Counting eggs

So many eggs! Stacks of eggs in pink and yellow egg cases, glued to rocks. Hundreds, thousands, hundreds of thousands of potential baby snails ...

Egg cases of the Frilled Dogwhelk. From 20 to 80 eggs in each case.

  

One corner of one of the egg-laying rocks.

These are the egg cases of Nucella lamellosa, one of the most common intertidal snails on our shore. It  goes by many names: Frilled Dogwinkle, Wrinkled Dogwinkle, Rock-Dwelling Dogwinkle, (why "dog"?) Wrinkled Purple Whelk, Roman Purple Snail, Dog Whelk, Oyster Drill, and so on. The many names may reflect the extremely variable shell colours, shapes, and porportions. The ones I see on our shore aren't all that "frilled", but often wrinkled, and mostly whitish or grey, occasionally orange.

In this one section of the intertidal zone, in the margin between pure sand and a rocky, seaweedy area, many of the rocks were already coated with egg cases, with a line of snails at the base, still busy making more. 

This I didn't know; like salmon, upon reaching sexual maturity at 4 years of age, these dogwinkles return to the sites where they were hatched. There, the females gather with their sisters to attach huge masses of stalked egg cases on their home rocks.

A dogwinkle lives from 10 to 15 years; that gives each female 6 to 11 years of egg making. At about 1,000 fertile eggs a year, that would bury us under 10,000 new snails for each two adults. Good thing they don't all hatch! And that there is high mortality among the young snails; N. lamellosa is carnivorous, and the first hatchlings will eat the eggs of their siblings; then there are the usual predators, crabs and starfish, so only about 1% of the baby snails will make it to their first birthday.

One egg-laying rock. I count 60 adults busy laying eggs on this side of  the rock. Thousands of egg cases.

The new snails will hatch, depending on the temperature, in from 90 to 140 days. They hatch as tiny, perfectly formed snails, but are only about 1 mm. long.

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Huevos. ¡Tantísimos huevos! Montones de huevecillos en cápsulas color de rosa o amarillo, fijadas en las rocas. Cientos, miles, cientos de miles de caracolitos posibles ...

1. Cápsulas de huevos de Nucella lamellosa, el buccino púrpura arrugado. Hay desde 20 hasta 80 huevos en cada cápsula.
2. Una esquina de una de las rocas donde los caracoles ponían sus huevos.

Estas son las cápsulas que contienen los huevos de Nucella lamellosa, uno de los caracoles intermareales en nuestras playas más comunes. Es un caracol bastante variable en color y forma; los que veo más frecuentemente son blancas o grises, a veces anaranjadas; sus conchas son más bien lisas, no arrugadas como presupone su nombre común.

En esta area limitada de la zona intermareal, en un sitio limitado por arena limpia de un lado y rocas y piedras cubiertas de algas marinas del otro, muchas de las rocas ya estaban cargadas con cantidades de cápsulas de huevos, y tenían a su base un grupo de caracoles que seguían produciéndolas. 

Esto no lo sabía: al igual que los salmones, al la edad de 4 años, al llegar a la madurez sexual, estos caracoles regresan a los sitios de donde originaron. Allí, las hembras se juntan con sus hermanas para fijar grandes masas de sus cápsulas de huevos a sus rocas nativas.

Una Nucella lamellosa vive de  10 a 15 años, lo que le da de 6 a 11 añon en que puede producir huevos. Y produce alrededor de 1.000 huevos fértiles cada año. O sea, unos 10.000 nuevos caracolitos para cada dos adultos; suficiente para enterrarnos bajo una pila de caracoles. ¡Buena suerte es que no todos eclosionan! Y suerte, también que la mortalidad entre los caracoles juveniles es alta; N. lamellosa es carnívora, y los que eclosionan primero se comen los huevos más tardíos.  Y luego los atacan los predadores de otras especies, especialmente los cangrejos y las estrellas de mar. Al fin del primer año solamente el 1 porciento de los caracoles siguen con vida. 

• Una de las rocas cargadas de huevos de caracol. Visibles aquí hay 60 caracoles que siguen poniendo huevos.

Los caracolitos nuevos eclosionarán en unos 90 a 140 dias. Salen como caracoles perfectos pero miniaturos, midiendo apenas 1 milímetro.

Eggs in urns

The whelks are laying eggs.

A small collection of egg cases. Each one holds about 20 to 100 eggs. Of these, only a dozen or two will mature into baby snails.

These egg cases are new; as the eggs develop, they show up as slowly moving dots inside the translucent casings. One has already been broached by a predator, probably a crab looking for an omelet.

The same eggs, with their blurry mother, a whelk. (Species not identified.)

The clear dot at the top of each egg case is a "cork" of gelatinous material. Over the incubation period, this gelatin dissolves, finally leaving an open passage for the baby snails' escape to the big world out here. (See A Snail's Odyssey; Whelks and relatives, for more info.)

Empty nest

Fresh, green veggies are good. And if they're eelgrass, they're being used as salad, as gym equipment, as shelter for a variety of critters.

But old, brown, even rotting veggies are even better, if you live in the intertidal zone. A blade of decayed eelgrass is a gourmet dish, if you're a hermit crab. Or an amphipod.

And they make a good nursery for babies just starting out into the wide world; the food underfoot is puréed already, the tough fibers and skins gone. Easy munching!

That's what I think happened here:

Five abandoned egg cases. There may be a baby or two still deciding to leave.

I don't know what animal laid these; I don't recognize the form of the cases. It's probably a snail, but not one I can identify.

The fuzzy stuff is a mass of diatoms, or possibly bacteria. A hermit crab will be along soon enough to clean all that out, leaving only the empty egg cases.

...

And there's more! I'm puzzling over a batch of green teeth. I'll post them tomorrow.

Maternity ward, underwater

Mike and Tillie, the large snails in my aquarium, have been together for 6 months now, and may be on the verge of becoming parents. They've been trying for a long time, at least in snail years.

Tillie has been here since last summer, and I brought Mike home in April of this year. By the end of April, Tillie had laid her first batch of eggs. Nothing came of them, though. Sometime around June, I scraped them off the wall, hardened and broken, dead.

She laid two more batches, on and behind the pump at the top of the tank, where I could monitor them closely. Nothing happened; they sat there until they shrunk and died. No snails showed up. (The ones I'd found on the beach two years before had one tiny infant snail on them, so I know these should be visible when they hatch.)

The pair kept trying. They like the pump site, and have glued down three more groups of eggs there. Numbers 4 and 5 were duds, too; buttery yellow vases with nothing happening inside.

But the eggs in batch number 6 are alive, growing and moving about inside their little "jugs", and almost out of room. Any time now . . .

Laying the second batch of eggs on the pump, in July.

A few eggs are visible, but they never developed beyond that stage.

Batch number 6, three days ago. One case is smooth and beautiful, but empty. In the others, eggs and darker snails are visible.

When I watch these, I can see movement, but it is so slow that I wonder if it was just my imagination, or my eyes getting tired. But I go away and come back half an hour later, and the babies are in different positions.

Day before yesterday. Compare the positions of the snails and remaining yellow eggs (or yolks?).

Yesterday. There are more dark snails, and they've moved about quite a bit.

And I continue to check on them every hour or so. At the last check, one of the lower cases had a crack in the pointed tip.

While we wait, here are the propective parents:

Mike, on sea lettuce in a bowl.

Tillie, stretching the surface of the water.

Now there's a third snail, the same species, in the tank; slightly smaller, very clean. A youngster. He/she has shown great interest in the egg laying activity, hanging around an inch away, but never attempting to take part. Nor does s/he attempt to mate with either of the other two. It makes me wonder; are these snails monogamous?

So many questions!

Jugs full of eggs

Two years ago, in April* of 2012, I brought home a clamshell that contained, under a crowded community of snails, hermits, worms, and more, a set of little brownish jug-like things. Eventually, commenters identified them, tentatively, as Murex snail egg cases, possibly trophon snails.

"Jugs" Photo from 2012.

And now, the mystery is solved! Yes, they are trophon eggs.

Remember the two-toned trophon snail that has been eating barnacles in my tank? I brought her** home a companion from our last trip to the beach; another trophon, slightly smaller.

For several days, they've been circling each other, warily, approaching then backing off. Neither showed an inclination to bury themselves in the sand, or eat another barnacle. Today, only the newcomer was visible, though, until Laurie found the other hidden behind an abalone shell in the back of the tank in the evening. She was busy; laying eggs, in a sort of grid pattern stuck to the glass.

After an hour or so, the newcomer joined her. She stuck herself to Snail #1's shell and waited until she had finished.

I rigged up some lighting, and a mirror behind the tank, and took their photo in the mirror, since I couldn't even get the camera into the small space.

More "jugs", with their bottoms glued to the glass, facing us.

Snail #1 is finished, now. She's moved to the bottom. She looks skinny, as if the shell were now too big for her. Snail #2 is twisting herself around beside the egg cases; getting ready to lay her own, maybe?

*It looks like April is the egg-laying month for these snails.

** I wrote then, "*Most snails are hermaphrodites, but these ones have separate sexes. I don't like calling a conscious critter an "it", so I've opted for calling this guy a male." I guessed wrong. She's definitely female!***

***She needs a name. I can't keep saying Snail #1, #2.

Testing a new lens

I took my new 85 mm lens (AF-S Nikkor 85mm f/1.8G) out for a walk yesterday: around the yard, over to the neighbours' gardens, and across the street to the vacant lot. I came home very happy with it, and am even happier now that I've seen the results on the computer.

First, I took only one shot at some subjects, and almost all of those photos turned out fine. Where I took three photos, I had trouble choosing which worked out better; only a very few were total duds.

Next, I stood at the edge of a garden and took photos of daffodils several meters away, and the flies perched on them turned out in focus. No need to trample a neighbour's flower bed.

The vacant lot was soggy and muddy; I had trouble finding secure places to stand; I didn't dare get down on my knees to get photos of critters, nor even bend over to shoot, for fear of losing my balance. I took photos through several inches of muddy water, and the ground underneath turned out nice and clear.

I turned over a board with my foot, and shot the underside, from a standing position. Here's what I found.

Centipedes, pill bugs, and a tiny blue-headed snail.

The lens is fast, and without the need to crawl in close, I could get the centipedes before they ran off. And get them in focus, too. I took three photos of this group of wood bugs; all three turned out ok.

Large egg case. The shadow turned out a bit noisy.

On the mud where the board had been. The cluster of eggs glowed a true lime-green. I don't know what laid them.

Egg case, in a pale yellow web.

There were a few miniature red ants running on one end of the board, so tiny I had to bend over to see them. The camera did get them, but barely.

More test shots tomorrow, maybe the water pics.

Collecting the eggs

"The time has come, the walrus said ..."  to put together what I've learned about my mystery critters.

A group removed from the clamshell

A single capsule

I was confused by these, but Brine Queen gave me the clues I needed. These are egg cases of an intertidal snail, and the tiny one seen near the exit at the top of one was probably a hatchling.

It's very tiny, but looks like a trophon, possibly Boreotrophon orpheus. At maturity, it would be about an inch long. This one is only a few millimetres.

We narrowed the family of snails down to Muricidae, the rock snails, or murex snails. These are predatory snails, and include our common whelks, and the trophons, like the ones that ate their way through my aquarium a year or so ago.

Muricids lay eggs in protective corneous capsules the size and shape of which vary with the species. Out of these capsules the crawling juveniles, or more rarely planktonic larvae, hatch. (From Wikipedia)

There was an adult whelk in the clamshell. It wasn't the egg layer, though.

Websites or books that include photos of egg capsules along with the adult snails are few and far between, but we found a few similar to the clamshell sample. None were quite a match.

We have often seen the egg cases of the common whelk, the dogwinkle.

Whelk eggs, found on the White Rock beach last spring.

Several snails that occur locally have the curved, "winged" shape: the Oregon triton,

Image from WallaWalla.edu

the Leafy hornmouth,

From Asnailsodyssey, with whelk eggs on the left.

Pteropurpura trialata (this is from California; I don't know if it comes this far north),

From Wikipedia

These are all similar, and obviously related, but they are more pointed than ours. And I have never seen any of these snails around here. So I'm tentatively sticking with the corded trophon, B. orpheus.

In this context, this afternoon we were back on the same beach, at low tide. We didn't go as far out as we had when I found the clamshell, but close. Among the trillions of mud snails, I found a different one, another Muricid:

A sculptured rocksnail, Ocinebrina interfossa, almost adult size. 

Bottom side, showing orange flesh.

This is the first of these that I have seen. Another species to look for, and someday, to find eggs for.

I was wrong, and I'm happy!

Another episode in the "Why I Love Blogging" series.

People are so helpful! See the comments on yesterday's post. Thanks to Kate and her daughter, Brine Queen, I've been corrected and steered in the right direction; the critters weren't tunicates at all, but egg cases. .

I'm still searching through hundreds of pages, looking for a good ID, and my eyes are giving out. Details tomorrow, and, I hope, a name for the parent snail.

Baby whelks, dressed in pink and cream.

Spring and small critters go together. So, on a warm spring day, so warm I regretted bringing a jacket, and with a low, low tide providing access to the barnacled rocks southeast of Kwomais Point, we spent a couple of hours peering into cracks and crouching to examine anemones and starfish.

Laurie and I made our finds at the same time, on separate rocks. These are Laurie's:

Whelk egg cases.

Zooming in. Each case has several to many eggs inside.

One of the whelks, a wrinkled dogwinkle. We found many of these, all along this stretch of shore, all beautiful, all different, from solid white to solid orange, or striped in many colours.

I'm still trying to identify the animals I found. I'll post them tomorrow.