LAB REPORT

Experimental Design and Data Analysis

Experimental Design and Data Analysis

Questions and Answers)

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Do isopods discriminate between moist and dry sites: lab report

The many different species of isopods around the world share certain characteristics. Isopods are crustaceans, distant kin of shrimps, crabs, and crayfish. Like all crustaceans, isopods have a segmented outer shell (seven overlapping plates) that provides a measure of protection from the environment and predators. Like their aquatic relatives, isopods get the oxygen they need to survive through gill-like structures located at the bases of their legs, rather than through lungs like most terrestrial organisms. Two kinds of isopods are of interest as classroom organisms. The genus Armadillidium is known casually as the pill bug or roly-poly. It gets these names from its habit of rolling into a tight sphere when threatened or stressed. The pill bug has a highly domed shape, short legs, and inconspicuous antennae. When in its defensive rolled posture, it is hard for a predator to grip, and it is also more resistant to drying out.

To make the trap, simply bore a 3/4-inch diameter hole through the potato lengthwise and then close up one end of the hole with a small piece of the potato plug. Place the "trap" in the garden or any other place where isopods are abundant and cover it with leaves. Let it remain there a few days. The isopods will come and feed inside the hole in the potato. To remove them, place the opening over a jar and strike the potato to dislodge them. The potato trap is especially useful for collecting small or young isopods and rare species too.

Colonies of one or more species can be easily reared indoors in a terrarium. A suitable vessel should be at least 12 in. long by 8 in. wide by 8 in. high so as not to crowd them and to facilitate observing their habits. Fill the bottom with pulverized soil about l-in. deep and moisten it with a little water. Place a few dry leaves, twigs, and pieces of bark on top. Add one or two small flat stones--supported by pebbles in such a way as to leave a small space beneath for the isopods to hide. Put a tightly folded paper towel soaked with water in the corner on the soil to give the isopods some water to drink and also to raise the humidity in the terrarium. Then place two or three small slices of potato or potato peels on the soil for food. A slice of raw carrot or some lettuce will provide variety. Then drop in the isopods and cover the terrarium with a piece of glass or plastic to keep the humidity high. Be sure to keep the terrarium out of direct sunlight. Once established, the isopods will reproduce and grow successfully, and the colony can be kept for many years with only a little attention. The paper towel may need rewetting or an additional piece of food may be needed ...