Experimental Tropical Marine Ecology

Day 4: Sea urchins! Starfish! Hermit crabs!
by -- October 12th, 2010

Today, we revisited the coral reef from yesterday, this time with a guide who showed us the different species of corals/anemones/sponges and named them for us. Then, we went to collect starfish and white sea urchins for our research projects this week. After lunch, labwork began!


This is a long one…

Today was another full day – they certainly keep us busy around here! It’s a good kind of busy, though – who doesn’t love daily rounds of snorkeling through coral reefs and seagrass beds? I’m even getting used to the jellyfish.

Which brings me to my next point – since jellies are so translucent, you’d think they’d be really soft and squishy… not! They actually have very firm, solid backs even though they’re something like 90% water.*

(*Note: I do not advocate touching strange sea creatures without supervision)

Anyway, we revisited our coral reefs from yesterday and the resident scuba diver Arcadio pointed out some different species. As it turns out, “bleaching” is the same in every language. After dinner,

I was talking to Humberto Diaz, one of our instructors, and he showed me an article posted just this past week by the Smithsonian Tropical Research Institute (whose station we live at) about coral bleaching. Apparently, the problem of rising sea temperatures is extremely recent in the Bocas del Toro region of Panama, a schematic of which can be seen on the right. Panama is the dark, snakelike object running diagonally through the picture. The body of water to the north is the Caribbean Sea, and to the south is the Pacific Ocean. The before picture is on top; after is on the bottom. As shown by the key, temperatures have risen dramatically, leading to bleaching of corals. The news article is pretty fascinating, here’s the link if you’d like to read up on more information:


After touring the coral reef, we headed out to pick starfish and sea urchins for our experiment. Before you wonder why our professors were having us pick up creatures with long, deadly spines, be assured that these were the more benign variety of white sea urchins, whose spikes have been reduced to mear nubs. They like to hide under coral/leaves/other animals, so finding them was lots of fun. Not surprisingly, the starfish were much easier to find. We grabbed some seagrass for the starfish to feed on, narrowly avoided an incoming boat, then headed back to lab for some lunch! I could go on and on about the food, but once again, it was fantastic.

Then came lab work! We have three sets of experiments going on, so we split into three groups to set them up. I worked with the ~200 hermit crabs we caught, setting up an experiment to determine their propensity to head towards a “refuge” or a “new shell.” Basically, we put them in a circular container with a blanket around it, so all they could see were the white walls of the container; they saw nothing inside the lab. We started with setting up a black strip of paper so that it covered a quarter of the container (or 90 degrees). This target symbolized a refuge, so we hypothesized that the crabs would move towards it. Our results showed that they did; 49 of our 60 crabs showed a positive response to the 90 degree target. Then we scaled down the target to 20 degrees, which symbolized a new shell for the hermit crabs. Our hypothesis was that crabs who were “too big” for their shell would move towards this target. We had a lot of positive response (around 70%), and tomorrow we’re going to weigh our crabs and shells separately to find any correlation with the data.

Another group got our aquarium tanks set up for the starfish and sea urchins and actually got the urchins to release sperm/eggs to begin fertilization. As I’m typing this, the embryos have gone through cell division enough so that they now have 8-16 cells! How did they make this happen? Injecting the urchins with potassium chloride makes them think they’re dying.. so they quickly release sperm/eggs (so their life won’t be in vain, I guess). Each group is going to rotate through the experiments, so I’ll have more info about the other experiments in the coming days.

Tonight a lot of us went back into town to pick up knick-knacks, which was a lot of fun. The jewelry, artwork, handbags, oven mits, etc are all hand-made. It’s nice to know we’re supporting the people who actually make the items (sometimes right before our eyes) rather than a third-party, as is the case in the States when you purchase something “Handmade in ____.”

Pictures! The coral reef pictures are from Dr. Forward amazing underwater camera, and Kia Fathi was awesome enough to snap up some pictures as we did experiments in the lab.

Arcadio pointing out some coral species. We were all really jealous of his scuba tank – for one thing, there’s only so long you can hold your breath underwater, and for another thing… we’re so positively buoyant thanks to our fins that staying underwater for more than a few seconds is almost impossible!

Not the urchins we collected…

One of our starfish. These guys covered the sea floor.

Cool pictures of featherdusters (which are worms, not plants!) and coral/sponges.

Top view of a lionfish we saw – doesn’t it look like a plant?

I think this is a sponge – there’s a red variety that looks similar to this.

Searching intently for starfish and sea urchins. We were very close to a mangrove forest, and some people checked it out while looking for organisms.

Alix, Katie, and Laurie gather sand for the aquariums.

One of our hermit crabs and his neighbors. Each morning, we come to lab to find empty cups – turns out some of them are very good at escaping. Infact, as I was writing this post, I looked down at the floor and saw one inching his way towards the dark corner!

Our so-called “voting booth” aka orientation chamber. TJ, Drew, and Martin do experiments on the hermit crabs.

The fuzzy white sea urchin, held by Alix.

Kia checking out the status of the sea urchins, which were fertilized just hours before.

Happy in their tank.

One of our neighbors on this island! The birds love walking through the algae-filled swamp outside the lab. Today we got to see the alligator. He didn’t do much, just stared at us as he sunbathed.


That’s all for now. I’ve emailed the admin about comments not working, so hopefully they’ll be getting that fixed. One the menu for tomorrow is snorkeling through the mangrove forests and experiments in the afternoon!

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