Critter leftovers

I caught another low tide in daylight hours, without rain!, a couple of days ago. 

(I grumble at the poor scheduling of low tides all winter, as if there were someone in charge. But it's all in the numbers. We get one lowish tide every day, and one slight dip. And they come approximately 25 hours apart, so they always show up an hour later than the day before. Then remembering that we only get 8 hours of daylight in the winter, and you need 2 hours to get to the bottom of the intertidal zone and back before the water catches you, that leaves only one week every month available for exploring. And it's usually raining that week. Shouldn't grumble, then; the tide table people are doing the best they can. And anyhow, we're up to 11 hours in a day now. Summer's coming!)

Anyhow, I found some ex-critters at Oyster Bay.

Tunnels made by burrowing shipworms, Bankia setacea.

Not a worm, though; the "worm" is a clam. A long, worm-shaped clam with its shell carried in front of its mouth. It doesn't hide inside like "normal" clams; the shells are too tiny. Instead, it uses them to scrape away the wood, which it eats. As it goes along, it secretes shell material to line the walls of its tunnel; the white lines in the photo.

Anatomy of the shipworm. From Andrew Han, OHSU.

The shipworm log was on the dunes just above the tide line. Down on the beach, there were crabs. Or crab molts, anyhow.

Cheliped of a Dungeness crab. 

The well-worn shield of a kelp crab.

This was just at the top of the intertidal zone, where all the old seaweed mixes with dried vegetation from the land. In this spot, there were dozens of these kelp crab molts, all equally worn. Made me wonder; do they go in for group molts? Or is it a calendar thing?

Adult crab populations tend to molt simultaneously, females in the spring, males in the late summer.  (Oregon Coastal Crabbing Facebook post.)

So these were all females, it seems.

Long pincers of a female kelp crab.

And a solitary purple shore crab molt.

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Otra vez pude visitar una playa anteayer.  La marea baja nos tocó durante el dia, y no llovía.¡Perfecto!

(Me quejo todo el invierno porque las mareas están mal programadas. Como si hubiera alguna persona encargada. Pero es cosa de números. Nos toca una marea baja por dia — la otra apenas baja un poquitito — y caen cada 25 horas, aproximadamente, cada una una hora más tarde que la del dia anterior. Y como los dias invernales son de apenas 8 horas, y se necesitan 2 horas si piensas ir hasta la orilla y regresar antes de que te agarre el agua, eso nos deja solamente una semana por mes para explorar en la playa. Y casi siempre está lloviendo esa semana. Pero es cosa de números, y no hay de que quejarme. Y además, ahora tenemos 11 horas de luz cada dia. ¡El verano está en camino!)

Bueno, encontré algunos animalitos en Oyster Bay. Sus huellas, por lo menos.

    1. Túneles en la madera hechos por un molusco bivalvo, Bankia setacea.

Aquí les damos el nombre de "gusano de barco". Pero no son gusanos, son almejas. Es una almeja extendida en forma de gusano que lleva su concha, muy pequeña, en frente de la boca. No se esconde adentro, como una  almeja "normal"; las conchas son minúsculas. Las usa, en cambio, para raspar la madera que le sirve de alimento. Mientras se adelanta, secreta sustancias para cubrir de concha las paredes de su túnel. Estas son las partes blancas en la foto.

    2. La anatomía de Bankia setacea. De Andrew Han, OHSU.

Este tronco estaba en las dunas en la zona alta intermareal. Más abajo, en la playa, había cangrejos. O por lo menos, las mudas de los cangrejos.

   

    3. Un quelípedo de un cangrejo Dungeness, Metacarcinus magister.

    

    4. El caparazón, muy desgastado, de un cangrejo quelpo, Pugettia producta.

Este estaba en la parte más alta de la zona intermareal, donde algas marinas viejas y secas se mezclan con hierbas de las dunas. En este sitio, había varias docenas de estas mudas de cangrejo quelpo, todas igualmente desgastadas. Me hizo preguntar; ¿es cosa que hacen estos cangrejos, mudarse en compañía? ¿O es algo que ver con la fecha?

Las poblaciones de cangrejos adultos acostumbran mudarse simultaneamente, las hembras en la primavera, y los machos al fin del verano.  (Oregon Coastal Crabbing Facebook post.)

Parece, entonces, que todas estas eran hembras.

5. Quelípodos largos de un cangrejo quelpo, hembra.

6. Y la muda de un cangrejito morado solitario, Hemigrapsus nudus.

Morning stroll

 Some random shots at Oyster Bay.

Morning stroll

Dungeness crab molt. It always amazes me how they back out of their old skin, legs and all, leaving behind even the eyes.

Large clamshell.Nutall's cockle, Clinocardium nuttalli, I think.

Grass gone to seed.

Gumweed flowers still half closed.

Happy dance.

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Algunas cosas que vi caminando en Oyster Bay.

1. Paseo matutino.
2. Cangrejo Dungeness, Metacarcinus magister. Siempre me asombra como es que los cangrejos se retiran de su carpacho viejo, con todo y patas, dejando atrás lo que parece un cuerpo entero, incluyendo hasta los ojos.
3. Almeja de Nuttall, Clinocardium nuttalli
4. Pasto alto, produciendo semilla
5. Grindelia integrifolia. Las flores se abrirán cuando calienta el sol.
6. Baile alegre.

Empty suits and a walk on the sand

The crabs I see on our beaches and rocky shores are mostly shore crabs: green shore crabs and purples. Lower down on the beach, in the tidepools and on pilings under the wharfs, the kelp crabs take over. In deeper water, local crabbers find Dungeness crabs. On the stretch of shore I visited this last low tide, I found the molted carapaces of two other species. 

Just the carapace. Graceful crab, Cancer gracilis.

To identify these crabs without access to the pincers, count the "teeth" on the outer edge of the carapace and the bumps between the eyes. The Dungeness crab has 10 teeth on either side, with the carapace at its widest point at the 10th tooth. This one, the Graceful crab, has 10 teeth, but the widest point falls at the 9th. The adult crab grows to about 5 inches across; the Dungeness reaches 11 inches.

Helmet crab, Telmessus cheiragonus.

This is a crab molt; the crab opened his abdomen and crawled out backwards, eyes, legs and all, leaving his too-small suit behind on the stones.

And there was a kelp crab, out for a walk a good distance from any shelter. Unusual behaviour for one of these.

Afternoon stroll

And not a crab, but a hermit crab:

Totally invisible.

I thought this was an empty shell. I could see no sign of pincers or antennae. I brought it home; my hermits are always needing new shells as they grow out of the old ones. But at home, while I sorted eelgrass, a hermit poked his legs out. A grainy hand hermit, of course; these are the ones that love to hide deep inside a shell.

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Los cangrejos que encuentro en nuestras playas son principalmente los cangrejos de la costa, los verdes y los morados. En la zona intramareal más baja, en las pozas intramareales, y en los pilares debajo del muelle, se hallan los cangrejos kelp, y mar adentro, los grandes Dungeness. En el tramo de la costa que visité el otro dia, encontré los caparazones mudados de dos especies de cangrejo que no había visto aquí antes.

Primera foto:  el caparazón de un cangrejo "gracioso", Cancer gracilis.

Se pueden identificar estos cangrejos contando los "dientes" al borde del caparazón y las protuberancias entre los ojos. El cangrejo Dungeness tiene 10 dientes de cada lado, y el caparazón alcanza su mayor anchura al nivel del décimo diente. El cangrejo gracilis tiene los diez dientes, pero el último es muy pequeño, y el noveno marca la amplitud mayor del caparazón. El caparazón del cangrejo gracilis llega a medir 12 cm., miehtras el del Dungeness puede alcanzar 28 cm.

Segunda foto: un cangrejo "casco", Telmessus cheiragonus.

Este es la muda entera. El cangrejo abrió su abdomen y se arrastró hacia atrás, saliendo del caparazón viejo, del revestimiento de los ojos y las patas y todo, y ahí lo dejó todo en la playa, ya que no le servía pues el cangrejo había crecido.

Tercera foto: un cangrejo kelp, caminando sobre la arena, bien lejos de cualquier escondite. Generalmente, estos cangrejos se quedan bien escondidos.

Y la última foto: no es un cangrejo, sino un cangrejo ermitaño. Pensé que era una concha vacía ya que no veía ningún señal de vida adentro. La traje a casa porque mis ermitaños siempre están en busca de conchas nuevas mientras van creciendo. Pero en casa, mientras preparaba las algas para el acuario, si no sale un ermitaño de la concha dizque vacía. Un ermitaño granosimanus, por supuesto; estos son los que siempre quieren esconderse.

Of stones and crabs

When I go out without a fixed end point, I usually go north or west, away from the cities and the noise, the road crews and the traffic. This Wednesday I decided to break the pattern and head south. I didn't know where I was going; somewhere beyond Comox, 45 minutes to the south of my place; somewhere between the Comox valley and Union Bay, probably.

I'd barely gotten to Royston when I saw the sign: Royston Seaside Trail. Destination found. I drove to several spots along the trail, going down to the shore in each spot. The tide was low and going out; I walked to the water's edge in each location.

The setting. Royston is on the far side of a bay with Comox and Courtenay on the other two sides.

The shore is flat and stony; there was no sand, some mud. Very slippery mud. After three steps, it slithered away underfoot and almost threw me. I moved back to the rocks.

The stones here are hard, angular, sharp-edged, firmly glued to the underlying mud. And everywhere I looked, tiny crabs were scuttling about, sometimes stopping to threaten me.

It was low tide, and the sun was hot, so I was surprised to see so many crabs out in the heat; usually they find shelter under stones or seaweed when the water goes away. Not here; maybe because the stones are so solidly embedded, maybe because there was almost no seaweed, except for a few patches of bright green stringy algae and the occasional lonely rockweed.

In an area with rounder rocks, a green shore crab finds a bit of shade.

This poisonous-green algae formed mats here and there. Possibly Urospora pencilliformis.

I collected a stone with barnacles for my snails at home, and wrapped it in some of the green algae; the crabs and hermits would appreciate it. Before I wrapped it, though, I shook out the seaweed, scattering tiny snails and crabs. Still, a dozen miniature shore crabs somehow made it home unobserved. They're in my tank now; I'll have to return some of them (the ones I can catch) back to the shore.

There were crabs everywhere. In this patch, I can see at least 6 crabs; more will be hidden under the rockweed and hair algae.

The other residents of the shore seem to be mostly barnacles and snails, and a few oysters. I looked, but found no worms, no anemones, no tiny swimmers. And surprisingly, no hermit crabs, which are usually in abundance where there are many snails to provide shells.

This crab molt probably came from lower in the intertidal zone. A young Dungeness crab, Cancer magister.

Another Dungeness crab, this one underwater. So clear the water!

There were a few patches of sandstone like what we find around Campbell River.

The trail website suggests that many of the rocks on this beach are not original to the site.

Starting in 1911, steam locomotives hauled logs from logging camps throughout the Comox Valley to the Royston log dump. ... Where it approaches Hilton Road, the railway grade was constructed in the intertidal area. From the end of Chinook Road, a mile long wharf extended into the water.  Logs were tipped off the wharf until the early 1950s when the railway stopped running. ... The wharf was taken down and replaced by a breakwater in the 1950s. ... The rocks that can be seen within the intertidal area during low tides most likely originate from the fill material placed to construct the railway grade. (Royston Seaside Trail website)

More rocks, the breakwater, and - what's that?

About those rusting hulks, tomorrow.

And a couple more crabs

This one is a baby.

Red rock crab juvenile, Cancer productus

I pick up loosely closed clamshells, especially those loaded with barnacles. Almost every one is serving as shelter for young critters. This one held the crab, three small stars, and a scale worm. Look for the worm in the hinge, above, one of the stars in the background, below.

The poor crab didn't know how to deal with sunlight and a giant black eye staring at it. First he tried cowering, then ...

... the challenge. "I'm big and brave and I'll pinch you!"

"Or maybe not. If I roll over and fold up, maybe the giant won't see me."

All these poses took less than a minute. Then I closed the clamshell and put it back down under the eelgrass.

The stripy carapace will be discarded as he grows; as an adult, he will be mostly a dark red. The underside, however, will still have those red spots on white.

Most of the young crabs I've been seeing are the Dungeness crabs, Cancer magister.

Two-inch crab, running, under knee-deep water.

The two crabs are cousins, but the differences are fairly obvious. The Dungeness has a smoother carapace, rougher, toothed, pincer arms, and prominent teeth along the edge of the carapace. The Red Rock crab's carapace is bumpy, but his pincer arms are missing the teeth. The teeth on the edge of the carapace are wavy, and fluted like a pie crust.

The Dungeness gets quite a bit bigger; up to 11 inches across the top. The Red Rock will grow to 8 inches.

At every low tide this time of year, the crabbers are out with buckets and nets and crab traps, wading out waist-deep with the traps, or tramping through shallower water with long-stemmed nets. It's the big Dungeness that they're after; sometimes size is a disadvantage.

Do they bite?

"I found a crab!" Three little boys, about 5 to 10 years old, were digging among the rocks on Centennial Beach the other day. "I found a crab!" the littlest one shouted again.

"Does it bite?" his brother asked.

No.  And it probably won't pinch. Not hard, anyhow. But the boys crouched there, poking gingerly at it with sticks. Such excitement! Such danger!

I remember. I was a kid, teasing crabs with a twig, long ago. And I still feel a bit of that excitement when I turn over a stone and a green shore crab dares me to "Come on!"

Looking for more crabs. Well armed.

Most of the crabs we see on the beaches are either dead or the cast-off molts. Live ones usually scuttle off under a rock or a knot of weed. We don't get much of a chance to count the "teeth" or compare the shapes of pincers.

But I still bring crab shells, and sometimes whole dead crabs, sun-dried, home. I have bowls and trays and shelves full of them. So I decided to count their teeth, for practice.

The crabs most accessible to us in the upper intertidal zone of the Lower Mainland are the shore crabs, green and purple. They show up just below the high tide line, mostly hiding underneath stones in rocky areas.

Two very small green shore crabs. The large one measures 1/4 inch.

The green shore crab, Hemigrapsus oregonensis, has a rectangular carapace and tiny hairs on the walking legs. (On these two, I could see them with the hand microscope.) It grows to about 2 inches across the carapace. Juveniles can be any colour from deep red to green, to white.

Another green.

And a purple shore crab carapace, with the broken pincer. And polka dots!

The purple shore crabs look like the greens; they may be green, too. But the legs are never hairy, and the pincers have red dots. (Unless the crab is green; then it's only the hair that separates them, and you may not see that on the beach.) Two other characteristics I don't find in the books, but see on the crabs, all colours, are the three teeth along each side of the front, and the smiley face in centre back, looking at them from the rear.

Dungeness crabs may be green, too, although the books say "reddish brown to purplish".

Reddish brown Dungeness, Cancer magister, with purplish tints.

The Dungeness is a large crab, growing to about 11 inches across the fan-shaped carapace. This one measured 6 inches; that's usually about the size of the big shells we find, mostly on the White Rock or Boundary Bay beaches. They like wide, sandy beaches, with few rocks.

We see the live ones only at low tide. Even then, they're difficult to see, since they bury themselves almost completely in the sand. I have looked at one for up to a minute without seeing it, then suddenly the shapes resolve themselves and I notice the eyes, watching me intently.

Here's where we count the teeth. The Dungeness has ten "teeth" on either side of the eye, ending at the wide point of the carapace.

"Teeth". Only the little white bumps on each paddle count as teeth; tooth, bump, bump, bump, and a valley.

The pincers are long and strong; be careful handling a live one! Pick it up from the top of the back, not the hindquarters; they can reach you there with the pincers.

Pincer. More "teeth". Sort of looks like locking pliers (vise grips). The tips are white or whitish.

Live Dungeness, underwater, on Centennial Beach at lowest tide. This one's more green than red. The pincers are white-tipped.

The red rock crab, Cancer productus, is similar to the Dungeness, and almost as large, up to 8 inches across the shell. They can be found on many types of beaches, from sand to gravel to rock, in quiet waters or strong waves, shoreline to deep underwater. I find it strange that I have only seen one, a tiny one, on the beach in Campbell River. I do have a pincer that I picked up on the White Rock beach, though:

These pincers are thick and strong, with black tips.

On websites with crab recipes, I find repeated warnings about these crabs; they are likely to attack, and their claw can cut through strong work gloves.

The red rock is the same general fan shape as the Dungeness, and more or less a similar colour. The distinguishing feature, again, is the teeth along the edge of the carapace. Instead of 10, as in the Dungeness, they have 9. (Try counting them while the crab hides under the seaweed and snatches at your toes!) In between the eyes, the shell makes 5 peaks. So does the Dungeness, sometimes; I have one with only 4.

It will be easier, when I see my first big live one, to check the rim of the carapace. It is fluted, like the wavy pie crusts I used to make.

One other shell I have, one that I can't remember where I found it, is from a kelp crab;

Small shell, about 2 inches long, sun-bleached.

This is a long-legged crab that lives in kelp beds. Kozloff lists it among the most common crabs in this area, but it's most likely to be found underwater at extreme low tide, in the eelgrass. It will be a dark olive green. Another critter to look for.