From the Archives: Barnacle Investigation

While I'm on vacation, I'm reposting some popular posts from last year.

Today's post was originally published August 1, 2010.

Here in Massachusetts, our library system runs a summer reading program meant to promote reading during the summer months. Students log the hours they spend reading, receive prizes, and attend various programs at their town libraries (each town puts their own particular spin on the programming). This year's theme is "Go Green," so Miss Lisa at Rochester's Joseph H. Plumb Memorial Library invited me to facilitate a program last Wednesday. I was happy to share my love of the ocean, particularly the Rocky Intertidal Zone with kids from our town.

The investigation is one you can do with your children or students if you live near the ocean. On the East Coast of North America we have a kind of barnacle called an acorn barnacle. When we were in the UK, I did some tide pool exploration with my son and they had the same barnacles, so my British readers can participate, too! On the Pacific Coast and as far away as Malaysia, there's a kind of barnacle called Goose barnacles (or stalked barnacles). I'm told these will work, as well, though I have never tried it myself.

You can do this right on the beach or bring the barnacle rock home to complete the investigation. PLEASE remember to return the rock to the ocean as soon as possible. DO NOT kill them by keeping them at home. If I keep them at home more than overnight, I place a small aerator in the water to provide oxygen. I've kept them this way for a weekend, but always return them after a weekend.

Here's what you need:
Access to a Rocky Beach during low tide
A small rock with barnacles on it
A container large enough to hold the rock with barnacles, plus enough room to cover it with water
Ocean water
A hand lens (magnifying glass) is useful but not necessary
blank paper and pencils (if you plan to record observations)
Resources to consult after the investigation (see suggestions that follow)
Procedure:

1. Take the barnacle rock out of water for 2-3 hours. (This simulates low tide). If you've just collected it during low tide, it has likely been out of water for some amount of time already.
2. Ask your kids/students to examine the barnacles closely.  Provide hand lenses for this purpose. Have them choose one individual barnacle to draw large and in as much detail as possible. They can label these drawings "Barnacle Out of Water." Older students (third grade and up) can draw a top view of the barnacle and a side view of the barnacle. (Think of the barnacle as a little volcano- a top view would be if you flew over the volcano and looked down, a side view would be if you stood at a distance and drew it). They can also use words to describe what they see.  Note: All of this could be done orally, but I strongly encourage you to ask kids to at least draw what they see. Drawing forces them to look more closely and notice more details.
3. Ask the kids to write down (or share) any questions they have. Here are some of the kids working a the library:

4. Place the barnacle rock in the container and cover it with ocean water. Wait patiently for something to happen. This can take as long as 15 minutes, but may only take a few minutes. Here's one of ours:

5. At some point, the kids will see something come out of the barnacle. Many may call it a "tongue." Encourage them to look even more closely to notice the details and draw them on a new drawing (or drawings) titled "Barnacle in Water." Have kids talk to each other and suggest ideas about what is happening. For kids younger than 8, this may take as little as 5 minutes. Kids 8 and up will probably need 15 or 20 minutes to complete their drawings. 
6. Once they've looked closely and noticed as much detail as possible, share some scientific renditions of what they've been observing.
7. My two favorite sources for these line drawings are:

This one is quite complex and is best for older students

(sophisticated/ motivated 4th graders or older)

SPOILER ALERT: What follows is a brief explanation of what you will observe. Even though grown-ups may think they're too old for this kind of investigation, I encourage you to participate right along with your kids/students. That is, don't read about what you will see before you actually see it. Try to make some inferences of your own before reading any further. I have done this investigation with hundreds of adults in my science workshops for teachers and graduate courses for teachers in training and the adults are always wowed and impressed. Quite frankly, it's fun! If you're a classroom teacher and like to be well prepared, go ahead and try it out before you do it in a classroom, but don't read the scientific explanation before you see it  for yourself. Enough said!

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Barnacles are Arthropods, that is, animals with jointed legs and a hard exoskeleton. They are related to crabs, shrimp, and lobsters. Unlike other arthropods, barnacles are cemented down to one place, typically a rock or piling, but also on the bottoms of boats and even whales. Inside that hard limestone exoskeleton, they are on their heads, upside down. The feathery appendages you see coming out of the shell are their legs "kicking" food into their mouths (they filter the water to catch microscopic plants and animals called plankton). When you took the rock out of the water, it simulated low tide- a time when the barnacles are exposed to sun and air and therefore sealed up tight. When the tide comes back in, bringing a fresh batch of plankton, the barnacles begin feeding.

I encourage you to use one of the resources mentioned above to get a sense of what the animal is like inside the exoskeleton. Barnacles have a mouth, stomach, intestine, and anus, so kids can compare barnacle anatomy with their own anatomy to make a further connection. Who knew those tiny white barnacles that cut your feet at the beach could have something in common with you?

Here's a video :

In case your older kids' interests take you further...
Most barnacles are hermaphrodites (they have both male and female sex organs). One reason they crowd so close together on rocks is so they can procreate- a barnacle can not reproduce by itself. One barnacle sends a long tube-like penis over to fertilize a nearby barnacle.
You can see that in this video (they are also feeding):



Goose Barnacles sticking their legs out (video from Malaysia)



If you're really interested, there are lots more videos on the internet and specifically at YouTube. I chose the ones that seemed the best to me. To find more, google "barnacles feeding."

Ok, time for truth telling everyone... Did you read past the spoiler alert before trying this out? What do you think of this investigation? Did anyone do it as written? How did it go? Are the directions clear? If you didn't do it, will you? If not, why not? Your responses will help me decide what kind of activities to post in the future.