14 November, 1998

November 14, 1998

THE LABWORK FROM THE PAST FEW DAYS

For a few days it was pretty frustrating because the gill cells were not looking like they should have. The DASPEI stain that was injected into the fish should have made the chloride cells glow green. But when I looked in the microscope, I couldn't find any chloride cells, although I could find a lot of glowing other cells. Some of these were football-shaped cells which looked like parasites, or perhaps cysts of parasites waiting to become activated by the right conditions. One of the fish had up to 35 of them in each field of view (at 400 X magnification) in 75% of the gill filaments. That's a pretty heavy parasite load! Some of these cells glowed much more brightly than the others. This suggests that there were more mitochondria in them. Maybe they were activated and getting ready to develop into parasites. Three of the five fish I observed also had flatworms related to Planaria crawling around in their gills. That was interesting but I felt sorry for the fish, although otherwise the fish seemed healthy and perky until they were killed (so I could study the gills). Ed said that when he dissects the fish to use their kidneys for his experiments, he has noticed other parasites like worms in different organs all over their bodies. He said he never wants to eat one of these fish because he would be grossed out by the thought of eating those parasites. Dr. Smith jokingly responded, "But think of all that extra protein you'd be getting"!

Another neat thing I saw when I looked at the gills was the blood still flowing through the blood vessels in the gill filaments, even though the gills had been removed from the body several minutes before. Fish blood cells are different from ours. They have a nucleus (which ours lack) and they are shaped more like two pyramids stuck together at the base. Trematomus bernacchii has red blood just like we do because in its red blood cells it has hemoglobin, the protein that carries oxygen. But some of the fish in Antarctica, the icefish, lack hemoglobin.

QUESTIONS TO THINK ABOUT: 1. All fish cells need oxygen so their mitochondria can work to make ATP, the molecule that provides energy for the cells to work. Why would it be adaptive for a fish to lack such an important protein? (Hint: think about energy conservation. Also think about blood viscosity.)

2. If the icefish lack hemoglobin how can they get enough oxygen to all the cells in their bodies?

3. Even though they don't have hemoglobin, the icefish do have some red blood cells (though much fewer in number). What do you think they have red blood cells for if they lack hemoglobin?

BACK TO THE RESEARCH

Finally we wondered if the concentration of DASPEI was too low so the chloride cells were not getting stained by it. To find out, we doubled the dosage yesterday and it worked like a charm. I am now excited about my project and the procedures are becoming routine. Everything seems to be working out all right. Today, the second day with the new technique should be the test. If it works well, I think I will be able to come up with some good data to determine whether or not fish in warmer water (about 4 degrees Celsius) have more chloride cells or bigger chloride cells than the fish in the normal sea water (-1.86 degrees Celsius). Then it will all get down to doing the mechanics of the counting and the measuring.

Well, I'd better go get lunch so I can start my afternoon work on schedule. Sierra injected the DASPEI into the live fish at 9:45 this morning. The DASPEI has to be flowing in the blood for 3 hours so she will harvest the gills for me at 12:45. At 12:15 I will drive the pick-up truck down to the old aquarium, put the fish in a cooler of 4 degree water, and bring it back up to the lab for her work on.

OH I ALMOST FORGOT

I found a great website about Weddell Seals. You can see photos, hear their sounds, and read about the research being done by them. Since their research is conducted right around here and their camp is near our fish hut by Cape Evans, their maps show the location of many of the areas I have mentioned. The address is http://siniff3.ecology.umn.edu

OK, I hope you have a good day and do something good for someone.

Fred Atwood

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Mr Atwood uses high quality photomicroscopy equipment to photograph the fluorescent chloride cells from the gills of a fish in the Crary lab at McMurdo Station.