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Thursday, June 30, 2016

Tiny pawns

Well, this has been an interesting week for cnidarians.  Do you remember the golden planulae (larvae) of the hydroid Abietinaria from a few days ago?

Eric is teaching a summer class right now, and he kept a few planulae around to show his students.  But when he checked on them today, this is what he saw:

Tiny yellow discs attached to the bowl the planulae had undergone metamorphosis!

Below is an even closer view.  I chose these three individuals because they're in different stages of development.  Can you guess which is youngest and which is oldest?

The youngest juvenile is on the far left, the oldest is in the middle (lowest), and the juvenile on the far right (highest) is at an intermediate stage.  You can tell by the number of divisions in the basal disc, and by the development (height) of the stalk growing up from the center of the disc.  

Remember that these juveniles are going to become tall, extensively branched colonies (reminiscent of a fern or a miniature tree).  These are the youngest hydroids we've ever seen.  They would be too small to see in the field, so we just got lucky that they metamorphosed in the lab.  In the next image you can see the central stalk extending upward.

Amazingly, when I looked around, I noticed a few juveniles that had the first developing zooids!  It did not appear that these zooids had formed tentacles yet, but two developing zooids are clearly visible attached to either side of the central stalk:

These little hydroids have grown very quickly.  It will be interesting to see how the branching pattern proceeds, and when the first feeding tentacles appear.

A fun side note: When I first saw the these juvenile hydroids as in the last photo, one of the first things that came to my mind was that they looked like tiny chess pieces.  And then later I read an article that described a stage similar to this as the "pawn" stage!  

P.S.  To review what an Abietinaria colony looks like when it's older, see the post from 27 June 2016.

Wednesday, June 29, 2016

Nice spotting!

A beautiful White-spotted Anemone (Urticina lofotensis, formerly Tealia lofotensis) discovered nestled among mussels during a field trip to Spud Point Marina on 27 June 2016.  

Although this species can reach sizes of up to ~150-200 mm (~6-8 inches) across (including the tentacles), this tiny individual was only ~8 mm (~0.3 inches) across!

The deep red or scarlet color is distinctive, as are the white spots on the columnmore easily seen when the tentacles are withdrawn (below).

Nice spotting, Chessie!  

Tuesday, June 28, 2016

A sparkling necklace

I'm very excited to share a beautiful invertebrate with you tonight.   (It's especially fun because finding it was an accident and unexpected!)

Eric was looking at a bryozoan, and he noticed this small, delicate cluster next to it:

He recognized it as an octocoral (or soft coral), but also realized it looked different than the species we've encountered most often in this area.  (For scale, the large polyp above is ~5 mm across, measuring from one tentacle tip across to the tip of the opposing tentacle.)

Here's a view from the side with multiple polyps extended:

Soft corals may be found under rocky ledges in the low intertidal zone.  In that position, the polyps hang upside down with tentacles extending downward:

The photo above is useful as it shows an important feature of this species.  Can you see the small, shiny pieces in the column — next to the tentacles and at the base of the polyp?  I'll zoom in so you can see them better:

The photo above shows the "necklace" of shiny sclerites encircling the polyp at the base of the tentacles.  

In the next photo, look for the larger, rough-looking sclerites at the base of the polyp where it is attached to the substrate (the tentacles are retracted).  There are so many sclerites embedded in the base of the polyp that it can look as if there are sand grains gathered around the colony (see second photo of this post).

Sclerites are small, calcareous skeletal elements.  They can be important for structural support and may also deter predators. (They are also helpful for species identification.)

This is the first time we've encountered Thrombophyton trachydermum.  Jeff Goddard documented it on Bodega Head years ago, but we haven't found it ourselves until now.

What a treat!  

P.S.  For views of two other soft corals found in northern California, see Cryptophyton goddardi on 25 January 2012 and Discophyton rudyi on 10 May 2012.

P.P.S.  Thrombophyton means "lumpy animal" and trachydermum means "rough skin" (probably in reference to the numerous sclerites).  So the scientific name of this coral basically means "a rough-skinned lump."  It seems this wonderful coral is worthy of a prettier name!

Monday, June 27, 2016

Golden -- Part 2

Okay, remember the mystery photo from last night?

I received some great guesses about the identity of these small organisms — and I need to congratulate Marni for submitting a correct answer! 

These are indeed planula larvae, in this case from a hydroid called Abietinaria.

Hydroids are colonial cnidarians (related to jellyfish, sea anemones, and corals) with many connected polyps.  Colonies often have a branching structure, and because of this they are often mistaken for plants.

Most of the polyps in the colony are feeding polypsthey can extend a ring of stinging tentacles to capture small animals from the water.  Other polyps are reproductive and produce the gametes that will form the next generation.

In this case, we were fortunate to have collected a female colony.  Within small capsules (gonozooids), there are attached medusoids that produce eggs which are retained and, once fertilized, develop into planula larvae.  When they're ready to disperse, the planula larvae emerge from the gonozooids and swim to a new location to begin another colony.

Here's an expanded view of the gonozooids filled with developing planula larvae:

And two more views so you can really see the individual larvae:

Intriguingly, I might have also found a male colony.  I'm not sure about this, but it's possible the white, flat-topped structures in the photo below contain male medusoids that will release sperm.

This picture is also helpful because you can see some of the tiny feeding polyps arranged along the branches.  I've circled a few in the next image, but I'm sure you'll be able to spot others:

So there you have it!  Planula larvae are so tiny that you don't often get to see them, so it's fun to be able to share them with you!

P.S.  On 30 January 2014, I showed a fun sequence with a planula larva (from a different hydroid species) emerging from a capsule.  To review those pictures, click here.

Sunday, June 26, 2016


Well, this will be tough, but I don't have much time tonight, so I'm going to post a mystery photo for you to ponder.  

Can you guess what these are?  Each one is only ~1 mm long.  They're found in the ocean.

I'll reveal their identity tomorrow night!

Saturday, June 25, 2016

Reds among the purples

Red Sea Urchins (Mesocentrotus franciscanus) among Purple Sea Urchins (Strongylocentrotus purpuratus) in tidepools along the Mendocino Coast.  The abundance of red urchins this year is notable.

Photographed in Mendocino County on 10 June 2016.

Friday, June 24, 2016

Silver stigma

A few days ago, Eric noticed this distinctive moth among the landscaping next to the house.  

I'm pretty sure this is a Bilobed Looper Moth (Megalographa biloba), but let me know if you have a different idea.  

Note the prominent, bilobed silver stigma in the center of each wing.