High zone explorer

  

Last week, Eric snapped a great photo of Ligia occidentalis.  You can find this interesting isopod scurrying across rocks in the high intertidal zone.

The hidden one

  

Alright, this is a little bit of a test.  Scan the image above — can you spot the isopod (an oval-shaped crustacean with a segmented body)?  Look carefully, it's a tough one! 

Okay, here's another view, a little bit more zoomed in (below).  Can you find it now?  (Hint: Look for something that doesn't look quite like sand grains.)

 

 

And now even closer — I'm sure you'll see it now!

 

 

And, because this isopod is so cool, here's a slightly different view:

 

 

Meet Tecticeps convexus!  Amazing to see how well its coloration matches the surrounding sand — black, orange, gray, white, and even pale blue!

 

It is so well camouflaged that it might still be hard to see, so here's another image without the sand.  [Note the two dark eyes and the short antennae on the head, and the large pale spots in the center and on the last segment.  You can use those features to locate the isopod in the photos above.]

 

 

 

We're so lucky that Suzanne looked down to see this isopod on the beach!  

 

Eric and I have been interested in finding this species for many years, but it probably lives mostly in the subtidal zone (so a little out of reach for biologists who spend most of their time in the intertidal zone).

 

One more extreme close-up so you can really appreciate the colors and patterns:

 

 

 

With many thanks to Suzanne for noticing Tecticeps and bringing it to our attention, and to Eric for the fantastic photos of this seldom seen species.

 

Isopod and friends

  

We've been busy doing surveys in the field during the low tides recently, but here's an isopod photo from back in February -- a Blunt-tailed Isopod (Idotea urotoma) photographed in the low intertidal zone.  

Among other things in the photo, you can see pale pink crustose coralline algae, a small iridescent snail, Lirularia sp., and a darker pink and red bryozoan (Integripelta bilabiata, formerly Eurystomella).

Looking around the corner

  

Okay, so when I've been working on the computer all day at work (it's the time of year for annual reports), one of the last things I want to do when I get home is to look at a computer! 

But here's a quick shot of Ligia pallasii — sometimes called a rock slater or a sea slater — a local isopod that lives in high rocky shore areas, especially near shaded freshwater seeps.  Photographed on Bodega Head on 2 August 2022.

Blocks of color

 

 

A fun isopod (Synidotea sp.) photographed in the low intertidal zone on 15 July 2022.  (There are two individuals in this image; the larger male is holding a smaller female underneath him.)

 

I was struck by the interesting blocks of colors.  And even more so a little while later when I was trying to photograph a cluster of sea spiders (pycnogonids).  

 

I didn't noticed it at first, but a smaller isopod with similar coloration was hidden among the hydroids and sea spiders.  Can you find the isopod in the image below?

 

 

 

The isopod is very close to the center of the image.  

 

I've circled it in the photo below.  (Its head is down and to the left side of the circle.)

 

You can see how well the various colors of the isopod blend in with the sand grains, hydroid stalks (red/brown), and scattered shell fragments.

 

 

Eye-catching

While doing field work yesterday (12 December 2020), we spotted some bright blue isopods in the intertidal zone.  Although quite small (only ~2-3 mm long), their bright coloration really made them stand out against the reddish-brown rocks:

 

 

 

We didn't have a lot of time, but we took a few photos for the record:

 

 

 

 

 

 

 

 

 

 

We think this is Dynamenella sheareri, but we are keen to learn more about them, so let us know if you've seen blue isopods like this in your area!

Up on the roof

  

Ligia pallasii, a high intertidal zone isopod.  This one was up high in a shady rock crevice.  If you look closely, you can see a very small juvenile isopod a bit below the left antenna of the adult (it has gold markings).  [You can click on the image for a larger version.]

Coralline camouflage

Did you spot the isopod clinging to the coralline algae?  Such amazing camouflage, with wonderful matching colors and patterns.  Even the segments on the isopod match the shapes of the segments on the coralline algae.

Meet Pentidotea schmitti!  I encountered a few of them in the low rocky intertidal zone recently.

Here's a view from the side.  Notice how well the leg color matches the algae:

(I think the algae is Calliarthron, but perhaps Kathy Ann will confirm or correct me if I'm wrong.)

Hidden but revealed

Here's a fun one.  Can you find the isopod hiding in this scene?

 

The isopod is very well camouflaged against the surrounding sand grains.  It's pretty much in the center of the image.

Here's a closer view:

 

Such a cool little crustacean!  I'm not sure which species this is, but it's one of the isopods in the Sphaeromatid family.  It's similar to a pill bug ("roly-poly") that you might find under a log, but this marine isopod was in a shallow sandy tidepool.

I love the little turquoise spotting at the posterior end.  And that's a neat little black-and-white design in the middle section.

P.S.  Here's a different individual from 29 June 2018.  You can see how these isopods can roll up into a "Little sphere."

 

At home under a log

During a neighborhood walk a couple of days ago, Eric peeked under a log and was surprised to see quite a gathering:

 

Arboreal Salamanders, a Sierran Treefrog, isopods, and a spider!  There must have been something special about that spot.  We gently replaced the log, but it's hard not to wonder how all of them might have been interacting.

With flare

 

Whew, it's been a little hectic lately, and I haven't had much time for working on photos.  But here's a picture of a nice little isopod.  It was hanging out in some Eelgrass earlier this fall.  Those are impressive appendages at the tail end!

On sand or rock

 

Meet Ligia occidentalis, a high intertidal isopod that can be found on sandy beaches and rocky cliffs along the Sonoma Coast. 

Recently we were appreciating how well they blend in with sand (above) as well as rock (below).  Can you spot the isopod in the next photo?  [It's the same individual in both photos.]

 

Above, the isopod is just right of center at the sand/rock interface. 

Here's a zoomed in view so you can see it a little better:

 

Watch for these intriguing isopods scurrying along the upper beach, and especially near cracks and crevices in high intertidal rocks.
 

Little sphere

 

Eric's summer students found a few intriguing isopods in the rocky intertidal zone this morning.  This one rolled up into a tight little sphere.  You can see its compound eyes and orange antennules at the top, and the last abdominal appendages — a broad pleotelson and a pair of uropods (made up of 4 curved appendages — 2 exopods and 2 endopods) at the bottom.  We believe this is a species of Gnorisphaeroma in the Sphaeromatidae family.  "Sphaero" means ball or sphere — a wonderful reference to this shape!

Down below

 

A few days ago we happened upon this little isopod crawling along a sandy beach.  

Below is another view in Eric's hand.  The isopod was ~15 mm (~0.5 inch) long.

 

Meet Alloniscus perconvexus!  [We've been calling this one "Allen" for short.  ;)]

This is a terrestrial isopod that lives on the uppermost part of the beach.  

Fun facts about Alloniscus:

• It's an air-breather.
• It's a burrower.  You might see its small mole-like burrows at the surface, but it can burrow 7.5-15 cm (3-6 inches) below the surface.
• It scavenges on beach wrack (seaweeds washed up at the high tide line) at night.
• Its pereopods (legs) are robust and adapted for burrowing:

 

This is the last view we had of Allen, burrowing head first beneath the sand: 

 

Since then I've been wondering about this little isopod's adventures.  What do you think Allen's been up to (or down to)?

Under a rock

 

Recently, Eric turned over a low intertidal cobble and noticed this interesting isopod.  It didn't seem like a familiar species, so we took a closer look.

[Isopods are crustaceans that are somewhat shrimp-like, but they are flattened dorso-ventrally, i.e., from top-to-bottom.  You might be familiar with terrestrial isopods found under woodland logs, also known as "pill bugs" or "roly-polies."]

This isopod had beautiful stripes and subtle speckling along its back:

 

Also noticeable were the white segments near the outer tips of the antennae:

 

And here's a close-up of the telson, the last abdominal segment:

 

When identifying marine isopods, the shape of the telson can be an important character.

For example, review illustrations of different species of local isopods (below).  Look at the shapes of the telsons — the tip of the telson is especially useful, e.g., how pointed it is, the angle of the edges to either side of the point, and whether the corners are rounded or squared.  Then compare the telson shapes below to the photo above.  Which species is the best match? 

Isopods of the Bodega Bay region belonging to the Family Idoteidae: (A) Pentidotea wosnesenskii, (B) Pentidotea stenops, (C) Pentidotea resecata, (D) Pentidotea aculeata, (E) Idotea urotoma.  Figure modified from the Light & Smith Manual (2007).

Did you pick Isopod E?  Yes!   We've observed the other four species previously,  but this is the first time we've documented Idotea urotoma on Bodega Head.

 

P.S.  Nice spotting, Eric!

Dynamite Dynamenella

 

Amazing, right?

How about another one? 

 

And a couple more?

 

 

We think these wonderful isopods are Dynamenella dilatata.  Eric spotted them in a Bull Kelp holdfast.  They ranged in size between 5-10 mm long.

There are a couple of important characteristics to pay attention to.  Believe it or not, the dynamite color pattern isn't one of them!  

According to the identification key in The Light and Smith Manual (2007), Dynamenella dilatata has (1) a distinctive "forehead" — that is, the frontal margin projects forward as a quadrangular process; and (2) inflated antennules — that is, the first two articles of the antennules are dilated.

Here's a closer look at both of those characteristics.  Note how there's a flat "shelf" in front of the eyes, and that the bases of the antennules are quite large.  The inflated antennule bases give this isopod a "moustached" appearance.

 

In this diagram of Dynamenella dilatata (see below), you can see the projecting frontal margin on the head, and the inflated antennules.  In the lower drawing, note also the three parallel ridges in the center of the pleotelson (basically the tail). 

From Richardson, H.R.  1899.  Key to the Isopods of the Pacific Coast of North America, with Descriptions of Twenty-two New Species.  Proceedings U.S. National Museum 21: 815-869.

These three raised ridges were easy to see on the larger isopods.  Look for them in the following image.

 

If you want to look at one more thing...or perhaps you've already noticed this?  The smaller individuals (first two images) have a shallow notch at the tip of their pleotelson.  The larger individuals (images three and four) have a very deep notch, like a keyhole (and see image directly above).

We don't know if the depth of the notch is related to the size of the isopod, and if all individuals will develop deeper notches as they get larger?  Or if the depth of the notch might indicate a difference between males and females?  Does someone out there know the answer?  The deeper notch was a little confusing to us at first because it isn't mentioned or illustrated in any of the identification keys.

We had trouble finding information about Dynamenella dilatata.  But Jim Carlton was kind enough to answer a few questions for us.  It appears as though their range extends from British Columbia to southern California.  [Jim told us that he knows of records between Washington and southern California, and there's an unidentified picture of what appears to be Dynamenella dilatata in Marine Life of the Pacific Northwest by Lamb and Hanby (2005).]

I don't know why Dynamenella dilatata is so colorful, or so variable, but it's fun to wonder about!

 

A teaser

 

This will have to be a bit of a teaser.  I'm having some technical difficulties with the blog tonight, so we'll continue this post tomorrow!  

A dynamite little isopod, isn't it?

Sponge surprise!

On 8 January 2012, I photographed this beautiful sponge cluster in the low intertidal zone.  It's a calcareous sponge called Leucilla nuttingi.  Each "vase" is about 1-2 cm tall.  When reviewing the photos, I was surprised to spot an animal emerging from between the sponges -- can you find the green isopod?

Here's another photo when the green isopod emerged into the open.

To my surprise, I then noticed some interesting objects at the openings of the sponges -- some pink and white, some red, some brown and white.  I think all of them might be isopods living in the sponges!

Here's a photo showing an isopod looking out from a sponge opening (on the left, look for its eyes and antennae) and the tail end of another isopod (on the right).

 

And here's one more showing the tail end of an isopod (at the top left) and I think perhaps another head (on the right).

Fish, shrimp, and other organisms are known to live inside some sponges, but I don't know if anything is known about the relationship between Leucilla and these tiny isopods!

ADDENDUM (16 January 2012)

We took a few pictures of these intriguing isopods under the microscope: