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16 April, 2003

Today I parcticipated in an amphipod bioassay using desmarestia anceps alga. The amphipods were the taste testers so to speak. The amphipods were collected at a dive site. They have been kept in one of the seawater tanks in the aquarium room. I put 25 amphipods in each of 10 plastic bottles. Then, I filled 10 more bottles with just seawater. The bottles were paired A 1, A2; B1, B2; C1, C2; etc. all the way to J. Next, I cut pellets from the extracts that had been made in petri dishes. I had to weigh each pellet and write down its weight. There were 3 extracts so, 3 pellets went into each bottle. One extract was taken from the substrate. One extract was taken from the primary or stem. One extract was taken from the lateral branches. See the journal entry for April 14, 2003 for more information about algae.

Now, it is waiting time. I have to wait for the amphipods to eat. This will and can take hours. When they have finished eating, I will take the pellets out of each plastic bottle and weigh them again. I will subtract the amount that the pellets weighed before I put them into the bottle from the amount that they weigh when the amphipods finish eating. This will tell me how much of each pellet the amphipods ate. The pellets in the sea water bottles with no amphipods will be weighed also because when the pellets are in the water, they absorb water, which makes them expand and weigh more. So, this means that the weight of the expanded pellet will be factored into the weight of the eaten pellets because even though the eaten pellets will weigh less, they will still have absorbed water.

I am looking for the part of the alga the amphipods like least. The least eaten part of the alga is the most defensive in behavior. The chemical compounds of that part of the plant will be analyzed to see what chemicals keep it from being preyed upon.

The insturment in the foreground is the scale called an analytical balance. The small plastic bowls on top are called weigh boats. The pellets are placed into the weigh boats and then the analytical balance gives the weight of each pellet. Pellets are weighed in grams.

Here I am getting the pellet out of the petri dish and onto the spatula to wipe off the excess calcium chloride.

I have gotten the pellet from the petri dish onto the spatula. Now I V-E-R-Y gently wipe the excess calcium chloride off with a tissue. Calcium chloride is a jelling agent. For more information about calcium chloride, look at the journal entry for January 30, 2003.

Now I put the pellet on the weigh boat to measure its weight.

Once the pellet is weighed, I have to record its weight on a log. Here you can see my entire work area. The black cubby is holding ice with plastic bottles of amphipods in them. We have to keep the bottles on ice because amphipods live in cold water. The petri dishes have the alga extract in them. On the right, is the analytical balance.

After the pellet is weighed, it is dropped into one of the bottles.

Once a pellet has been dropped into a bottle, the spatula and weigh boat are wiped out and cleaned for the next pellet.

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