All very busy

Tiny things are so much easier to see if they're moving. Here's a short video of the bryozoans and dorids from yesterday's post.

The eggs are probably from the Frost Spot Dorid, Corambe pacifica, because they're arranged in a circle. The other nudibranch that feeds on these bryozoans, Doridella steinbergi, lays its eggs in a semi-circle or shorter arc. There were a few of these on the hydroids growing on the kelp.

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Los animales miniaturos se ven mucho más claro cuando se mueven. Aquí subo un video corto de los briozoos y nudibranquios.

Los huevos probablemente son los del Doris Corambe pacifica, porque están dispuestos en un círculo. El otro nudibranquio que vive en estos briozoos, el Doridella steinbergi, pone sus huevos en un arco de medio círculo o menos. Había unos cuantos de éstos en los hidroides que crecen en el kelp.

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.

Destroyer of cities

The tide was coming in on the White Rock beach, and we were wading through the shallows, to see what treasures the waves were washing ashore. Mostly, last Sunday, we were dodging Lion's Mane jellyfish (of which more, later), but a long strip of bull kelp tickled my ankles, and I noticed these circles on it.

Membranipora serrilamella, Kelp-encrusting bryozoan

Bryozoans. At least I recognize them now. Tiny colonies, each animal in its own separate calcium "box", in this case, spreading out to form a crust on the kelp. I brought the whole strip home to photograph it at leisure.

Bird's-eye view of the walls.

Where the colonies don't compete with others, they form almost perfect circles. If you look closely, you can see the bump of the tentacles at one end of each "brick".

In the water, the rolled edge of the kelp allows a side view of the tentacles, one tube with a spray of tentacles per case.

As always, I looked up my find in "Marine Life ..." and Kozloff. "Marine Life" had a decent photo and a brief description, but in Kozloff, I found,

Some colonies of Membranipora, after being taken out of the water, have what look like little lumps of jelly of about the same color as the colony. If the colony is submerged in clean sea water and examined with a strong hand lens ... the little blobs may prove to be one of the marine zoologist's delights, Doridella steinbergae.

The accompanying photo showed Doridella and its half-circle egg masses. And I remembered seeing tiny white semi-circles among the bryozoans; I should have been paying attention, but I was looking for unblemished colonies.

The kelp was in my aquarium. I fished it out and spread it full length in shallow water. Oh!

Egg masses of Doridella steinbergi, Cryptic nudibranch.

Another cluster of egg masses.

Where there are eggs, there should be egg layers. But where? With reason, the sea slug is called "Cryptic"; they're a miniature blob of translucent jelly, with white lines to match the walls of the bryozoan. I looked directly at several without seeing them, thinking they were small colonies of Membranipora, until I noticed the pattern of white lines, squiggly rather than rectangular.

Two sea slugs, and the edge of a colony of membranipora.

Another Doridella, with egg masses.

I poked this one with a plastic toothpick, and it woke up and started to crawl over the kelp. It's about as fast as a land-based slug. Here it is, crawling onto a bryozoan colony:

The two white ear-like protrusions on the front end are sense organs, the rhinopores.

Most nudibranches have prominent gills at the back, but as part of this one's camouflage, the gills are hidden underneath a flap of skin. Another nudibranch, the Corambe pacifica, also feeds on the kelp bryozoan; it is almost identical to Doridella, except that its gills show through a small notch at the tail. Photos for comparison: Doridella, (They call it Corambe steinbergae here.) and Corambe pacifica. The C. pacifica lays its eggs in a spiral, which helps with the identification.

In my search for information, I came across a great blog, Biological Tales from the Brine Queen. In her post on this sea slug, she writes,

They feed on Membranipora by creating a suction seal, using their rasping tongue (called a radula) to cut through the outer membrane, then they suck out the insides.

And they leave the bryozoan colony with bare patches and irregular edges. Which is why I missed them on the first photo shoot.

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