Thursday, April 29, 2010

Of paddles and orgies

One of the great things about a blog is that it serves as an aide-memoire; what I saw, when, where; it's all there, and searchable. So I was able to review my experience with the big polychaetes.

I find that I brought home a pair, both under 4 inches long, from the White Rock beach, in the first week of October, last year. Digging through the sand, then, I found a worm that stretched out to 7 inches long.

It's been almost seven months since then. Those three have turned into eight, at least twice the size of the biggest one, back then, plus a few more 4-inch specimens.

I had narrowed the species down to Nereis, possibly vellixosa, which grows to about 6 inches. I'll have to revise that. I think, now, that they are Neries vixens, recently renamed Alitta virens, or possibly A. brandti, which is also common and virtually indistinguishable from vixens. Both of these, the Giant piling sea-nymph and the Giant clam worm, grow to at least a foot, like mine.

One thing that confused me is that the parapodia on these big worms are different from those on the smaller ones. Those are like pencil points with hair on the end; these are triangular paddles, with no hair visible.

Yesterday's worm, with non-hairy paddles.

Last October's worms, with hairy pencil points. The smaller ones I have now are like these.

A website from Wales reassured me that I was on the right track; their A. vixens, which they call King Ragworms, have paddles, although near the head end, the hairy points are still visible. (Look at the middle of the second worm for the paddles.)

I found the explanation in Kozloff. He writes, about N. vexillosa,
"... the sexually mature phase of this species is rather unlike the phase typical of mussel beds and bay habitats. The fleshy parapodia become expanded into paddlelike structures for swimming, and periodically during the summer the ripe males and females swarm at night near the surface. ... The worms do not survive long after their nocturnal orgy, during which they simply spew out their eggs or sperm through openings that develop in the body wall."
The Giants swarm, too. Kozloff says it's an "exciting spectacle.I can imagine; think of yesterday's video, but with dozens of worms in the open water, thrashing about in the moonlight.

So I've sent my critters out into the big world, just in time to !!PARTY!! I'll have to keep an eye on the few that I kept at home.

I found a couple of interesting head shots of these worms; interesting, if not exactly cute. PZ picked up one from an underwater image competition, back in 2006. The original site is no longer available, but the photos are still on Pharyngula. The third one down is Nereis.

And Ugly Overload has two face shots, from Alexander Semenov. This second link goes to his Flickr page; it's worth clicking over there to see the rest of his macro photos. Amazing and wonderful!


  1. I am amazed. A foot long? Really? I just can't picture a worm being that long ... I think I prefer the younger, fuzzy ones. So glad you let most out to the beach so they can, er, party!

  2. I believe their blood is red as well...more than once, have I gone digging clams and sliced one of these clean in half.

    I can also attest to their being wonderful swimmers. You'd expect it would be snake-like, but their "oars" propel them much like a millipede moves its legs. It's not uncommon to see them darting about at the surface while doing some night-fishing off a pier. This kind of propulsion is rare in the animal kingdom, as far as I am aware.

  3. Clytie, according to some sites, these worms get to 4 feet. Around here, Kozloff has them at 18 inches.

    I'd love to see them at night. Yes, they show great control, swimming straight up against a wall, or skimming just above the sand, so I think the thrashing is more a reaction to unfamiliar surroundings.

    The blood is red. The main artery is visible, running down the centre back.


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