Title

Effects of Ploidy on the Tuning of Hearing in Female Hyla versicolor and H. chrysocelis Treefrogs

Poster Number

30

Lead Author Major

Biological Sciences

Format

Poster Presentation

Faculty Mentor Name

Marcos Gridi-Papp

Faculty Mentor Department

Biological Sciences

Abstract/Artist Statement

Two sister species of gray treefrogs, Hyla versicolor and H. chrysocelis, share identical morphology, ecology and behavior but differ in ploidy level and call structure. Hyla chrysocelis is diploid and produces fast-pulsing calls, whereas H. versicolor is tetraploid and produces slow-pulsing calls. Polyploidy always increases cell size and this could potentially bias the tuning of the auditory system. This study examined females of both species to determine if ploidy level affects tuning in these species. Hearing was characterized via two methods: tympanic vibration and multicellular neural recording. Measurements of tympanic vibration are informative of transmission biases in the mechanical portion of the ears, whereas brain responses recorded from the torus semicircularis indicate actual hearing sensitivity. Preliminary results did not reveal differences in tuning that could not be attributed to body size, suggesting no significant effect of ploidy level on hearing. Such outcome could be explained by any of three mutually exclusive hypothesis: 1) increased cell size does not alter the mechanical properties of any of the components of the ear and it does not alter transduction by the hair cells; 2) natural selection prevents the increase of cell size in the auditory system; or 3) additional morphological changes have been selected to compensate for biases produced by increased cell size. Examination of the morphology of the auditory structures and the sizes of their cells is now necessary in order to identify the correct explanation.

Location

Grave Covell

Start Date

21-4-2012 10:00 AM

End Date

21-4-2012 12:00 PM

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Apr 21st, 10:00 AM Apr 21st, 12:00 PM

Effects of Ploidy on the Tuning of Hearing in Female Hyla versicolor and H. chrysocelis Treefrogs

Grave Covell

Two sister species of gray treefrogs, Hyla versicolor and H. chrysocelis, share identical morphology, ecology and behavior but differ in ploidy level and call structure. Hyla chrysocelis is diploid and produces fast-pulsing calls, whereas H. versicolor is tetraploid and produces slow-pulsing calls. Polyploidy always increases cell size and this could potentially bias the tuning of the auditory system. This study examined females of both species to determine if ploidy level affects tuning in these species. Hearing was characterized via two methods: tympanic vibration and multicellular neural recording. Measurements of tympanic vibration are informative of transmission biases in the mechanical portion of the ears, whereas brain responses recorded from the torus semicircularis indicate actual hearing sensitivity. Preliminary results did not reveal differences in tuning that could not be attributed to body size, suggesting no significant effect of ploidy level on hearing. Such outcome could be explained by any of three mutually exclusive hypothesis: 1) increased cell size does not alter the mechanical properties of any of the components of the ear and it does not alter transduction by the hair cells; 2) natural selection prevents the increase of cell size in the auditory system; or 3) additional morphological changes have been selected to compensate for biases produced by increased cell size. Examination of the morphology of the auditory structures and the sizes of their cells is now necessary in order to identify the correct explanation.