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The startle reflex in echolocating odontocetes: basic physiology and practical implications

The acoustic startle reflex is an oligo-synaptic reflex arc elicited by rapid-onset sounds. Odontocetes evolved a range of specific auditory adaptations to aquatic hearing and echolocation, e.g. the ability to downregulate their auditory sensitivity when emitting clicks. However, it remains unclear...

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Autores principales: Götz, Thomas, Pacini, Aude F., Nachtigall, Paul E., Janik, Vincent M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Company of Biologists Ltd 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7075047/
https://www.ncbi.nlm.nih.gov/pubmed/32165452
http://dx.doi.org/10.1242/jeb.208470
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author Götz, Thomas
Pacini, Aude F.
Nachtigall, Paul E.
Janik, Vincent M.
author_facet Götz, Thomas
Pacini, Aude F.
Nachtigall, Paul E.
Janik, Vincent M.
author_sort Götz, Thomas
collection PubMed
description The acoustic startle reflex is an oligo-synaptic reflex arc elicited by rapid-onset sounds. Odontocetes evolved a range of specific auditory adaptations to aquatic hearing and echolocation, e.g. the ability to downregulate their auditory sensitivity when emitting clicks. However, it remains unclear whether these adaptations also led to changes of the startle reflex. We investigated reactions to startling sounds in two bottlenose dolphins (Tursiops truncatus) and one false killer whale (Pseudorca crassidens). Animals were exposed to 50 ms, 1/3 octave band noise pulses of varying levels at frequencies of 1, 10, 25 and 32 kHz while positioned in a hoop station. Startle responses were quantified by measuring rapid muscle contractions using a three-dimensional accelerometer attached to the dolphin. Startle magnitude increased exponentially with increasing received levels. Startle thresholds were frequency dependent and ranged from 131 dB at 32 kHz to 153 dB at 1 kHz (re. 1 µPa). Startle thresholds only exceeded masked auditory AEP thresholds of the animals by 47 dB but were ∼82 dB above published behavioural audiograms for these species. We also tested the effect of stimulus rise time on startle magnitude using a broadband noise pulse. Startle responses decreased with increasing rise times from 2 to 100 ms. Models suggested that rise times of 141–220 ms were necessary to completely mitigate startle responses. Our data showed that the startle reflex is conserved in odontocetes and follows similar principles as in terrestrial mammals. These principles should be considered when assessing and mitigating the effects of anthropogenic noise on marine mammals.
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spelling pubmed-70750472020-03-17 The startle reflex in echolocating odontocetes: basic physiology and practical implications Götz, Thomas Pacini, Aude F. Nachtigall, Paul E. Janik, Vincent M. J Exp Biol Research Article The acoustic startle reflex is an oligo-synaptic reflex arc elicited by rapid-onset sounds. Odontocetes evolved a range of specific auditory adaptations to aquatic hearing and echolocation, e.g. the ability to downregulate their auditory sensitivity when emitting clicks. However, it remains unclear whether these adaptations also led to changes of the startle reflex. We investigated reactions to startling sounds in two bottlenose dolphins (Tursiops truncatus) and one false killer whale (Pseudorca crassidens). Animals were exposed to 50 ms, 1/3 octave band noise pulses of varying levels at frequencies of 1, 10, 25 and 32 kHz while positioned in a hoop station. Startle responses were quantified by measuring rapid muscle contractions using a three-dimensional accelerometer attached to the dolphin. Startle magnitude increased exponentially with increasing received levels. Startle thresholds were frequency dependent and ranged from 131 dB at 32 kHz to 153 dB at 1 kHz (re. 1 µPa). Startle thresholds only exceeded masked auditory AEP thresholds of the animals by 47 dB but were ∼82 dB above published behavioural audiograms for these species. We also tested the effect of stimulus rise time on startle magnitude using a broadband noise pulse. Startle responses decreased with increasing rise times from 2 to 100 ms. Models suggested that rise times of 141–220 ms were necessary to completely mitigate startle responses. Our data showed that the startle reflex is conserved in odontocetes and follows similar principles as in terrestrial mammals. These principles should be considered when assessing and mitigating the effects of anthropogenic noise on marine mammals. The Company of Biologists Ltd 2020-03-12 /pmc/articles/PMC7075047/ /pubmed/32165452 http://dx.doi.org/10.1242/jeb.208470 Text en © 2020. Published by The Company of Biologists Ltd http://creativecommons.org/licenses/by/4.0This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
spellingShingle Research Article
Götz, Thomas
Pacini, Aude F.
Nachtigall, Paul E.
Janik, Vincent M.
The startle reflex in echolocating odontocetes: basic physiology and practical implications
title The startle reflex in echolocating odontocetes: basic physiology and practical implications
title_full The startle reflex in echolocating odontocetes: basic physiology and practical implications
title_fullStr The startle reflex in echolocating odontocetes: basic physiology and practical implications
title_full_unstemmed The startle reflex in echolocating odontocetes: basic physiology and practical implications
title_short The startle reflex in echolocating odontocetes: basic physiology and practical implications
title_sort startle reflex in echolocating odontocetes: basic physiology and practical implications
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7075047/
https://www.ncbi.nlm.nih.gov/pubmed/32165452
http://dx.doi.org/10.1242/jeb.208470
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