Meeting Abstract
45.1 Jan. 6 Evolution and function of communication signals in Apteronotus KOLODZIEJSKI, Johanna A.*; SMITH, G.T.; Indiana Univ; Indiana Univ hkolodzi@indiana.edu
Within the electric fish genus Apteronotus, communication signals known as �chirps� are produced by modulating the frequency and amplitude of an otherwise constant-frequency electric organ discharge (EOD). The number and structure of chirps vary across species and sex. Chirping is highly sexually dimorphic in the brown ghost knifefish, Apteronotus leptorhynchus. When stimulated with an electric signal simulating a conspecific, males chirp far more than females. Males also produce high frequency chirps that are rarely produced by females. These high frequency chirps are produced by males most often in response to female-like electric signals. They have therefore been hypothesized to be �courtship chirps.� The more common lower frequency chirps, produced by both males and females in response to same-sex signals, are hypothesized to be �aggressive chirps.� To test the validity of these hypothesized functions across species, we examined the chirp response of a closely related species, the black ghost knifefish (Apteronotus albifrons). This species produces fewer chirps than A. leptorhynchus and shows no sex difference in the number of chirps produced. In this study, both male and female A. albifrons produced low frequency chirps most often to same-sex signals, a pattern similar to that seen in A. leptorhynchus. A. albifrons also produced more high frequency chirps to same-sex stimuli than to opposite-sex stimuli. Therefore, although male A. leptorhynchus direct their high frequency chirps preferentially at female EODs, A. albifrons direct their high frequency chirps preferentially to same-sex EODs. This suggests that high frequency chirps in A. albifrons, unlike those in A. leptorhynchus, may not function as courtship signals. This behavioral evidence indicates that the use of high frequency chirps during courtship may be a derived feature in the lineage leading to A. leptorhynchus.
