Watch out for the coat!

On the underside of a rock at the end of the boat ramp at Boundary Bay - almost at the high tide line - I found a white and brown, squirmy, translucent bit of live jelly and wavy bits. It wouldn't sit still for its portrait, so I popped it in a bag with seaweed for protection, and brought it home.

He* wouldn't sit still in a bowl of clean water, either. I gave up and added him to the tank, where he promptly disappeared. He showed up two days later, and this time, he posed for me.

The opalescent nudibranch, Hermissenda crassicornis, hanging head down, belly outward. Isn't he beautiful?

Also known as the long-horned or thick-horned nudibranch, for the two long extensions in front. ("crassi ..." = L. "thick", "cornis" = L. "horn", as in unicorn, ".)

He's  about one inch long, usually, but sometimes stretches a good bit beyond. The "horns" are part of the foot. In this belly-forward photo, we can see the mouth and the two rhinopores. (More ancient languages, this time Greek: "rhinos" =  ῥινός, "nose", "phore" = φορος, "bearing".) All nudibranchs have these; they are scent or taste receptors. And on the right side, facing us, just above the head, that round, pearly button is the anus.

Along his back, he wears clumps of cerata, that function as gills; they wave about continuously in the current. In many of his cousins, the inner coloured area is orange; this guy only has tiny specks of orange.

Side view, showing the cerata and rhinophores.

He looks so soft and helpless; when my largest hermit came over to check him out, I cringed. Those huge pincers could have chopped him in two with no trouble, it seemed. But the hermit backed off and lost interest immediately. And "Herm" just kept on about his business, not in the least worried. He has his own hired bodyguards, in his coat.

This nudibranch eats anemones and hydroids. And digests everything but the stinging cells; those he stores in the tips of the soft cerata. And they still work, even in a foreign body, protecting the sea slug just as they protected the original anemones.

Browsing in the red algae; top of the head, with its distinctive markings.

He seems to have settled in happily to my aquarium; he wanders about, nibbling on whatever's growing on old stones and shells, and spending a lot of time in the red algae bushes.

 It eats hydroids, but the diet also includes small sea anemones, bryozoans, colonial ascidians (Aplidium solidum, botryllids), annelids, small crustacea, tiny clams, dead animals of any sort.  Will eat other Hermissenda. (From Wallawalla.edu.)

He shouldn't starve in the tank. Even though there's no other "Herm" for him to eat.

*These nudibranchs are hermaphroditic, with both male and female organs. Since this guy has no mate, he's not a mother, so "he" will do for him. For now.

Not a mini-dolphin

I brought home a few blades of eelgrass, a sheet of sea lettuce, and a clump of brown, feathery stuff, plus some sand for rooting the miniature eelgrass, and added them to the aquarium. (To the great delight of the hermit crabs.)

Half an hour later, this critter was out exploring ...

It's a Spotted Aglaja*. It was probably buried in the sand, where these usually hang out, just under the surface.

... it preys on bubble snails along with other small mud dwellers including copepods.  Lacking a radula or rasping tongue, it sucks in it's prey whole. (From Puget Sound Sea Life.)

Here are a few more photos.

These animals are hermaphrodites; each one is both male and female. There's a good series of mating photos of a similar species on DORIS. (In French, but Google will translate, sort of.)

Mine (Spotty) is a young one; the average size is about 3/4 of an inch, although they grow up to about 2 inches.

After s/he did the rounds of the walls, s/he headed down towards the sand, and hasn't been seen since. There's plenty there for her to eat; copepods, amphipods, a few tiny clams, and loads of infant polychaete worms.

* Or possibly Diomede's Aglaja, but I think the head on DA is too rounded and narrow.

A time machine would have helped with this

We were sitting quietly in the evening after another strenuous day in the garden, half dozing, half watching a slide show of our recent photos. "We have a good life," I said. "So much beauty, so much to do, so many new things to learn ..." So many questions to find answers to, I could have added.

Here are a couple of those questions.

On White Rock beach last Tuesday, the tide was low and going out, there was no wind and the water was smooth, the wavelets retreating down the sand gently, barely stirring the sea lettuce as it went. We walked west, towards Kwomais Point, staying mostly on the drying sand.

Something else had been going the same way.

What made these?

Small footprints went straight along the beach, a purposeful walk, with no meandering and only a couple of stops to dig at something in the sand.  They went on and on, directly west, crossing several of the streams emptying onto the beach, a long walk out in the open for most woodland creatures.

Four toes with sharp claws, and a rounded heel.

About an inch and a half long.

This was not a dog; it traveled in a straight line, it kept a steady pace, and its gait was unusual; four steps in a group, one in front of the next, then a long space, then four more. And although sometimes human footprints went alongside (as mine would, too), they varied; barefoot, or shod with an assortment of sole prints. Mostly, the tracks went on alone.

After a time, I met tracks coming back towards me, then the end of the line; the animal did a U-turn, for no perceptible reason, and headed back in the same manner, four steps, jump, four, jump ...

Going and coming, with the U at the end. Barefoot human alongside here.

So what was it? I've spent the evening looking at animal tracks, comparing the shapes, the number of toes, the claws, and the gait. First, the most common around here; raccoon, skunk, fox, coyote. It's none of those. It's not a domestic cat; they sheathe their claws.

The animal whose tracks are most like this is a mink. They have five toes, but the fifth often does not show up on their tracks. And they bound, rather than walk, making a pattern of four steps and a pause. So do other mustelids, like otters (but they're bigger). So do skunks. (Remember Pepe le Pew; bounce, bounce, bounce!)

But. Minks are nocturnal. What would one be doing walking brazenly down a public beach in broad daylight? And they usually hunt in fresh water. (But here's a photo of mink tracks on a Vancouver Island beach.)

So I am left with the question unanswered. I am inclined to go with mink, but it's not quite a match. What do you think?

Question # 2:  We passed 7 dying Lion nudibranches, Melibe leonina.  I had never seen any so big before; most I've found have been under 2 inches long, even with the hood extended. These were all around 4 inches long.

The tentacles on the left are along the rim of the feeding hood. The paddle-like shapes are cerata; defense and decoy organs; they also help with respiration. 

Another one, with foot for a measuring stick. 4 inches.

What made these wash up on the beach and die?

At least this question was easily answered. Melibe lives for one year. In the spring, she* mates, lays her eggs on kelp and eelgrass, then dies. These would have finished their egg-laying, and are moving aside for the next generation.

*Most sea slugs, Melibe included, are hermaphrodites; each animal has both male and female organs. And they all lay eggs. "She" just works better for them.

There's a beautiful photo of Melibes mating, here, on the Sea Slug Forum. This was in February, but I've found records of egg-laying in this area from March to July (photos).

Open and shut case

Every so often, we find a Hooded Nudibranch, Melibe leonina, on the White Rock beach. Usually, they're dead, ripped out of their eelgrass beds by strong winds and waves. A live one turned up last week, swimming and hunting for food in a pool on the sandy flats.

Hood open.

A nudibranch is a mollusk, a gastropod like snails and slugs. Like snails, the other sea slugs have a toothed radula, which they use to scrape and gnaw at their food. Melibe doesn't. She instead has this great hood, with tentacles taking the place of teeth; the tentacles serve to lock in the prey when the hood closes. (Think Venus fly-trap.)

Hood closed.

Young Melibes still search for prey along the floor, like a snail does; they

"hold the hood out horizontally, just above the bottom, and gradually move along feeling, with the tentacles around the edge of the hood, for small prey." (Sea slug forum)

Adults fish for their food, waving the open hood around in the water, closing it to trap the goodies. This one was one of the larger ones, and while we watched, cast her* "net" and drew it in, over and over.

Hood open.

And closed.

Prey include amphipods, copepods, mysids (shrimp-like animals), other small crustaceans, small mollusks, small jellyfish and ctenophores, larvae of other invertebrates and in some cases small fish. (Wikpedia)

We didn't see her catch anything, and the pool looked empty, but the water here teems with tiny amphipods and copepods; we wouldn't have seen those, nor the many transparent larvae of other critters.

Hood open again. The sun came out briefly, casting a shadow almost more solid than the slug.

Melibe leonina is basically colourless. The colours we see come from the food she has been eating, in this case green things. She also eats nematocysts, the stinging cells of cnidarians, such as anemones and jellyfish. On her own, she has no protection against predators. And I know because I've watched it; crabs and hermits fight over pieces of Melibe. Anemones like them, too, getting a bit of their own back. So somehow she eats the anemones, stinging cells and all, without triggering the firing mechanism, then transports those nematocysts to her own cerata.

Closed again. The cerata at the other end look like fingers on a hand. But there are about 6 to 8, in all.

She has other tricks up her sleeve, too: the cerata are loosely attached. When she is threatened, she drops a few. (They grow back.) Hopefully, her attacker will take the easy morsel, and let her escape. If they make him sick, all the better.

Hood open again.

Note the rhinophores ("nose bearers"); they're more visible in some of the first photos. They are sensory organs, capturing tastes and scents in the water, as well as currents. Food, enemies, and company (the nudibranch is a social critter); it's all done by the rhinophores and the tentacles around the hood. The nudibranch has no eyes.

*Most sea slugs are hermaphrodites, with both male and female characteristics. I use the feminine pronoun, "she"; I can't see calling an egg-layer, "he".

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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