Tenuous hand?

 I promised you hermits.

Widehand hermit.

This is the same hermit I posted a few weeks ago, from the side. This view shows the reason for his name, Widehand, Elassochirus tenuimanus. It's a bit confusing, looking at the Latin name; "tenuis" means "thin, drawn out, meager, slim, slender". (Online Etymology Dictionary) And "manus" is, of course, "hand". But looking at it again, I see what they mean. The "hand" is wide, because it's flattened out, thin, in other words.

Smaller hermit, on a sand dollar. Possibly a blackeyed hermit. The sand dollar is very much alive, walking on his hundreds of tiny, black tube feet.

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Les prometí ermitaños.

#1: Un cangrejo ermitaño "de mano ancha", Elsasochirus tenuimanus. Subí una foto de este ermitaño hace unas semanas, pero visto desde el lado. Aquí, visto de frente, se ve porque le llamamos "de mano ancha". Aunque el nombre scientífico, E. tenuimanus, parece contradictorio, pues en Latín, "tenuis" quiere decir "delgado, tenue, reducido". Pero mirándolo otra vez, lo entiendo; la "mano" será ancha, pero solo porque en la dimensión opuesta está bien aplastada.

#2: Un ermitaño más pequeño encima de un dólar de arena. Puede ser que es un ermitaño "de ojos negros". El dólar de arena está vivo y activo, caminando sobre sus millares de pies tubulares negros.

Divided by five

Thinking about echinoderms: the sea stars, the sea urchins, the sand dollars, the cucumbers that I see at low tide.

Sand dollar, alive. Dead ones lose the blackish hairs. Look closely: they move!

Green sea urchin, Strongylocentrotus droebachiensis. (What a name for a small critter!)

Everything else, the crabs and the fish and even the worms are arranged in a way that seems "normal" to us; with two similar, sometimes identical, halves: whether they have six, ten, fourteen or umpteen feet, they come arranged in pairs.

But the echinoderms are arranged with five points around a central axis. Usually; some of the sea stars may have more, from 6 up to 50. But it's usually 5.

No reason: Ma Nature does what she wants.

But reading about them on Wikipedia, I discovered this:

Although adult echinoderms possess pentaradial, or five-sided, symmetry, echinoderm larvae are ciliated, free-swimming organisms that organize in bilateral symmetry which makes them look like embryonic chordates. Later, the left side of the body grows at the expense of the right side, which is eventually absorbed. The left side then grows in a pentaradially symmetric fashion, in which the body is arranged in five parts around a central axis. (Wikipedia; Echinoderms:Anatomy and Physiology)

Ma Nature does what Ma Nature wants to.

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Estaba pensando en los equinodermos, tales como las estrellas de mar, los erizos, los dólares de arena y los pepinos de mar, todos los que veo en las playas cuando la marea está baja.

Fotos:

1. Un dólar de arena, también conocido como galleta de mar. Está vivo; muertos, pierden los pelos negros rapidamente. Míralos de cerca; están en continuo movimiento.
2. Un erizo de mar Strongylocentrotus droebachiensis. Un nombre muy largo para un animal tan chico.

Todo lo demás; los cangrejos y los pescaditos y aun los gusanos están organizados en una forma que a nosotros nos parece "normal"; con dos mitades por lo menos similares, muchas veces idénticas. Aunque tengan o seis, o diez, catorce o una multitud de patas, se organizan en pares.

Pero los equinodermos se organizan con 5 regiones alrededor de un eje central. Casi siempre; algunas de las estrellas de mar tienen más brazos, desde 6 hasta 50. Pero por regla general, tienen 5 brazos o lados o regiones.

No se puede saber el porque; la Madre Naturaleza hace lo que quiere.

Pero leyendo las páginas en Wikipedia, encontré esto:

Los equinodermos son animales originalmente con simetría radial, menos las larvas, que poseen simetría bilateral. (Wikipedia/es)

El sitio en inglés explica con más detalle:

Aunque los equinodermos adultos poseen una simetría pentaradial, o sea de cinco lados, las larvas son organismos con cilia que se organizan en simetría bilateral, lo que las hace parecer cordatos embriónicos. Más tarde, el lado izquierdo del cuerpo crece, abandonando el lado derecho, el cual finalmente es absorbido. El lado izquierdo desde entonces crece en forma de simetría pentaradial, en la cual el cuerpo se organiza alrededor de un eje central.

La Madre Naturaleza hace lo que le da la gana.

Over-exposed

At low tide on the open sandy areas north of Oyster Bay, almost all that can be seen are the sand dollars. Underneath ( I dug down) there are more sand dollars. Many more. And the occasional clam.

One of the sand dollars. To my naked eye, the live ones looked black, but the camera saw the red colour.

The exposed sand dollars were all waving their spines, trying to bury themselves in the sand as the water receded. They look helpless, but they're quite efficient diggers.

And one lonely crab molt.

Coming up to the ship graveyard, the sand dollars peter out, and other critters show up.

One of the old ships innards, draped with sea lettuce.

Those round lumps in the sand? Sand dollars, sheltering. Every few steps I could feel one crack under my foot. Sorry, guys!

Beside the ship above, I found this unhappy Opalescent nudibranch, Hermissenda opalescens. Also a worm poop.

The very low tides can be hard on creatures from the lower intertidal zones. Out of the water, those rusty iron ship bones get hot. I found a couple of limpets belly up in the heat beside this boat. I brought them home wrapped in cool, damp sea lettuce: one survived and is now cleaning the wall in my tank.

And this nudibranch was moving sluggishly, out exposed on warm sand. I took a few photos, then covered it with several layers of wet sea lettuce.

Orange starfish, with one new arm.

I found green anemones, a pink anemone, a very red one (mostly buried, keeping away from the sun), and this orangey one, under a couple of inches of water. A hermit crab is sheltering under its shadow.

A row of whelks, closed down to preserve moisture. The sea lettuce here is still wet, and if you look closely, you'll see a green anemone (or is it two?) still open for business.

Starfish can move quickly when they want. On the far side of the boat, I saw a big purple starfish. By the time I went around to that side, having to go up onto the headland to dodge shoe-eating mud, I couldn't find the star anywhere. It had probably buried itself under the sand; starfish don't like sunshine.

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Cuando la marea está baja, en la playa arenosa al norte de Oyster Bay, todo lo que se ve son los dólares de arena. Y debajo de la arena (excavé varios hoyos) lo que se encuentra son más dólares. Y una que otra almeja grande.

Los dólares de arena vivos se ven, a mis ojos, negros. Pero la cámara ve el color rojizo. Todos los vivos estaban agitando las espinas, tratando de enterrarse bajo la arena, fuera del alcance de los rayos del sol. Parecen no tener defensas, pero son capaces de desaparecer en pocos minutos.

Un cangrejo había dejado su muda de carapacho. Al tostarse se hace más rojo.

Estas mareas bajas son un episodio difícil para muchos animales de la zona baja; no toleran el sol. Y junto a los barcos viejos, que normalmente proveen habitat para muchos, ahora se siente el calor; los fierros viejos se secan y se hacen un hornito. Al lado de este barco, encontré dos lapas boca arriba, lo que no se ve si están sanos. Me los traje a casa envueltos en un poco de alga marina húmeda; una sobrevivió y ahora está felizmente limpiando la pared de mi acuario.

Y un nudibranquo, Hermissenda opalescens, sufría en la arena; apenas se movía ya. Le saqué unas fotos y luego la cubrí de varias capas de algae.

Luego había una estrella de mar anaranjada, con una pata nueva.

Y una anémona anaranjada en un poco de agua. Un ermitaño se estaba escondiendo en su sombra.

Vi anémonas verdes, color de rosa, y una de un rojo muy fuerte, casi por completo enterrada en la arena, escondiéndose del sol asesino.

Junto a los caracoles hay una anémona verde escondida entre la alga.

Las estrellas de mar se pueden mover muy rapidamente si quieren. Vi una grande, morada, al otro lado del barco. Pero cuando fui a verla, después de tener que dar toda la vuelta para evitar el lodo comezapatos, no la encontré en ninguna parte. Se habrá enterrada ya; a las estrellas de mar no les gusta el calor.

Magenta and blue-green

In a grey and white world, I walked on the salt-washed beach, and found colour.

Boot-top deep snow near Oyster Bay

Sand dollar test and stones.

The purple tones are what's left of the sand dollar's living colour. The green, I think, is algae.

The snow is still coming down.

With my nose to the glass

I've been watching some of the smaller life in my aquarium.

Like this female Calanoid copepod carrying her egg sac behind her.

The copepod is the basic food group for many marine organisms, including my anemones.

Some scientists say they form the largest animal biomass on earth. ... copepods almost certainly contribute far more to the secondary productivity of the world's oceans, and to the global ocean carbon sink than krill, and perhaps more than all other groups of organisms together. (Wikipedia)

In my tank, the copepods are about 1 mm. long, and visible only when the light hits them against a dark background.

The sand dollar was trying to climb the wall, pushing with the stripy spines until he was almost vertical. But there was nothing to eat on the wall, and he gave up and crawled back into the sand.

A tiny piece of broken crab shell, with the remains of a barnacle.

When the lined chiton came close to the glass, I was able to see the tiny hairs on its girdle.

I brought home two stones with big barnacles for the leafy hornmouth snails to eat. Once they were in the tank, the sand that came along with them got up and started to walk about. With a lens, I could see that they are snails, as small as fine sand grains. And in short order, they had all crawled down and merged into the sand on the bottom of the tank.

Talented half dollar

The little sand dollar in my aquarium (more like a 50-cent piece) wanders all over the tank, usually underneath the sand and shells, but sometimes coming out in the open for a brief look around.

He moves more quickly than I would expect, travelling only on spines a couple of millimetres long. When I clean the tank, I remove him carefully so as not to break off those fragile spines, and then put him back on the surface of the sand at the front of the tank when I'm done. Within minutes, he's upended himself, and is burrowing back down out of sight.

Sandy, feeding. Much larger than life.

A few days ago, he showed up right by the glass wall, and I got a video of him feeding and "walking". Once again, I was amazed at his talents; with those hair-like tube feet, he picks up fat grains of sand, lifts them to the mouth to check them for edibles, then drops them.

And he manages to walk and chew sand at the same time. Smart critter!

Here's the video. It helps to watch it on the full screen.

Sandy

Sand dollar test, half buried in sand.

Just because I liked the textures and patterns.

I'm still working on the rest of the photos from the eelgrass beds, and photos of a couple of obstructionist hitchhikers. And some pink eggs, too.

Tomorrow: beasties green, orange, purple, and red.

Sand dime

It's too small to be a dollar.

So I measured it: 11/16 inch. The size of a Canadian dime.

Flowery pancake animal

At low tide, well out towards the bottom of the intertidal zone, we often find sand dollars. They're usually hard and whitish; the bare, empty skeletons of the living animal. Rarely, we see a live one. These are black, and have spines all over, top, bottom, and edges. When I look closely, I can see the spines moving.

We found one of these last week, and I brought it home to add to the aquarium, where it settled in happily, burrowing slowly under the sand.

I fished it out two days later, to see if it had survived the transfer. It had; it was trying to walk out of my hand, on its spine "feet".

Top side. One edge is broken.

Under the light, it wasn't really black. And where the edge is regrowing, the spines had a pink tinge to them. When I had a photo, I checked the coloring; the main colour is muted down so it looks brown or black, but when I saturated the photo, the spines were all red.

Detail, central "flower".

I looked at the spines under my little microscope. They're beautiful, transparent as glass, but with dotted lines running the length of each spine. There are two types; long, tapered pillars, and between them, short, thin hairs with a knob on top. And all of them, all the time, are swaying in all directions.

They are far too small for my camera, but I found a photo on the web that is more or less what I saw.

Microphotograph from the University of Queensland, AU. I've lightened it up for better visibility.

Back in the tank, the spines went to work, sliding the sand dollar over and under the sand until it disappeared from view.

For a flat plate, moving on microscopic fur, the dollar manages to cover a lot of territory. Here's a time-lapse video of one in California, from mrjustin5 on YouTube.

This was about 25 min(ute)s of footage condensed into 1 min 30 s.

A mini-Roomba! All it needs is a mini-kitten.

The sand dollar can live up to 10 years. This one is about 3 inches across, half the size of the largest I've seen, so it's probably still young. I hope it does well in the tank, away from its hungriest predators, starfish and gulls. Hermit crabs will eat them, too, so I'll watch for that and remove it if necessary.