thriving community, more diverse than I had expected. I've been trying to get photos ever since, difficult since I needed it to stay underwater so that the waving, feeding critters would be out. There was so much activity that, even in still water, the eelgrass blade floated to and fro.

Side view.

In the peak of the limpet shell, a new eelgrass plant is growing. Under its shade, there's a circular patch of bryozoans. The red blob above this, and red lines in other spots, are feeding tubeworms. At the rim, two tiny (less than a millimetre long) mussels are hanging on.

Empty worm cases (Spirorbis) on the top of the shell.

The feeding tentacles of many tubeworms, in the crevices between stalks and spiral worm shells, are only visible under a microscope; among them tiny crawling and swimming things wander about.

A mussel on the eelgrass. Maybe a millimetre long. And on its tip (look closely) there's another shell, possibly a limpet.

It would be much easier to examine this limpet shell without all the weeds cluttering up the view. Or so I thought, until I came to my senses and paid attention to them, too.

One branch, covered with buds.

More than buds.

The "weeds" are animals: hydroids, one of the Obelia* species. They are cnidarians, related to the jellyfish; the adults form stalked colonies, but the young start out as medusas, miniature jellies. The "buds" are polyps, some feeding, some reproductive. In the photo above, just above the centre, you can see one open polyp, feeding. The tentacles are tipped with stinging capsules that explode when a prey animal touches them, incapacitating it so that the tentacles can bring it down to the mouth.

When a polyp is disturbed, it shuts down quickly. Most of the ones I saw were closed. I guess I was scaring them.

A closed polyp, with the tentacles pulled inside a thin case.

Life cycle of an Obelia. Image from Kent Simmons, U of Winnipeg.

The reproductive polyp has no tentacles. Inside it, baby medusas form and are set free as they mature.

Empty reproductive polyp.

I saw one tiny stalk with the open tentacles at the top, hiding at the base of the eelgrass blade, either a new branch on the old colony or a young polyp, recently settled. It was too small, too transparent for my camera.

*Obelia. Sounds like a woman's name. Would you name a kid Obelia?