Not far from the tree...

During one of our recent intertidal zone surveys, Eric noticed this tiny little orange blob on a rock:

 

Although the blob was only ~2 mm long, Eric's eyes are good enough that he wondered if it might be a very young Scarlet Sea Cucumber (Lissothuria nutriens).  I looked with a hand lens and I thought I could see tube feet, which meant that sea cucumber was a definite possibility.  Then we thought — since Lissothuria broods its young, if the blob is a tiny sea cucumber perhaps the mother is nearby.  You've heard that old expression, "The cucumber never falls far from the tree..."?  [Instead of growing up in the plankton, the embryos develop on the mother's back and then the juvenile sea cucumbers walk away from the mother as smaller versions of her.]

We looked more closely and there she was!  Here's a zoomed out view.  Although Scarlet Sea Cucumbers are red, they hold small bits of seaweed and other debris on their backs, so they can be very hard to see at first.  In the photo below, there's one adult sea cucumber and five juveniles.  This will be tricky, but can you spot them all?

 

Below the sea cucumbers are circled, mom in blue and juveniles in orange:

 

Since this is one of the species we're tracking, we documented them with some microscope photos and yes, a video!

These are beautiful little sea cucumbers, so it's a treat to see them up close:

 

With a ruler for scale (marks are in millimeters):

 

At this stage, the sea cucumbers are almost transparent, so it's a wonderful view of their ossicles.  Look for the shiny plates in the body wall and the tentacles.  (For more info about ossicles, see the post called "Scarlet fire" on 12 February 2017.)

 

 

And as if those pictures weren't enough, Eric captured some amazing video.  Check it out!  [If you can't see the video player in your e-mail, click on the title of the post to go directly to the website.]

Goodbye, Rubra Tuesday

A couple of months ago, Eric noticed this interesting sea cucumber in the rocky intertidal zone.  Its coloration caught his eye.  We've encountered quite a few small white sea cucumbers in this area, but this one had orange at both ends.  (Note, the cucumber was ~16 mm long.  The dark areas are bits of woody debris.)

 

Eric has been trying to document the local sea cucumbers.  Over the years, we've realized there are several species of little white cucumbers that can appear very similar to each other.  So far we've found Eupentacta quinquesemita, Pentamera pediparva, and Pseudocnus lubricus.  When we looked closely, this individual didn't look quite right for any of the aforementioned species.  

Here are a few close-ups taken under a microscope.  Note that the tubefeet are scattered across the body — i.e., they aren't arranged in regular rows.

 

 

Also, this sea cucumber's ossicles (tiny calcified plates embedded in the skin) are dense!

 

We couldn't find this sea cucumber in Phil Lambert's Sea Cucumbers of British Columbia, Southeast Alaska, and Puget Sound (1997).  We also had trouble locating it in the Light and Smith Manual (2007).  We kept trying to identify it via the key.  Most of the characters seemed right for Pachythyone rubra, but the key said this species was red or reddish- orange.  So we decided to look at the ossicles.

Here are a few pictures of the ossicles that Eric photographed under a high-powered microscope:

 

The Light and Smith Manual didn't include an illustration of Pachythyone rubra's ossicles.  But we found a diagram in another publication and it was a perfect match!

 

Ossicles from body wall, including (A) 4-holed buttons; (B) reticulated plates; and (C) supporting tables from tube feet.  Modified from Bergen. M.  1996.  Class Holothuroidea.  In J.A. Blake, P.H. Scott, and A. Lissner (eds). Taxonomic Atlas of the Benthic Fauna of the Santa Maria Basin and the Western Santa Barbara Channel (Vol. 14, Miscellaneous Taxa, pp. 195-250).  Santa Barbara: Santa Barbara Museum of Natural History.

The ossicles confirm that this species is Pachythyone rubra.  Although the Light and Smith Manual described the adults as red/reddish-orange, perhaps the coloration can vary, especially in juveniles and small individuals?  

This more southern species of sea cucumber primarily occurs from Monterey and south.  It has been found one other time in Bodega Bay (in 1976).  As far as we can tell, Bodega Bay is the northern range limit for Pachythyone rubra.  If you find one north of Bodega Bay, we'd love to hear about it!

P.S.  An interesting side note: Pachythyone rubra is a brooder.  Females brood the embryos within the body cavity and release juveniles when they're ~1-5 mm long.

P.P.S.  If felt good to finally hang a name on this cucumber!

Scarlet fire

 

About two years ago, I shared a post about the Scarlet Sea Cucumber, Lissothuria nutriens (see post on 22 January 2015).  At that time, I noted this species was rare in Bodega Bay, but we also wondered if this southern sea cucumber might increase in abundance if sea water temperatures became warmer.  It appears that has happened!

The Scarlet Sea Cucumber reaches its northern range limit in Bodega Bay.  There are some records from Duxbury Reef in Bolinas, but so far we haven't been able to find any records from further north.  (This would be a good time to look for them in northern California!)

Remember that this is a small sea cucumber.  Here's a picture from the rocky intertidal zone with some fingertips for scale.  It shows several Scarlet Sea Cucumbers on the rock — look for three reddish blobs in the center of the picture:

 

When the cucumbers are out of water, their tentacles are retracted.  And note that they cover their bodies with bits of debris.  (Recognizing this "covering" behavior is helpful when searching for these sea cucumbers — it differentiates them from red sponges and sea squirts.)

Here's another example, this time a close-up of a single Scarlet Sea Cucumber:

 

Because this species has been rare in our area, we wanted to be certain about the identification.  So Eric double-checked the ossicles (the calcareous plates inside the body wall, tube feet, and tentacles that help identify different species of sea cucumbers).

Below is a diagram illustrating the different types of ossicles found in Scarlet Sea Cucumbers:

 

Ossicles of Lissothuria nutriens.  (A) Curved supporting plate from tube foot, (B) end plate from tube foot, (C) smaller, hourglass-shaped bodies from dorsal body wall.  Modified from Deichmann, E. (1941).  The Holothuroidea collected by the Velero III during the years 1932 to 1938. Part I. Dendrochirota.  Allan Hancock Pacif. Exped. 8: 61-194.

For comparison, here are a few of the ossicles from one of the local specimens.  You can see that the shapes match the drawings above, confirming the identification:

 

If you get lucky and spot a Scarlet Sea Cucumber in a tidepool, along with the red oblong body you might see the tentacles extended.  Interestingly, the tentacles vary in color from fiery orange to scarlet red:

 

These sea cucumbers feed by catching organic material on their tentacles and then moving it to their mouth in the center of the tentacles.  Eric filmed some of this behavior under a microscope in the lab, and he made a wonderful video clip so that you can see the tentacles in action.  (Also watch for the shiny ossicles embedded in the tentacles and tube feet.)

scarlet_sea_cucumber_sanford from Jackie Sones on Vimeo.

We have counted quite a few Scarlet Sea Cucumbers in the low intertidal zone while conducting surveys this past week.  We're also wondering if the warm ocean temperatures during the last couple of years might have allowed this species to move even further north, beyond Bodega Bay.  We'd be very interested in any Scarlet Sea Cucumber observations in northern California, so let us know if you spot one!

 

Cool as a cucumber

Last night I shared a video of a small sea cucumber (the video is also at the end of this post) and I promised more information about it.

This sea cucumber (Cucumaria pseudocurata) is found in the rocky intertidal zone along our coast.  Recently we encountered quite a few of them nestled in shallow depressions below mats of algae.

In the field, the sea cucumbers look like little brown blobs (maximum size is ~3.5 cm, or ~1.5 inches):

 

As you probably saw in the video, when viewed under a microscope their features are easier to see, including tubefeet (for holding on), tentacles (for gathering food), and large shiny ossicles (for skeletal support):

 

Ossicles are plates made of calcium carbonate.  The shape of the ossicles helps distinguish different species of sea cucumbers.  Below is a selection of ossicles from Cucumaria pseudocurata viewed under very high magnification:

 

You can compare the real thing (above) with a book illustration (below) and look for similarities:

 

Modified from Sea Cucumbers of British Columbia, Southeast Alaska, and Puget Sound (Lambert 1997) 

And here's a wonderful close-up view of the ossicles inside the body wall and a tubefoot:

 

Perhaps you remember that the sea cucumber in last night's video was only ~3 mm long.  Cucumaria pseudocurata is a brooder and a direct developer — females lays eggs in January, males release sperm to fertilize the eggs, the female shields the developing embryos with her body for about a month, and eventually tiny juvenile sea cucumbers are visible among the adults.  

The individual in the video was probably about 3-4 months old.  Here's a still picture with a ruler to help you visualize the size (the marks on the ruler represent millimeters):

 

And in case you missed it, here's the video:

cucumaria_juvenile_sanford from Jackie Sones on Vimeo.