Whew, I am wrapping up the season’s experiments and packing up gear in preparation for heading home to Alabama. It is hard to believe that on January 28 I will once again sail away from Palmer Station. My thirteenth visit to the Antarctic has been almost 13 weeks in duration.
It has been a busy time for me science-wise, despite what my previous entries may indicate. So just what have I been doing other than skiing, enjoying holidays and hosting visitors to Palmer? Well mostly I have been doing feeding experiments. Instead of preparing pie crusts or stuffing for people to savor, I daily would prepare fixings for the projects’ animal taste testers: sea stars, shrimp-like amphipods (less than 1/4” long) and fish.
The basic ingredient for each of the fixings fed to the 3 types of tasters was ground up dried algae. The sea stars and amphipods preferred Cladophora, a green alga, and the fish preferred Palmaria, a red alga. The next ingredient used in both preparations was liquefied alginate, commonly used as a thickener in people food, like ice cream and salad dressing, and it served the same purpose in this case. The alginate and the dried algae were mixed together in a small dish resulting in a syrupy slurry. A cold solution of calcium chloride was poured over on top of the mix to solidify the syrup — sort of like adding ice to set a bowl of jello. Unlike most Jell-O desserts though, this creation was a very thin layer, less than a ¼" deep, and did not jiggle. The recipe just described was the control food for the test. Experimental food was made in the same way except that to the dried algae, I would add unique ingredients the project had chemically extracted from other plants or animals. When chocolate chip cookies are baked for people for instance, vanilla extract (the brown liquid is chemically derived from the vanilla bean) is added to the batter for flavor. For each taste test I would have a dish of control food and a dish of experimental food to feed each of our tasters. Using essentially a small circular cookie cutter, I would then punch out little disks of the control and experimental preparation to feed the tasters.
How can you tell when a sea star, amphipod or fish likes a food? Scientists commonly do two types of feeding experiments: choice experiments and eat/do not eat experiments. The fish and the sea stars experiments were considered the latter type. I would offer the animals a disk and watch to see whether is was eaten or whether it was rejected. To feed the fish, I put on warm, waterproof gloves, picked the food disk up with a pair of long blunt tweezers, stuck my hand holding the tweezers into the water in front of the fish’s mouth. Most times the fish was cooperative and took the disk without much fuss. Other times I had to chase it around the tank to encourage it to try. It brought back memories of feeding fussy young nieces and nephews using the spoon-airplane trick. Once I was able to make contact with the fish, I watched to see whether it swallowed the disk and spit it out. Each fish was fed a control disk and an experimental disk. Ideally, the control disk was always eaten. Many times, the experimental disk was eaten too indicating that the added extract did not affect the taste of the disk. The exciting result though, was when the experimental disk was spit out, rejected, not eaten as it implies the extract added was for some reason not appealing to the fish.
The sea stars were usually more cooperative than the fish with the eat/no eat experiments. For some reason, when kept in an aquarium, the sea stars crawl up the wall and upon reaching the water-air interface, will outstretch one or two of the five arms. The undersides of each arm are lined with tiny little structures called tube feet which are sort of like mini suction cups. The tube feet aid not only in movement such as climbing up the aquarium wall but also in feeding as each tiny foot has chemotactic ability — essentially little taste buds. Small morsels of either the control disk or the experimental disk were placed atop the tube feet on an extended sea star arm. I would then watch to see if the tube feet started moving that morsel conveyor belt fashion toward and eventually into the mouth and eaten or toward the tip of the arm and eventually dropped into the water and rejected.
The amphipod experiments were choice experiments (“choosy mothers choose Jif”). Twenty amphipods were placed in bottle of seawater along with pre-weighed control and experimental disks. Approximately 12 hours later those disks were reweighed. The change in the weight of the disks indicated which preparation, if either, the amphipods preferred. Since the disks themselves tended to swell and gain weight in seawater, a duplicate bottle with just the 2 preweighed disks was set up and treated the same as the bottle with the amphipods.
Taste tests are always conducted using many tasters to enhance the statistical validity or confidence in the observed reactions or apparent preferences. A single experiment therefore involved feeding multiples of our three testers. Each fish and sea star experiment involved feeding 12 individuals. An amphipod experiment entailed 10 bottles with 20 amphipods for a total of 200 amphipods per experiment. Lots of mouths to feed for just one suite experiments. How many experiments did I do you during your stay at Palmer you ask??? I ran 34 fish experiments which means that each fish hand fed from me 68 times. Twelve fish multiplied by 68 feedings equals 816 fish mouths I fed! I did 32 experiments with the sea stars which means I placed morsels on 768 sea star arms. Finally, I conducted 34 amphipod experiments which means I counted and fed 6800 amphipods and weighed 1632 disks (initial and final weights)!
I am savoring the thought of working in my own kitchen soon and preparing non-algal based recipes. I look forward to subjecting family and friends to tasty people foods as we share experiences of the last 13 weeks. I’d better get packing....