Along for the ride

 

 

Well, I've wanted to share this photo for a while, but it's been a little busy since Michael first let us know about this fascinating observation in mid-September.  

 

Meet Coronula diadema, sometimes known as a whale barnacle!

 

A young Humpback Whale washed up in Fort Bragg on 12 September 2022.  Michael was part of a team from the Noyo Center that went to document it and he took a few photos of the barnacles living on the whale.  It's not often that we get to see this species of barnacle up close as they live exclusively on whales!

 

You can see that the barnacles are quite rounded; they're often described as cask-shaped (or barrel-shaped).  They have sets of very prominent ribs and in some cases there is black coloration visible if the tops of the ribs have worn away or broken off.  The black is whale skin!  The barnacles anchor themselves in the whale's skin by incorporating it into the inner parts of their shells.

 

If you zoom in and look at the central area of the barnacle, you can see the orangish membrane and a pair of tiny white shells embedded in the membrane.  In other barnacle species, those plates (called scuta) help the barnacle close up entirely (like a trap door), but in Coronula diadema the plates are highly reduced.

 

 

 

  

These barnacles were alive when photographed, and the feeding appendages (known as cirri) were extended in one of the individuals (see below).  In Coronula, the appendages are relatively short.  Interestingly, I read that they have small hook-like structures at the tips of the cirri, perhaps indicating that they feed on larger types of zooplankton.

 

 

 

I can't help sharing one more close-up.  Check out the tiny "beads" at the base of the barnacle shells.  I don't recall seeing this texture in other barnacles.  That's new shell growth (barnacles add new shell at their base) and it's likely the beaded texture is worn away with time.

 

 

I hope you enjoyed this introduction to Coronula diadema!  Many thanks to Michael Brito and the Noyo Center for sharing these wonderful photos.