Literature: Is Copulation Risky for Female Bed Bugs?

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Literature: Is Copulation Risky for Female Bed Bugs?

Is Copulation Risky for Female Bed Bugs?

Stutt, A. & Siva-Jothy, T. 2001. Traumatic insemination and sexual conflict in the bed bug Cimex lectularius. Proceedings of the National Academy of Sciences, 98(10): 5683-5687.

Article Summary:
Bed bugs provide an interesting and compelling example of a conflict of interest between mates. Generally, scientists have assumed that both male and female parents have similar interests in reproduction. However, bed bugs mate in a peculiar manner that is advantageous for males but downright dangerous for females. The genitalia of the female bed bug do not function in copulation. Instead, the male injects sperm through the abdominal wall into a paragenital organ, a phenomenon known as traumatic insemination. Traumatic insemination wounds the females and may also result in infection.

Alistair Stutt and Michael Siva-Jothy (2001) have explored the nature of the conflict between male and female bed bugs experimentally. They began by videotaping groups of bed bugs to observe the mating frequency. Typically, females mated five times after a blood meal. Females reached maximum fertility after mating only once, but were mating much more often. The authors also investigated last sperm precedence using irradiated (sterilized) males: numbers of inviable eggs fertilized by the irradiated male were compared to numbers of viable eggs sired by the non-irradiated male. The last male to mate fertilized more eggs.

In an experiment designed to evaluate the effects of remating on female bed bugs, Stutt and Siva-Jothy (2001) assigned female bed bugs to two treatment groups. In the low mating frequency treatment, they placed virgin female bed bugs with virgin male bed bugs initially. After one week, they replaced the male bed bug with another male whose intromittent organ was glued to his abdomen and therefore nonfunctional. In the control group, each virgin female bed bug was placed with a virgin male for four weeks. Females in the low mating frequency treatment produced eggs at the same rate as the control bugs, indicating that additional copulation does not increase female fitness. However, females in the control group died at a higher rate, resulting in reduced lifetime reproductive success.

Stutt & Siva-Jothy (2001) conducted a second experiment designed to test whether there are indirect benefits of traumatic insemination for females. In this experiment, they compared the eggs of females allowed to copulate just once with one male to those allowed to copulate one time with each of five males. They observed no differences in egg numbers, hatching success or adult size between the two treatment groups.

1. Why does mating in bed bugs represent a conflict between males and females? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

2. Why is traumatic insemination adaptive for male bed bugs? Why is it less likely to be adaptive for female bed bugs? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

3. The authors present two options to explain the evolution of the female paragenital system, female choice and natural selection for female survival. Which do their experiments support, and why? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

4. Why haven’t female bed bugs evolved a behavioral defense against traumatic insemination? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

5. In the experiment designed to test the cost of remating, Stutt & Siva-Jothy (2001) suggest that the reduced longevity of bugs in the control group may result from either the energetic cost of repairing the abdomen or from infection. How would you design an experiment to test one or both of these possibilities? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

6. Male bed bugs often attack other males with their intromittent organs. This may represent another form of competition among male bed bugs. Alternatively, it may not be adaptive at all (see chapter 8). How would you test whether this behavior is adaptive for male bed bugs? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.




1.	Why does mating in bed bugs represent a conflict between males and females? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



2.	Why is traumatic insemination adaptive for male bed bugs? Why is it less likely to be adaptive for female bed bugs? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



3.	The authors present two options to explain the evolution of the female paragenital system, female choice and natural selection for female survival. Which do their experiments support, and why? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



4.	Why haven’t female bed bugs evolved a behavioral defense against traumatic insemination? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



5.	In the experiment designed to test the cost of remating, Stutt & Siva-Jothy (2001) suggest that the reduced longevity of bugs in the control group may result from either the energetic cost of repairing the abdomen or from infection. How would you design an experiment to test one or both of these possibilities? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



6.	Male bed bugs often attack other males with their intromittent organs. This may represent another form of competition among male bed bugs. Alternatively, it may not be adaptive at all (see chapter 8). How would you test whether this behavior is adaptive for male bed bugs? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

Chapter 12: Activity

Literature: Is Copulation Risky for Female Bed Bugs?