So egg-citing!

  

So cool!  This is a female Ochre Sea Star (Pisaster ochraceus) spawning.

We had to work a little late tonight, but it paid off because just before we were getting ready to leave, Eric noticed that a few sea stars were spawning in one of the tanks at the lab!

It's possible they were triggered by the recent change in the weather.  When the NW winds are strong, seawater temperatures are usually cool; then when the winds calm down, seawater temperatures often rise.  Yesterday the seawater temperature was 9°C (48°F), but it increased to 13°C (55°F) today. 

Here's an even closer view where you can see a large number of eggs being released through pores in the surface of the sea star:

 

 

Some of the eggs gathered on a piece of kelp below:

 

 

 

 

We were curious about whether other animals might also be triggered to spawn, so we checked another nearby tank and...voilà!

 

 

 

This is a male Red Abalone (Haliotis rufescens) releasing sperm.  The raised pores in the shell act like little volcanoes when the abalone is spawning:

 

 

 

 

 

We don't get to see sea stars and abalone spawning that often, so it was a fun way to end the day!

 

Eggs in neon

  

After field work this morning, I noticed a couple of Giant Green Anemones (Anthopleura xanthogrammica) were spawning, so I took a couple of quick photos for the record.

Sometimes spawning is triggered by a large change in water temperature.  During the past week we saw extremely cold temperatures  of ~8.5°C (~47°F), and then when the winds dropped temperatures rose to ~12.5°C (~54.5°F). 

Here's a close-up of the eggs:

 

 

 

And a zoomed out view of the entire female anemone with the beige eggs accumulated on the lower edge of her oral disc:

 

 

 

 
There were a few males spawning, too:

 

 

 

P.S.  I haven't seen anemones spawning that often, but I wrote about another observation back in 2013.  See "Fortuitous" on 28 June 2013 and "Little narwhals" on 23 July 2013 (the latter includes photos of anemone larvae).

Now that's a brood!

  

Meet Lisbeth's Brooding Sea Anemone (Epiactis lisbethae).  This is the first time I've encountered one in Sonoma County (or anywhere!).

In comparison to the more common Proliferating Anemone (Epiactis prolifera), note the very high abundance of juveniles ...and that the juveniles are uniform in size (rather than a large variety of sizes).  (For an example of a brooding Epiactis prolifera, check out the post called "Ring around the anemone" on 18 February 2021.)

Yes!  Those are tiny juvenile anemones clustered between the base of the anemone (on the left) and the tentacles (on the right).  Here's a close-up of the juveniles:

Photographed along the Sonoma Coast on 19 May 2022.

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).

 

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.