Synopsis

One of the most important decisions a female makes is how much energy to invest in reproductive parameters such as egg size and clutch size. A factor often constraining maternal investment in offspring is the nutritional status of the parent. This laboratory activity investigates how a female bean beetle's nutritional history (that is, the type of bean in which she was raised) influences the investment she makes in her offspring. Before the lab, students look up the nutritional content of two different bean types (mung beans and blackeye peas). With the help of the instructor, students develop a hypothesis regarding the effect of maternal nutritional history on the amount of energy invested in her offspring, develop an experimental procedure for testing their hypothesis, perform the experiment, and analyze the data using appropriate statistical tests. A typical student experiment involves (1) rearing virgin female and male bean beetles in mung beans and blackeye peas, (2) allowing mung bean-raised females to mate with mung bean-raised males and blackeye pea-raised females to mate with blackeye pea-raised males, (3) placing the resulting inseminated females on mung beans for a specified period of time, (4) measuring the sizes and numbers of eggs produced by the females, and (5) comparing the data from mung bean-raised females with the data from blackeye pea-raised females. In a postlab discussion, conclusions are drawn from the data, implications of the conclusions are discussed, and directions for future research are proposed.

Topic: Reproductive Physiology

Level: Intermediate or upper-level majors

Class time:

• Discussion (either in lecture or in a lab period prior to the one in which the experiment is designed) of the natural history of bean beetles and of parental reproductive investment strategies (50 minutes)
• Laboratory period in which beetles are mated and placed on new beans (75 minutes)
• Second laboratory period in which egg number data (75 minutes) and/or egg size data (90 minutes) are gathered
• Follow up discussion (either in lecture or in a subsequent lab period) (20 minutes)

Karin Gastreich and Gregory Fitch

Department of Biology, Avila University, Kansas City, MO 64145