Ma crab and the "hairy spine thingy".

The mystery is solved!

We've got a fairly close identification of the "Hairy spine thingy". (First post about it, second post.) A couple of days ago, among other things, various biologists suggested crustacean pleopods, but I was unable to find any to match, and no-one could be positively sure.

Then, this morning, Dr. Tony Irwin, of the Norfolk Museums and Archaeology Service (in the U.K.) posted a link to a previous ID made by the Natural History Museum (London). And there are good photos! I'm not sure about copyright issues here; so here are the links: Female crab abdominal carapace, the part usually visible outside. And F. crab abdominal plate, inside.

The pleopods are the end segments of the six hairy "legs", three on each side, folded towards the centre of the photo. Dr. Irwin says that in a large crab, they would be about 3 cm. long, the length of the piece that I found.

A crab is a decapod, which means that she has 10 legs.

As their name implies, all decapods have ten legs; these are the last five of the eight pairs of thoracic appendages characteristic of crustaceans. The front three pairs function as mouthparts and are generally referred to as maxillipeds, the remainder being pereiopods. In many decapods, however, one pair of legs has enlarged pincers; the claws are called chelae, so those legs may be called chelipeds. Further appendages are found on the abdomen, with each segment capable of carrying a pair of biramous pleopods, the last of which form part of the tail fan (together with the telson) and are called uropods. Wikipedia

Repeating myself from long ago: Simple and logical, isn't it?

Well, sort of. The legs and the mouthparts and pincers, which also count as legs for the name, are on the thorax. The abdomen, the part that crabs fold underneath so that they look as if they were all one piece, has its own set of "pods", but they aren't legs, so don't count for the "decapod" name, even if they are built more or less on the same pattern.

Males have two sets of pleopods, which they use to transfer sperm to the female. Females have several sets. These are used to hold the eggs under the abdomen while she is in berry, to fan them and oxygenate them.

I found a couple of photos of local crabs where the pleopods are recognizable:

Dungeness crab, a large crab, up to around 20 cm (8 inches) across the shell. 

"Hairy spine thingies", aka pleopods under her abdominal plate.

One of our small purple shore crabs, also showing off her pleopods. (Not very happy about it, though.)

Her abdominal plate, as it would normally be seen.

(All these photos are from Walla Walla University, Department of Biology.)

So there we have it. My "hairy spine thingy" is a pleopod of one of our larger crabs. I still want to find a dead one and confirm the species, if possible.

"Wacky appendages"

An update on the hairy spine thingy:

In brief, it still has me (us) stumped. History, to date:

The post with the photos and description (here) was cross-posted to my Facebook timeline and my Facebook page. A friend there (JG) suggested that I try the burn test for fabric. Was it vegetable or animal? I broke off a tiny piece and burned it; it smelled of hair or feathers. Animal, then.

Another friend (Fred Schueler from the U. of T.) asked the TAXACOM list of experts for help. They came up with various suggestions, from feathers to the tip of a whale's baleen plates, to an abdominal appendage of a crab.

"Crustaceans are jam-packed with wacky appendages:" - Doug Yanega (Entomology).

They sent me off to search crustacean pleopods. Some of the images look sort of, almost, but not quite,* right.

JG then volunteered to take the photos to the Marine Biology meeting of Nature Vancouver. I took more photos for her, destroying another tiny piece of the sample to look at its "innards".

I de-haired two segments as well as I could.

It turned out to be a semi-hollow tube. Here's the inner lining.

One side has a rough section, that on closer examination looks like a groove lined with some sort of fibers.

The inside of a broken segment. This was very fragile, and snapped like a too-thin eggshell. From the inside, what looked like a dark line turns out to be transparent; the dark colour came from the inner stuff.

The Nature Vancouver marine biologists suggested e-mailing Andy Lamb, one of the authors of the Encyclopedia I use, Marine Life of the Pacific Northwest. I just now got an answer from him: he's stumped, too, and is forwarding the lot to several other people.

So that's where we are now. My next step is to go to the beach at a lowish tide and find a large, dead crab, with all his appendages, and examine them. I'll report then, or as soon as anyone else provides an identification.

A big "Thank you!" to all who have helped so far!

*Pleopod of female blue crab. Not on this coast.

This has me completely stumped.

I brought home some eelgrass and sea lettuce from White Rock beach for my hermits. This hairy spine-like thingy came along with it.

Just over 3 cm. long, broken off at the wide end. Still wet.

The "spine" looks like a fish spine, but even under the microscope, I can't see segmentation. It may be all one piece. The hairs, under the microscope, look like human hair, on the fine side, more like a baby's hair. I can't see any sign of individual cells, like the hairy seaweeds have. Each hair sprouts from a row of pores around the stem; two to three deep, then a space, then a gray line, then the white gap before the next circle.

The stem is smooth and white on the outside, grainy in the centre. Wet or dry, it is flexible.

Dry, and combed with a soft paint brush. Very soft to the touch.

Detail of the wide end, showing the rows of hairs.

I have pored through my books and the web. I've looked at weird worms, hairy plants,horsetails, seaweeds, legs of assorted critters . . . I can't find anything like it. I don't know where to look next.

Help!

*UPDATE:
A commenter on Facebook suggested the smell test with a burning piece. I tried that. It smells like burnt hair or feathers.