Leavings, left and taken

 Someone found the crab leavings before I did. On the cut end of a log, they left the carapace of a helmet crab:

Telmessus cheiragonus. Also known as "bristly crab". Because it's bristly.

I don't know that I've ever seen one of these alive, only their molted carapaces. They live in kelp beds and, the Encyclopedia says, are "one of the fastest moving Pacific Northwest crabs." The molted carapaces are lightweight compared to our usual shore crabs, the same size. They feel fragile.

Then there was this, laid out neatly on a frayed log:

Abdominal plate of a female crab.

No, not the same species. This is just the abdominal plate, and it was bigger than the whole helmet crab carapace. Too large to be a shore crab, too.

The crab was a female. The males' abdominal plates are narrow arrows coming from a broad base. The females have a wide, rounded covering; it will protect the eggs when she's in berry.

I turned the abdomen over. Not so pretty. When she molts, the crab leaves behind several of her internal organs; the esophagus, the stomach lining, part of her intestine, the framework of her gills and the pleopods. She will grow all of these new, from scratch.

Inside of the abdominal plates. Pleopods.

At home, I looked at those pleopods under the microscope.

5 of the pleopods on the right.

Males only have two pleopods on each side. Females have 4, and they are biramous; they each have an extra branch. She attaches her eggs to these appendages, and waves them about in the water to keep them clean and oxygenated.

A dozen years ago (so long ago!) I posted a video of a female shore crab in berry, cleaning her eggs and pumping water around them.

Here it is, again;

I left the helmet crab carapace where I found it, for the next beachcomber.

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Alguien las encontró antes de que yo llegara. Y me las dejó encima de troncos. Primero, la muda de un cangrejo "casco", Telmessus cheiragonus.

Foto #1: La muda, nada más el caparazón superior. También se conoce este cangrejo como el "erizado".

No sé si alguna vez haya visto uno de estos cangrejos en vivo, sino solamente las mudas. Viven en los bosques de quelpos y son, según comenta mi Enciclopedia, "uno de los cangrejos del noreste Pacífico que se mueve con más rapidez." Las mudas son más ligeras que las de nuestros cangrejos de la costa, que son del mismo tamaño. Se sienten como si serán frágiles.

Y luego hubo esto:

Foto #2: La placa abdominal de una muda de cangrejo hembra, dejado sobre un tronco viejo.

No, no es la misma especie. Esta placa abdominal es más grande que la muda entera del primer cangrejo.

Esta fue una hembra. Las placas abdominales de los machos son angostas, puntiagudas, saliendo de una base amplia. Las hembras llevan una placa amplia, redondeada; aquí es donde lleva protegidos sus huevos.

Volteé el abdomen. No era tan fácil de comprender. Cuando muda, el cangrejo deja atrás muchos de sus órganos interiores: el esófago, el interior del estómago, algo del intestino, la forma de las branquias, y los pléopodos, que se ven aquí. Volverá a crecer todo esto nuevecito.

Foto #3: El interior del abdomen, con los pléopodos.

Foto #4: En casa, miré esos pléopodos bajo el microscopio. Aquí se ven 5 de los del lado derecho.

Los machos solo tienen 2 pléopodos en cada lado. Las hembras tienen 4, y estos tienen 2 ramas cada uno. Fija sus huevos a los pelos de estos pléopodos y los agita en el agua para mantenerlos limpios y provistos de oxígeno.

Hace 12 años subí un video de un cangrejo de la costa hembra llevando huevos, limpiando y agitándolos. Aquí lo subo otra vez.

Video: "In Berry"

Dejé la muda del primer cangrejo allí sobre el tronco para la próxima persona que visitara la playa.

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.

Discarded finery

Scattered all along the upper levels of Crescent Beach this week, we saw dozens of these crab carapaces:

Helmet crab shell, in shallow water. About 2 inches tip to tip. They may grow to 4 inches.

At first, I thought there had been a die-off, and then I looked more closely. Each one was just the clean upper carapace, unbroken, with no legs or "innards" attached. So it was a general molt, which signals mating time. The crabs come up to the intertidal zone, and the males choose their mate and hold onto her until she molts. Females are not able to mate until they have a new, still soft, carapace.  Within a day or so, the shell has hardened, and the opportunity gone for this year.

We don't usually find these crabs (Cancer cheiragonus) live in the intertidal zone, so this is all the evidence of crabby romance that we will see.

A small collection of sun-dried shells, inside a larger Dungeness crab shell.

I love the textures of these crab shells, especially the pale yellow inner wall of the helmet crab on top. The shell of the Dungeness is quite different, sort of like a stuccoed wall. Click on the photo to see these full size.

Mud shrimp, crab and coconut

I'm getting 'way behind on what I want to blog about; I still have critters left over from our vacation, birds from Reifel Island, beetles and mites and a sad slug. I'm going to have to double up, or resign myself to be blogging the summer months while the snow falls in January. (If it does.)

And today, to top things off, I'm just going to tie up a couple of loose ends from previous posts, which doesn't get me any further ahead. Ah, well ...

1. Nebalia pugettensis, the "Blue-eyed beach critter". A couple of weeks ago, I posted two photos of the live nebalia, almost invisible in the water. This Sunday, I brought home a small handful of sea lettuce and eelgrass washed up with the tide, as a treat for the hermits and crabs in my aquarium. When I washed it, as I always do, a couple of almost transparent animals floated to the top, dead. I scooped them out, and left them in alcohol to preserve them. Yesterday, I dried them out and took their photos. They were no longer transparent:

Nebalia pugettensis, the Hooded mud shrimp.

These are the strangest of all the shrimpy, crabby animals on our shores, I think. They look like they're put together out of spare parts.

The "hood", or carapace, is not fused to the body like a crab's is, but loosely attached with a muscle. It has a long, sharp spine at the top back. And that thing is tough! I accidentally touched it with a finger, and it jabbed in like a cactus spine, and stuck. Another, shorter spine aims forward from the hinged cap between the eyes. This is not a beast to be tangled with; imagine being a fish who grabs for a nice mouthful and gets those spines, front and rear!

And the tail looks like it belongs to another animal altogether.

If the spines on the carapace are strong, the tail has to be different; it finishes off with a soft, feathery plume, extremely fragile.

And this one's eyes are neither red nor blue.

The other animal turned out to be a small helmet crab moult:

Both critters were about 9 mm. long (nebalia) or wide (crab).

2. The coconut. I washed it and dried it thoroughly. Tonight, we cracked it open. We got about a cup of clear coconut liquid; the meat was white and solid. But some sea water had seeped in between the shell and the meat; on the outside, it was covered with green slime that washed off easily.

The juice smells good, if slightly alcoholic. It reminds me of a tepachería in Coyoacán, Mexico, a place where they used to sell tepache and other mildly alcoholic fruit drinks; even across the plaza, the fruity, sweet, nutty aroma competed with the scent of flowers and fresh bread.

My kitchen, however, smells like a coconut-oil soap factory.

Laurie says the birds will like the meat. I know the squirrels will. I'm wondering about the juice. If I put it out for them, will they get drunk on it?

Toothy morsel

A couple of months ago, I was counting crabs' teeth, reviewing the crabs we've collected on our local beaches, in the intertidal level.

There are always more, of course. Some live in the lower intertidal zone; many are subtidal. We won't find those, unless the molts get washed up. Or unless we take up scuba diving. (I wish we could!)

Close to the lower edge of Boundary Bay intertidal zone, we found this carapace:

Telmessus cheiragonus, the helmet crab.

As far as I know, this is the first helmet crab I've seen, probably because they live in eelgrass and kelp beds, hiding in the shadows from galumphing human waders. And they're "one of the fastest moving Pacific Northwest crabs". (MLotPN)

This little crab, under 5 inches long at maturity, has 6 teeth along each side, starting the count at the back of the eye. With the crab alive and running about, they'd be a bit harder to count than they are here, because he's also really hairy. NOAA has a photo of one; try your hand. Can you see all 6? I can't.

Ours is a youngster. Besides being only about an inch long, he still has a touch of green on the carapace. A mature crab could be red or brown or orange; kelp colours, for maximum invisibility.