And the bryozoan eaters

Nothing grows in isolation. There are layers upon layers.

On a blade of kelp, a map of bryozoan colonies provides habitat for dorid sea slugs, nudibranchs. They break into the little zooid boxes and scrape out the animal inside. They are well camouflaged: their bodies are transparent, with white lines that mimic the white walls of the bryozoans.

With the naked eye, all I could see were pinhead bumps on the bryozoans. I searched for them with the microscope and found a half dozen, busily feeding.

This is the bryozoan colony, without dorids. Each little box is about 0.4 mm long.

A dorid, outlined by reflections from the 'scope's lights. About 2 mm. long.

There are two almost identical species of these tiny nudibranchs; Corambe pacifica and Doridella steinbergi. Only with a higher-power microscope could I tell the difference. But the two species happily live together on the same colonies.

A smaller one. The white markings are visible here.

A larger dorid, more visible on hydroids. This is probably the Corambe pacifica, aka the frost spot nudibranch.

This one shows a few yellowish spots.

Even with the microscope, these are often hard to see. Unless they're moving. I probably missed quite a few; there can be up to 240 dorids on one blade of kelp.

And this I didn't know yesterday, when I posted photos of the bryozoan colonies; the bryozoans respond to predation by these nudibranchs by building spines on the top of their walls. Here's yesterday's photo, with the spines, that I didn't recognize when I saw them.

"Keep off!"

Tomorrow, I'll have a video of these crawling about.

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Nada vive solito. La naturaleza viene con capas. Encima del alga "kelp", existen las colonias de briozoos; encima de los briozoos, se deslizan los nudibranquios, animales del grupo de caracoles y babosas; como caracoles marinas sin concha. Se alimentan de los zooides, rompiendo sus cajitas. Tienen exelente camuflage, siendo transparentes y con lineas blancas que se parecen a las paredes de los briozoos.

Con el ojo solo, apena podía ver unos pequeñísimos protuberancias sobre las colonias de briozoos. Cuando los busqué con el microscopio, encontré una media docena.

Las cajitas de los briozoos miden aproximadamente 0.4 mm. de largo. Los nudibranquios (aka doris) miden desde 2 mm. de largo.

Hay dos especies que viven en estos briozoos; Corambe pacifica y Doridella steinbergi. Son casi idénticos, pudiendo identificarse únicamente por la formación del ano, lo cual no es posible con mi microscopio. Sin embargo, las dos especies viven juntas, así que las fotos aquí pueden representar ambas.

Es muy difícil verlos cuando son tan pequeños, a menos de que estén caminando. Probablemente se me escaparon varios; en una hoja de kelp pueden vivir unos 240 doris.

Y esto no lo sabía ayer cuando subí las fotos: los zooides de la colonia de los briozoos se defienden del ataque de los nudibranquios construyendo espinas encima de sus paredes. Volví a subir la foto donde se ven estas espinas. Ayer no supe que eran.

Mañana, subo un video.

Is this Doris?

Mystery critter #2:

I took a photo of a pale turquoise and green sea star; as so often happens, something else showed up when I blew up the photo.

Starfish, yellow eggs, bryozoan cases, green worm, sponges, tubeworms, more eggs. And ...

Look up at the left corner, to the right of the green worm. There's a white blob. Look closely; it has spiky, white projections all over.

It could be a nudibranch that I have never seen before. My encyclopedia has three white blob nudibranchs with white projections, all under an inch and a half long. The starfish was about 5 inches across.

So this may be the Nanaimo nudibranch, Acanthodoris nanaimoensis; the Pilose Doris, Acanthodoris pilosa; or, less likely, the Hudson's Dorid, Acanthodoris hudsoni.

Whichever it is, it's a lifer. *Does lifer dance.*

Noble lemon, shaggy mouse, and little Doris

Those are all nudibranchs. Aka sea slugs. And one, the noble lemon nudibranch, was definitely sluggish when I woke her up from her afternoon nap.

Peltodoris nobilis, the noble sea lemon.

When I turned over her stone, she was just a circular yellowish blob, not moving, almost looking like a mass of eggs. I took photos of the sea cucumbers I found under her stone, and looked at crabs, then went to replace the stone. But now, she was awake, and stretching out, s l o w l y, s l o w l y.

Now I could see a bump on one end (on the right, above); one of her two sensory organs, the rhinopores, still retracted.  I waited, took photos, measured her (2 inches, still half hunched up), waited some more. Finally, the circle of gills at the back started to expand, millimetre by millimetre. I took pity on her, then, there exposed in the sunlight and air, and carefully flipped the stone back onto the wet sand. She probably went right back to sleep.

She feeds on several species of sponges, when she's awake. No rush; they're not going anywhere.

On the underside of another stone just below the mid-intertidal zone, a group of small barnacle-eating dorids were sitting around the table.

Onchidoris bilamellata, with barnacles, some already eaten. The tiny nudibranchs drill through their shell to get at the meat.

Zooming in. I don't see the two rhinopores at the front end. At the rear (lower right on the bottom nudi here), are the feathery gills. 

And I found a shaggy mouse laying eggs.

Shaggy mouse, aka shag rug nudibranch, sea-mouse, Aeolida papillosa. With eggs. Front end, lower right.

The shaggy mouse eats anemones, mostly the stinging tentacles. She doesn't get stung, but saves the stinging cells and moves them to her shaggy cerata to serve as a defense. A slow, soft-bodied, sluggish creature needs that extra bit of protection in a world full of hungry crabs and fish.