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Saturday, March 30, 2013

A delicate touch

Today I was watching a pair of ravens foraging on Salmon Creek Beach.  They were delicately picking along the drift line left behind by the receding waves.


The ravens were very focused and were spending a lot of time searching for and apparently finding quite a few small food items.  

 
At first I thought they might be eating beachhoppers.  But their method of feeding didn't match the abundance or behavior of beachhoppers.  They seemed to be picking up prey quite regularly and in a narrow search area.  If they had been feeding on beachhoppers, I would have expected them to find fewer and to be more sporadic and random in how they caught them.

Also, the ravens would lean down and pick up the food from the surface of the sand with the very tip of the bill (see next images). 


  

Unfortunately, even with binoculars, I couldn't see what they were finding.  But eventually I had been watching long enough that I was really wondering what could be so interesting to the ravens.  So I walked up to a similar tide height, knelt down, and started looking at the sand.  Here's what I saw:


Can you see the small pinkish shrimp-like animals?  It's the best I could do in the field, as most of these animals were very small (less than 1 cm long).  Below is another example.  Note also the very large dark eyes.


I didn't have much time, but decided to bring a few back to look at them under the microscope.  This is the animal that the ravens were spending so much time looking for and eating on the beach:


I'm not an expert, but I'm pretty sure this is a type of euphausiid, or krill.  The ravens were feeding on krill!  [I know there are other people out there who have a lot more experience with these crustaceans, so if you can identify the species (or genus), or tell us anything more about them, please do.]

Here's one more picture of a different individual:


And I can't resist showing a close-up of the compound eye.  Although I've known about krill for a long time, I've never looked at their eyes under a microscope until today.  Beautiful!


I'm so thankful to the ravens for leading me to the krill on the beach.  It's made me realize that there's a lot I don't know about krill in this area, so I have some research to do.  And who knew that ravens ate krill!

Friday, March 29, 2013

Wide mouth and ribbon-like muscles

Sometimes when you discover gelatinous bits washed up on the beach, it's hard to tell what animals they came from.  But other times, if you take a closer look at those mysterious bits of transparent "jelly," you might find structures that provide more clues.

Here are a few photos of a gelatinous animal we found washed up on Salmon Creek Beach on 23 March 2013.  It was roughly cylindrical and ~3 cm long. 


Under the microscope the dramatic ribbon-like muscle bands encircling the animal were quite prominent.

In the photo above, note the wide mouth near the top of the photo (see close-up below).


And the small reddish spot at the bottom of the "V" below the mouth.  I'm not 100% certain, but I think this is the brain/eye of this animal (again, see close-up in next image).


At the posterior or tail end, there was a pointed projection and a pale mass which is probably the gut.  Here are two slightly different views.



This is a type of pelagic tunicate called a salp.  Salps are much more common offshore.  They don't often wash up on beaches unless there are strong onshore winds.

Many of them are very strong swimmers, hence the well developed muscle bands.  The large slit-like mouth is the equivalent of a siphon.  It takes in water which, after passing through the body, is released out the back end.  This water current is used for jet propulsion, gas exchange, and feeding.  As the water flows through the barrel-shaped body, food is captured in sheets of mucous and ingested.

I don't have a lot of experience identifying local salps, but I think this could be Iasis zonaria.  I'll be sending out the photos for confirmation.

If you are having trouble envisioning the animal with all of these parts, here's a basic illustration with labels:

Modified from The Biology of Pelagic Tunicates (Bone 1998)
 

Reproduction in salps is somewhat complicated.  They alternate between a solitary form and an aggregate (or chain) form, and one form produces the other.  The solitary form reproduces asexually and releases a long chain of aggregates.  The aggregate form reproduces sexually; each aggregate form produces one (or a few) solitary individuals.

Earlier in March we found a solitary individual that was producing a chain.  I'm not sure if this is the same species as the one pictured above.  It's possible, but either way, it's still worth showing you what a salp chain looks like.  I hope you can make out that there are lots of tiny individuals all lined up next to each other.  If this salp hadn't washed up on the beach, eventually the chain would have been released and would have been free swimming in the ocean.


This seems to be a good time of year to find gelatinous animals on local beaches.  I'll feature a few more during the next few days.

Thursday, March 28, 2013

Delphinium

Coast Larkspur (Delphinium decorum)
flowering in the coastal prairie on Bodega Head on 28 March 2013


Here's a close-up of this beautiful early spring wildflower.  Unfortunately, they're rare on Bodega Head.  This species is a California endemic (it's not found outside of the state).


Tonight I read in The Jepson Manual account that the genus, Delphinium, comes from the Latin for dolphin, and is named after the shape of the bud.  I was a little puzzled by this, so I checked a few photos to look at the buds.

Here's one from today (see below).  I'm not quite seeing "dolphin" here.  (Maybe tadpole.)  Are you?


But if the buds are dolphin-like, and a group of dolphins is called a pod, is the next image a pod of Delphinium buds?


Okay, seriously, if someone out there does know how to see a dolphin in a Delphinium bud, I'd love to hear more about it.


P.S.  If you were intrigued by the worm last night, after receiving a little more information I included an addendum to that post.

Wednesday, March 27, 2013

Full Worm Moon

Earlier this month I looked at the calendar and noticed that the full moon this morning (on March 27th) was called a Full Worm Moon.  Although the name originates from earthworms becoming active at this time of year, below is one of my most recent worm stories.

I was looking through a microscope at a small piece of a kelp holdfast (from Salmon Creek Beach) and noticed a very long, slender orange-colored worm crawling along.


The worm just kept going and going and going...it was like watching a train go by...and I just kept seeing orange and orange and more orange.  And then all of a sudden the tail end of the worm appeared and it was...

 
...purple!  A beautiful pale purple!


Here's a close-up of the tail end outstretched:


And one more, even closer.  There was a neat squiggly pattern on the very tip that somehow reminded me of rattlesnake's tail.

  
This worm was very fast moving, so I had some trouble taking pictures of it.  Here's the only image I managed to get of the head.


Sadly, I'm not sure which species this is.  I'll be asking around for some help with the identification. If you have any thoughts about it, I'd be grateful for any assistance.


ADDENDUM (28 March 2013): Leslie Harris from the Natural History Museum of Los Angeles County wrote that this worm belongs to the Family Syllidae.  In addition, she notes:

"The pink tail is packed full of eggs & developing into an epitoke.  At some point that section will produce a pair of eyes, drop the normal setae & produce specialized setae with oar-shaped blades, then break away from the parent in order to swim up to the surface to spawn.  The "rattles" are the margins of the digestive tract seen through the skin."  

Thanks, Leslie!

We had wondered whether the tail end was developing into an epitoke, but I didn't want to assume anything without knowing more about the species involved.  As you can see from Leslie's description, an epitoke is basically a swimming stage of a polychaete worm that is capable of sexual reproduction — it will release eggs or sperm (depending on whether it's a female or male).  Epitokes often form synchronized swarms that are coordinated with lunar cycles.  Swarming is thought to increase the chances that eggs will be fertilized.

Tuesday, March 26, 2013

Rock slides and rugged reefs

After seeing the Surfbird photos last night, Peter Connors kindly sent a few images of rocks he collected from Surfbird nesting habitat in Alaska!  It's wonderful to see these rocks (and the lichens growing on them), as it allows you to envision Surfbirds in breeding plumage nestled among the colors of that northern landscape: blacks, grays, whites, and rusty orange.  (The colors that the Surfbirds are acquiring now will enhance their ability to blend in with the backdrop of their breeding grounds.)

Here's a photo of the rocks alone:


And one with a small owl sculpture (~5 cm tall) for scale:


About the rocks, Peter says:  "I collected them and backpacked them out over the mountains to a small lake where we had arranged to be picked up in a float plane.  The mountains are just north of the Yukon River delta, almost to the Bering seacoast.  It is the only place I have ever encountered nesting Surfbirds."

Although native Alaskans suspected that Surfbirds nested away from the coast, the first Surfbird nest wasn't formally documented until 1926.  Here's a quote from the article in which Joseph Dixon published a description of the long sought-after nest (From Dixon, J. 1927. The Surf-Bird's Secret. Condor 29: 3-16):


"One of the most striking things about the Surf-bird is the remarkable difference between its winter and summer habitat.  Near the end of their northward migration in the spring these birds abandon the sea coast and take up their summer residence far in the interior, from 300 to 500 miles from salt water.  This involves a great altitudinal shift.  Instead of living at sea level as they do at other seasons, during nesting time they are to be found on barren, rocky mountains high up above timber line.  During the entire summer we never found these birds below 4000 feet elevation...

The rocky character of the Surf-birds' surroundings appears to remain fairly constant throughout the year.  In summer the birds are to be found most frequently near the summits of the rock slides where the broken rocks are much the same as the rugged reefs they inhabit during the winter."

 
I love that Surfbirds link the rocky shores of Bodega Head with the interior mountain slopes of Alaska!


Here are a few more Surfbird images from this past weekend.  I cropped the images closely so you can compare the colors and patterns of the feathers with the rocks above.




Monday, March 25, 2013

Molting

Just a few pictures from 24 March 2013 highlighting Surfbirds (Aphriza virgata) molting into breeding plumage.  Look for their new scapular feathers in the shoulder region.  

After looking gray throughout the winter, Surfbirds are now replacing their feathers with more colorful versions in preparation for the breeding season.  They haven't replaced all of them yet, so you'll see a combination of old and new feathers in these birds.  The new feathers look much "neater" and less worn.  Although variable among individual birds, many of the new feathers are black or dark gray with pale fringes, but some have very pretty rufous spots or blotches.




It's nice to see the Surfbirds getting dressed up for the breeding season!  (Remember that they'll be heading north to nest in the mountains of Alaska and the Yukon.  Most of them will depart the Bodega Bay region by the end of April.)

Sunday, March 24, 2013

Like a fine Oriental rug

During a quick walk through the Bodega Dunes campground this afternoon, I was pleasantly surprised to see this little butterfly flutter down on to the sunlit vegetation in front of me.  I only managed a few distant photos before it took off again, but here's one for the record:


This is a Western Pine Elfin (Incisalia eryphon).  In A Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, Art Shapiro and Tim Manolis describe the pattern on the underside of the hindwing as "reminiscent of a fine Oriental rug."

It's too bad these butterflies are on the small side — with a wingspan of about 1 inch (2.5 cm) across.  Otherwise, I think they'd get a lot more attention.  Next time you see a brownish butterfly land near a pine, you might want to take a closer look!

Western Pine Elfins are spring fliers.  Watch for them between March and June.

Saturday, March 23, 2013

Morning song

Bird song has increased noticeably during the mornings in the last few weeks.  Yesterday I recorded this species outside of our house in Sebastopol.  Although small in size, it's known for its loud and complex song.  Do you recognize it?

(To see the audio files, click on the title of the post above to go directly to the web page.)


pawr2 by nhbh


This is a Pacific Wren (Troglodytes pacificus).  Here's another clip.  This time the wren sings twice with about a 12-second pause in between.

pawr3 by nhbh


In the next recording the wren sings twice again, but with only a very slight pause in between...and note that a Brown Creeper sings during the pause!

pawr by nhbh


Last September, I took a few photos of a Pacific Wren in Owl Canyon on Bodega Head.  So you can visualize the singer of the songs above, one of those photos is below.


To review the post from the fall and to learn a little more about Pacific Wrens, click here

Friday, March 22, 2013

How many?

A few days ago on 19 March 2013, the ocean was extremely calm and the light was very gray.  Looking offshore from Bodega Head, there were scattered dark patches that looked like rafts of drifting kelp at first glance.


Upon closer inspection, these were large flocks of Eared Grebes (Podiceps nigricollis).

To prove it, here's a zoomed in view of a smaller group, with a few individuals that were starting to dive.  (Entire flocks often submerge at the same time.)



But returning to the first flock. I'm wondering how many birds were in this flock.  It seemed like a large number.  What do you think?  Do you have an estimate?  


If you're up to this challenge, here are two additional pictures that might make it easier to see individual birds — the first showing the left side of the flock, and the second showing the right (note the same piece of kelp floating in front of the flock in both photos).  

I haven't actually tried to count yet (although now I may be counting grebes as I go to sleep)...but let me know if you come up with a number!  (Warning: My estimate is below these photos.)



ADDENDUM (24 March 2013): If you're wondering and would like to compare, I did a quick estimate and came up with 1055 grebes!

Thursday, March 21, 2013

The ensnaring predator

Last night I introduced the unusual hydroid, Candelabrum fritchmanii.  Tonight I promised to share a little more about its remarkable feeding behavior.

It may be hard to tell from the photographs, but this hydroid can change shape dramatically.  Sometimes it contracts and may only be ~5 mm long, but other times it elongates and becomes very slender and vermiform (worm-like), up to ~30 mm long.

When it's extended, the hydroid polyp acts as a "sensitive contractile snare" (Hewitt and Goddard 2001).  It's deceiving, because at first it just looks like a soft, pink "worm" waving around slowly.  But remember that this hydroid is completely covered with stinging tentacles.  Each tentacle tip is loaded with harpoon-like nematocysts that will discharge upon contact with prey.

What we didn't appreciate at first was just how fast the polyp would react to prey.  We read that Candelabrum eats small amphipods and isopods.  [Amphipods and isopods are small shrimp-like crustaceans.]  So we innocently placed an amphipod nearby (Sorry, Rebecca!). 

The polyp wrapped around the prey so quickly that we could only see a blur of coils and tentacles.  In the next image, you can barely see the blue-gray amphipod at the lower edge of the hydroid's coils.



The tentacles became elevated and started flicking rapidly (sometimes in small waves), in contrast to how they mostly lie flat against the body at other times.


The hydroid then began to engulf the amphipod whole.  (This amphipod was ~4 mm long.)  The body wall of the hydroid is partially transparent so you can see the amphipod even though it's now inside the hydroid.  Look for the dark black eye of the amphipod.



The hydroid repositioned the amphipod so that it was narrow-end down and then started to swallow it.




Through some intense contractions, the hydroid moved the amphipod towards the base of the polyp.  Here are two more pictures, one with the amphipod about mid-way down and then another when it's near the bottom. 



This is Candelabrum with its "belly full."


When Candelabrum is in a resting position, it's hard to imagine the extensible serpent-like coils and the sudden ferocity of this extraordinary predator!

Wednesday, March 20, 2013

Candelabrum

During the past week Eric and I have had a remarkable experience with an amazing marine invertebrate.  Between us, we have nearly 50 years of experience with this group of animals (yikes, are we that old?!).  But on Sunday we found ourselves looking at a marine invertebrate that we couldn't even place in a phylum at first.  We would look at the animal, and then at each other, and then at the animal again...then we'd shake our heads...and then we'd start all over again.  

We found this animal in a kelp holdfast washed up on Salmon Creek Beach on 17 March 2013.  I didn't take any pictures in the field, because it didn't look like much at the time.  But here's one of the first photos under the microscope.  This part of the animal was ~1 cm long.


A closer view highlights the luminous array of tentacles covering the surface:


The base of the animal was quite puzzling (see below).  It makes more sense now that we know what it is, but initially we had a hard time identifying the different structures.  I'll let you see it as we did, before revealing the names of things.  The animal is attached to the kelp at the top of the image, but all of the other "alien" structures in the picture belong to the animal.


The next photograph shows the entire animal all at once. 


In the end, we decided this might be a cnidarian, related to sea anemones, corals, hydroids, and jellyfish.  So we sent the photographs off to a few experts.  Luckily, it turned out that one of them had described this species in 2001.  Thanks, Jeff, for helping us out!

This is a very unusual hydroid called Candelabrum fritchmanii.  It's only the second time this species has been recorded in California!  And the first time was by Cadet Hand, the founding director of the Bodega Marine Laboratory.  (He and Frank Gwilliam found three individuals in San Mateo County on a single day in 1950.)  Otherwise, it's only known from two sites in Oregon, so this is a rarely seen invertebrate.

To make it easier to understand, here's a diagram with the various parts labeled.   

Modified from The Light & Smith Manual 2007


- The tall column is a mature polyp covered with capitate (globose) tentacles.  There is a mouth at the tip, but it's not visible in the photographs.

- The hydroid colony is attached to the substrate with tentacles at the base.

- The small, rounded, bud-like structures close to the base are gonophores — reproductive structures that will produce gametes.

- The small column is an immature polyp.  Below is a close-up and an illustration of a young polyp.   


Modified from Hewitt, C.L. and J.H.R. Goddard.  2001.  A new species of large and highly contractile hydroid in the genus Candelabrum (Hydrozoa: Anthoathecatae) from southern Oregon, U.S.A.  Can. J. Zool. 79: 2280-2288.

 
Not only is the form and appearance of this hydroid unexpected, but the behavior is even more so.  It's a highly active ensnaring predator.  More on that tomorrow night!

We feel very fortunate and humbled to have encountered such a rare and fascinating invertebrate and are excited to introduce you to Candelabrum.