|Target age or|
|Advanced biology class, may be modified for beginning biology.|
|Two 50-minute class periods for lab, two more for analysis.|
|Materials and equipment:||Microscopes or magnifying lenses|
Dissecting kits: tray, scalpel, forceps, probe, needle, scissors
Sample jars for parasites (with labels for source)
References: Wall chart for naming fish works well, but texts are useful for names as well as fish anatomy
|Summary of activity:||This lab involves the survey and dissection of as many fish as possible (I used 150). Students count nematodes, cestodes and crustaceans on the fish, fill out autopsy reports, and transfer data to a chalkboard data table. The results of the entire class are graphed and used to explore coevolution.
Extensions from this activity may include electrophoresis studies of nematode proteins, Hardy-Weinberg calculations and other ecological studies. Literature searches are a natural follow-up to student questions about the huge quantity and variety of parasites found.
|Prior knowledge, concepts or vocabulary necessary to complete activity:||Introduction to invertebrate parasites and life-styles. The advanced version may require introduction to population dynamics.|
Advance planning is necessary for obtaining the animals. I obtain mine from a fish packing plant that fillets the fish and makes the carcasses available for study. Thirty-gallon trash cans, plenty of ice, and a utility trailer are valuable. Disposal of carcasses may be critical as well, since your custodians may resent this kind of mess. My school has a composting pile, and some of the fish were rototilled directly into the garden.
1.To investigate the ecology of parasitism in marine teleosts.
2.To quantify variation in host infestations.
3.To practice dissection skills early in the year and learn some fish anatomy.
Questions and further study:
Data analysis usually invites more questions than answers. Virtually all of our fish were infested, but a small number had no nematodes or cestodes establish colonies. If questions are solicited from the students they can usually be sorted into parasite and host-related inquiry opportunities. Population dynamics, speciation and selection pressures are interesting follow-up lessons.
How common are parasites like nematodes and cestodes (tapeworms) in fish? This lab will provide you with some background on the numbers and variety of these organisms throughout fish populations. Your textbook or other source will be useful in identifying internal and external anatomy of a fish for the initial survey, and more detailed internal anatomy of the digestive system for the worm count.
|Fish Number:||Fish Type:||Length:|
|Small Intestine:||Large Intestine:|
B. Make a bar graph of the class data. Plot the number of parasites per fish organ for both schooling fish and bottom fish.
1.From your graph, describe the frequency of parasites in the marine fish we studied.
2.If the fish and parasite genotypes were stable and balanced with each other, describe the changes that might occur if a single mutation left a fish more able to resist the parasites.
3.What if the fish mutation in question #2 was followed by increased numbers of nematode variants that could invade the new fish, but made them less adapted to the original fish?
4.Describe how the interactions between parasites and hosts might lead to new species.
Noble, E.R. and Noble, G. A. Parasitology: The Biology of Animal Parasites. London: Lea and Febiger Publishing, 1971.
Rollinson, D. and Anderson, R. M. (editors). The Ecology and Genetics of Host-Parasite Interactions. Orlando, FL: Academic Press, 1985.
Smith, J. D. Introduction to Animal Parasitology. Cambridge University Press, 1994.
On to Charlotte and Her Relatives
Visit the Classroom
Back to Index