20 January, 1997
Rotifers in the lakes:
Today I had a chance to start my own research project on the feeding behaviors of rotifers. I am now called the rotifer wrangler. Some of the mat structures around the edge of the lake are red. I found a small pond quite near the edge of the Canada Glacier that is covered with red mat. The red mat is covered with grazing rotifers and tardigrades. The rotifers are thought to be the top of the food chain in these small ponds and perhaps even in the lakes. Have you seen rotifers before? If you do any water quality work and look at plankton, you probably have seen some of them The ones that I find here are bdelloid rotifers with two ciliated "APEARENTLY ROTATING" filters that create a flow of water into the mouth area. I am asking the question "What is the rate of feeding by these rotifers?" "How much water are they filtering in a given period of time?" Can you help me design the experiments? Why might knowing the answers to these questions be of some value to the LTRE? As far as I know, no one has done any work on rotifers yet in the Antarctic lakes. Had I known about rotifers being here in such abundance, I would have checked the literature before coming here. We might even be able to publish
a paper of our results, so lets collaborate. Let me tell you what I have done so far today. First, I collected a piece of mat about 6cm by 5cm, under the lake water, into a petri dish, put the lid on and took it back to the lab. I want to see how many rotifers are on a small piece of mat. Under the stereo scope in one field of view I counted 87 rotifers and two kinds, one large with bright red pigment and one much smaller with much less pigment. I think I will use only the large rotifers. Do you think that the small ones are just babies or are they a different species? Bdelloid rotifers are all female and lay eggs - very strange. Do they have no genetic variation with this method of reproduction? There are no male bdelloid rotifers. I have decided to feed the rotifers flourescently labeled microsperes(FLMs) so I can see that they have actually eaten a specific item that I can count. The FLM beads will glow green when put under fluorescing light from the microscope. I first have to see if they will even take up the FLMs. Then I have to see if they can be counted. I also have to figure out the concentration of the FLMs that I put into the water. The FLMs can be ordered from a scientific supply company. There are beads of several sizes available - .5, 2.5, 6.2 micrometers are the sizes available in this lab and they come in very high concentrations. I need todilute the beeds and count them under the epifluorescent microscope and make a concentration similar to what might be found in the lake water. I selected beeds of 6.2 micrometers in size because they are most similar to the size of the flagellates upon which the rotifers feed. The bead concentration that I am using is 4.6x10^6 or 4.6 million beads per ml. Next I set up a feeding experiment in which I placed 6 rotifers into a titre plate of filtered lake water and kept they there for 24 hours. This is to make them really hungry! Then I put them into 2mls of fresh lake water with 400 microliters of FLMs and left them for a while to see of they would even eat those FLMs. After an hour I put two of them under the epifluorescent microscope and held my breath. Did they take up those beads, did they spit them out or did they swallow the beads? Did they eat so many that I can't count them? What do you think happened? How can I now measure the rate of grazing? What things do I need to consider? How many rotifers should I use? How much water should I put in with them? What kind of water should I use? How many trials should I run? What other things do I need to be aware of that I haven't thought of? I need your help now so please send me some answers. You might try to collect some rotifers your selves. I had to break through the ice to get to this piece of mat. While I was working on the rotifers in the lab, Maria Stenzland, a photographer from National Geographic magazine came in. They are doing an arcticle for the magazine. She spent an hour looking at the rotifers and taking photographs.
Today was overcast and when the sun is gone, the temp drops rapidly. All of those flowing streams are now frozen. This was a good day to be in the lab all day. There were about 10 helicopter runs from the field camp today. Every time a helo comes or goes, the lab and the microscope shake like crazy. When in the field lab it is easy to forget just where I am until the helos rattle the lab. Bye for now
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