Friday, November 22, 2013

Red-eye special

My aquarium setup now includes two tanks. In one, the hermits and crabs, a big polychaete worm, four or five kinds of snails, the big (and still growing) anemone from Campbell River, and a varying assortment of temporary visitors all go about their business; eating, mating, climbing, watching me. There's a strong pump with a filter, and a bubbler; everything is constantly in motion.

The other tank is quieter. I don't stir it up; there's no filter, just a smaller bubbler. Here amphipods and copepods breed happily, without being swallowed by the filter. Here, too, the occasional miniature snail or hydroid appears, seemingly out of nothing. It's a good place for babies.

A couple of times, I've seen a transparent bubble with tentacles resting on the glass. Tiny things; I had to bring out the microscope to see the bubble part. A few days ago, I saw a larger one, and thought it might be big enough now to handle the active tank.

One of the first photos.

Here it is, from the bottom, parked on the glass, tentacles streaming in the current. The circle is about 3 mm. across. In the center (the "yolk" of the "egg") is the column, seen from the bottom. The tentacles sprout from nine radiating arms; they're beaded all along their length.

To the naked eye, the whole thing is transparent jelly; the colour comes from the lighting and the background.

Disturbed, the critter bounces away, and swims, bubble first, tentacles following behind. It's really cute to watch, almost impossible with my equipment to photograph. Imagine one of those deep, transparent umbrellas with streamers hanging from all the tips. Now, watch it swim by opening and shutting itself. With each quick closing, it zooms off in a different direction, completely unpredictable. It coasts for half a second, then opens-shuts, and it's gone.

Resting on sea lettuce. Side view, showing the bell and the central workings.

I think this is a baby Red-eye jellyfish, Polyorchis pencillatus. ( I could easily, easily, be wrong.) These are common on our coast, growing to about 3-4 inches high. They are mentioned on several sites in eelgrass beds; that's probably how they have come to my tanks, riding the eelgrass that I collect for the hermits' jungle gym.

The tentacles can shrink or stretch to much longer than the bell. I saw this happen a couple of times, when the swimming jelly miscalculated and swam into the tentacles of a small anemone on the wall. The anemone didn't try to reel it in, and after a few minutes, the jelly extricated itself, and dropped to the bottom of the tank. I thought it was dying, but it recovered right away and swam off. But for several minutes, the tentacles were shrivelled and twisted.

Look at the base of the arms; see those dark dots? They are eyespots, red when the light is right, which gives the species its English name. They don't see much, but they are light sensitive, helping the jelly to orient itself. Two similar local species do not have these spots.

Side view, showing central column.

Usually, at least when I've been looking, the central section is a column the entire height of the bell. In most photos of mature specimens, it's a tangle of organs dangling from the central top.

It's been in the big tank for 3 days now, and seems content. Right now, it's riding the eelgrass.

2 comments:

  1. So cool. You find the neatest things.

    ReplyDelete
  2. Wonderful find! The ocean's biodiversity is endless.

    ReplyDelete

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