Biology 425/525- Animal Behavior

Biology 360 Entomology Courtship in the Madagascar Hissing Roach

Introduction In sexually reproducing animals, courtship behavior functions to bring the two sexes of conspecifics together for mating. Courtship behavior is defined as pre-mating activities for stimulation, partner attraction and mating initiation. Patterns of courtship among species vary greatly, but the functions are uniform: 1) for species, sexual and individual recognition, 2) brings about competition through sexual selection and 3) insures stimulation and synchronization.

The Madagascar hissing roach, Gromphadorhina portentosa, is purchased through supply companies and maintained in laboratories throughout the United States. Its family, Blaberidae is one of the most successful animal families in the world, demonstrating high reproductive potential and following human habitation throughout the globe. Before you start the lab, note general morphological characteristics of your focal animals. Cockroaches are dorsoventrally flattened, allowing them access to small cracks and crevices. They have supersensitive cerci on the posterior of their abdomens which are responsive to minute air currents and these structures coupled with large motor neurons allow for an extremely rapid escape when predators threaten. Cockroach reproductive success is largely due to efficient courtship behavior. Species and sexual recognition are achieved through pheromones, and female receptivity, also influenced by pheromones, depends largely on physical displays performed by males. You will examine these aspects of courtship in this laboratory.

Your Objectives- To observe and describe the courtship behavior of the Madagascar hissing roach and demonstrate inter-sexual pheromonal communication.

Procedure A. Pheromone communication Obtain two of the large, glass Petri plates and cut cardboard dividers from box fragments. Use a wax pencil to divide the plates (marking the bottom half on the outside) into four, equal quadrants. Label each A, B, C, and D respectively. Choose one quadrant and tape cardboard dividers in place so as to isolate it from the remaining three. Place the Petri plate covers on the bottom upside down so it slides freely over the base.

Carefully capture two female adult roaches from the stock colony in either our lab or Richardson’s research lab and place them into the isolated quadrants and quickly slide the covers closed. Allow them to remain in the chambers for 5 minutes, then carefully remove them. Be certain that they make no contact with the other quadrants-if they do, you must wash the plate and start again! Return the females to the appropriate colony.

Carefully remove the cardboard dividers, turn the covers right side up and obtain a male from the colony in the other room (if you got your females in our lab, get a male from 264). Place a small amount of petroleum jelly on your thumb and forefinger and gently stroke each of the male’s antennae from base to tip (you breaky-you start overy). Do this several times to ensure even covering of the antennae. Place this male in one of the chambers and quickly close the cover. Obtain a second male from the male colony (the non-female) and place him directly into the second chamber. The latter male is “normal” and the former is “antennal block” on the data sheet. Tally their quadrant position (A, B, C, or D) every 5 seconds for 10 minutes. Record these data on the data sheet. Upon completion, return the normal male to his colony and the jellied male to a gallon jar to recover.

Wash your Petri plates with Alconox solution and repeat the entire procedure, reversing the colonies you use for males and females. Count your tallies and enter them under your run 1 and run 2 totals. You need to get everyone’s data from the class this week. B. Courtship behavior Carefully clean the Petri plates and obtain a fresh male and female. Place the pair in a clean Petri plate and carefully record what you see. How does the male use his antennae? What motor patterns are involved in his courtship display? Which modes are used in communication (tactile, olfactory, auditory, visual, etc.)? How is copulation attempted? Analysis

Using the “normal” and “antennal block” scores, determine whether the antennae are responsible for locating the female’s position by calculating the Mann-Whitney U-statistic. This test will tell you if the “normal” cockroach spent a significantly greater amount of time in the quadrant where the female had been then the male with “antennal block”.

To calculate U all the data (all 8 values from the class) must be ranked. Below is a sample set of data gathered from two experimental situations, A and B, with three sets of data from each:

A B Scores 49 62 57 81 69 94

Ranking, we have: A A B A B B 49 57 62 69 81 94

Note that we keep each score associated with its respective experimental condition. Our null hypothesis is that there is no difference between the two situations. To calculate U simply tally how many times A occurs before each B value, from left to right, and we find:

U=2+3+3=8

The sample size for condition A is n1=3 and condition B is n2=3. On checking the probability on the table you note that no value for U=8 is found on the table-this means that we calculated U’. To find U, use the following:

U=n1n2-U’ =3(3)-8 = 9-8 U= 1 Now, checking the table “n2=3” look for the associated probability at the intersection of U=1 and n1=3 . . . which is 0.10. We can not reject our null hypothesis. To do this we need p<.05 or a U value of 0.

Calculate U for your data and determine if there is a difference between the two males’ behavior. Also carefully outline and describe the courtship behavior you observed.