All pink and shiny

In the sand at the bottom of my aquarium, there lives a worm. He's a shy critter, and I used to only see him when I cleaned the sand, sifting through it thoroughly. Even then, all I usually saw of him was his quickly disappearing curves. He moves fast, even in dense sand.

But he's been growing. The last time I caught him, he measured about 6 inches long; he can easily grow to four times that. And he's hungry. So hungry he's forgotten to be shy. When I drop shrimp pellets into the tank for the crabs and hermits, he comes out to get his share, quickly retreating into the sand once he's got a mouthful. But he comes back for more; it takes a lot of food for his long, fat body.

I tempted him with pellets right up against the glass.

Pileworm, aka clam worm. Probably Nereis brandti.

He's a segmented worm. Each segment has two sets of leafy "paddles" which help with movement, and also serve for respiration. On the head he has two fat palps and four sets of tentacles, two small antennae, a huge mouth, and four eyes. With all that sensory equipment, he responds instantly to any movement, or change in lighting. And he smells the food from far away, under the sand.

And his coat is shiny, pink, and iridescent. He glows!

Found a pellet, and opened that enormous mouth. One gulp, and it's gone.

~~~~~~~~~~~~~~~~~~~~~~

En la arena en el fondo de mi acuario, vive un anélido, un poliqueto Nereis. Es una criatura bastante tímida; acostumbraba verlo solamente cuando hacía una limpieza completa del tanque, removiendo y lavando la arena. Aún así, normalmente apenas lograba un vistazo mientras se enterraba con toda prisa. Hasta en arena apretada, se mueve rapidamente.

Pero ha estado creciendo. La última vez que lo saqué de la arena, medía más o menos 15 centímetros. (Puede crecer hasta cuatro veces ese tamaño.) Y tiene hambre. Tanta hambre le motiva a atreveserse a salir a la vista en busca de comida. Cuando les doy de comer a los cangrejos y ermitaños, que comen bolitas de camarón, el poliqueto las huele y sube a capturar su cena. Agarra una bolita, y se retira a su hoyo en la arena para tragarla, pero pronto sale a buscar más. Ese cuerpo largo y gordo requiere muchas calorías.

Es un anélido segmentado; en cada segmento del cuerpo lleva dos pares de patas en forma de hojas; estos le sirven para movilizarse, y además contienen su sistema respiratorio. En la cabeza lleva dos palpos, órganos de tacto, cuatro tentáculos, dos antenitas, cuatro ojos, y una boca enorme.

Y su piel es de un color rosa, brillosa, e iridiscente. ¡Resplandece!

Micro beasties

I bought myself another microscope. A cheap one, for students, with low magnification, but like the even cheaper one I'd had a few years back (that didn't last long), with the ability to take photos. The one I had been using up to now was for my eyes only.

Tonight, I set it up and collected some stuff from my aquarium; a teaspoonful of sand, a fragment of seaweed, a few empty (or so I thought) shells, and one of the smaller hermit crabs. Arranged them on plastic lids, since they needed to be kept in water, shoved them under the 'scope, and tried to focus. It's a bit difficult when your target keeps running away; even the seaweed was carrying mini-critters on the move.

Pacific rose seaweed, Rhodymenia pacifica. With worm and snails.

This delicate (but oh, so durable in my tank) seaweed is a sheet with one layer of cells. Here, each cell is visible. The fragment was about 3 mm wide. The worm, that looked like a hair, but crawled about slowly, is about as wide as one seaweed cell. Even through the microscope, I didn't recognize the dark patches, but once I blew up the photo, I see that they're all snail shape. No wonder I always have a batch of new tiny snails climbing the walls!

Another snail. Shell only, abandoned in the sand.

This was in the teaspoon of sand. The snail shell is about as large as the larger sand grains. Still tiny. With everything under a film of water, the microscope LED lights produce glitter. I edited out what I could without destroying what is underneath, but the tiniest white specks are moving critters, all constantly in random motion, sort of like a swarm of midges. Some of the brighter patches of light were pulsating, squirming something-or-others. I managed to see a couple of worms and something with legs before they hid under the sand grains again. Some of the sand grains were bouncing; there was something busy underneath.

On an old cluster of empty barnacle shells, a colony of orange-striped green anemones has settled in.

One of my smaller hermit crabs.

I've been wanting to get a good look at these hermits for a while. They look like hairies (Pagurus hirsutiusculus), but never seem to grow up to the expected size. Maybe I'm not giving them enough time. This one certainly looks like a hairy; banded green antennae, blue marks on the legs. But those two rows of lumps on the pincer arm look interesting: I'll have to examine more of these little guys.

A couple of periwinkles.

And a tiny snail, half the size of the smallest periwinkle, on the move. With sand grains for size.

This is fun! Let it rain!

Spying on Spio

I've been staring at a worm so long these last two days, getting to know its habits and likes, I almost think I should be giving it a name. Everyone else does; some call it the Jointed Tube worm, some the Three-jointed TW, or the Jointed Three Section TW, some say it's a Bamboo worm. It's a Spiochaetopterus costarum*; I'll call it Spio for short.

It hates lamps and flashlights, but doesn't mind the flash, and has built a new tunnel right up against the glass, so I've managed to get a few photos.

Under the sand, there doesn't seem to be a sheath. The two tentacles (or palps) go up through the little sand tube. (The red tentacles are an observant grainy hand hermit, and what looks like his one big eye is a limpet on the glass.)

Seen up close, this is a polychaete, a bristle worm. Along both sides, it has a series of little paddle feet (parapodia, meaning "beside feet"), here sprouting out of the centre of each ringed section. These may end in bristles; I zoomed 'way in, but I couldn't be sure.

The parapodia are clearer here.

If you look closely, you can see that its belly is to the left in the first photo, and to the right in this one. The worm is constantly moving inside its tunnel, swinging itself back and forth to enlarge the tunnel. The paddles operate in a series, so that it looks like waves moving downwards, more or less the same movement as a millipede walking, but from front to back. (The millipede looks as if the feet were moving back to front. They aren't.) And except that the worm stays in place, unless it's disturbed, in which case it retracts deep into the tunnel, shrinking down its entire length instantly.

A closer look at the sections and the parapodia.

It quickly moves to a new location if a crab starts digging, but doesn't mind the hermits, who just wander about, picking up tidbids and nibbling on them. They don't touch the worm's tentacles; fair's fair.

From around the web: The worm's sheath is a coating of mucus. The sand would be stuck to that. Those papery tubes that turn up on the beach at low tide, an inch or two long, are remnants of these sheaths, left behind when the worm retracted for protection deep into the sand. Waves or animals rip them off, but no-one is harmed; the worm makes himself a new one. Overnight, as this one did the other day.

Buzz says, "Palps extending from tube remove waste from tube.
(The worm) feeds using cilia to produce water current and captures food with mucus balls.

As the worm grows, the tube will probably lengthen; we see them on the beach, up to about 4 inches long. The tube, not the worm.)

Long ago, we found a bamboo worm dying on Crescent Beach, this one identified tentatively* as Axiothella rubiocinta, the Red-banded bamboo worm. It was about 6 inches long.

A. rubiocinta does not have the two tentacles, and it has exactly 22 segments. I counted the ones I could see on mine; there are 25 or 26 visible. They make sand tubes, larger that Spio's, and often live in communities containing both species.

Bamboo worm, Crescent Beach

Worm, Campbell River

*"Tentatively". All my id's are tentative. Give me another 20 years or so to learn. Meanwhile, corrections are appreciated.

Life's little mysteries

Some interesting links for you:

The Northwest Dragonflier answers the question, "How do dragonflies manage to fly and mate at the same time?" The Foot High Club. (Didn't you always wonder about that?)

What lives in your belly button? More than you would expect. Guest post in Scientific American by Rob Dunn.

And why is this good news? Carl Zimmer, writing for the NY Times, explains.

The project and other studies like it are revealing some of the ways in which our invisible residents shape our lives, from birth to death.

And what is a cormorant doing with a camera? CBC News, Saskatchewan (Canada).

Do worms have teeth? HuffPost Green.

And my own volunteer worm: this little critter has built himself a tube near the glass of the aquarium. He showed up two days ago, and that night the largest crab dug up his home site, right down to the floor. What one destroys, the other builds; the newest tube is longer than the previous one.

Two-tentacled tubeworm, Spiochaetopterus  costarum.

He's much larger than any I've seen feeding so far; the tentacles are about 1/2 inch long.

The first one to show up here, two years ago, was microscopic, too small for the camera; I had to draw it.

I have tentatively identified it as the three-sectioned tubeworm, which lives in this area, but I have my doubts. This little critter coats his tube with grains of sand; the photos of S. costarum show it with a sheath that looks like fabric with the seams (many seams) turned outwards. (Sample photo)

My own links: here's one, eating. And a worm genius.

So, another mystery. If I scrape off the sand, will I find a separate tube inside? Or is the sand glued on too tightly to be removed without killing the worm? I'll have to invent some way of checking that out.

Great Expectations - Interplanetary Rock Flipping Day, 2012

Is there a space rock in our future? Why not? We've flipped rocks everywhere else, haven't we?

This weekend, dozens of intrepid rock flippers have ventured out into the world to discover the wild critters, known and unknown, that inhabit the secret places. So alien to us they are, and yet so like us in many ways; our cousins, actually.

Here's a partial list of who we are and what we found. (Some reports are still to come in; I've heard that I should expect moose. We've got camels and leopards already.)

In no particular order:

• Troy Bartlett (founder - or founding member - of BugGuide; we owe him a debt of gratitude) took some amazing harvestman photos. See them on Nature Closeups. Butt shot! A stare down!
• Alex Wild, posting in   Scientific American, joins us for the first time, with ants and millipedes and an ant cricket from his backyard.
• Roberta flipped river rocks; some of her findings are posted in Growing with Science, the rest in Wild about Ants.
• Lynda at Mainly Mongoose doesn't flip any rocks, but finds toothy Dwarf Mongooses underneath some, anyhow. 

'There are older and fouler things than orcs in the deep places of the world.'

• Margy, at Powell River Books Blog, for the second year running found no crawling or creeping critters. Not for lack of effort; what's going on with the shoreline at Bellingham Bay? At least she got some eelgrass this time.
• Patrick, a student of lunar petrology (Told you we'd gone interplanetary!), blogs at poikiloblastic.    I never knew a rock had defense mechanisms before! And he has a photo of a cute (really!) slug.
• Hugh, at Rock, Paper, Lizard, gifts us with another Interpreter wildlife expert story. "A rubber boa?" I'd never heard of these before. Yes, they do exist. Did they find one? Read the story.
• Clytie, at Random Hearts remembered. Didn't find critters, but there was a pretty heart, so all is well.

Some kind of twirly insect casing ...

• Olivia, at Beasts in a Populous City, learns a modicum of humility.
• Benet, at Walking with Henslow, flipped rocks in Starkweather Creek. Sow bugs with lime green spots!
• Pablo at Roundrock Journal, reports on another of his biodegrading experiments, and finds a cricket and a companion rock flipper; an armadillo.

Some kind of stripy insect casing ...

• Bill, at Fertanish Chatter, checks in with some pretty millipedes, a "nifty" spider, and is this a toad bug? A sight for sharp eyes!
• And then there's a toad, no easier to see than the toad bug. Judy's husband found it; Judy blogged it at LilacGate.

 Then husband said "What is that?" and I finally saw the toad, settled in for the winter.

• Kate St. John, at Outside my Window, flipped a rock, found a leopard. And a pair of camels!
• Rebecca in the Woods; an ant and a beaver. (The beaver was not under the rock.)
• Bug Girl posted an announcement on Skepchick, and a couple of flippers turned up in the comments. Here's Greenstone123's story. Ant kitchens! And scribe999? Don't give up. Not even in Jersey!
• Also in comments, on Rebecca's blog, Madhu in Sri Lanka found a couple of ants.  And Christopher (in Missouri) found ticks, and got too many tick bites to count. It's a wild and dangerous world out there!
• And on to the Flickr group! We have photos from Sara (mamasara4), from Georgia (georgiabkr), Dean (Ontario Wanderer), Benet (benet2006), Upupaepops (Upupa4me), Bug Girl (bug_girl_mi), and Pablo (Paul Lamble). Beetles, crickets, slugs, and so on, including an angry isopod, making threats to Upup...'s fingers.

Not under a rock; all around the rock piles. In blazing sunlight, on my grandson's shirt. Fuzzy, but I like the contrasts.

• And then, there's me. I still haven't written up my post. (That should give comfort to a few others who haven't logged in yet. There's still time!)
• NASA's stone is still unflipped. Of course, they take years, decades even, to get anything done. And there's always that transmission time to take into account.
• Update: Here's my post: Hard-scrabble existence.
• And an e-mail from Gail Bellamy reports, "Jamestown, New York----nothing but a few small ants----then a split large rock with the first layer had 2 black ants, but the bottom had a large fat toad resting comfortably. All are still in place." She doesn't include photos, unfortunately.
• Update # 2: Fred sent in his report from the Muskrat River, Ontario, via e-mail attachment. I've posted it here.
• Update # 3: And Mark, operating on the Celtic calendar, sent in his results today, Sunday the 16th.
• I think that's the lot. Have I missed you?

I'll send an e-mail with the list to all the participants, but feel free to copy this list and paste it on your own blogs. Thanks for Rock Flipping with us!

The eelgrass dwellers

The tide was coming in.

(I remember how, when I was growing up on Vancouver Island's west coast, how our stories always began with the tide. It was high tide, it was low tide, the tide was going out ... For weather, we had seasons; rain every day, or fire season. What defined the state of our surroundings at the moment was the eternal tide.)

Last week on Boundary Bay, off Centennial Park, the tide was coming in. It was still far enough out that we could barely see the water beyond a great expanse of empty sand, so we didn't know that. I hurried straight out to the edge, hoping to get to where the seaweeds and crabs start. Too late; knee-deep in the water, I could see ahead where the green showed through the waves. Behind me, I could see that the crab shell I had placed just above the water line as a marker was now floating away. Time to head back.

All that first half-mile of the beach is lugworm and sea snail territory; we don't see much else, beyond an occasional crab molt or shattered clam.

The invasive Batillaria snails, and snail trails.

In the shallow pools near the edge, we noticed some strange brown blobs, floating like furry balloons on six-inch strings.

This one has several blobs. The dark patches are the shadows of the bubbles floating on the surface.

They were soft and mushy to touch, but held together when I pulled at them. They didn't break away from the stem. I dug a few up; they were on a strand of tiny eelgrass, and the roots went deep into the sand. But what were the blobs? Eelgrass is a flowering plant, were they flower heads? I thought they were supposed to be inconspicuous.

Blob, bubbles, and a barely visible eelgrass stem.

I dropped a few into my plastic bag to investigate at home. While I was at it, I collected a tangle of eelgrass roots from the dry sand.

The snails feed around these. There's one of the blobs in this knot, too.

Back home, I looked over my harvest. The blobs, spread out in water, turned out to be made of fine, brown hairs, baby-hair soft.

I had imagined that they would be populated by small critters; amphipods or snails, maybe. But there was nothing but the hair to be seen.

There was nothing like this in the Encyclopedia; I finally found it in Kozloff. The eelgrass is dwarf eelgrass, Zostera japonica, a small, introduced eelgrass, growing to about 8 inches tall; the leaves are half the width of native eelgrass blades. And the blobs ... I'll quote from Kozloff:

In certain places, especially during the summer months, the leaves of eelgrass become colonized by a variety of essentially microscopic plant organisms. Most obvious among these are the diatoms, which, if present in large numbers, constitute a furry, olive brown coating. If some of the diatoms present are of the chain-forming type, a good deal of the coating will seem to consist of fine filaments. Bacteria will also be plentiful, and once the biological ball starts to roll, detritus tends to become incorporated into the film.

The diatoms, bacteria, and detritus, as well as the decaying tissue of eelgrass leaves themselves, feed the mouths of many protozoa, microscopic worms ... and small crustacea.

It is still early in the season; the colonies were still free of detritus. Any other organisms were microscopic.

I turned my attention to the eelgrass roots. This is the larger, native eelgrass; the leaves are long, up to the length of my arm and more. The leaves grow out of a thick, brown rhizome that anchors it in the sand; small roots grow from the rhizome.

This rhizome, at least as it deteriorates, provides hollow tubes where small organisms can hide. Once, while I was nursing a broken flatworm back to health in a little bowl, I provided it with an inch of eelgrass rhizome for shelter. After a few days, it disappeared. I looked for it several times a day for three days, then it crawled out of the rhizome. So I put the eelgrass, roots and all, in water, and watched carefully.

There were amphipods, of course; there are always amphipods. And a couple of tiny snails. And a whole collection of worms:

Polychaete, (pronounced "Polly Keet"), after I'd liberated it into a tub of water and sand.

A ribbon worm. This is the head. It was blood-red under the light.

The ribbon worm entertained us for quite a while; it slid up to the surface along the rim of the bowl and spent the evening going round and round, occasionally lifting its head about an inch above the water line. Round and round and round; it only stopped when I dumped it in the tub outside. It was about 4 inches long, very red, very smooth, and featureless, except for the little triangular head.

Tube worm.

There were a couple of these tubes; this smaller one was about a inch long. I wouldn't have noticed it, except that it twitched occasionally.

The tube is decorated with sand grains cemented on.

The larger worm, about 3 inches long, kept extending its head (or maybe proboscis) and waving it around, in a searching pattern.

I looked it up in the Encyclopedia and on the web, but couldn't identify it.

And there was one more, not exactly worm-like, but I think it's a polychaete, going by the tufted "feet" along the sides:

Tiny worm, under the microscope. About 5 mm. long.

There are four appendages visible on the head end; two pale antenna-like things, and these two with a black spot at the tip, like a snail's eyes. My first photos didn't turn out, and when I went back to try again, I couldn't find it. It's somewhere in the tub; maybe someday I'll find it again, grown up a bit.

The worms crawl in, the worms crawl out ...

I never would have imagined that one day I would be handing out treats for worms.

I have at least three fair-sized polychaetes, probably sea nymphs, living in the sand at the bottom of the aquarium. I don't usually see them, unless I empty the tank and comb through their hiding places. In the last couple of weeks, I've done that twice; once in a periodic cleanup, and once because Big Green, the crab, made such a mess of the place. Each time, the nymphs have had to make themselves new burrows, and, as luck would have it, a couple ended up right beside the glass.

I caught the biggest sticking his nose out of the sand, stretching and waving around, as if sniffing for food. When I moved, and my shadow fell on him, he shrunk back into cover instantly. I polished off the glass and waited; after a bit, the cirri (long tentacle-like face decorations) poked through the sand, then the face followed. Slither, slither, left, right, straight ahead, over a rock, always leaving the bulk of his length securely inside the tunnel. When a hermit crab came near, he reacted even faster than he had before; a quick convulsion and he was gone.

Face of the sea nymph.

Worming his way across the bottom.

This was when I decided to break out the goodies. I have some tiny dried minnows I bought at a Chinese food store. (For myself, but I don't mind sharing.) I broke off a little head, crumbled it, and dropped it near the place where the worm had emerged. The crabs and hermits dashed over to collect, but after a bit, here came Mr. Worm, reaching, retreating, stretching out again. He found a piece of fish. I didn't see exactly how he did it; he was far too fast, but back he went into the hole, the fish trailing along in his wake.

He was greedy, and came back for more several times, enough for me to get these photos.

Friday, when I re-organized the tank again, three much smaller worms ended up near the glass. These are ones I had not seen before, except maybe as tiny red hairs. Now they are about as thick as a pencil lead. And they are out looking for food.

The biggest of the three

These look green, unless they come out into full light; then they are as pink, shot with blue, as the big ones. And the one face that I got a good look at is the same; long, hooked jaws in front, and those eight waving cirri.

I was wondering, earlier, what they eat. Kozloff says they are algae eaters, but other researchers call them predators. These ones, at least, are meat eaters, whether as scavengers or predators on live animals, I can't tell.

These aren't the only worms in the tank; doing the last tidying up, I removed a shell where one of the flatworms was hiding. After I refilled the aquarium and all was at peace, he was wandering around on the glass.

Flatworm and orange-striped anemone. 

This is the underside, seen through the glass. The worm's head is to the left. Its mouth is towards the front of that long central tube. There is a simple eyespot on top that discerns changes in the light, but does not capture images. It travels on thousands of tiny cilia. And, fragile though it seems, it is a voracious predator.

When I brought these home, six weeks ago, they were about 6 or 7 mm., just over 1/4 inch, long. Now this one is as long as the first joint of my thumb, almost 3 cm, or over an inch. It must be getting enough to eat. I wonder what that is.

He slip-slid all the way around the tank, roaming from the top to the bottom, then back again. Eventually, he came across this big black-tailed barnacle. I watched as he left the glass and flowed over the rough shell. ( I wondered how that felt; didn't it scratch his tender flesh? Guess not.) He came to the lip, flowed over it, covering the mouth, then slid farther down between the plates and completely disappeared.

Very scratchy barnacle

Later on, I saw the flatworm on the glass again. It was heading down, towards the sand. When it got there, it flowed down between the sand grains and disappeared without leaving a trail or hole. A few seconds later, a green polychaete burst out of the sand an inch away, squirmed across a pile of shells and went to earth again.

Do these flatworms eat polychaetes? Do they eat barnacles?

Hermit Rex, out of harm's way, on eelgrass.

Some interesting flatworm sites:  MuseumVictoria (Australia), Wikipedia. And see "penis fencing".

It's been a wormy weekend

We picked up a handful of small pink clam shells in the mud flats at Boundary Bay this afternoon. These two flatworms came home with them.

Shell, 1.7 cm. Flatworms, about 6 or 7 mm. One in the shell, and one on the underside.

Two clusters of eye spots and a gut in a smear of soft jelly.

At least 126 species of free-living flatworms dwell in the marine waters of the Pacific Northwest ... (Marine Life, Lamb and Hanby)

This one is probably the Bivalve flatworm, Pseudostylochus ostreophagus, an invasive species from Japan. Like all flatworms (polyclads, referring to the many branches of the digestive tract), it has a two-way gut; there is no anus, so waste materials are expelled through the mouth, on the underside of the worm.

I was intrigued by the way these critters moved, flowing as if they were a liquid, but folding themselves over the lip of the clamshell or pushing at the "skin" of water droplets. I posted a video to YouTube: Flatworms demonstrate the slither.

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Worm in a coat of many colours

The tide was high Friday afternoon on the White Rock beach, and still coming in. In the few feet between the waves and the mounds of rotting seaweeds, Laurie started idly flipping rocks, looking for crabs. At this level, there's usually not much else.

Under the rocks just lying on the surface, there was nothing. Rocks embedded just a bit yielded tiny shore crabs and squirming, hopping mounds of blue-green amphipods.

"Smiley"

The slowpokes; the rest are long gone.

I turned over a rock that was buried just a bit deeper, and something pink slithered out of sight down a hole. I dug it out and dumped it on a rock; it was a worm, at first glance looking like an earthworm, but in the sunlight, it shimmered with blue, green and yellow highlights. Frilly legs on the side identified it as a polychaete.

Worm #1

Under another rock, we found a second worm, a smaller one. Turning its rock around for a better view, Laurie inadvertently broke a couple of rings off the tail. (This is important; you'll see why in a bit.)

The two polychaetes at home, in a soup bowl. The long one is just under 4 inches.

I photographed these as well as I could, given that they never, ever, stop moving. Then I dumped them into the aquarium with the rest of my critters. They disappeared into the sand at the bottom.

Later, sorting the photos, and attempting an identification, I was stymied by the lack of detail in the faces; these were Nereids, it seemed, but I couldn't be sure.

There was only one solution: I emptied all the water out of the aquarium, carefully removed rocks and shells and seaweeds, making sure I didn't squish any of the anemones. Crabs and hermits scuttled out of the way; the barnacles and snails shut down. They would be fine.

I ran my fingers gently through the sand, and exposed a worm. Hooray! I fished it out and dumped it in clean water. But wasn't it bigger than I remembered? Seemed so. Maybe my memory is going.

I found the second and added it to the bowl. But -- what was this? Its tail isn't broken!

And no, my memory is fine. This second one is Worm #1, the 4-inch one. Worm #2 is still in the sand. The other one has been living in my sand bed -- how long? And how did it get there?

This worm is over 7 inches long, stretched out. It's as squirmy and wriggly as the other two, but I was glad of this; with each twist, its colours changed; it's a multi-legged rainbow!

These photos are blurry, and don't do justice to the iridescence of the original, but will give an idea of the variety of colours:

Tail end of worm #2, on the rock in the sunshine. The red line is the main blood vessel, running from head to tail.

Worm #3, in a plastic container. Every movement sent shivers of blue down the spine.

Under more gentle light, the colours are muted, but the pink reflects in the water around.

And I got my head shots, more or less.

Yes, those are eyes, two large and two small, just above. The little "V" in front are antennae; on either side, shaped rather like a Tegenaria's fangs, are the jaws or palps. The four spikes on either side are cirri.

Side view of the head.

And the tail, with a cute little button at the end.

Looking at the head, I think I can identify it as a Nereis, probably vexillosa, known variously as the sea-nymph, mussel worm, sand-worm, piling worm, etc. It grows to about 15 cm, although some may reach up to 30. (One foot.) Kozloff (Seashore Life of Puget Sound) says it eats algae, tearing it with those heavy jaws; some websites tell me it's a "active predator" that feeds on soft-bodied animals. If it's been living in my tank for a while (and it must have; the only way it could have arrived would be as a tiny red worm in a pill-bottle of sand), then it hasn't been feasting on the other animals; they are all multiplying happily in there.

I found a page of a lab manual on dealing with Nereids; I read,

They are difficult to handle before they are completely relaxed.

No kidding!

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Underwater menu

I found a dead mussel in my dishpan aquarium yesterday morning. Dead, empty, cleaned out; not a morsel of mussel flesh left. One of the whelks is probably still digesting it.

The assorted other animals in the water get along nicely with each other. The isopods, limpets and periwinkles graze on the algae; the barnacles, anenomes and clams strain plankton out of the water; the crabs clean up the trash. But the whelks eat mussels and barnacles.

So white, so angelic, so bloodthirsty.

Whelk, showing white flesh and orange operculum.

I've been watching them; they settle on a mussel or a clump of barnacles and stay put, boring through the shell. The largest mussels are most at risk; a couple of little ones wander through the tops of the seaweed, where the snails can't reach them. The barnacles, stuck on the rocks, aren't so fortunate. A couple of days ago, three snails were working together on the largest barnacle, which now stays closed up, whether dead, anethesized, or trying to protect itself, I don't know.

A Nature Coast Marine Group (Australia) page gives a general timetable:

When feeding the whelk crawls onto the barnacle, tubeworm or shellfish and drills a hole in the calcium carbonate covering of its prey. In the case of barnacles, whelks usually attack the doors that open to allow the animal to feed. The whelk releases an acid from a gland in the front part of its foot. This softens the calcium carbonate which is then licked away by the rasp-like tongue (radula) of the whelk. When a hole has been made in the prey the whelk inserts its tube-like mouthpart into the victim and, with its radula, tears off and eats the soft tissues.

... It takes 30-40 minutes for each application of the acid then about a minute of rasping before the process is repeated. The whelk takes about 8 hours to penetrate a shell 2mm thick and can take up to 4 days to get into a larger barnacle.

My poor barnacles!

These miniature snails don't bother even the tiny barnacles: they are algae eaters.

Sitka periwinkles.

This one may have been a young Amphissa. It's just over 4mm. long. It would have been eating dead algae and other detritus.

I saw this next snail first crawling upside down on the undersurface of the water, suctioned on just as a larger snail would attach itself to a rock. It crossed the whole dishpan this way. Here it has moved to a leaf of sea lettuce.

Another algae eater.

These are a couple more residents of the mini-ecosystem: I'm not sure what they are, but I would guess some type of sponge. Alive or dead, I don't know, but they seem to provide housing for some of the smaller shrimpy things.

A yellowish, branched spongy substance, with random tunnels.

And a more rounded, purply sponge, with one hole in each "branch".

This long worm was travelling through the eelgrass and seaweed. It's a polychaete, with bristles on each foot, and a carnivore, like the whelks. It's probably eating the tiny, hair-like red worms that live in the sand.

Click on the photo to see the head structure.

And, since I don't have any starfish (nor gulls), nothing eats the clams.

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