Sea urchins–purple urchins especially–have a bit of a bad reputation on the West Coast of the United States right now. They are currently forming and maintaining urchin barrens, which are kelp forests’ “evil twin” or alternative stable state. But that’s a complicated story for another time!

Even though urchins aren’t exactly universally loved, I am fond of them. It probably has something to do with my general love for marine invertebrates. Regardless, there’s lots to learn about urchins! Let me show you with the help of some specimens, starting with their spines.

This is one of my specimens–a dried purple sea urchin with its spines still intact. As you can see, several of its spines have broken off over time. They can move each spine individually to defend against attacks. If you “tickle” an urchin on its exoskeleton, its spines will respond in a matter of seconds.

For reference, here’s a smaller, living purple sea urchin:

The color has faded in the dead specimen–living urchins are a brighter purple.

Typically, dead urchins don’t retain their spines for long. The spines tend to fall off, along with the skin, revealing what’s known as the test. The test is the urchin’s main, circular exoskeleton.

The spines have sockets that connect to the ball-like bumps protruding from the test. This enables them to rotate each spine. Unlike arthropods, urchins grow their test and spines continuously–no need to molt!

Urchins exhibit pentaradial symmetry, which means that their bodies are radially symmetrical in multiples of five. Sea stars and other echinoderms are also pentaradial. This test shows how urchins have alternating stripes of spine-bump sizes.

The little holes in the test are for the tube feet to extend from. You’ll hear more about tube feet in a future blog post!

It’s important to mention that some urchins have venomous spines–particularly tropical species. Neither purple urchins nor the closely related red urchins have venom in their spines, so they are completely safe to touch. The only threat these temperate urchins pose to humans is the threat of getting spines stuck in your skin.

Urchins can drop spines when living for a variety of reasons, including disease, duress, or trying to dispose of a fouling organism. It’s possible for urchins to recover from dropping a few or many spines if given enough recovery time, especially if it has enough nutrients in the water and in its diet.

Those are the basics about urchin spines! Stay tuned for more urchin facts and pictures!

Quite a lot has happened to the jar ecosystems since I last wrote. For one, the first ecosystem did not go as well as hoped.

As it turned out, there were a few more polychaetes than expected…as in, approximately five. I discovered them shortly after posting the first update.

There were also two larger roundworms and several smaller worms that were extremely difficult to photograph!

Although I’d hoped to return the polychates to the ocean in the morning, there was unfortunately not enough dissolved oxygen for them to survive the night. After they died, the nutrient influx was massive and caused the ecosystem to collapse.

I still had another jar to fill with seawater, but I waited. My Marine Ecology course was starting in only a few days and I wanted my students to be involved in the jar creation process. In the best case scenario, our class jar would illustrate how ecosystems function and ecosystem processes. In the worst case scenario, it would illustrate how ecosystems are very difficult to get right and how we can learn from every experiment, regardless of whether it turned out correctly.

I polled the class and they decided to create the jar as follows:

• With both coarse and fine sand
• Water from “As far out into the ocean as Emma can reasonably wade”
• Green intertidal algae and red intertidal algae
• Mussel shell and a small rock as decorations

After a quick trip to the ocean, our jar was created!

After a week and a half of slow deterioration, the class decided to add more algae and remake my first jar attempt with the same characteristics as before.

Back to the ocean I went. Once I returned, I rearranged algae and tried to aerate the jars a bit to get more dissolved oxygen in the water. My dorm room had definitely smelled better! I attempted to capture as much diversity as possible, since diversity generally increases ecosystem stability.

In exciting news for the class, our new jar had unknowingly brought home a new class mascot: a little nudibranch!

The class voted to name them “Peanut butter.”

Unfortunately, after a couple days, Peanut butter disappeared. We came to terms with the loss as a class with a moment of silence.

The original jar wasn’t doing well either, even with the addition of more algae. However, this was a great example of alternative ecosystem states for the class to learn from! It can be very difficult to push a jar ecosystem back into a different ecosystem state.

Fast forward a few weeks and both jars had seen better days.

Before moving back home for winter break, I noticed that there seemed to be a growing layer of white around the circumference of the jar. My students and I were very interested in what this could be, so I took a sample to school and took a look under the microscope.

The consensus was bacteria, especially since I also saw paramecia (which feed on bacteria). There might be hope for life in these jars!

Today, the jars are doing about the same.

I’m looking forward to watching them as they progress in these alternative stable states!

I realized a dream of mine today– a dream to create my very own miniature marine ecosystem. As a marine ecology student, the idea immediately appealed to me.

I’d been researching the concept for months and finally had the materials to put it into action! So I drove up to Davenport (where it’s legal to collect algae) this morning and created my brand-new ocean-in-a-jar.

The red algae has some interesting animal life of its own. It has some sort of bryozoan species encrusting on it, which I’m still in the process of identifying. It also has a few tiny ostrich plume hydroids. I’m interested to see if they have survived/will survive. Although I was sad to take them from their habitat, I rescued this algae and its epibionts from the wrack line. If the bryozoans and hydroids aren’t already dead, they would’ve been shortly thereafter.

I included this mussel shell and another mussel half-shell in an attempt to provide algae a place to settle and provide shelter for organisms.

The algae has already begun photosynthesizing, which I was extremely happy to see! You can see some of the air bubbles still attached to the Cladophora.

Earlier today, there was an interesting development.

It seems that a stowaway came along! I rinsed off all the algae in the ocean, but it seems that this one is good at holding on.

Polychaetes are a type of annelid (segmented) worms. The term polychaete means many bristles, which are attached to the little extensions (parapodia) along its body. This particular polychaete uses its bristles and parapodia to “swim” through the water.

I decided that it was a little big to be in the jar so back to the ocean we went. Although it seems that this is some sort of clam worm, which does eat algae, it seemed like too much to have in a jar that was just starting out.

The release went well and the little polychaete scurried away from the sunlight fairly quickly. When I returned, I was shocked to find another surprise waiting for me!

Apparently, one of these types of algae is a common hiding place for these polychaetes! Since this one is a little smaller, I’m going to see how it does in the jar for now. I can’t find it right now, so hopefully it’s found a good place to live.

I’m looking forward to watching the jar change and finding out what other organisms appear!

If you are interested in creating your own ecosystem, I highly recommend checking out the YouTube channel Life in Jars?, which offers tutorials, information, and entertaining jar updates:

https://www.youtube.com/channel/UC0XNssyypOLiq4vVgXm9NtQ

Stay tuned for updates on this jar and on the next ecosystem I create…