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: 10.1007/s00360-017-1106-5.
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 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 capacities.
This manuscript was recently published online through the Journal of Comparative Physiology B, and the article can be accessed here:
http://rdcu.be/s9fM
Best,
Nicole Thometz
--
Nicole M. Thometz, Ph.D.
Assistant Professor, Department of Biology
University of San Francisco
2130 Fulton Street, San Francisco, CA 94117