A Mystery from Poppy

By The Marine Detective on December 30, 2022

Hello Dear Community,

I’ve saved my favourite 2022 marine mystery for you until now.

It’s from Poppy who was in British Columbia visiting from England with her father, sister Maya, grandpa and grandma.

Poppy found these on a beach on Malcolm Island and they were photographed on the back of a cell phone.

It actually hurt my head to try to figure this out. I knew that I SHOULD know what they were but just not make the ID take shape. In wanting to get the answer to Poppy as soon as possible, I reached out to expertise greater than my own. I suspected I would have a big face-palming moment of “but of course” when the shells were identified.

And indeed that happened.

Take a moment to try to determine the ID yourself? Then scroll down for the answer.

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Are you sure you want to see the answer?

Here goes!

Of course! 🤦‍♀️ They are the parts of the shell of a barnacle that open and close!

The answer that came from naturalist supreme Bill Merilees was: “What you have here is a barnacle valve – one of the ‘flaps’ that opens to allow the feeding tentacles to strain food from the water column. Great photo of this unusual shell exoskeleton!”

This led me to try to figure out what barnacle species these might come from and what the names of the structures were.

I believe the most specific ID is that these are the opercular plates of a Thatched Acorn Barnacle. The two parts are the tergum and scutum.

Below are some of my photos of another barnacle species, the Giant Acorn Barnacle (Balanus nubilus) which might help in recognizing the shells. Isn’t it wondrous? All barnacle species start off a plankton and then form their own intricate shells so that their foot can extend out to rake in food.

Happy New Year to you. May the next year be filled with happy mysteries, wonder, and empowerment for positive change.

Sources of illustrations:

Coletti, Giovanni & Bosio, Giulia & Collareta, Alberto & Buckeridge, John & Consani, Sirio & El Kateb, Akram. (2018). Palaeoenvironmental analysis of the Miocene barnacle facies: Case studies from Europe and South America. Geologica Carpathica. 69. 573-592. 10.1515/geoca-2018-0034. 

Oregon Institute of Marine Biology, Semibalanus cariosus – A thatched barnacle