Table Of ContentSENSORY EVOLUTION THRESHOLD
on the
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SENSORY EVOLUTION
THRESHOLD
on the
Adaptations in Secondarily Aquatic Vertebrates
Edited by
J. G. M. Thewissen
and Sirpa Nummela
UNIVERSITY OF CALIFORNIA PRESS
Berkeley Los Angeles London
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University of California Press
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© 2008 by the Regents of the University of California
Library of Congress Cataloging-in-Publication Data
Sensory evolution on the threshold : adaptations in secondarily aquatic
vertebrates / edited by J.G. M. Thewissen and Sirpa Nummela.
p. cm.
Includes bibliographical references and index.
ISBN 978-0-520-25278-3 (case : alk. paper)
1. Aquatic animals—Sense organs. 2. Aquatic animals—Adaptation.
3. Sense organs—Evolution. I. Thewissen, J. G. M. II. Nummela, Sirpa.
QL120.S47 2008
591.4—dc22
2007039518
Manufactured in the United States of America
10 09 08
10 9 8 7 6 5 4 3 2 1
The paper used in this publication meets the minimum requirements
of ANSI/NISO Z39.48-1992 (R 1997) (Permanence of Paper).
Cover photograph: Ian Murphy / Getty Images
contents
Contributors / vii Hearing
1 • Introduction: On Becoming Aquatic / 1 11 • The Physics of Sound in Air and Water / 175
12 • Comparative Anatomy and Function of
Chemical Senses
Hearing in Aquatic Amphibians, Rep-
tiles, and Birds / 183
2 • The Physics and Biology of Olfaction and
Taste / 29 13 • Hearing in Aquatic Mammals / 211
3 • The Chemical Stimulus and Its
Balance
Detection / 35
4 • Comparative Anatomy and Physiology of 14 • The Physics and Physiology of
Chemical Senses in Amphibians / 43 Balance / 227
5 • Comparative Anatomy and Physiology of 15 • Comparative and Functional Anatomy of
Chemical Senses in Nonavian Aquatic Balance in Aquatic Reptiles and
Reptiles / 65 Birds / 233
6 • Comparative Anatomy and Physiology of 16 • Comparative and Functional Anatomy of
Chemical Senses in Aquatic Birds / 83 Balance in Aquatic Mammals / 257
7 • Comparative Anatomy and Physiology of
Chemical Senses in Aquatic Mechanoreception
Mammals / 95
17 • The Physics and Physiology of
Mechanoreception / 287
Vision
18 • Mechanoreception in Secondarily Aquatic
8 • The Physics of Light in Air and Vertebrates / 295
Water / 113
9 • Comparative Anatomy and Physiology of Magnetoreception and Electroreception
Vision in Aquatic Tetrapods / 121
19 • Magnetoreception / 317
10 • Structure and Function of the Retina in
Aquatic Tetrapods / 149 20 • Electroreception / 325
21 • Toward an Integrative Approach / 333
Index / 341
v
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contributors
GUIDO DEHNHARDT, University of Rostock, Insti- LEO PEICHL, Department of Neuroanatomy, Max
tute for Biosciences, Sensory & Cognitive Ecology, Planck Institute for Brain Research, Frankfurt am
Rostock, Germany Main, Germany
HEATHER L. EISTHEN, Department of Zoology, HENRY PIHLSTRÖM, Department of Biological and
Michigan State University, East Lansing Environmental Sciences, University of Helsinki,
Finland
JUSTIN A. GEORGI,Doctoral Program of Anatomi-
cal Sciences, Stony Brook University, New York JOHN O. REISS, Department of Biological
Sciences, Humboldt State University, Arcata, Cali-
SIMO HEMILÄ, Department of Biological and Envi- fornia
ronmental Sciences, University of Helsinki, Fin-
land TOM REUTER, Department of Biological and Envi-
ronmental Sciences, University of Helsinki, Fin-
THOMAS HETHERINGTON, Department of Evolu- land
tion, Ecology, and Organismal Biology, The Ohio
State University, Columbus KURT SCHWENK, Department of Ecology and Evolu-
tionary Biology, University of Connecticut, Storrs
TOBIN L. HIERONYMUS, Department of Biological
Sciences, Ohio University, Athens JUSTINS.SIPLA, Department of Rehabilitation Sci-
ences, University of Texas at El Paso
MICHAEL H. HOFMANN, Department of Biology
and Center for Neurodynamics, University of Mis- FRED SPOOR, Department of Anatomy and Devel-
souri-St. Louis opmental Biology, University College London,
London, UK
GADI KATZIR, Department of Biology, University
of Haifa at Oranim, Israel J.G.M. THEWISSEN, Department of Anatomy,
Northeastern Ohio Universities College of Medi-
RONALD H.H. KRÖGER, Department of Cell and cine, Rootstown
Organism Biology, Lund University, Sweden
LON A. WILKENS, Department of Biology and Cen-
BJÖRN MAUCK, Institute of Biology, University of ter for Neurodynamics, University of Missouri-
Southern Denmark, Odense, Denmark St.Louis
SIRPA NUMMELA, Department of Biological and
Environmental Sciences, University of Helsinki,
Finland
vii
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1
Introduction
ON BECOMING AQUATIC
J. G. M. Thewissen and Sirpa Nummela
Natural Experiments to live in humid environments. With the origin
Aquatic Tetrapods of amniotes (reptiles, birds, and mammals)
Senses in Evolution around 320 million years ago, the transition to
Goal and Scope land was complete: the embryo is protected
Amphibians from dehydration by being bathed in a fluid
Aquatic and Semiaquatic Reptiles bubble surrounded by membranes. Moreover,
Aquatic and Semiaquatic Birds amniote skin is covered by keratin, a waterproof
Aquatic and Semiaquatic Mammals protein that minimizes water loss through
evaporation, allowing amniotes to live away
from humidity. Dry land offered a host of
Vertebrate life became terrestrial about 370 mil- opportunities and challenges to the newly ter-
lion years ago when a lobe-finned fish evolved restrial tetrapods.
into the giant-salamander-like shape of a In the period since the origin of tetrapod
labyrinthodont amphibian. The transition is well land life, many vertebrates have returned to
documented in the fossil record, and important the water. Some, such as crocodiles, became
discoveries continue to fill out its details. Over amphibious and never left these transitional
the eons subsequent to the water-to-land transi- habitats. Others, such as whales, returned to
tion, vertebrates became more and more inde- the oceans completely and are unable to live
pendent from water. The new land vertebrates on land. In spite of their deep watery roots,
are called tetrapods, a group that includes mod- these secondarily aquatic vertebrates started
ern amphibians, reptiles, birds, and mammals. their evolutionary journey with bodies that
The term refers to their extremities: the replace- were adapted to live on land and in air. Occa-
ment of four paired fins by four paired legs. sionally they evolved adaptations similar
Amphibians still return to the water to avoid to those of their fish ancestors, such as the
dehydration of their eggs and larvae and have multirayed, multisegmented forelimbs of
skin that is permeable to water, restricting them ichthyosaurs. In most cases, though, their
1
