Hi,
Can you please post this announcement regarding a new research article
on the hearing in finless porpoise.
It is open access so people can download directly from the Journal of
Experimental Biology or contact me at the email below.
thank you.
Hearing pathways in the Yangtze finless porpoise, Neophocaena
asiaeorientalis asiaeorientalis
T. Aran Mooney, Songhai Li, Darlene R. Ketten, Kexiong Wang and Ding Wang
February 1, 2014 J Exp Biol 217, 444-452.
* Author for correspondence (amoo...@whoi.edu)
Abstract
How an animal receives sound may influence its use of sound. While ‘jaw
hearing’ is well supported for odontocetes, work examining how sound is
received across the head has been limited to a few representative
species. The substantial variation in jaw and head morphology among
odontocetes suggests variation in sound reception. Here, we address how
a divergent subspecies, the Yangtze finless porpoise (Neophocaena
asiaeorientalis asiaeorientalis) hears low-, mid- and high-frequency
tones, as well as broadband clicks, comparing sounds presented at
different locations across the head. Hearing was measured using auditory
evoked potentials (AEPs). Click and tone stimuli (8, 54 and 120 kHz)
were presented at nine locations on the head and body using a
suction-cup transducer. Threshold differences were compared between
frequencies and locations, and referenced to the underlying anatomy
using computed tomography (CT) imaging of deceased animals of the same
subspecies. The best hearing locations with minimum thresholds were
found adjacent to a mandibular fat pad and overlaying the auditory
bulla. Mean thresholds were not substantially different at locations
from the rostrum tip to the ear (11.6 dB). This contrasts with tests
with bottlenose dolphins and beluga whales, in which 30–40 dB threshold
differences were found across the animals' heads. Response latencies
increased with decreasing response amplitudes, which suggests that
latency and sensitivity are interrelated when considering sound
reception across the odontocete head. The results suggest that there are
differences among odontocetes in the anatomy related to receiving sound,
and porpoises may have relatively less acoustic ‘shadowing’.
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