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Saturday, February 6, 2016

Little swimmers

Remember the Purple Sea Snail (Janthina umbilicata) egg capsules?

When I took this picture, the embryos were still developing inside the capsules.  A few days later, some of the larvae emerged from the capsules as active swimming veligers.

These Janthina larvae are extremely small, and are good swimmers.  Here are two still shots (the best I could manage), but at the end of this post there's a short video clip that's much better.

View from the side:

View from above:

Mostly what you're seeing is the reddish shell and the ciliated velar lobes.  In the video, watch for the long cilia beating along the edges of the velar lobes the motion is useful for both swimming and feeding.

Note that this video was made under a microscope — it's magnified 200x!

By the way, from what we can gather, not many people have filmed Janthina larvae, so although this is a short video, you're probably one of the few people in the world to watch a swimming Purple Sea Snail veliger! 

[If you're receiving this via e-mail, click on the title of the video below to watch the clip.] 

Friday, February 5, 2016

Foamy Friday

Strong winds and waves this week have created perfect conditions for foam:

I don't know why, but I'm fascinated by the conditions that create this thick foam, as well as the movement and structure of the foam. The foam is very dynamic as it interacts with the water surging through the channels.  And it's fun to look at the foam up-close — to see the details of the differently-sized bubbles and how the bubbles fit together, change position, and reflect light:

I haven't looked into this before, but it looks like there's quite a bit of research about the complicated behavior of bubble clusters (or the physics of foam).  See here for an example from UC Berkeley.

Thursday, February 4, 2016

Following the grain

Lichens on driftwood 

(from the archives, near Salmon Creek Beach, 11 February 2012)

Wednesday, February 3, 2016

Mystery uncovered

Okay, I know you've been waiting for the answer to last night's mystery photo, so here's another hinta zoomed out version:

Perhaps you can get a sense that this is an animal with a circular shape?  In the picture above, it's mostly buried below the sand.  

Sometimes, we'd see a vaguely circular outline followed by a faint trail:

Below, I'll show the entire animal, no longer covered by sand.

So this is a warning the next photo will give away the answer:

Did you guess sand dollar (Dendraster excentricus)?  This was probably difficult, because you couldn't see much of the animal itself.  The mystery photos only revealed the outer rim with short spines and slender tube feet.  Sand dollars live partially buried in the sand where they gather and consume organic material from the sediment (deposit feeding).  In some situations, they capture food particles from the water (suspension feeding).

We saw individuals of various sizes and colors:

The smallest were less than ~1 cm across, indicating they were probably quite young (less than a year old?):

Have you been seeing sand dollars, too?  If so, we'd love to hear about it.

P.S.  For some microscope views of a small sand dollar, see the post from 12 January 2013.  And for information about sand dollar skeletons, review the post from 11 September 2012.

Tuesday, February 2, 2016

Harboring a mystery

A close-up mystery photo for you:

The next image might make it a little easier:

I'll provide the answer tomorrow night!

P.S.  These pictures were taken in Bodega Harbor on 2 February 2016.

Sunday, January 31, 2016

Gimme shelter

A gale warning was in effect todayand the ocean confirmed it!  Northwest winds were blowing at ~30 mph (25 knots), with gusts to ~40 mph (35 knots).  The marine forecast called for 11-14 foot waves, but the offshore buoy was reading 17 feet at ~5 p.m.

I could barely hold the camera steady for these pictures.

A Sanderling found shelter behind some driftwood:

Saturday, January 30, 2016

Enjoying the wind

A quick look at an adult Peregrine Falcon off Bodega Head this afternoon.  I'm not sure, but it looks like some new feathers are growing in on the right wing tip.  What do you think?