Tuesday, January 06, 2015

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.





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