Sisters under the shell

I was a minute too late. I had come to add ice to my aquarium, and saw a pair of periwinkle snails doing what pairs of snails do, on the glass wall where I would have a chance of a photo. I was too late; by the time I got back with the camera, they were going their separate ways, each trailing a blobby string of mucus.

I followed the larger of the two, then, as he ambled over to inspect a limpet; there is always a good meal of algae on the roof of a limpet.

"Hello, little limpet. Mind if I look for algae on your shell?"

And then he munched his way over the limpet, mouth working busily. And over the other side. She (sex assigned for convenience) didn't mind at all, and kept on eating as if nothing was weighing her down, nothing dragging her off the glass.

"Thanks!"

Watching the two of them, both scraping away at the glass with their rasping radulae, both waving a pair of tentacles with small eyespots at the base, both moving along on their whitish feet (the snail going faster now, but the limpet can keep up if she wants to); if it weren't for the shape of their shells, they could be brothers. Or sistren.

Scene at the bottom of the tank. Snails eating a slice of kelp.

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Llegué tarde. Iba a añadir hielo al acuario, cuando vi una pareja de caracoles acoplados. Pero cuando regresé (corriendo) con la cámara, ya se habían separado e iban en direcciones opuestas, cada uno trayendo consigo un hilo de moco.

Seguí al más grande, mientras se deslizó sin prisa hasta donde una lapa estaba comiendo alga en la pared. Siempre hay alga en la concha de una lapa, más que lo que el caracol hallaba en el vidrio.

Fotos:

#1: El caracol y la lapa. Le dice — ¿Me permites cosechar las algas en tu concha?

Y se montó a la lapa, y se veía como se movía su boca, limpiando la concha de la lapa. Y luego cruzó al otro lado y siguió su camino, todavía raspando el vidrio. A la lapa no le importó; siguió comiendo como si no sintiera el peso del caracol, como si no se le hiciera difícil seguir pegado a la pared.

#2: Los dos separados ahora.

Mirando los dos, ambos raspando el vidrio con sus rádulas, los dos agitando sus dos tentáculos con los ojitos en la base, ambos deslizándose sobre sus patas únicas blancas (el caracol se movía más rapidamente por el momento, pero la lapa le puede alcanzar si tiene ganas): si no fuera por la forma de sus conchas, se podría decir que eran hermanos. O hermanas.

#3: Una escena al fondo del acuario. Caracoles comiendo una rebanada de quelpo.

Radula tracks

I had scrubbed the algae off the glass wall of the aquarium, but left a patch where a biggish limpet was feeding: I could get that later, when he moved on.

I stopped to watch him for a bit. He browses much like a cow on a hillside. Lick, swallow, lick, swallow, move on a small step, repeat. With each bite, his mouth opens, exposing the radula for a half a second, as scratchy as a cow's tongue. It scrapes from front to back and closes down again.

I took a few photos, trying to capture that split second when the radula is exposed. Not quite. But in a few of the photos, I noticed the pattern the limpet was creating.

The algae is splotchy where he hasn't fed yet, stripy where he's been.

Zooming in. See the radula tracks?

Zooming in still more. Each little scratch is about as long as the distance from the mouth to the back of the radula slit.

He's harbouring a few copepods; the shell is not clamped down tight to the glass unless he's disturbed, as when I clean around him.