Wednesday, February 07, 2018

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.)

1 comment:

  1. That's really interesting about the anemones and being able to capture it on film. - Margy


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