Experimental Tropical Marine Ecology

“Alright guys, we need starfish and urchins- go to it!”
by -- October 4th, 2009

A morning easter egg hunt then afternoon in the lab.

Hey everyone! I’m writing from lab (on one of the only working computers at STRI) where 10 of us are conducting orientation experiments using the hermit crabs we collected from Bastimentos yesterday. There are two stations; each station consists of a wooden frame with a shelf where a circular arena is placed. The plastic container is marked with angles (from 0 to 360 degrees) and has a lid that lowers the intensity of the light that enters from above. Around each station is a curtain, which is designed to eliminate any outside shadows that could affect the crabs’ reactions. Think of a weird shower like contraption with a hanging bulb instead of a showerhead.

So why all the equipment? We are testing the orientation of hermit crabs to light- i.e. when we place a “dark area” along the edge of the arena, do they run toward it? I am amazed by how much everyone has applied themselves to the task; each of us has been in the lab since after lunch (the highlight of which was definitely the fried plantains) and we’ve been up since 7:00! It’s one of a handful of experiments that we have planned; the rest of the group is out setting up the “feeding” tanks (where we will test the reaction of starfish to urchin odors). We’ve also put together wheels for the larger hermits that we collected (think hamster wheel made out of old tortilla containers, pipes, and switch sensors). These will allow us to track movement and determine whether the crabs follow a circadian rhythm (i.e. a 24 hour cycle). Because we are spending so much time in the field, actually collecting and interacting with the animals, all this lab “work” is actually fun. We’ve even started to name and recognize individual crabs (out of all 120 of them!).

This morning we snorkeled among mangrove roots. The trees’ long thin fingers reached down to the sandy bottom, providing protection for the white grunts that darted quickly through the shallow waters. Some roots were covered in a variety of algae, a few red, others brown and black. Giant red starfish cruised along the substrate among blades of furry sea grass. I never knew them to move so quickly! When we picked them up we found that they extended their lines of tiny suction cups and began to inch along our palms- a strange, sticky sensation. Because we need starfish (as well as urchins) for our feeding experiment, our first mission was mass collection. The sea stars were easy; the bright glow of the five-pointed animals made them easy to spot. The urchins were another matter, and it wasn’t until we realized that they cling to the underside of mangrove leaves that buckets began to be filled. It became an absurdly fun easter egg hunt with an incredible view of the layers of green-gray mountains in the distance.

Everyone’s starving, so that’s all for now. But if tonight is anything like last night- we’re in for a torrential downpour.

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