Name:______

Date: ______Per: ____

Nasonia Males and Females:

How Structure and Function are Related

Background

An adaptation is any trait that aids the chances of survival and reproduction of an organism. Arthropods are a very diverse group of animals that have survived millions of years of change on Earth because of their adaptations. Adaptations of arthropods have enabled them to live in many different environments and in greater numbers than members of any other phyla. Some examples are ladybugs, millipedes, shrimp, mites and spiders. Arthropods are diverse in appearance; however, they share similar internal and external features such as jointed appendages, segmentation, exoskeletons, open circulatory systems, and malpighian tubules. Insects are by far the largest group of organisms on Earth with more than 700,000 named species. They are characterized as mostly terrestrial and share the same general body plan: a head, thorax, and abdomen.

Many well-adapted structural differences exist between males and females of various organisms that are directly related to survival and reproduction. For example, male widow birds grow a long, colorful tail during mating season in order to attract female widow birds, IN plants, the female pistil has been adapted in such a way as to maximize the chances of collecting male pollen, while the structure of the male stamen in plants is adapted for easy dispersal of pollen.

Now, let’s take a look at some differences between males and females in other species. For each difference, hypothesize why you think these structural differences have been adapted.

  1. Female Kangaroos have pouches. Why?
  1. Male deer have antlers. Why?
  1. Female insects are generally larger in body size than male insects. Why?
  1. Male lions have a mane. Why?

Introduction

It is crucial when studying behavior, genetics, or most aspects of an organism, that scientists first determine how to tell one sex from the other. In this activity, you will be investigating make and female characteristics in a small parasitic wasp, known as Nasonia vitripennis.

You will determine the differences between male and female Nasonia by looking at the structures of each sex. You will then relate these structures to their functions in order to investigate the concept of evolutionary adaptation.

Materials

1 euthanized adult Nasonia (type A)

1 euthanized adult Nasonia (type B)

1 unknown live adult Nasonia (type A)

1 unknown live adult Nasonia (type B)

microviewing chamber

stereomicroscope

small paint brush

Procedure

A. Observation of Nasonia Characteristics

  1. Place the euthanized adult Nasonia type A onto the stage of the stereomicroscope. Note some of the characteristics of the “A” Nasonia so that you can recognize it when you place the “B” Nasonia next to it.
  2. Carefully place the euthanized adult Nasonia type B to the right of the “A” Nasonia on the microscope stage. Compare and contrast the “A” and “B” Nasonia. In Table 1, list all of the traits that you would consider unique to the “A” Nasonia and to the “B” Nasonia.
  3. As a class, pool your data. Record and observe any characteristics that you may have missed.
  4. Once completed, discard the “A” and “B” Nasonia as directed by your teacher.

B. Determining Male and Female Nasonia Based on Behavior

You will now try to determine which of the culture tubes, “A” or “B”, contains males and which contains females. In order to do this, you must first place the Nasonia together and observe mating. You can determine which Nasonia is the male because he will approach the female and eventually mount her as part of their mating ritual.

  1. Obtain an “A” tube with a living adult and tap the tube on the workbench so the Nasonia falls to the bottom.
  2. Repeat with tube “B”.
  3. Working quickly, remove the cotton plugs and put the two Nasonia together in a single tube. Replace the cotton plug in the tube with the two Nasonia.
  4. As soon as the Nasonia are together, observe mating behavior.
  5. Once you determine which is the male Nasonia, go back to Table 1 and fill in the sexes of the Nasonia contained in tubes “A” and “B”.
  6. Carefully add a Sarcophaga pupa to the Nasonia pair and observe the behavior of the male and the female.


Table 1: Characteristics of Male and Female Nasonia Figure 1: Drawings of “A” and “B” Nasonia

“A” Tube“B” Tube “A” Tube “B” Tube

Sex: _____Sex: _____

Analysis

  1. Male Nasonia can’t fly. Based on your observations, what characteristic suggests that?
  1. Why would the ability to fly be an advantage to the female?
  1. If the males can’t fly, how do they find mates?
  1. If you watched very carefully, you may have noticed that the male was “grooming” the female’s antennae with his mouth during the mating ritual. What do you think he was doing and why?
  1. Look back to Table 1 and review your observations. In the space below, list all of the differences between the males and females. For each one, give a possible reason for the difference.

Extension

The Nasonia that you used hatched from pupa with out coming in contact with any other flies. Keeping that in mind design and conduct one of the following experiments, or design one of your own. Record your question, your hypothesis and your procedures.

Add a virgin female to a sarcophagi pupa and observe her behavior.

Add several males to a single virgin female (with a sarcophagi pupa) and observe their behavior.

Add several males and several females (with a sarcophagi pupa) and observe their behavior.

With all experiments, we will incubate them at room temperature with 24 hour light and observe the results.

© Ward’s Natural Science Establishment, Inc.8/29/04