Caught in the act

I happened to glance at the aquarium at just the right moment to see an anemone spawning.

Pink-tipped green anemone, releasing sperm!

I've checked several videos, all showing fogs of sperm floating out in a slow, continuous stream. This little guy spit out three (that I saw) quick bursts of cloudy material, with a few seconds interval between. I had time to run for the camera and catch the third. There was no fourth. (Hooray for autofocus!)

Anemones in aquaria usually reproduce by splitting in half, creating two separate animals that each go in their own way. This is generally the case in my tank; there are two pink-tipped greens half-way through a split today and another couple of new pairs starting to move apart.

Sexual reproduction is rarer, at least in tanks. The anemones, although they were "born" by cloning, still manage to become either male or female, not necessarily the gender of their parent individual. This one is male.

A study on Anthopleura elegantissima in north San Francisco Bay, California shows that gonads build in size through spring and summer, and spawning occurs in late summer/early autumn.  Gonad indices peak coincidentally with high surface seawater temperatures. ... Eggs are released in brown mucousy masses, while spermatozoa are released in milky-white masses. (From A Snail's Odyssey)

Note: the schedule may be different because my tank didn't suffer the more extreme winter that outside waters would.

There is some evidence that males begin spawning earlier than females, and perhaps this stimulates the females to spawn. (Same site, Research study 2)

I'll be monitoring the anemones more frequently in the next few days. I have no idea which are female; I hope some are.

There's not much chance of this producing more anemones here; the fertilized eggs swim in the current for a while, and will probably be caught in the filter. The critters are smart to use the splitting strategy in captivity.

Spring fever already

I turned over an oyster in my tank and crashed an amphipod party.

It's orgy season!

The amphipods scattered, but most of them were moving slowly because they were travelling in pairs. The male chooses a female and holds onto her until she's ready to mate, sometimes for a week. In this photo, I caught 4 couples and one lonely singleton.

Spring is on its way; even in my tank, inside, away from the tides and disrupted by on-again-off-again lighting, the critters know it. Several of the male hermit crabs are dragging around their chosen mates, too. And the anemones are multiplying like rabbits.

Pink-tipped green anemone, "Stretch", splitting in two.

Most of these anemones elongate to about twice their width, and then separate, but this one is ambitious and has spent several days stretching out to start the clone at a good distance from the parent. I just went to measure it; from one end to the other, it's 7 cm. And now the bridge between is shredding. By this afternoon, the youngster will set off on his own path.

This species of anemone is capable of reproducing both sexually and asexually. As adults, A. elegantissima release gametes into the water that join to form genetically unique individuals that settle on intertidal rock. This genetically distinct individual can then proliferate through binary fission. (Wikipedia, Aggregating anemone)

"Stretch" may be slightly confused as to the time of year; sexual reproduction starts in February, but the resulting gametes are usually released in summer. However, two weeks ago, before starting the stretching exercises, this anemone released a whitish cloud from its mouth. There's a YouTube video showing a spawning anemone here; this is what "Stretch" was doing.

These anemones, Anthopleura elegantissima, are either male or female (many others are hermaphrodites) and groups that have reproduced by splitting are clones, all the same sex. So spawning in my tank may be a wasted effort; the whole colony may be all males. Or females. (The only way I could know for sure would be to break the anemone off its site and look for sex organs; the female's are brownish pink, and the male's are yellowish white.)

Cloning is easy!

There were four pink-tipped green anemones in my aquarium. Now there are five.

Two anemones, January 22

Same two, February 5th. The one in focus is stretching out.

February 6. Starting the split.

February 7. Two half-mouths.

February 8. Now each half has a complete circle of tentacles.

February 9. Just holding hands now.

And they've stayed that way, just touching, for the last two days. Each one feeds on its own, and reacts to stimulus (like a poke from a hermit's foot) independently.

Aggregating anemones live on rocks in tide pools and crevices, either alone or in dense masses. Each mass is a group of clones that are genetically identical and of the same sex. To clone themselves, anemones split in half—literally tearing themselves apart (asexual reproduction). Asexual reproduction spreads new animals rapidly over rocks. Aggregating anemones also reproduce sexually by broadcasting eggs and sperm. Sexual reproduction results in new combinations of genes, and larvae that establish new colonies in other locations. (From Monterey Bay Aquarium)

Clones can live jammed tightly together; when they meet another anemone with a different genetic makeup, they fight with poisoned darts, even if they originated from the same parents. Sibling rivalry at it's worst!

Life must cycle

Sea anemones reproduce in a variety of ways: by cloning, (splitting or tearing off a part of the parent's body, which then continues to grow as an adult); asexually by budding: or sexually, producing free-swimming planulae, which find a spot and settle to grow into the adult stage.

Hydroid bud. Released medusas will eventually reproduce sexually. Unlike these, the anemones' buds grow directly into adults.

Clones can be quite large; up to half the parent's body, but the buds and larvae are microscopic. Even the infant anemones, already settled, may be only a couple of millimetres across the base.

Like the ones I found in the clamshell:

One of several patches, on this and a second clamshell. What species? Time will tell.

The orange-striped green anemones outside of their home territory, reproduce by splitting. "At home," they also release sperm and eggs. Whether they consider my tank a home away from home, I don't know.

Orange-striped green anemone. Their colours and shapes are variable, even in the same individual at times.

Are these orange-striped? Probably. See the two at bottom left. The stripes are green.

These little anemones are appearing in large numbers all around the tank. They are obviously not produced by splitting; no mature anemone has been racing all around, dropping bits of himself as he goes. It looks like these grew from babyhood.

Another of the same anemones, on rotting sea lettuce.

And then there's the little blue anemone, rescued from certain death on the beach last October:

Brooding or Proliferating anemone, Epiactis prolifera, about 1/4 inch across. On a third clamshell, with several orange-striped babies, kelp, and green algae.

This anemone has a unique sex life. Young adults are almost all functional females; as they mature they become simultaneous hermaphrodites (having both male and female gonads at the same time, as opposed to being first one sex, then developing into another) capable of fertilizing themselves and others. (From Oregon Coast Aquarium)

She's still young; adults can be up to 2 inches across, so for now, she's female only. Since there are no males, she won't be reproducing for a while yet.

(So the infant green anemones in the clamshells aren't hers; they must have come with the kelp holdfast.)

Once she reproduces, she'll brood her babies for up to three months.

... larvae? ... Live on mother's column (digesting yolk, then catching prey) until at least 3 months old and 4 mm diameter, then crawl off. (From wallawalla.edu.)

She knows her own:

When starved, Proliferating Anemones will ingest young anemones that have become detached from the parent’s base; however, these are normally regurgitated unharmed, even after several hours in the gut. (OCA)

I can't forget Val, the largest anemone in my tank.

Burrowing anemone, Anthopleura artemisia. 4 inches tall and still growing.

These anemones reproduce sexually, which won't happen here, since she's a loner. Or by splitting, which she shows no inclination to do. She's probably had enough of that; when I got her, she was just a blob of torn tissue left on a beach, probably by a bird.