[MARMAM] new article - porpoise hearing

Aran Mooney amooney at whoi.edu
Mon Feb 3 02:48:40 PST 2014


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 (amooney at 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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