Abstract
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.
Highlights
Marsupials evolved separately from eutherian mammals in the Cretaceous period and form a highly diverse group with populations in the Americas and Australia (Luo, Yuan, Meng, & Ji, 2011; Nilsson et al, 2010)
The fat-tailed dunnart (Sminthopsis crassicaudata), is a small (10-20g) insectivorous Australian marsupial (Frey, 1991; Morton, 1978a) that is named after its characteristic swollen tail that contains stored fat (Godfrey, 1968)
In view of the fact that the fat-tailed dunnart has specific adaptations in its visual system, this paper explored functional and anatomical aspects of its auditory system to investigate whether this sensory system has distinct features compared to other marsupials
Summary
Marsupials evolved separately from eutherian mammals in the Cretaceous period and form a highly diverse group with populations in the Americas and Australia (Luo, Yuan, Meng, & Ji, 2011; Nilsson et al, 2010). The fat-tailed dunnart is a solitary animal with a widespread distribution across the southern and western parts of Australia inhabiting a variety of arid environments including open woodland, low scrublands, grasslands on clay or sand soils and farmlands (Morton, 1978a). Within these varied environments, the nocturnal dunnart hunts predominantly insects while itself being preyed upon by other predators such as snakes, feral cats and barn owls (Morton, 1978b). Previous work in a range of marsupial families such as northern quoll (Dasyurus hallucatus) (Aitkin, Nelson, & Shepherd, 1996), brush-tailed possums (Trichosurus vulpecula)
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