Just in time for Easter -- lots of eggs!

  

We went out to the rocky shore early this morning to start some surveys.  Right away Eric noticed that the tidepools looked unusual.  All of them appeared cloudy or milky.  We were aware recent ocean conditions might trigger spawning in some marine invertebrates, and sure enough, this was a massive spawning event of California Mussels (Mytilus californianus), probably the largest we've encountered.

In the photo above, the orange coloration is eggs released by female mussels.  Here's another example, with clusters of eggs concentrated along the edge of a pool:

 

 

In other pools, the color was white or gray, clouded by vast quantities of sperm released by male mussels:

 

 

Nearly every tidepool we observed on Bodega Head appeared to have mussels spawning, so the extent of this synchronous mass spawning event was truly remarkable.  Even the largest pools were visibly cloudy:

 

 

 

The ocean temperature went up from 11°C (52°F) to 13°C (55°F) yesterday, and there was a phytoplankton bloom nearshore — both environmental cues that are thought to trigger spawning in some invertebrates.

Amazing!  Let us know (and send photos) if you notice local marine invertebrates spawning, too!

Cued by a temperature change?

  

Eric was doing an end-of-day check on some tanks in the lab last night and noticed some sea urchins spawning!  Above, a male Purple Sea Urchin (Strongylocentrotus purpuratus) with clouds of sperm being released from the gonopores on the upper surface.  

Looking around, we eventually noticed a few female Purple Sea Urchins releasing eggs (more yellow-orange in color):

 

Our guess is that warmer ocean temperatures during the past couple of days triggered spawning.  There's been a lot of upwelling this year, with water temperatures as low as ~8.8°C (~47°F).  But winds calmed down at the end of the week and temperatures rose to ~12°C (~54°F).

There were also a couple of other echinoderms spawning.  Here's a male Red Sea Urchin (Mesocentrotus franciscanus) releasing sperm:

 

 

 

And a female Ochre Sea Star (Pisaster ochraceus) releasing eggs:

 

 

 

What's that saying, "Spring is in the water"?  ;)

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).

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.