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Thursday, October 30, 2014

October colors


A couple of weeks ago, Jason and Matt mentioned they'd been seeing these nudibranchs at the Spud Point Marina docks.  I've been saving the pictures because they seemed perfect for Halloween!

This is Polycera atra.  I've seen it called a Black Dorid, or an Orange-spike Polycera.  (Halloween Nudibranch wouldn't be such a bad name either!)

Although there is a consistent color theme, individuals are variable.  In contrast to the first individual, others are quite dark see below:


The combination of black and white longitudinal stripes with yellow-orange spots is quite striking.  The next image is a close-up of one individual's head, showing the frontal veil with spiky processes and two spiraled rhinophores (sensory organs) extending upward.

 
Polycera atra feeds on Bugula, a common bryozoan growing on the docks.  Although the nudibranchs can blend in with their dark bryozoan prey, their eggs ribbons are bright white.  The easiest way to find the nudibranchs was to look for the egg ribbons and then to search for a nudibranch nearby.  [These nudibranchs were about 2 cm (3/4 inch) long.]


Happy Halloween!

Wednesday, October 29, 2014

Wedge-shaped


Common Raven (Corvus corvax) off Bodega Head, 24 October 2014

The wedge-shaped tail stands out in this classic silhouette.

Tuesday, October 28, 2014

Not quite the end

On 19 October 2014, I wondered if we'd seen the last of the live By-the-wind Sailors (Velella velella) washing ashore in 2014.  Well, I don't know if anyone else has seen others since then, but Eric and I spotted three individuals on Salmon Creek Beach on 27 October 2014.

All three were very small10, 12, and 15 mm long.  Here's one example:


Bieri (1977) proposed a growth rate for Velella of ~0.5 mm per day.  If this estimate is accurate, these individuals could be ~20-30 days old, and it's possible they're the offspring of the adults that were visible in late summer/early fall. 

So it's not quite the end of the 2014 Velella strandings yet.  Let me know if you see others washed ashore (or floating at sea)!

Monday, October 27, 2014

Elegant lines

 
After visiting the Bolinas Museum (exhibits on nudibranchs and plastic debris in the ocean) and Keith Hansen's Wildlife Gallery & Studio this weekend, we made a quick stop to admire these Northern Pintails (Anas acuta) along the shoreline of Bolinas Lagoon. 

The Birds of North America account says that pintails are ducks of "slender, elegant lines..." and it's easy to see why.

Sunday, October 26, 2014

From the south

One of the strangest things about keeping a blog is that I don't really know who's reading it or what they think of it.  It's always helpful to me to get feedback about the types of posts that people enjoy.  Recently Claudia mentioned that she liked "the blobs" on the beach.  So here's one of my favorite blobs from this summer/fall that I haven't had a chance to post yet.

These clear, gelatinous "blobs" were most often washed up singly (as below).  They were about 3 cm (a little over an inch) long.



Rarely, I found two still attached:


You probably noticed that these animals actually have a recognizable shapewith a distinct point at one end, and a wider base at the opposite end.

Although they get a little "beat up" after going through the surf zone and being tossed onto the beach (their normal habitat is the open ocean), the rest of the animal is much easier to see when placed in a small aquarium (see below).

The "pointed blob" I showed above is the swimming bell (or nectophore) of a siphonophore called Diphyes dispar.  Although not visible on the beach, in the aquarium you can see the siphonophore's tentacles.  The tentacles can be retracted inside the bell, or extended for feeding.  Compare the two photos below (this is the same individual).




Ernst Haeckel illustrated Diphyes dispar in 1888:

From: Haeckel, E. 1888. Report on the Siphonophorae - Scientific Results of the Voyage of H.M.S. Challenger during the years 1873-76, Zoology 28: 1-380.


Why was this one of my favorite "blobs" from this summer/fall?  

Well, first of all, I just love siphonophores.  If you need an introduction to them, or a review, see the posts from 23 January 2012 and 3 April 2013.

Second:  Siphonophores are challenging to identify, but I figured this one out and then received confirmation from Phil Pugh (Thanks, Phil!).  I almost second-guessed myself, because this species is not known to be common in northern California, but the teeth at the base of the nectophore are distinctive (see microscope image below):


Third: As mentioned, Diphyes dispar is a southern species.  The Light and Smith Manual (2007) says that it is, "More likely to be encountered in the southern range of this book [Point Conception], continuing down Baja California, but has worldwide distribution in warmer waters."  It's rare for this siphonophore to be in northern California, and I will always remember it as a symbol of the warm water event we experienced in 2014.

Saturday, October 25, 2014

Seeing spots

I looked through the microscope and all I saw was spots.  Bright orange spots!


I've seen lots of snail larvae, formally known as veligers, but I'd never seen one with orange spots on its velum!

Here's a closer view (below).  How many orange spots do you count?


We counted at least 13 spots.  This velum is divided into four large lobes (two on each side).  Three of the four lobes have three spots, while the fourth lobe (in the upper right corner in the photo above) has four spots. 

The next image shows the veliger and spots from a slightly different angle.  Note also the cilia along the edge of the velum.  The cilia beat very quickly to help the veliger swim.



Of course we wanted to know the identity of such an intriguing veliger.  However, we couldn't find a match in the Larval Marine Invertebrates of the Pacific Northwest or by doing quick searches online.  We have been narrowing down a possible identity in a somewhat unusual way.  

When I searched for "veliger with orange spots on velum," Google showed us a small portion of text from a book with a description that seemed to match but for which we couldn't see the species name.  Eric kept working on it and eventually figured out that the text was probably referring to a British snail known as Mangelia nebula.  Then he found a paper that described the eggs and larvae of the family of snails (the Turridae) that included this species.  The veligers of some British turrid snails (e.g., see Mangelia nebula below) look very similar to our mystery animal, with spotted velar lobes:


Modified from Lebour, M.V. 1934. The eggs and larvae of some British Turridae. Journal of the Marine Biological Association of the United Kingdom 19: 541-558 


So although we don't know for sure, our best guess right now is that this wonderful polka-dotted veliger could be some type of turrid snail.  [There are a number of turrid snails in California, so we're contacting experts to find out if this veliger could be a match for one of them.] 

To help with the identification, we also tried to get pictures of the snail's shell: 



Why does this veliger have such bright orange spots?  You might think that the orange would make it more visible to predators.  Could the spots be distracting?  Could they draw attention to the edge of the velum, rather than the shell?  Could they somehow look like surrounding particles in the water and help to camouflage the veliger?  Can you think of other reasons it might be valuable for a larval snail to have orange spots?



See below for a short video clip of this tiny snail veliger swimming:


Thursday, October 23, 2014

Not ribbon candy!


This is a little out of order, but I didn't have a chance to share this picture last week.  Do you recognize this shrub?  

I wish we had manzanita growing on Bodega Head.  This picture was taken in Yosemite.  

The red and copper-colored bark is so appealing [a-peel-ing? ;) ]!  Not having spent a lot of time studying California shrubs, it's easy to start asking questions about manzanita bark.  Why is it so red?  Why does it peel?  Why is it so smooth underneath?  I wondered if there would be something protective about these features.  

Sure enough, when I looked for a quick answer on the Internet, I found a Bay Nature article entitled, Why is manzanita bark so smooth and red?  It's worth reading, but the basic idea is that the peeling bark may help prevent things from growing on the trunk/stems...and the red color is an indicator of tannins, chemicals which taste bitter and thereby reduce herbivory.

It's the total opposite of ribbon candy, which is what these beautiful shimmery peels reminded me of when I first saw them.  Perhaps that dates me somewhat, as ribbon candy doesn't seem to be as common anymore.  It used to be shared during holiday events when I was young.