The fat-tailed dunnart (Sminthopsis crassicaudata) is a small (10–20 g) native marsupial endemic to the south west of Western Australia. Currently little is known about the auditory capabilities of the dunnart, and of marsupials in general. Consequently, this study sought to investigate several electrophysiological and anatomical properties of the dunnart auditory system. Auditory brainstem responses (ABR) were recorded to brief (5 ms) tone pips at a range of frequencies (4–47.5 kHz) and intensities to determine auditory brainstem thresholds. The dunnart ABR displayed multiple distinct peaks at all test frequencies, similar to other mammalian species. ABR showed the dunnart is most sensitive to higher frequencies increasing up to 47.5 kHz. Morphological observations (Nissl stain) revealed that the auditory structures thought to contribute to the first peaks of the ABR were all distinguishable in the dunnart. Structures identified include the dorsal and ventral subdivisions of the cochlear nucleus, including a cochlear nerve root nucleus as well as several distinct nuclei in the superior olivary complex, such as the medial nucleus of the trapezoid body, lateral superior olive and medial superior olive. This study is the first to show functional and anatomical aspects of the lower part of the auditory system in the Fat-tailed dunnart.

The fat-tailed Dunnart (Sminthopsis crassicaudata) is a small (10-20g) native marsupial endemic to the south west of Western Australia. Currently little is known about the auditory capabilities of the dunnart, and of marsupials in general. Consequently, this study sought to investigate several electrophysiological and anatomical properties of the dunnart auditory system. Auditory brainstem responses (ABR) were recorded to brief (5ms) tone pips at a range of frequencies (4-47.5 kHz) and intensities to determine auditory brainstem thresholds. The dunnart ABR displayed multiple distinct peaks at all test frequencies, similar to other mammalian species. ABR showed the dunnart is most sensitive to higher frequencies increasing up to 47.5 kHz. Morphological observations (Nissl stain) revealed that the auditory structures thought to contribute to the first peaks of the ABR were all distinguishable in the dunnart. Structures identified include the dorsal and ventral subdivisions of the cochlear nucleus, including a cochlear nerve root nucleus as well as several distinct nuclei in the superior olivary complex, such as the medial nucleus of the trapezoid body, lateral superior olive and medial superior olive. This study is the first to show functional and anatomical aspects of the lower part of the auditory system in the Fattailed Dunnart. PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.27783v1 | CC BY 4.0 Open Access | recAbstract 25 The fat-tailed Dunnart (Sminthopsis crassicaudata) is a small (10-20g) native marsupial endemic 26 to the south west of Western Australia. Currently little is known about the auditory capabilities 27 of the dunnart, and of marsupials in general. Consequently, this study sought to investigate 28 several electrophysiological and anatomical properties of the dunnart auditory system. Auditory 29 brainstem responses (ABR) were recorded to brief (5ms) tone pips at a range of frequencies (4-30 47.5 kHz) and intensities to determine auditory brainstem thresholds. The dunnart ABR 31 displayed multiple distinct peaks at all test frequencies, similar to other mammalian species. 32ABR showed the dunnart is most sensitive to higher frequencies increasing up to 47.5 kHz. 33 Morphological observations (Nissl stain) revealed that the auditory structures thought to 34 contribute to the first peaks of the ABR were all distinguishable in the dunnart. Structures 35 identified include the dorsal and ventral subdivisions of the cochlear nucleus, including a 36 cochlear nerve root nucleus as well as several distinct nuclei in the superior olivary complex, 37 such as the medial nucleus of the trapezoid body, lateral superior olive and medial superior 38 olive. This study is the first to show functional and anatomical aspects of the lower part of the 39 auditory system in the Fat-tailed Dunnart. 40 41 42

The fat-tailed Dunnart (Sminthopsis crassicaudata) is a small (10-20g) native marsupial endemic to the south west of Western Australia. Currently little is known about the auditory capabilities of the dunnart, and of marsupials in general. Consequently, this study sought to investigate several electrophysiological and anatomical properties of the dunnart auditory system. Auditory brainstem responses (ABR) were recorded to brief (5ms) tone pips at a range of frequencies (4-47.5 kHz) and intensities to determine auditory brainstem thresholds. The dunnart ABR displayed multiple distinct peaks at all test frequencies, similar to other mammalian species. ABR showed the dunnart is most sensitive to higher frequencies increasing up to 47.5 kHz. Morphological observations (Nissl stain) revealed that the auditory structures thought to contribute to the first peaks of the ABR were all distinguishable in the dunnart. Structures identified include the dorsal and ventral subdivisions of the cochlear nucleus, including a cochlear nerve root nucleus as well as several distinct nuclei in the superior olivary complex, such as the medial nucleus of the trapezoid body, lateral superior olive and medial superior olive. This study is the first to show functional and anatomical aspects of the lower part of the auditory system in the Fat-tailed Dunnart.