Ecophysiology of Amphibians Inhabiting Xeric Environments

193 Pages·1997·5.04 MB·English

by  Prof. Dr. Michael R. Warburg (auth.)

Adaptations of Desert Organisms
Edited by J.1. Cloudsley-Thompson
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Ecophysiology of Amphibians Inhabiting Xeric Environments
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Michael R. Warburg
Ecophysiology of Amphibians
Inhabiting Xeric Environments
With 39 Figures and 18 Tables
Springer
Prof. Dr. MICHAEL R. W ARBURG
Department of Biology
Technion - Israel Institute of Technology
Haifa 32000
Israel
ISSN 1430-9432
ISBN-13:978-3-642-64369-9 e-ISBN-13:978-3-642-60357-0
DOl: 10.1007/978-3-642-60357-0
Library of Congress Cataloging-in-Publication Data. Warburg, M.R. (Michael R.). 1931 Ecophysiol
ogy of amphibians inhabiting xeric environments/Michael R. Warburg p. cm. - (Adaptations of
desert organisms) Includes bibliographical references and index.ISBN-I3:978-3-642-64369-9(hardcover)
L Amphibians - Ecophysiology. 2. Amphibians - Adaptation. 3. Xeric habitats. I. Title.
II. Series_ QL669.8.W37 1997 597.8'1754 -dc21 97-39317
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© Springer-Verlag Berlin Heidelberg 1997
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This book is dedicated to the memory of my late mother,
Ilse, who never discouraged me from bringing all kinds of
curious animals into our home, and to my late sister, Hana,
who so much wished to see the book I wrote but passed
away too soon.
Preface
The main difficulty in this subject is to clarify the cardinal problems
facing amphibians in seasonally xeric habitats. These problems are
basically the same whether an amphibian inhabits xeric, semi-arid
or arid habitats; the differences are solely a matter of magnitude.
Thus, if we find that an amphibian must be well adapted and con
sequently capable of reducing its body water loss, the length of time
it is exposed to such adverse conditions is the main distinction
between these habitats. Likewise, it is the duration of time during
which high temperatures prevail that varies. Therefore, we are deal
ing with two kinds of mechanisms: short-term and long-term sur
vival. In order to be able to evaluate these adaptations, we need to
look into the structure of various key organs such as skin, kidney,
bladder, lung and ovary, among others. This knowledge will enable
us to appreciate the ways the organs are involved in effecting these
different kinds of adaptations.
Whereas these adaptations may concern the welfare of an indi
vidual animal, entirely different problems face the species that
inhabits such habitats. To survive, a species must be capable of
reproducing more of its own kind. Even if the individual can sur
vive long periods of water shortage and lengthy exposure to high
temperatures, this does not necessarily imply that the aquatic
stages or young post-metamorphic juveniles can survive. In that
case the animal must adapt in a different way by spreading out its
reproductive efforts over a longer period. This, on the other hand,
would involve different kinds of structural and ecological adapta
tions. Are amphibian species adapted to xeric environments long
lived, and if so, do they live longer than similar forms inhabiting
less hostile habitats? Are they iteroparous (capable of reproducing
more than once) or perhaps semelparous (producing one large
cohort only)? Are they opportunistic breeders, prepared to seize
any chance enabling them to breed? What kind of adaptations are
required to be able to carry out such different reproductive pat
terns? These and many other kinds of questions were the ones I had
in mind when setting out to write this book. Whether I succeeded in
clarifying some of these points or raising several more instead will
VIII Preface
be judged by the reader. I personally feel profoundly rewarded by
having had the good fortune to read so many interesting papers,
while accumulating the kind of information needed here. I only
regret that I could cite only a fraction of these most interesting
studies; consequently, the decision concerning which papers
should be discussed here and which not was a very difficult one for
me.
As preparing this book required learning about various subjects
some of which I understood less well than others, I am certain that
the reader will notice the transitions. I apologise for any taxonomic
errors, especially since I preferred using the original taxa name
rather than the most current one (Scaphiopus rather than Spea, for
example). I take comfort in the fact that the species' names change
continuously, and thus one can never be fully up to date, as in all
other fields. However, the basic picture is not likely to change
because of that.
Haifa MICHAEL R. W ARBURG
December 1996
Acknowledgements
Much of the research for this book was done during my sabbatical
leaves at the Universities of New Mexico (USA) and New South
Wales (Australia). I am greatly indebted to Prof. Cliff Crawford and
to Prof. Hal Heatwole for their kind hospitality in their labs at these
respective institutes, and for having the opportunity to study in the
libraries there. I wish also to thank Prof. Hal Cogger, formerly of the
Australian Museum, Sydney, for providing the beautiful photo
graphs of Australian frogs, Profs. Eduard Linsenmair and John
Loveridge for the valuable prints of African frogs, Prof. Bill
Duellman for enabling the representation of some South American
amphibians, and Dr. Catherine Propper for providing Fig. 2.12. I
am also indebted to Prof. John Cloudsley-Thompson for reviewing
the original manuscript and for his most valuable suggestions.
Over the years I have benefited from the assistance of several
students, some of whom are now my colleagues. Thus, I am in
debted to Shoshi Goldenberg, Mira Rosenberg, Rakefet Sharon and
Olga Gealekman for their enthusiastic collaboration. In particular, I
enjoyed the support of Dina Lewinson and Gad Degani, former
students and later colleagues. Mira Rosenberg, my assistant over the
last 25 years, has devoted much of her life collaborating on the
structural aspects of amphibian tissues. I am most indebted to her
for making this partnership such a happy period. Finally, through
out my research over many years, I have enjoyed the encourage
ment of my family. First, my late father, Sigmunt, who introduced
me to observing, handling and keeping animals, and to my late
mother, Ilse, who tolerated all kinds of strange animals in our home.
Later, I was actively helped by my wife, Hava, who joined me on
many collecting trips in deserts of various continents, on hot days
and sometimes rather cold, wet nights observing amphibian life.
Later, my children joined in, each at his time. First, my son Ittai, who
also prepared a beautiful school project on the salamander larva.
Then my daughters, Sharon and Meirav, all of whom loved to go out
on freezing cold, stormy nights to observe salamanders migrating to
their breeding ponds, and who tried to identify them individually. I
am very fortunate indeed to have had such support from all of them.
Contents
1 Introduction .................................... 1
2 Xeric Habitats and Their Amphibian Inhabitants ..... 3
2.1 The Habitats .............................. . 3
2.1.1 The Xeric Habitat .......................... . 3
2.1.2 The Semi-arid and Arid Habitats ............. . 3
3 Structural and Functional Adaptations of Key Organs. . 19
3.1 Structure and Function of the Integument ...... 19
3.1.1 The Epidermal Structure of Amphibians
Inhabiting Xeric Environments ............... 19
3.1.1.1 The Epidermis Structure of the Anuran
(Pelobates) Tadpole ......................... 20
3.1.1.2 The Epidermis Structure of the Anuran
(Pelobates), Post-metamorphic, Terrestrial Stage. . 22
3.1.1.3 Epidermal Thickness ........................ 22
3.1.1.4 Other Anurans Inhabiting Xeric Environments .. 22
3.1.1.5 Cell Dynamics ............................. 25
3.1.1.6 The Epidermis of the Urodele Salamandra
salamandra, Aquatic Stage ................... 25
3.1.1.7 Specialized Cell Types of the Urodelan
(Salamandra) Larva ......................... 28
3.1.1.8 The Urodelan Leydig Cell .................... 28
3.1.1.9 The Larval Mitochondria-Rich Cell, MRC ....... 28
3.1.1.10 The Epidermis of the Urodelan (S. salamandra),
Terrestrial, Post-metamorphic Stages. . . . . . . . . . . 29
3.1.1.11 The Flask Cell .............................. 29
3.1.1.12 Conclusions ............................... 29
3.1.1.13 Epidermal Cell Layers ....................... 30
3.1.1.14 Epidermal Cell Diversity ..................... 30
3.1.1.15 The Leydig Cell of Larval Urodeles ............ 31
XII Contents
3.1.1.16 S. salamandra Larval MRC and the Flask Cells
of the Adult ............................... . 31
3.1.2 The Dermis ............................... . 32
3.1.2.1 The Anuran Calcified Dermal Layer ........... . 32
3.1.2.2 Dermal Glands ............................ . 33
3.1.2.3 Chromatophores .......................... . 34
3.1.3 Moulting ................................. . 35
3.1.4 Cocoons ................................. . 35
3.1.5 Transport of Ions Across the Skin ............ . 37
3.1.6 Water Movement Across the Skin ............ . 38
3.1.7 Nitrogen Excretion Across the Skin ........... . 39
3.1.8 Conclusions .............................. . 39
3.2 Respiratory Organs and Respiration .......... . 39
3.2.1 Structure and Function of the Gills ........... . 39
3.2.1.1 The Gill Integument of Salamandra Larvae .... . 40
3.2.1.2 Specialized Cells in the Salamander
Gill Integument ........................... . 41
3.2.2 Structure of the Lungs and Respiration ........ . 41
3.2.2.1 Structure ................................. . 41
3.2.2.2 Respiration ............................... . 43
3.3 The Endolymphatic System as Calcium Reserve .. 45
3.4 Kidney Structure and Function ............... . 45
3.4.1.1 Kidney Structure .......................... . 45
3.4.1.2 Kidney Function ........................... . 47
3.4.2 Endocrine Control of Excretion .............. . 47
3.4.3 The Urinary Bladder ....................... . 51
3.5 Structure and Function
of the Female Reproductive System ............ . 53
3.5.1 The Ovary and Oogenesis ................... . 53
3.5.1.1 Oogenesis ................................ . 54
3.5.2 Mating, Sperm Storage, Fertilization
and Gestation ............................. . 54
3.5.3 Conclusions .............................. . 55
4 Receptors, Perception and Behavioural Responses .... 57
4.1 Photoreception and the Response to Light ..... . 57
4.2 Acoustic Behaviour ........................ . 58
4.3 Olfaction ................................. . 58