Here's the scoop!

  

Quite a few folks guessed correctly that last night's mystery close-up (above) is a worm tube.  Here's the entire tube as we found it washed up on the beach:

 

 

Meet Pectinaria californiensis!  These interesting worms are commonly called "ice cream cone worms."  Perhaps you can see why in the next photo:

 

 

 

 

Although I'm holding the tube with the wider end up, the worm lives buried in the sand with the broader end of the cone facing downward, as in the illustration below:

 

Modified from Gordon, D.C.  1966.  The effects of the deposit feeding polychaete Pectinaria gouldii on the intertidal sediments of Barnstable Harbor.   Limnology and Oceanography 11: 327-332. 

The worm's head extends outwards from the wide end of the tube.  They are deposit-feeders, so they'll use their tentacles to gather sand particles, pass them to their mouth, remove organic material, and then eject the particles from the narrow end of the tube at the surface.

Although the older illustration below shows the worm on the surface, you can see the relationship between the worm and its tube.  (For those of you who spend time along freshwater streams, this is somewhat similar to a caddisfly.)

Modified from Sowerby, J.  1806.  The British Miscellany: or, Coloured figures of new, rare, or little known animal subjects; many not before ascertained to be inhabitants of the British Isles. London.

I appreciated how the grains of sand were painted in the plate shown above.  The tube with its cemented sand grains is quite a work of art -- with the light behind it, it looks a bit like stained glass:

 

 

 That's the scoop on the ice cream cone worm!

Leaving the lair

  

Okay, have you been wondering about the Turquoise Dragon and her developing larvae?  (See posts on 24 July 2023 and 29 July 2023.)

The larvae hatched on 2 August 2023 and Eric caught some of them crawling and swimming away in the video clip below.

The epitoke (reproductive stage of the worm) brooded the embryos/larvae for at least 12 days.  It's likely that the larvae will spend some time swimming in the plankton and growing (adding more body segments) before settling to the bottom and metamorphosing into juvenile worms.

[If you can't see the video player in your e-mail, click on the title of this post above to directly to the NBHB website.]

Thanks to Eric for sharing this great video clip!

The Dragon's Treasure

 

 

As you’ll recall, last week Eric’s class found an amazing reproductive worm swimming in the plankton (see "Turquoise dragon!" on 24 July 2023).  She was protecting a brood of fertilized eggs, but they were very early in development.   

 

Eric kept the worm in the lab, and now about a week later her embryos have developed into a treasure hoard of crawling 4-eyed larvae (called trochophores).  We suspect that sometime soon the larvae will break free of the brood sack and swim away!   

 

Here's a short video clip where you can see the larvae.  They're quite active!  [If you can't see the video player below, click on the title of this post to watch the video on the NHBH website.]

 

Turquoise dragon!

 

Last week, Eric’s summer class collected plankton tows in Bodega Bay and examined them under the microscope.  One of the students (Pachia) spotted this very striking polychaete worm that was turquoise in color and carrying a mass of bright orange eggs!    

 

The worm was quite small (only ~2.5 mm long).  Those are millimeter marks on the ruler below:  

 

 

 

This worm is known as an epitoke, a type of reproductive individual that occurs in some species of polychaetes.  Epitokes swim up from the bottom to the surface where mass spawning events occur.  In most cases, both male and female epitokes free-spawn their gametes into the water where fertilization occurs.   

 

However, the species shown here is unusual in that females do not free-spawn, but instead hold onto an egg mass and protect their fertilized embryos for some time while they develop.  Although we aren’t able to identify the species, this worm is likely a member a member of a particular group of polychaetes (Family Syllidae, Subfamily Autolytinae). 

Luckily, Eric was able to capture some video of this beautiful worm, whose appearance reminds us of a tiny turquoise dragon.  [If you can't see the video player in your e-mail, click on the title of the post to go directly to the NHBH website to watch the video.]

 

With many thanks to Pachia for spotting this wonderful worm, to Bruno and Richard for helping with the identification, and to Eric for putting together the story with photos and video.

Mystery on the tidal flats

Last week Eric and I were exploring the tidal flats in Bodega Harbor when we noticed these patches of orange and white in shallow pools on the surface of the mud:

 

 

 

When we looked closer, we could tell that something had been spawning — releasing eggs (orange) or sperm (white) — but we weren't sure what type of animal was responsible.

 

Here are two close-ups showing the vast number of eggs:

 

 

 

 

 

 

 

We kept wondering who was releasing these eggs/sperm, and eventually we came across an animal in the act of spawning:

 

 

 

This is a fairly large polychaete worm.  We're not sure which species it is, but after consulting with some experts, it's possible it's in the family Amphinomidae.  [I'll update this post if we learn more.]

Many marine invertebrates reproduce by broadcast spawning — releasing gametes into water.  The strategy involves some luck in that the sperm need to encounter the eggs.  In the situation below, you can see how that might happen (with the sperm drifting over the eggs), but if they were farther apart, it might be less likely:

 

 

Although many marine invertebrates spawn in this manner, you don't get to see it that often in the field.  Because larval forms can sometimes be useful for species identification, we decided to mix some eggs and sperm together to see if they'd develop into planktonic larvae in the lab.  A week later, here's what we found under the microscope!

 

 

 

This is a larval form called a trochophore.  Those long spines (or chaetae) are likely used to defend the larva against predators and might also slow sinking in the water (they can spread the spines out to the side).  Many worms might spend weeks developing and growing in the plankton before undergoing metamorphosis into a juvenile worm that will burrow in the mudflats.

 

Many thanks to Eric for this wonderful photo of a fascinating trochophore larva!

 

P.S.  For a couple of other examples of broadcast spawning, see the posts called "Fortuitous" on 28 June 2013 (sea anemones) and "Broadcast news" on 2 May 2019 (sea stars).