Adaptations of Fishes for Survival in Polar Environments (DRAFT) OVERVIEW In this set of activities students compare the anatomy of temperate and polar fishes and discuss reasons for the differences. They learn about the adverse effects of cold on metabolism and physiology and discuss how polar fishes are adapted to circumvent these effects. They learn about the effects of salt and antifreeze on the freezing point of water and they apply this knowledge to polar fish adaptations enabling them to survive at -1.9 C. They compare the DNA sequences of unrelated Arctic and Antarctic fish, look at their phylogenetic tree, and discuss convergent evolution. They learn about the specialized chloride cells in the gills of fish that enable them to control the salt concentrations of their body fluids so they donšt freeze and they brainstorm ways to study the effect of temperature on these chloride cells. Then they discuss actual data from experiments performed in Antarctica and try to draw conclusions from the data and propose additional questions for investigation. RATIONALE It is always fascinating to learn how organisms are adapted to live in the ultimate of extreme environments, enabling them to live on the edge of the conditions that life can tolerate, and to discuss reasons for the similarities and differences between them, ourselves, and the more familiar organisms around us. Antarctic fishes are perfect examples of this extreme specialization. The water in which they live is -2 C, cold enough to kill a human in just a few minutes, but just the right temperature for them. These fishes live in a very stable environment where the temperature fluctuates by less than 1 C. As a result, though these fishes are wonderfully adapted for this extreme environment, they cannot tolerate any change. In fact, if their temperature is raised just a few degrees, these fishes will die. COMPONENTS ACTIVITY 1: THE EFFECT OF COLD ON ..... Possibly different lab groups can do each of these and report results to the class. The Effect of Cold on the Rate of Diffusion The Effect of Cold on Enzyme Activity. Compare the activity of two enzymes at 4 different temperatures: one enzyme which works best in a warm environment (catalase or amylase) and one which works best in a cold environment (a laundry powder with enzymes?) Two groups. The Effect of Cold on Nerve Activity: Activities designed to show how poorly our warm-blooded bodies work when they get cold. Sensitivity to touch, reaction time, coordination. The Effect of Cold on Lipids and how this might relate to cell membranes. The Effect of Cold on the Amount of Dissolved Oxygen in the water. ACTIVITY 2 THE FREEZING POINT OF WATER Activities designed to show the effect of salt and antifreeze on the freezing point of water. The effect of a seed crystal (of ice) on freezing of an almost-freezing solution. Effect of subzero salt water on a piece of cold beef. Check with Arlene and Linda and with Sarah at FHS re activity with lowering freezing point using ice (competition to see who can get it lowest?) supercooling of water and its sudden freezing when a seed crystal is added). ACTIVITY 3 COMPARATIVE FISH ANATOMY Dissection and study of a fish-market fish (including microscopic investigation of its gills) and comparison with statistics and drawings of the anatomy of a typical Notothenioid fish of the Antarctic. Possible things to measure and to compare with temperate fish: body weight before dissection, salt concentration (conductivity CBL probes), lipid content (how?), heart weight, gill weight, ratio of bone to cartilage in skeleton, weight of skeleton, skin weight/sfc area ratio, kidney weight, spleen weight, red blood cell count, eye weight, number of nasal lamellae and their weight, dimensions and location of lateral line, (Sense organ measurements are to see if temperate and Notothens have different or same sense dominance for discussion). Difference seen might be related to living under ice, or to whether they are predators or scavengers. It may have nothing to do with polar vs temperate and more to do with feeding style but this would be a great thing for the kids to uncover by comparing their data.) ACTIVITY 4 BECOMING NEUTRALLY BUOYANT Some Notothenioid fishes are neutrally buoyant even though they lack the air sac found in most other fishes. Why is it important for them to be neutrally buoyant? How can this be? Modify a non-buoyant model of a fish to make it buoyant without the use of an air sac. ACTIVITY 5 DESIGN A FISH If the principles demonstrated in Activities 1 and 2 are true, how can a Notothenioid fish move, maintain its metabolism, and sense its environment? You will be given some constraints/guidelines to consider as well as a description of the physical environment in which the fish lives and you will design (and sketch) your view of what it would take to survive as a fish in the icy waters of Antarctica. Then you will discuss what the fishes are actually like. ACTIVITY 6 THE ADAPTIVE RADIATION OF NOTOTHENIOID FISHES When the ancestor of Notothenioid fishes was isolated from other fish by the circumpolar current which restricted it to the cold water of the Antarctic it evolved into 95 species, each with a different ecological niche. This is called adaptive radiation and is one of the few known examples in the fish world. In this activity you will compare the anatomy of some of these very different fish and hypothesize about what niche each might occupy before your teacher gives you the answers. ACTIVITY 7 CONVERGENT EVOLUTION OF ANTIFREEZE Convergent Evolution: The evolution of an antifreeze gene from that of a digestive enzyme and a comparison of the antifreeze genes in unrelated fish from the arctic and the Antarctic. ACTIVITY 8 REGULATION OF SALT CONCENTRATION IN THE BLOOD Fish Chloride Cells: Design some hypothetical experiments to test how temperature affects the activity of these cells which regulate salt concentration in the body. Then analyze real data from experiments performed in Antarctica to answer this question.