A story with a point

Last September I wrote about a fascinating predator-prey interaction that involved an inducible defense.  The bryozoan responds to being preyed upon by a nudibranch by growing significant spines.  I showed the nudibranch and the bryozoan, but I didn't have pictures of the spines.  Are you ready to see them now?  

To review, here's the nudibranch, Corambe steinbergae, and the bryozoan, Membranipora sp.  The nudibranch is so well camouflaged that you'll need to look carefully along the left side of the image to find it.  The darker zooids (members of the bryozoan colony) just behind the nudibranch have probably been eaten.

 

Below is a close-up of the nudibranch, showing its head that was exposed while it was probing the bryozoan colony:

 

And now for the spines.  First, here's an illustration to help you know what to look for.  The inset shows a close-up of a single zooid with elongated spines at the corners and numerous smaller spines along the edges.

 

Modified from Harvell, C.D.  1990.  The ecology and evolution of inducible defenses.  The Quarterly Review of Biology 65: 323-340.

Now here's the real thing, from two different angles:

 

Would those spines deter you from eating this bryozoan?

Eric is so impressed with this nudibranch-bryozoan interaction that he filmed some video and set it to music.  This has to be one of his best invertebrate music videos.  Follow the link below to watch it on YouTube — you don't want to miss it!

"Nudibranch predator (Corambe steinbergae) and bryozoans"

P.S.  For the record, these bryozoans and nudibranchs were found on kelp blades washed up on Salmon Creek Beach on 8 August 2014.