🔎Field Notes:🔎Barnacle Sex! (Patreon)

Hey Deep Look Fans! Have you seen our 🎉150th episode🎉 about the surprisingly vigorous love lives of barnacles? They might just look like crusty little rocks but barnacles are actually crustaceans related to shrimp and crab.

To film 🎥 this milestone episode, Josh Cassidy, Deep Look’s lead cinematographer and producer headed out to Tiburon, California to San Francisco State University’s Estuary & Ocean Science Center, Romberg Tiburon Campus.

Josh films barnacles at the Romberg Tiburon Campus in Tiburon, California. (Jenny Oh/KQED)

Josh did most of the close-up filming in a saltwater aquarium he set up on location using fresh bay water to keep the barnacles happy. Barnacles like to have a current of water running over them so Josh added a small propeller to the tank to get them in the mood. That seemed to do the trick and Josh was able to capture some intriguing underwater romance.

Josh at the Romberg Tiburon Center. (Jenny Oh/KQED)

If you’ve watched our episode you already know that barnacles have the longest penis of any animal relative to their body size. It’s up to eight times the length of the barnacle itself!

A barnacle’s penis, pictured here on the left, reaches to mate with a neighbor. The penis can also taste and smell, and the tip can feel around, probing to see which neighbors have ripe eggs inside. Eight pairs of delicate legs called cirri absorb oxygen and strain food from the water. (Jenny Oh/KQED)

Here are a few more interesting facts about barnacles.

• ➡️They stick to one spot by secreting a fast-curing natural cement that is one of the strongest we know of in nature. (tension strength of 5,000 pounds per square inch)
• ➡️They also secrete hard calcium plates that fully encase their soft tissue. A cone made up of six calcium plates forms a circle around the barnacle and four more plates form a “door” that the barnacle can open and close.
• ➡️When the tide is low, barnacles close their “door” to keep in moisture so they don’t dry out. 
• ➡️When the tide is high they open up so their feathery “legs” called cirri can catch/filter out  plankton and organic debris from the water. They also open their “door” to reproduce.
• ➡️Most barnacles are hermaphrodites so they have both male and female sex organs. Self-fertilization is theoretically possible but rare.

Tell us where you have come across barnacles and if you think differently about their hidden lives after having watched our episode.

(Special thanks to Katharyn Boyer, a professor of biology at San Francisco State University who gave Deep Look access to barnacles and permission to film at the Romberg Tiburon Center, and to Anne Slaughter who made it possible to film the barnacle larvae under a microscope.)