Orchestra pit?

  

We were tidepooling on 22 December 2022 when I noticed this interesting orange fish among the rocks.  When I looked more closely, I realized it didn't look like a fish I'd ever seen before.

It was "bumpy" everywhere — there were bumps covering the head and running down the tail:

 

 

Speaking of the mouth, it had very unusual rough edges and coloring:

 

 

 

  I also appreciated the variety of colors and patterns in its fins:

 

 

 

 

But what was most peculiar was the deep pit on the top of its head:

 

 

 

At first we thought this fish had an injury — perhaps a wound that was healing?  But later after doing some research into what type of fish this is, I discovered that the dramatic "cranial pit" is a normal feature of this species!

 

This is a Rockhead (Bothragonus swanii), sometimes called a Deep-pitted Poacher. 

 

An older paper hypothesized that the pit might serve as camouflage, mimicking the openings of sponges or sea squirts.  However, more recently researchers have uncovered hints that the pit might have an auditory function.  Research is underway to study how sound sources might be received in this "orchestra pit", so perhaps we'll learn more in the years ahead!

 

P.S.  Many thanks to Peter Wainwright, Adam Summers, and Daniel Geldof for sharing information with us about this intriguing fish!