[MARMAM] New Publication: Comparative physiology of vocal musculature in two odontocetes

Nicole Thometz nthometz at usfca.edu
Tue Jun 13 12:35:19 PDT 2017

Dear MarMam Community,

We are delighted to announce our most recent publication:

Thometz NM, Dearolf JL, Dunkin RC, Noren DP, Holt MM, Sims OC, Cathey BC,
Williams TM (2017) “Comparative physiology of vocal musculature in two
odontocetes, the bottlenose dolphin (*Tursiops truncatus*) and the harbor
porpoise (*Phocoena phocoena*)”. Journal of Comparative Physiology B. doi:

Abstract:     The mechanism by which odontocetes produce sound is unique
among mammals. To gain insight into the physiological properties that
support sound production in toothed whales, we examined myoglobin content
([Mb]), non-bicarbonate buffering capacity (β), fiber-type profiles, and
myosin heavy chain expression of vocal musculature in two odontocetes: the
bottlenose dolphin (*Tursiops truncatus*; n=4) and the harbor porpoise
phocoena*; n=5). Both species use the same anatomical structures to produce
sound, but differ markedly in their vocal repertoires. *Tursiops* produce
both broadband clicks and tonal whistles, while *Phocoena* only produce
higher-frequency clicks. Specific muscles examined in this study included:
1) the nasal musculature around the phonic lips on the right (RNM) and left
(LNM) sides of the head, 2) the palatopharyngeal sphincter (PPS), which
surrounds the larynx and aids in pressurizing cranial air spaces, and 3)
the genioglossus complex (GGC), a group of muscles positioned ventrally
within the head. Overall, vocal muscles had significantly lower [Mb] and β
than locomotor muscles from the same species. The PPS was predominately
composed of small diameter slow-twitch fibers. Fiber-type and myosin heavy
chain analyses revealed that the GGC was comprised largely of fast-twitch
fibers (*Tursiops*: 88.6%, *Phocoena*: 79.7%) and had the highest β of all
vocal muscles. Notably, there was a significant difference in [Mb] between
the RNM and LNM in *Tursiops*, but not *Phocoena*. Our results reveal
shared physiological characteristics of individual vocal muscles across
species that enhance our understanding of key functional roles, as well as
species-specific differences which appear to reflect differences in vocal

This manuscript was recently published online through the Journal of
Comparative Physiology B, and the article can be accessed here:

Nicole Thometz

Nicole M. Thometz, Ph.D.
Assistant Professor, Department of Biology
University of San Francisco
2130 Fulton Street, San Francisco, CA 94117
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