Convalescence. Flatworms have it down pat.

Thanks to everyone who sent me "Get better" thoughts or comments; it worked. I'm feeling much better, and so is Laurie. We're hoping it was just a three-day bug.

I slept all morning, and worked on a video all afternoon and evening. Kept me too interested to feel sorry for myself. (Lemon juice, chicken soup, and camomile tea helped, too.)

I found a flatworm on the White Rock beach last week, and brought it home, damaged. What happened next is in the video:

And now I'm going to bed. Can't risk getting worse again.

Circumstantial evidence

"Give him enough rope," I said, dumping a flatworm suspected of mussel slaughter into a canning jar with a fresh mussel as bait.

The questions I was attempting to find answers to were;

1. What does this marine flatworm I picked up on the beach eat?
2. Did it and its friend eat all those 24 mussels in my aquarium?
3. Will it eat my barnacles and clams? What about the other worms, the polychaetes?

On the way to answering those questions, I discovered much more ...

There had been two flatworms, but I had only captured one. It sat in the jar for a couple of days, doing nothing, ignoring the mussel attached to the clamshell it had chosen as a resting spot. I used the time to search for more info about flatworms; maybe I was doing something wrong.

I found a "tree" to be helpful in understanding what I was looking at.

• The flatworms belong to the phylum Platyhelminthes, which could be simply translated from the Greek as "Flat Worms". A nice, simple descriptive term.
• The class is Turbellaria, referring to the turbulence created by the cilia that they use for locomotion. These flatworms are mostly free-living; the other classes are parasitic. Mine are free-living. They are usually, but not always carnivorous. They are all hermaphrodites, with both male and female reproductive organs. Some of the larger ones mate through "penis fencing". I'm wondering about mine; this I've got to see. There is a great video of a pair of fencers on the Shape of Life.
• The order is Polycladida. "Poly", as in "many"; "clad", meaning gut. Their intestine branches out through the whole body. The mouth is not on the head, but towards the center of the belly.

Underside of a large polyclad flatworm. The intestines extend almost to the edges. The mouth is in the center.

• The family is Leptoplanidae, which means "thin and flat". Nothing new here.
• The species, I think, is Phylloplana viridis. "Phyllo", a sheet, and "plana", flat. And "green". Which it is, sometimes. My "Marine Life" says it eats bivalve mollusks. There go my mussels!

Back to the live beasties. On the morning of the 28th, I found the second of the flatworms in the aquarium and captured it. While I was doing that, I discovered a hermit crab eating the remains of a good-sized mussel. Hmmm... Was it the hermit, the flatworm, or something else that killed the mussel? Looking at the worm, I noticed that there was an extra something in the center of its gut; see the photo above. Mussel meat?

I put the second flatworm (and now, I'll name the two, for convenience. #1, because it is almost leaf-like, is called "Lief". #2 is quite a bit bigger; it's "Long".) in the canning jar with Lief and the maybe-doomed mussel. And Lief woke up and started to roam, sometimes following Long, sometimes wandering about alone.

(These photos were all taken through the scratched, warped glass of the canning jar. I must get a container of perfectly clear, new glass.)

Long, between the glass and the clamshell. The food is breaking up now. This worm, at least at the moment, is much darker than Lief. Still, if you look closely, you can see the algae pattern on the clamshell, and the dark mussel, right through the worm flesh. The two eyespots are visible at the front end. They distinguish light, but not much more.

Lief. Note the tidy central gut area. Nothing in it but flatworm, and maybe some green algae. The white branching "leaf" is the pharynx; it unfolds through the mouth and wraps around the prey.

Long checked out the mussel, sliding over and around it, then went away. It couldn't be hungry, anyhow. After a while, reading that some flatworms are scavengers, I decided to test that. I broke a head off one of those dried minnows and dropped it in the middle of the jar. When I came back after a bit, here's what I found:

Lief, with fish eye. I checked. The fish head was now missing one eye.

By 1PM the next afternoon, the fish had been digested.

Ok. One thing is established; my flatworms are scavengers. Whether they are killers, I don't know. Yet.

At 10PM, I checked the jar again. Here's Lief:

Almost pure white, except for a pinkish tinge around the edges.

And Long:

Long, with more or less empty mouth area, but lots of colour in the rest of the intestine.

At 5 the next afternoon, I noticed that both flatworms were sluggish. And Lief was almost as dark as Long:

Lief, sleeping it off inside the clamshell.

I worried; maybe they were sick, maybe the water was not cool enough, or the light was too strong. I poured off some of the water, stirred it up a bit; maybe they missed the current of the aquarium. I looked at them closely under the light. And discovered the mussel. Open, dead, about 2/3 eaten. Oh. No wonder they're sluggish!

So that question is answered, more or less. I think they do eat mussels. Not that I've caught them in the act, but the circumstantial evidence does add up.

They're back in the aquarium with the other critters. Six mussels are still alive; I'll keep tabs on them. But it looks like I'll have to supply them with new prey occasionally, if I'm to keep them from extending operations to an attack on the clams.

Four and twenty mussels ...

Yesterday I was asking, "Do flatworms eat barnacles?"  I've been searching for an answer, without much success. The websites I visited mention mollusks, especially oysters, other worms, and dead organisms, but don't differentiate between different flatworm species.

I wanted more info. The real question I was asking was, "What specific animals does this species of flatworm eat? And how did mine grow so fast?" And I kept remembering the giant worm that was destroying coral in a UK aquarium. Could my little tank support a "voracious predator"? Would it attack my clams? Or my one big thatched acorn barnacle?

Laurie suggested I remove the flatworm from the aquarium. So, for the third time running, I emptied the tank. This time, I sifted the sand, counted all the live critters I found, removed empty shells. I found only one flatworm. Whether the other died, or is hidden too well (remembering how it disappeared inside the shell of a live barnacle), I don't know. At least I captured one.

And I think I might have found out what he has been eating. I counted 24 empty mussel shells.

Corpora delicti

That's a lot of mussel meat in 40 days!

But maybe I'm jumping to a conclusion too soon; it's possible that something else killed them and then the hermits and crabs emptied the shells. So I've confined the flatworm to a canning jar, added clean sand, sea water and, reluctantly, one healthy mussel. Give him enough rope ...

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".