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Vocalizations by a sexually dimorphic isolated larynx: peripheral constraints on behavioral expression
1Department of Biological Sciences, Columbia University, New York, New York 10027.
Summary
Female Xenopus laevis frogs cannot produce rapid laryngeal muscle contractions needed for mate calling, unlike males. This physiological limitation, even with androgen treatment, explains sex-specific vocalization differences in these aquatic animals.
Area of Science:
- Bioacoustics
- Comparative physiology
- Animal behavior
Background:
- Xenopus laevis exhibits sexually dimorphic vocalizations: male mate calls and female ticking.
- Vocalization relies on rapid click production within the larynx.
- Male mate calls (71 Hz) are significantly faster than female ticking (6 Hz).
Purpose of the Study:
- Investigate if peripheral laryngeal mechanics limit vocalization rate differences between sexes.
- Examine the role of androgens in sex-specific laryngeal muscle function.
Main Methods:
- Isolated male and female Xenopus laevis larynges were studied.
- Laryngeal muscles were stimulated via nerves to record electromyograms and tension transients.
- Responses were analyzed in intact, castrated, and androgen-treated individuals.
Main Results:
- Laryngeal muscle response is sexually dimorphic in amplitude potentiation and tension transient production rate.
- Both sexes produce discrete tension transients at 6 Hz (ticking rate).
- Only male laryngeal muscle produces discrete tension transients at 71 Hz (mate call rate); androgen-treated females do not.
Conclusions:
- Discrete tension transient production is essential for click generation.
- Female Xenopus laevis laryngeal muscles are physiologically incapable of producing the rapid tension transients required for mate calling.
- This peripheral limitation, rather than central neural control, explains why females do not mate call, even when exposed to androgens.