Monday, February 25, 2013

Tiny discoveries, and a mysterious bubble beastie

One of the anemones was getting itchy feet, wandering about, so I cranked up the camera to take his photo in transit. And got sidetracked by a few things I hadn't seen before.

First, the usual:

Hermit crab, with a tiny frozen shrimp. Nom, nom, nom!

Then, to smaller beasties:

A periwinkle snail. I keep trying to get photos of them eating.  This is the best so far, but a video would be better. 'nother day.

An amphipod, clinging to a blade of eelgrass, legs every which way. There are both green ones and brown in my tank.

Cropped down to show his marvellous compound eyes.

Amphipod eyes are compound as in other arthropods, and sessile, that is, unmovable.  Each eye consists of several hundred individual ommatidia, each of which has its own lens system, light-sensitive retinal cells, nerve leading to an optic ganglion, and each is thought to produce a single image.  Visual fields of adjacent ommatidia overlap, presumably producing good motion detection, but possibly less good resolution . . . it is probably safe to assume that they have good resolution and motion detection, and probably see in colour.  Hallberg et al. 1980 Zoomorphol 94: 279. (From A Snail's Odyssey)

And then I discovered a snail I didn't know was in my tank:

1/8 inch long, climbing on one of the thinnest eelgrass blades. I haven't identified him yet.

Smaller still; I went chasing limpets, to see if I could catch them eating. All around them, the copepods were cavorting:

Female copepod, carrying her egg case at the rear. She has one red eye, in the center of her forehead. (And when she is good, she is very good . . .) About 1 mm. long.

Something half the size of a copepod crawled off a limpet shell and went hiking up the glass wall.

A marine mite, about 0.5 mm.. I found 4 of them, all near limpets. The mess on its right middle leg is made up of diatoms and other debris.

Unlike the few insects and spiders which may be found in marine habitats but must breathe air, mites are able to absorb oxygen from the water so they can live at great depths. (From WallaWalla.edu Halacaridae.)

I didn't know this, so it seemed really weird to see this spider-like thing walking about underwater. It has 4 pairs of legs, like a spider, but holds one pair out in front as if they were antennae. Confusing little beastie.

Some marine mites are phytophagous (suck from plants/algae), some are predators, and some are parasites.

And while I tracked down these mites, with my hand microscope jammed up against the glass wall (and my neck twisted at an impossible angle; they insisted on hanging out on the wrong side of the tank), I noticed many even tinier groupings of bubbles on the glass. This was strange, because I'd scrubbed down the inside wall before I started taking photos. Where did these come from?

Two collections of bubbles and a copepod beside a limpet.

I thought I saw one group of bubbles move, so I zoomed in on it. But no; it was just there, not moving. And just as I was giving up, thinking maybe it was some sort of algae, it suddenly convulsed, waving 4 separate groups of bubbles about, like legs, for a moment, then settling down to rest again.

Other groups I checked showed the same behaviour. They come in different sizes and number of nodes or maybe branches, and they're all over the wall where the light is good, but not on the front (where my neck would be happier) with less direct light.

I haven't the faintest clue what they are. Help!

And I never did get a decent photo of the anemone. And now he's gone and jammed himself into an impossible corner. I hope he doesn't like it there.


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2 comments:

Sara Rall said...

Wow, I just love your blog, particularly all these creatures you find in your tanks.

And there are so many cool detalis, like the hairy edge of the limpet shell and the eyes on your amphipod, and snail mouth, and underwater mites....

Susannah Anderson said...

Thanks, Sara. I'm glad you noticed the edge of the limpet shell. I'm wondering if the "teeth" are the ends of ridges on the shell.