Little narwhals

Remember the Giant Green Anemones (Anthopleura xanthogrammica) spawning in late June?  (You can review that post here.)  Well, there's more to the story.

I mentioned that you don't see anemones spawning in the field very often.  Eric's in the middle of teaching a summer class about marine invertebrates.  So when I noticed the anemones releasing eggs and sperm, I ran up to the lab and called him to see if he wanted to take advantage of the rare opportunity.

He appeared at the site a few minutes later with a flask and pipette.  He obtained a few eggs from a female anemone (look for all of the orange dots in the flask in the picture below).

 

 

Then he sucked up a tiny bit of sperm from a male anemone and released it into the flask (also note the nice upside-down reflection of the Bodega Head cliffs and waves at the bottom of the flask) :

 

A couple of days later there were healthy, swimming, Giant Green Anemone larvae!  This is what they looked like when 5 days old:

 

This is called a planula larva.  You can see that the edges of the larva are covered with short hair-like structures (cilia).  These are used to propel the larva through the water — they are very fast swimmers! 

Note the very long apical tuft.  This long, pointed structure is sometimes twisted (it's made of several strands held close together)...and the planula larva swims with the tuft pointed forward.  Perhaps it's my wild imagination (is that possible?), but they remind me of little narwhals as they swim along!

 

Arthur Siebert did a study on these larvae in 1974 at the Friday Harbor Laboratories.  He tried to get the larvae to settle on various substrates (and metamorphose into little anemones), but they never did.  And as far as we can tell, no one has ever been able to get them to settle in the lab, so no one knows how long they stay in this larval stage before becoming the anemones we know so well.

 

I hadn't seen Giant Green Anemone larvae before, so it was quite an experience to see how different they look in the larval stage.  Who knew that Giant Green Anemones look like little narwhals when they're young?