Sea star art

  

Close-up of the upper surface of a Bat Star (Patiria miniata).  Those are papulae (in purple) among clusters of spines (in pink).  (Papulae are finger-like projections for gas exchange). 

September star

  

Nice view of a Forbes' Sea Star (Asterias forbesi) in a shallow tidepool in Scituate, Massachusetts, on 20 September 2025.

Eric was able to zoom in for an amazing closeup, too:

 

 

Visible above are short white calcareous spines, the orange madreporite (sometimes called a sieve plate, which is an opening to the water vascular system), and the transparent papulae (finger-like projections involved in gas exchange).  

Thanks for the great photos, Eric!
 

Little one

  

A tiny Six-armed Sea Star (Leptasterias sp.) photographed in Mendocino County on 31 May 2025.  This juvenile sea star was only ~3-4 mm across from arm tip to arm tip.  

If you look carefully, you can see some of its tube feet extending away from its arms.  And the small red eye spots at the tips of the three arms in the foreground are also visible. 

Rather than releasing eggs into the water column, Leptasterias broods its embryos and the young sea stars crawl away from the adult.  Back in 2012, I shared photos of an adult Leptasterias with its brood of embryos and an image of an adult with many juveniles in the surrounding area (it's likely the juveniles recently crawled away from the adult).  To review those photos, check out the post called "Four brooders in one" on 29 February 2012.

P.S.  Thanks for the great photo, Eric! 

Twinkle, twinkle

  

Juvenile Short-spined Sea Star (Pisaster brevispinus) photographed in late December 2024.  This individual was only ~20 mm across (arm tip to arm tip).

Winter star

  

Juvenile Ochre Sea Star (Pisaster ochraceus), about 6 mm across, on 30 December 2024

Pinky

  

Okay, this isn't a recent photo, but I've been busy working on a presentation about sea stars...so here you go!  A young Short-spined Sea Star (Pisaster brevispinus), photographed on 23 May 2015.

Reaching

 

 

Leather Stars (Dermasterias imbricata) haven't been common in our area during the last few years, so it was nice to catch up with a few this past week.

Octiria?

  

Yes, you saw that right.  This Bat Star (Patiria miniata) has eight arms!  They typically have five.  We've seen them with six, and once we found one with seven arms (see "7 for the 7th" on 7 March 2017).  This is the first Bat Star we've seen with 8 arms.  (Just for fun, we've been calling it "Octiria" instead of Patiria.)

Many thanks to Sam for spotting this unusual specimen and sharing this great photo!

P.S.  For the record, we've also found an 8-armed Ochre Sea Star (Pisaster ochraceus) — see "Octoaster?" on 29 April 2020.

Little Henry

  

Eric's sharp eyes spotted this juvenile Dwarf Mottled Henricia (Henricia pumila) yesterday, 12 June 2021.  We were excited to see it because this species of sea star has been absent from Bodega Head (local populations were likely impacted by a harmful algal bloom back in 2011).  [We've observed Henricia at sites to the north and south, but not in Sonoma County in quite a few years.]  This individual was only ~5-7 mm across.  We hope there are more out there!  

P.S.  Our nickname for Henricia is "Henry," hence the title of this post.

Feet first?

  

Although you might have heard that sea stars use their tube feet to grab hold of mussels and to pull the two valves open slightly (enough to insert their stomach inside the shell), you don't always get to see the tube feet in action.  

Often the sea star is hunched up over the mussel, so it's hard to see what's going on.  In this case, the Ochre Sea Star (Pisaster ochraceus) is pulling on a very large mussel and it hasn't yet moved into a position where the tube feet are hard to see.

Here's an even closer view: 

 

 

Impressive!

 

One extra

  

Whew!  It's been a busy week.  Sorry for the lack of posts!  Here's a photo from field work this evening.  You might remember that we've been monitoring local sea star populations since 2013.  Tonight Eric spotted this juvenile Ochre Sea Star (Pisaster ochraceus) with six arms (they usually have five).  We occasionally see six-armed adults, but we haven't seen that many juveniles with this configuration.  This individual was ~2.5 cm (~1 inch) across.

 

Wishing on a star

Maybe I keep thinking about stars recently because I've been hoping and hoping that the night skies would be clear enough to see Comet NEOWISE.  Have you seen it?

No luck here yet, but below is a juvenile Ochre Sea Star (Pisaster ochraceus) photographed a couple of days ago.

 

Octoaster?

Many of you are probably familiar with the common intertidal sea star in this area, the Ochre Sea Star (Pisaster ochraceus).  Ochre Sea Stars typically have five arms (or rays).  From time to time you might come across one with six arms, but we hadn't encountered an individual with eight arms (!) until Eric spotted this one.  Because this is a rare occurrence, we thought it would be good to document it for the record.

Here's another view showing the oral side:

 

We're still puzzling over the possible paths that could have led to an eight-armed Ochre Sea Star.

 

Like blackberry swirl

A mystery close-up for you.  Can you tell what type of organism this is?

 

The next image shows the entire animal:

 

 

Bat Star (Patiria miniata), photographed in Pacific Grove, CA.  In the first photo, the little bumpy curved purple and cream-colored pieces are spines.  Aren't they intriguing?

We were impressed with the diversity of Bat Star color morphs we saw this afternoon — red, orange, gray, brown, in various mottled combinations.

Pisaster palette

I've been busy with field surveys recently, so here's a quick photo from the rocky intertidal zone:

 

Ochre Sea Stars (Pisaster ochraceus) — in three color forms — and Giant Green Anemones (Anthopleura xanthogrammica)

 

A farewell to arms

We were at a rocky intertidal zone site in northern California this morning and started noticing Six-armed Sea Stars (Leptasterias sp.) with fewer than six arms.  Here's one with three arms:

 

We also observed many Six-armed Sea Stars that were regrowing lost arms.  Below is an example of a "comet"— an individual that has one remaining original arm (the longest), with the rest of the arms regenerating:

 

We were curious about the cause of arm loss, when Eric discovered some possible evidence:

 

This Six-armed Sea Star was being ingested by another sea star.  

And the responsible sea star was...

 

...a Leather Star (Dermasterias imbricata)! 

We found at least three examples of Leather Stars eating Six-armed Sea Stars.  In one case, the Six-armed Sea Star had been completely digested.  But in two cases, some of the Six-armed Sea Star's arms had yet to be ingested.  We're wondering if it's possible that sometimes enough of the Six-armed Sea Star survives the predation attempt and escapes to regrow the arms it has lost.

If you're not familiar with Leather Stars, here's a photo from above:

 

Although it doesn't sound like this is the first time Leather Stars have been observed eating Six-armed Sea Stars, we're not sure how common it is.  (Leather Stars often eat sea anemones as well as a variety of other prey.)

Guess who?

 

This is an extreme close-up.  Do you have any guesses about what type of animal it is?

The next photos show zoomed out views that might provide more clues. Hint: The phylum that this animal belongs to is known for being spiny.

 

Any ideas yet?  

You can see lots of small rounded spines.  Scattered among the spines are tiny claw-like pincers called pedicellariae.  The large white spot is a special structure called a madreporite (or sieve plate).

One more view before I show the entire organism:

 

Okay, here you go...and the answer is: 

 

It's a Six-armed Sea Star (Leptasterias sp.)!  It was fun to photograph close-ups of this species in the field.

I mentioned a few different structures above.  To learn more about the pincers or pedicellariae, check out these posts:

"Armed with pincers" on 5 March 2013

"A star from the depths" on 10 September 2014

"In a pinch" on 22 August 2013

And if you're interested in learning about madreporites or sieve plates, you can start with these posts:

"Spiny and groovy" on 14 June 2018

"Take five" on 7 May 2013

 

Exploring stars and waterfalls

 

Whew!  It's been a busy spring with lots of field work.  Today we were working farther north in Mendocino County.  It was nice to see this mottled sea star, Henricia sp.

I can't help showing a few more images.  We were a little salty by the time we finished several hours of work in the rocky intertidal zone.  In the photo below, can you see Eric's solution? 

 

While walking back, we noticed a little waterfall at a small pocket beach.  After some discussion, Eric decided to take a quick shower!

 

P.S.  Do you think Helly Hansen will see this and offer us a free set of rain gear?  One can only hope!  ;)

 

Broadcast news

On 28 April 2019, Barbara was exploring the rocky intertidal zone with her family.  They saw something unusual under the boulders:

 

Did you notice the bright orange patches?  

Any guesses about what it could be?

The next image will be closer and might give away part of the answer.

 

Now you can see that the bright orange patches are concentrated below upside down Ochre Sea Stars (Pisaster ochraceus).

Here's another example:

 

The bright orange patches are pools of many tiny eggs!  Ochre Sea Stars are broadcast spawners — they release their gametes into the water during the spring.  Females release eggs which tend to be orange, while males release sperm which are white.  [Unless you happen to catch a sea star spawning, you can't tell its sex from its external appearance.]  Fertilization occurs in the water and then the larvae will spend ~76-228 days in the plankton before undergoing metamorphosis and becoming juvenile sea stars.

Barbara captured some excellent footage of the sea stars shedding their gametes.  Below is a short video clip showing a female first and then a male.

Note that spawning occurs more commonly when sea stars are fully submerged under water, but Barbara documented several sea stars spawning while out of (or partially out of) water.  You don't get to see spawning sea stars very often, so I thought it would be worth including a video.  [If you're viewing this in an e-mail and can't see the video player below, click on the title of this post to go to the web page.]

Many thanks to Barbara for sharing this observation as well as her images and videos.  And thanks to Eric, also, for putting together the video clips. 

Up in arms?

 

Somehow I missed them when I was taking this picture in the field, but when I was reviewing photos, I noticed two peanut worms (Phascolosoma agassizii) extending their introverts up between the arms of this juvenile Ochre Sea Star (Pisaster ochraceus). 

The visible parts of the peanut worms are tubular and grayish with black stripes.  If you'd like to learn more about peanut worms, you can review the post called "Introducing the introvert" on 31 January 2013.