Beach Bugs (That's an Arthropod???)
**This post is part of a PNW Blogger Scavenger Hunt! For more information on how to play and win prizes read the details here: http://www.metrofieldguide.com/2015-pnw-nature-blog-scavenger-hunt
When we tell people that we make videos about insects, spiders and other arthropods people get really excited. Ladybugs! they say. Bees! they exclaim. Butterflies! they scream. Yes, Yes, Yes! we concur. And also...
We strive to teach people about the amazing diversity of the arthropod world and help people to see that the 'bug' world is much larger and more varied than they ever imagined. And whoa! we proclaim- Oregon has some REALLY COOL ARTHROPODS!
In September of 2013, we drove a green couch across the country to inspire kids to get off the couch and explore America's wilderness. We filmed the whole trip (in post-production now). Our show starts on the Oregon Coast to explore some ancient (and very distant) relatives of the bugs we see everyday.
OREGON COAST
Our green couch, lounging at Bandon Beach, OR. The site of our first stop to explore America’s awesome arthropods. Beach bugs are the best! Photo: Peter C. Blanchard, 2013
Oregon's coastline is gorgeous and with so many large rocks at the shoreline, it makes for great tide pooling. People know about crabs and small shrimp but when you walk across the sand there are thousands of these little animals that hop, skip and jump out of your way. People call them all sorts of names, like sandhoppers or sand fleas but they are actually little crustaceans called amphipods.
First things first. Crustaceans are arthropods that have 5-7 pairs of legs and 2 pairs of antennae. They are found all over the world, can live in fresh- or saltwater and on land. The little animal to the right is easy to identify as an amphipod because it is laterally compressed, meaning it looks like someone picked it up and pinched it a bit between a thumb and a forefinger. That is the scientific definition of laterally compressed. Swear.
An amphipod found at Bandon Beach, OR. Can you see the two pairs of antennae? Photo: The Bug Chicks, 2013
We found thousands of these amphipods just up from the surf on the wet sand. Many species are detritivores, which means they eat decomposing matter. They are little scavengers (Hey! You're scavengers!) looking for an opportunity. They hop and jump as you approach them so getting this picture was difficult. Amphipods are found all over the world in marine and freshwater alike. Some species are terrestrial but live in moist or damp areas.
Another arthropod that people overlook when at the beach is a barnacle. Huh? Barnacles are arthropods? Aren't arthropods supposed to have segmented appendages (like legs & antennae), exoskeletons and bilateral symmetry? (See how I did that there? Taught you about the key characteristics of arthropods...)
Yup. Barnacles are arthropods. They are just a little different looking. After a free-living larval stage they attach themselves head-down using a cement gland at the base of their antennae. You can find these kinds of barnacles on rocks, boat hulls and even whales! Once attached they become sessile arthropods, or non-motile. (**Non-motile is a bit confusing because it means non-moving but barnacles can move their bodies, they just don't change location.) Their legs are modified into feeding appendages and they catch tiny plankton that drift by on the tides.
These are acorn, or volcano barnacles. These animals will remain attached to this rock for the rest of their lives. That’s one long head stand, folks. Photo: The Bug Chicks, 2013
A close-up view of an acorn barnacle. They create 6 hard plates that surround the body for protection. The central part (that looks like a clam shell) is called the operculum. They also called moveable plates. Plates are not molted, but barnacles do have internal exoskeleton that is molted just like other arthropods! Photo: The Bug Chicks, 2013
Some barnacles are parasitic. So instead of attaching themselves to rocks or structures, they attach themselves to living organisms like crabs. (There's one that lives on the reproductive system in crabs, effectively sterilizing them and preventing them from mating!)
We hope you learned a bit about other-a-pods in this post. Next time you're at the beach take a look at the hoppy, jumpy things and the look-like-part-of-the-rocks things and try to determine if they are arthropods!
GOOD LUCK SCAVENGERS!