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Friday, February 28, 2014

It's in the details


Sometimes I just can't help it.  This is an extreme closeup of a common marine species.  It ends up looking very abstract at this magnification, but I'm drawn in by these detailed views and I'm tempted to share the wonder and beauty of them.

The pale lavender points are short spines.  The smooth, transparent structures are papulae (used for respiration).  And the tiny beak-like jaws (some are open, some are closed) are pedicellariae.

Any guesses yet?

Another hint is the dark brown pentagon shape near the center of the photograph.  This is a clue that the animal has five-part radial symmetry.

If you scan the image above very closely there's another structure that may help you identify this animal.  It's pale yellow and has a few lines crossing through it — in this case, some of the lines form a Y-shape (at least to my eye).

I've circled this structure in the image below:

  
That's a madreporite or a sieve plate, through which water can be pulled in to be used in a water vascular system.

Okay, here's the entire animal:


It's a juvenile Ochre Sea Star (Pisaster ochraceus).  This is another animal that we encountered in a Bull Kelp holdfast not too long ago.  It was only ~12-14 mm across.

Thursday, February 27, 2014

Different mates

In January I mentioned that there is male parental care in sea spiders.  Here are a few pictures to continue that story.

This is Pycnogonum stearnsi, a common local sea spider often associated with sea anemones.  Its legs are pulled in, and it's "hiding" a large mass of fertilized eggsthe white mass barely visible below the sea spider.  Males have specialized legs (ovigers) for carrying the developing embryos.  [For orientation, the anterior or head end (note the brown eyes) is pointing towards the top of the image.]


Viewed from below you can see the impressive number of embryos.  And if you look very carefully, you should be able to see something else that's notable.  Not all of the embryos are alike!



It may help if I zoom in.  (And remember that you can click on the picture for a larger version.)



Can you see that there are two different masses of embryos, in different developmental stages?  The uppermost embryos have reddish spots and are more mature...while the lowermost embryos are pure white, lack those spots, and are younger.

Here's an even closer view of the uppermost embryos (below).  The reddish spots are eyespots.


Male sea spiders often gather different egg masses from multiple females.  It's possible that the two egg masses are from the same female, but in a study done where they tested this (extensively), it was much more likely that different egg masses carried by one male were from different mates.  (The egg masses could be from up to 4 different females, but more often they were from 1-3 females.)

The males will carry the embryos for 1-2 months until the larvae hatch.

Facts above from:  Barreto, F.S. and J.C. Avise. 2010. Quantitative measures of sexual selection reveal no evidence for sex-role reversal in a sea spider with prolonged paternal care.  Proc. R. Soc. B 277: 2951-2956.

Wednesday, February 26, 2014

Fairies of the holdfast


When we found these tiny pink brittle stars in a Bull Kelp holdfast recently, Eric called them "fairies of the holdfast."  Somehow it seemed like a perfect match.

I know it's hard to tell how small these animals are when there's nothing in the pictures for scale.  The individuals I'm showing in these first few images were only 5-10 mm across from arm tip to arm tip.


The smallest brittle star was the palest:



The largest was the pinkest:



Brittle stars species can vary quite a bit in overall size.  Some species are very small even as adults.  So at first I wasn't sure if these were full-size animals or not.  

When I looked under a microscope I noticed that there were lots of spines.  In the picture below, that's a small section of the brownish central disc in the lower right corner covered with tiny spines.  And that's one arm pointing to the upper left corner.  Even the dorsal arm plates and the lateral arm spines projecting out to the sides are spiny!  Although not a given, this made me suspicious that I was looking at juvenile brittle stars (rather than adults) as juvenile echinoderms are often very spiny.



While I was looking at these small brittle stars for identification clues, I was surprised to catch a glimpse of these at the tips of their arms:


Check out those hooks!  Wow!  I haven't looked at that many brittle stars under the microscope before, so I didn't know if these hooks were common.

We scanned a few books and I couldn't find a species description that mentioned these hooks until once again Philip Lambert (and William Austin) came to the rescue.  In their book, Brittle Stars, Sea Urchins and Feather Stars of British Columbia, Southeast Alaska and Puget Sound (1997) they describe hooks like this for the Daisy Brittle Star (Ophiopholus kennerlyi).  

Well, I am familiar with Daisy Brittle Stars as adults, but I hadn't identified juveniles before.  But it so happens that we had also found an adult Daisy Brittle Star on the same day.  I wondered if I could find the hooks on the adult.


The adult was very active...and the hooks were hard to see...but there they were!  Look closely to see them in the photo above.  They're adjacent and just to the left of each tubefoot.  (Yes, the tubefeet are papillated in brittle stars.)

I had lots of questions after that...I was hooked!  How do the brittle stars use these hooks?  For grasping the substrate?  Are they more important for juveniles than for adults?  Are they an adaptation for wave-swept environments?  Do the hooks play any role in capturing prey (as they do in basket stars)?  Could the hooks be used in defense?

I posted about adult Daisy Brittle Stars last February, so you can review those pictures here.  And if you'd like to see a closeup of the adult from this year, the following is an exceptional view of its central disc.  And now we know that Daisy Brittle Stars start out pale pink and brown and gradually transition to having a highly patterned disc and arms!


Tuesday, February 25, 2014

At the end of the trail

Do you have a guess about what kind of animal made this trail on the beach?


I almost walked by...but then I stopped and gently probed one end of the trail.  


Here's another clue.  It's an extreme closeup taken under the microscope:


Those black spots with gold flecks are eyes looking to the left.  (But the eyes look different at this stage than they do later in the life of this animal.)


This next image will give it away:


The trail was made by a tiny Mole Crab (Emerita analoga)!  There were several of them scattered along the beach on 24 February 2014.  These crabs had a carapace length of only ~4-5 mm, which means they settled out from the plankton not too long ago.

Here's one more view (below).  Watch for these meandering trails and new Mole Crab recruits at a sandy beach near you!

 
P.S.  For a picture of an adult Mole Crab and a little more information about them, see the post from 25 February 2012.

Monday, February 24, 2014

Mystery cucumber

On 14 December 2013, I posted pictures of an interesting sea cucumber that I identified as a Stiff-footed Sea Cucumber (Eupentacta quinquesemita).  But now I think that identification was wrong.

Recently, in a Bull Kelp holdfast, we found two more sea cucumbers that looked similar.  This time one of them was extending its feeding tentacles, so I placed it under a microscope to document the tentacles (the first one kept its tentacles hidden).

Here's a view of this cucumber and its exquisite tentacles:




Of course, the dendritic form of the tentacles and the silvery ossicles are beautiful.  But did you happen to notice the dark brown pigment spots?  When I saw those, I became concerned about my original identification because I hadn't seen that coloration described for Eupentacta.

So I embarked on a journey to find out if this could be a different species of sea cucumber.  I couldn't really find a species description that matched this color pattern.  So we decided to look at the shape of the ossicles which is useful for sea cucumber identifications.

The ossicles are the tiny calcified plates visible in the tubefeet, body wall, and tentacles.  They're what make this sea cucumber look so sparkly.



Here's what we found when we looked at the ossicles under a high power microscope.  This is a selection showing a variety of shapes from a tubefoot.



And we had one ossicle photograph from December, too:



Well, these ossicles aren't a match for Eupentacta.  And the closest match we can find is for a sea cucumber called Pentamera trachyplaca.  For comparison, here's an illustration of the ossicles of Pentamera trachyplaca:

Modified from  
Sea Cucumbers of British Columbia, Southeast Alaska and Puget Sound by Philip Lambert (1997).  
Scale bar = 0.1 mm

 
Interestingly, Pentamera trachyplaca has only been recorded from a few locations: British Columbia, Monterey, and Santa Cruz Island.  So we'll need to confirm that this is the species we've found.  If so, it may be an unusual record for northern California.  We'll report back! 

Sunday, February 23, 2014

So many songs

Remember the Marsh Wren photos from early January?  (If not, this is one of them and you can review others here.)



Last week I recorded a Marsh Wren singing just before dark.  Below is an audio file so you can hear its complex song sequence. 

A single Marsh Wren song only lasts 1-2 seconds.  But an individual Marsh Wren has a very large song repertoire and may sing over 100 different song types.  And they often sing one song after another after another.  According to the Birds of North America account, the highest rate of singing is about 20 songs per minute.

If you're not familiar with it, a Marsh Wren song might sound a little unusual at first.  It's made up of short notes and buzzy trills and squeaks and gurgles.  And each time the wren sings it puts all of those components together in a different way.

When you listen to this recording, there are a few different things you can do.  Appreciate the diversity of Marsh Wren songs.  Count the total number of songs in the recording.  Choose your favorite song.  And listen to see if you think any of the songs repeat.  (This is like trying to find two snowflakes that look alike!).  Remember to turn up your volume.  I found it easier to appreciate these songs by closing my eyes when listening to them.


mawr by nhbh


I counted fourteen songs during this minute and a half recording.  I didn't hear any songs that repeated, but it was challenging to know for sure.  Later I read that Marsh Wrens might not repeat a song until after 5-6 minutes have gone by, so it's probably not surprising that there aren't any repeat songs in this short recording.  It's interesting to wonder about why Marsh Wrens sing so many different songs!
  

Saturday, February 22, 2014

Fish for dinner?


Forster's Tern (Sterna forsteri) photographed in a dive just before entering the water in Bodega Harbor, 22 February 2014.

This picture was a bit of a mistake.  Sadly, I'm having problems with my camera.  I was doing some tests, taking some random shots here and there, without thinking that any of them would result in images that I would keep.  

But when I looked at this one it was interesting enough that I thought I'd show it to you.  I like the dramatic swept-back wings of the tern...and how you can feel the intense focus of the bird...and how you wouldn't want to be the object of its attention!

It also made me wonder about what type of fish Forster's Terns eat.  Do you know?  

I found one article published in Western Birds in 1979 that described the prey of Caspian Terns and Forster's Terns in Elkhorn Slough (Monterey County):

Baltz, D. M., G. V. Morejohn, and B. S. Antrim. 1979. Size selective predation and food habits of two California terns. Western Birds 10:17-24.

The authors documented Forster's Terns eating Shiner Perch (Cymatogaster aggregata), Northern Anchovy (Engraulis mordax), Night Smelt (Spirinchus starksi), Topsmelt (Atherinops affinis), Arrow Goby (Clevelandia ios), and other unidentified gobies.

I wonder if they're eating similar species in Bodega Harbor?

Friday, February 21, 2014

Feed your head


Bet you didn't expect to see that!  ;)  


These are the wonderful, swirling, medusa-like tentacles of a terebellid worm, also known as a spaghetti worm.  It's another species that we found recently in a Bull Kelp holdfast.

Here's a picture of the entire animal with its tentacles extended outward:


Whenever I see a terebellid worm like this, I think of the phrase, "Feed your head."  I know that sounds strange, but it comes from a few summers ago when one of Eric's students created a music video with a terebellid worm and Jefferson Airplane's song White Rabbit (Nice job, Zander!).  It was an excellent match, as the video footage of the worm's frenzied tentacles began to crescendo and peaked with the song's lyrics, "Remember what the dormouse said...Feed your head...Feed your head!"

And indeed, one of functions of the tentacles is to pull in food particles.

Below is a closeup of the tentacles.  If you look carefully, you should be able to see that the tentacles are grooved and ciliated.  The cilia move food particles from the distal ends of the tentacle tips along the grooves towards the mouth at the base of the tentacles.  (The cilia show up as bright shiny highlights in the image.)


The tentacles are also used for gathering materials for tube building.  And sometimes they help with locomotion.  

In the next image, look for the tentacles that are expanded or flattened (they're broader than the others).  The worm appeared to be using them as anchors.  It would pull itself along in the direction of these "anchor tentacles" to shift into a new position.  Doing this over and over (anchoring, pulling, anchoring, pulling) allowed the worm to cover substantial distances fairly quickly.



Although you can probably tell that I just love this worm's tentacles, here's a view of its body, too.  It was generally bright red, with a bit of pink and yellow mixed in.  We'll be consulting with experts about the specific identification. 



P.S.  If you were wondering, the red color in the tentacles is due to hemoglobin which aids in gas exchange.

Thursday, February 20, 2014

Recruits

 
A beautiful Purple Sea Urchin (Strongylocentrotus purpuratus) recruit, ~3 mm across (photographed under a microscope).  We found four individuals of this size in one Bull Kelp holdfast.  Note the very long, outstretched tubefeet, and the hints of purple in the spines.

Wednesday, February 19, 2014

Subtle shades of blue

Eric has been finding some very nice chitons lately.  This individual was discovered in a Bull Kelp holdfast and was only ~1 cm long.  When photographed under a microscope the subtle shades of blue became easier to discern.

Here's a fun thing to look for in the picture below.  The head valve and tail valve are slightly different shapes, but sometimes it's hard to know which is which.  In this case, the central points on the middle valves point backwards.  So can you tell which is the head end and which is the tail end?  (Answer below the picture.)


(The head valve is on the right and the tail valve is on the left.)



To appreciate some of the colors and patterns, the next image shows a close-up of the middle valves (click on the image for a large version):



The photograph below shows a close-up of the edge of the girdle, the fleshy portion surrounding the valves:



I'm still working on the identification of this chiton.  Perhaps it's a species of Cyanoplax?  If you have any thoughts about its identity, please let me know!  
 

Tuesday, February 18, 2014

Pink clouds, purple fog


Sunset over Bodega Dunes, 18 February 2014

Monday, February 17, 2014

Three-lined


Eric and I have continued our survey of Bull Kelp holdfasts.  This nudibranch is one of the most recent discoveries. Three-lined Nudibranchs (Flabellina trilineata) are fairly common along local rocky shores, but this is the first time we've encountered one in a holdfast.  

Here's a close-up of the cephalic (head) tentacles, with white stripes and orange tips...and the rhinophores (chemosensory organs), with their wonderful spiral structure.  [When rhinophores have this shape they're formally called lamellate or perfoliate.]


I was struck by the bright orange tips to both the tentacles and the rhinophores.  Sometimes this species has orange tips, and sometimes it doesn't.

The "three lines" in both the common name and the scientific name come from the white lines running down the back and along each side of the nudibranch.  It's hard to see all three in one picture.  This view shows the dorsal (top) stripe and one of the side stripes:


While the next image shows all three: the dorsal stripe between the cerata (orange/red projections) and the two lateral stripes converging at the posterior end of the foot.


Most of the Three-lined Nudibranchs I've seen in this area have been between 1-2 cm in length and have been associated with hydroids.  When they're around, their combination of white and bright red-orange coloration is hard to miss!

Sunday, February 16, 2014

Ever elusive

Yesterday, while I was driving along the road (on Bodega Head) I noticed an animal in the distance that I couldn't quite identify at first.  I slowed down and then realized what it was.  A badger!  

I stopped the car right away and pulled over.  But the badger turned around and disappeared into the shrubs.  I didn't want to disturb it, but I was interested in seeing if it would come into view again.  There were dense shrubs along the side of the road, but open grassland just beyond the shrubs.  I wondered if the badger would head back to the grassland, so I decided to walk a wide arc around the shrubs for a better view of the grassland.  From a distance, I scanned with binoculars, but I didn't have any luck spotting the badger again.  The ever elusive badger!

While walking back to the car among the shrubs, out of the corner of my eye I noticed a large pile of dark soil.  I thought it might be badger diggings from a previous day, but it could have been something else, so I decided to take a quick look to confirm.  I walked up to it and noticed that it looked very moist and newly excavated.  And then I was surprised to see just a little bit of soil shift at the burrow entrance!  It wasn't my imagination, the soil moved!

The badger was probably down inside that burrow at that very moment.  Amazing.  Later I learned that badgers will dig burrows for all sorts of reasons that we usually think of, such as for shelter and foraging, but also for escape, and that's what I was probably seeing.  [I read that Joseph Grinnell reported that badgers can dig these escape burrows in under 2 minutes!]  

Unfortunately, it's likely that the badger was escaping from me...or at least the circumstance of being frightened or disturbed when my car approached it along the road.  I took a couple of quick pictures (below) and then left the area.



 
I encountered this newly dug badger burrow by accident.  But if I had known the badger was in the burrow at the time, I wouldn't have approached it so closely.  American Badgers are rare in California and so care should be taken not to disturb them.


P.S.  In April 2012 I posted a few other examples of badger diggings and one of the only badger photos I've taken you can review that post here.
 

Saturday, February 15, 2014

Formidable

Last night I was helping Eric wrap up some field work in the rocky intertidal zone when a Western Gull (Larus occidentalis) landed nearby.  It started walking around on the rocks and definitely looked as if it had a purpose — it was focused on finding something to eat.

A few minutes later we were both surprised to see the gull emerging from a shallow plunge-dive with an octopus!

The Western Gull flew to a ledge and dropped the octopus at its feet:


The gull then proceeded to manipulate the octopus with its bill, stabbing it, and picking it up and dropping it several times before finally swallowing it whole after about a minute and a half.

These pictures aren't greatI didn't have the right lens, and it was getting dark.  But it's an interesting behavior and I don't think you'll have any trouble appreciating this predator-prey interaction.



Pretty soon after swallowing the octopus the gull started searching for food again.  It dropped into a nearby channel and was fairly close to me so I decided to take a picture of the searching behavior as the gull swam along and scanned the rocks and crevices.



I was tracking the gull while looking through my camera and I couldn't believe it when it caught another octopus!  This was ~5 minutes after swallowing the first octopus, and ~1 minute after entering the water!



Once again, the gull flew to a nearby ledge and dropped the octopus a few times. 



And then it flew off to a more distant location.


I must admit, this was both fascinating and difficult for me to watch.  I'm so fond of octopus that it was a little hard for me to see them appearing so vulnerable.  But I also have great respect for predators and their hunting skills and their importance in food webs.  

I've heard a few other reports of gulls eating octopus, but it was interesting to see that octopus were not mentioned as food items for Western Gulls in the Birds of North America account.  The authors list many fish and other marine invertebrates (including squid), but octopus are not among the documented prey in that account.  

It made me wonder whether feeding on octopus happens occasionally among many individual gulls, or whether just a few individual gulls specialize and learn to find octopus?  Although it's a very small sample size, this particular gull seemed especially good at it!