Experimental Tropical Marine Ecology

March 6: Day 3 – A Glimpse of Galeta
by -- March 3rd, 2011

As we settled into Galeta, we commenced our experiments on the local hermit crabs…

The ocean view from Punta Galeta

The ocean view from Punta Galeta

Our first day at Galeta commenced with us collecting hermit crabs. We needed two hundred of them for our experiments, which seemed like an easy matter, but, after foraging around under logs and leaves for an hour, it turned out to be quite a formidable task. Though we found quite a few hermit crab hotspots underneath the trees and in rock crevices, many of them were too small to be collected. After another hour of searching, we had 198 hermit crabs, which we decided was sufficient to start testing.

We put each crab in the center of an arena we had constructed and noted how they would respond to differently sized targets placed along the arena wall. Some would approach the targets, perhaps thinking they were an available shell or refuge. Others would flee from them. Naturally, we had a few that were too timid to emerge from their shells and acknowledge the arenas. By the end of the day we had a number of positive, negative, neutral responders for each target.

We removed these crabs from their shells and determined their shell fit by weighing the crab and the shell and determining the volume of the crab and the shell. We selected a few  of these crabs to freeze. We would later generate conspecific odor from these crabs. Our plan was to later use this odor, along with dead snail odor to attract hermit crabs in the field that would be actively looking for shells. We would then test these crabs in the arena as well and see how well their responses correlated with the random crabs we collected this morning.

Back at the station there were a series of outdoor tanks housing a variety of animals the station kept for educational and rehabilitation purposes. One tank held many echinoderms, ranging from brilliant sea stars and large brittle stars, to sea cucumbers that softened into mush in your hands as they relaxed their mutable connective tissue. There were also quite a few urchins in the tank, such as smaller white-spined ones–who seemed to collect various bits of shell and ocean debris onto their spines – and long needle spined black ones, which we learned were quite venomous and common out on the reef.We also explored some of the natural wonders of the research station. Punta Galeta lies on the Caribbean side of Panama, and is bordered by ocean (buffered by the coral reef) on one side and by a serene mangrove lagoon on the other. We spent a lot of time on the docks in the lagoon, peering down into the water and spotting schools of fish darting about the columns supporting us. Susan even spotted a parrotfish weaving its way through the water.

Some of the other tanks housed vertebrate life. There were a few hawksbill turtles, along with a turtle, which was being rehabilitated from a fishing accident. Slim barracudas and gliding sting rays danced about in the tanks. There was also a massive puffer fish that approached the edge of the tank whenever we were near, his large black eyes begging at us like a puppy.

Beyond the wide variety of cute and dangerous animals in the tanks were our own hermit crabs, which often provided us with amusement. Sharon decided to play Extreme Makeover: Home Edition and took a few of the non-responding crabs and put them in a bucket with a few empty shells. The cascade of shell swapping and that ensued transfixed us for well over an hour. By the end of it, some of us were even playing matchmaker–trying to match a hermit crab with his or her “ideal” shell.

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