Table Of ContentContributors
R. J. Berger Marilyn B. Renfree
G. L. Florant Graham M. Simpson
S. F. Glotzbach Ian M. Sussex
H. C. Heller Virginia Walbot
Arthur M. Jungreis J. M. Walker
Larry D. Nooden James A. Weber
Dormancy
and
Developmental Arrest
Experimental Analysis
in Plants and Animals
Edited by
Mary E. Clutter
Department of Biology
Yale University
New Haven, Connecticut
ACADEMIC PRESS New York San Francisco London 1978
A Subsidiary of Harcourt Brace Jovanovich, Publishers
COPYRIGHT © 1978, BY ACADEMIC PRESS, INC.
ALL RIGHTS RESERVED.
NO PART OF THIS PUBLICATION MAY BE REPRODUCED OR
TRANSMITTED IN ANY FORM OR BY ANY MEANS, ELECTRONIC
OR MECHANICAL, INCLUDING PHOTOCOPY, RECORDING, OR ANY
INFORMATION STORAGE AND RETRIEVAL SYSTEM, WITHOUT
PERMISSION IN WRITING FROM THE PUBLISHER.
ACADEMIC PRESS, INC.
Ill Fifth Avenue, New York, New York 10003
United Kingdom Edition published by
ACADEMIC PRESS, INC. (LONDON) LTD.
24/28 Oval Road, London NW1 7DX
Library of Congress Cataloging in Publication Data
Main entry under title:
Dormancy and developmental arrest.
Includes bibliographies and index.
1. Dormancy (Biology). I. Clutter, Mary E.
QH546.D67 574.5'4 78-18482
ISBN 0-12-177050-8
List of Contributors
Numbers in parentheses indicate the pages on which the authors' contributions begin.
R. J. Berger (269), Thimann Laboratories, University of California, Santa
Cruz, California 95064
G. L. Florant* (269), Department of Biological Sciences, Stanford
University, Stanford, California 94305
S. F. Glotzbach (269), Department of Biological Sciences, Stanford
University, Stanford, California 94305
H. C. Heller (269), Department of Biological Sciences, Stanford University,
Stanford, California 94305
Arthur M. Jungreis (47), Department of Zoology, University of Tennessee,
Knoxville, Tennessee 37916
Larry D. Nooden (221), Department of Botany, University of Michigan,
Ann Arbor, Michigan 48109
Marilyn B. Renfree (1), School of Environmental and Life Sciences, Mur-
doch University, Murdoch, Western Australia 6153
Graham M. Simpson (167), Crop Science Department, University of
Saskatchewan, Saskatoon, Saskatchewan, Canada
Ian M. Sussex (297), Department of Biology, Yale University, New Haven,
Connecticut 06520
Virginia Walbot (113), Department of Biology, Washington University, St.
Louis, Missouri 63130
J. M. Walker (269), Thimann Laboratories, University of California, Santa
Cruz, California 95064
James A. Weber (221), Biological Station, University of Michigan, Ann
Arbor, Michigan 48109
* Present address: Albert Einstein College of Medicine and Mortefiore Hospital Medical
Center, Department of Neurology, 111 East 210th Street, Bronx, New York 10467.
vii
Preface
"Eels in blighted Wheat"
In a month of August 1743, a small Parcel of blighted Wheat was sent by Mr.
Needham to Martin Folkes, Esq; President of the Royal Society (with an
Account of his new Discovery) which Parcel the President was pleased to give to
me, desiring I would examine it carefully. With this material he was very soon
"entertained with the pleasing sight of this wonderful Phenomenon". He
repeated these experiments at different times and even with grains kept dry for 4
years, always with the same success and demonstrated it to Mr. Folkes and some
other friends. "We find [he writes] an Instance here, that Life may be suspended
and seemingly destroyed; that by an Exhalation of the Fluids necessary to a liv-
ing Animal, the Circulations may cease, all the Organs and Vessels of the Body
may be shrunk up, dried, and hardened; and yet, after a long while, Life may
begin anew to actuate the same Body; and all the animal Motions and Faculties
may be restored, merely by replenishing the Organs and Vessels with a fresh sup-
ply of Fluid. Here is, I say, a Proof, that the Animalcules in the Grains of
blighted Wheat can endure having their Bodies quite dried up for the Space of
four Years together, without being thereby deprived of their living Power: and
since, after they are become thus perfectly dry and hard, there seems little room
for farther Alteration, unless their Organs should be broken or torn asunder;
may they not possibly be restored to Life again, by the same Means, even after
twenty, forty, an hundred, or any other Number of Years provided their Organs
are preserved intire? This Question future Experiments alone can answer.
Henry Baker (1698-1774) biologist, microscopist,
Fellow of The Royal Society, in Employment for the
microscope, Chapter IV as reported by D. Keilin in The
Leeuwenhoek Lecture: The problem of anabiosis or
latent life: history and current concept delivered at the
University of Cambridge, June 19, 1958 [Proc. R. Soc.
London B 150, 1959].
This report by Henry Baker in 1743 provides the question of the present
volume.
The possibilities and potentialities of the condition variously known as
dormancy, hibernation, diapause, cryptobiosis, anabiosis, anhydrobiosis,
abiosis, quiescence, aestivation, latent life, and other synonyms of sus-
pended animation have long held a compelling fascination not only for
ix
X Preface
scientists and students of biology and exobiology, but also for religious
thinkers, philosophers, writers of science fiction, tellers of tales, such as
"Sleeping Beauty" and other fairy stories, and cryonics entrepreneurs. In
short, any mechanism which might serve to extend life, especially human
life, has been of longstanding interest.
There are a variety of states of developmental or metabolic arrest which
occur in microorganisms, plants and animals. Keilin (1958) placed them on
a scale of metabolic activity ranging from cryptobiosis (0%) to active life
(100%). The following scale was adapted from Keilin's:
Active Life (normal metabolism)
Hibernation
^- Dormancy or Torpor
Aestivation
Anhydrobiosis (hypometabolism)
Diapause
Cryobiosis
Hypobiosis ^- Quiescence
Anoxybiosis Cryptobiosis
Osmobiosis (ametabolism) Abiosis
I
Anabiosis
Latent Life
Death
Dormant states can occur over time spans as brief as minutes as some-
times occurs in sleep or torpor or as long as hundreds of years in the case of
spores or seeds. An exciting idea advanced in the last century was the doc-
trine of panspermy. It is no longer widely believed but it is postulated that
life may have been introduced on earth from an origin in outer space via
dormant spores released from fallen meteorites. Intriguing as this idea is
there is no direct supporting evidence, except that spores are known to sur-
vive extremes in environmental conditions.
Some seeds are also known to remain viable for many years. The famous
case of the viable lotus seeds found in peat of an ancient lake bed in
Manchuria brought forth speculations that the seeds may have been
deposited in the Pleistocene, about 50,000 years ago. Other evidence sug-
gests that they may have been only a few hundred years old. Whether the
seeds were hundreds or thousands of years old is immaterial. The
importance is that development was discontinued or arrested for a period of
time, then resumed without damage to the organism.
Experimentation on states of suspended animation did not begin or were
not recorded until Henry Power, a physician and Fellow of the Royal
Society, reported on his experiments on freezing and thawing eel-worms
(Turbatrix aceti) in 1663 and Leeuwenhoek reported his discovery in 1702
that certain "Animalcules" (rotifers) could be resuscitated after having been
evaporated to dryness. As a result experimentation for the next two
Preface XI
centuries was largely centered on microorganisms which could be placed in
a cryptobiotic or hypobiotic state by physical or chemical means and then
revived. Similar experiments are being done today, albeit on a more
sophisticated level. However, the state of the field is probably best indicated
in the title of a 1971 paper by J. H. Crowe, "Anhydrobiosis: an unsolved
problem."
Contemporary research on dormancy encompasses the whole range of
hypo and ametabolic states in all forms of life and has been extended to
include metabolic arrest of whole organisms as well as parts of organisms,
organs, tissues, and cells, either as a natural or developmental phenomenon
or as a controlled artificial arrest.
The present book grew out of a AAAS symposium entitled "Mechanisms
of Dormancy and Developmental Arrest" held in December 1972. Since all
living organisms exhibit some form of dormancy, the objective of the book
is to examine experimental evidence that may shed light on some of the
common underlying mechanisms.
The plant and animal examples were selected to show that dormancy may
occur at a particular stage of development, or that it may be a recurrent
phenomenon occurring in relation to changes in the environment. The
chapters illustrate the range and complexity of the phenomenon. It is not
simply a cessation of development, but is an interconnected process involv-
ing structural, physiological, and molecular alterations in the organism
which causes it to enter the arrested state, to maintain that state for a
period of time, then to exit from it into another period of activity.
The timing of events of these phenomena is critical. It may be controlled
by environmental stimuli, but the primary mechanism appears to be an
endogenous rhythm which is phased by photoperiod or other environmental
factors.
Recent efforts to discover the connection between physiological responses
to environmental signals and cellular metabolism have been increasingly
directed to the level of gene activity. In many examples of dormancy, nuc-
leic acid and protein synthesis cease prior to entry into the dormant state
and resume rapidly when this state is broken. Experimental evidence favors
a transcriptional mode of regulation, but there is increasing evidence for
regulation at the translational level as well. The examples presented here
examine the phenomenon at all levels. It is hoped that they will provide
insight into the complex problem and stimulate further research in this field
so that at last Baker's questions can be answered.
I should like to thank the authors of the chapters for their patience and
cooperation.
1
Embryonic Diapause in Mammals—A
Developmental Strategy
MARILYN B. RENFREE
I. Introduction: Patterns of Delay—Obligate and Facultative 1
II. A Brief Survey of the Nature and Occurrence of Diapause 7
A. Characteristics of Diapause 7
B. Occurrence of Diapause in Mammals 10
III. Embryonic Diapause in Three Wild Species 16
A. Western Spotted Skunk, Spilogale putorius latifrons 17
B. Roe Deer, Capreolus capreolus 20
C. Tammar Wallaby, Macropus eugenii 22
IV. Diapause as Developmental Strategy 28
A. Physiological Basis and Regulatory Mechanisms 29
B. Diapause as a Stratagem for Adaptation and Survival 37
References 41
I. INTRODUCTION: PATTERNS OF
DELAY—OBLIGATE AND FACULTATIVE
Early studies of reproduction in mammals led to the finding that each
species had a characteristic period of gestation with a fairly narrow range.
1
DORMANCY AND DEVELOPMENTAL ARREST Copyright © 1978 by Academic Press, Inc.
All rights of reproduction in any form reserved
ISBN 0-12-177050-8
2 Marilyn B. Rentrée
In the roe deer, however, although the rut occurred in the beginning of
August, there was no embryo visible in the uterus until January. It was
assumed that mating must have occurred during a period of "silent heat,"
for the observed matings seemed well separated in time from the first
obvious signs of pregnancy.
Ziegler in 1843 and Bischoff in 1854 made the discovery that in the roe
deer, Capreolus capreolus, mating was followed by a period of quiescence
and an almost complete cessation of growth of the embryo (Short and Hay,
1966). This led to a new concept that certain species manifest a delay in
implantation, quite distinct from a delay in fertilization following sperm
storage, which came to be known as "delayed implantation" or "embryonic
diapause." The roe deer is the only ungulate whose embryo has so far been
found to show a delayed period of growth. Several other workers at the turn
of the century subsequently described the occurrence of embryonic diapause
in a variety of species, for example, badgers, rodents, and armadillos
(reviewed by Wimsatt, 1975). However, most of the impetus to study dia-
pause has occurred in the last two decades; diapause was discovered in mar-
supials only relatively recently (Sharman, 1954, 1955a, 1955b).
Reproduction and development generally occur when environmental con-
ditions are favorable for a species. Unfavorable conditions, especially when
they recur periodically, may be avoided by migration or by the intervention
of a resting or dormant stage in the animal's life cycle. Dormancy can
involve the suspension of some physiological activity in the organism, or it
may comprise the suspension of reproductive growth and development.
Seasonal reproductive cycles are distinct from suspension of reproductive
activity. In insects, for example, where adults can suspend metabolism, the
condition is usually considered true dormancy or diapause. Among mam-
mals in contrast, there are seasonally breeding species that have developed
such adaptations to take advantage of favorable conditions, whereas species
with a reproductive dormancy have often evolved mechanisms to avoid
unfavorable periods in what would otherwise be a continuous reproductive
life.
There are many different forms of dormancy among mammals. There is
differentiation among the various kinds of quiescence, torpor, estivation,
and hibernation, on the one hand, which are all clearly related to environ-
mental conditions, and "embryonic diapause," on the other, which is
probably more closely related to the physiology of early development.
This account is restricted to the latter type of dormancy in mammals,
that is, "delayed implantation" or "embryonic diapause," and emphasizes
the characteristics of the phenomenon in three disparate wild species that
have recently been studied in depth: the roe deer, Capreolus capreolus; the
Embryonic Diapause in Mammals—A Developmental Strategy 3
western spotted skunk, Spilogale putorius latifrons; and the tammar
wallaby, Macropus eugenii.
The usual mammalian development pattern begins with fertilization of
the ovum. The resultant zygote spends a predictable period of time in the
oviduct and eventually reaches the uterus. During the passage down the
oviduct, numerous cleavage divisions occur, resulting in the formation of a
hollow ball of cells known as the blastocyst. The blastocyst continues to
expand by cell division and by accumulation of fluids from the uterine secre-
tions. Eventually it attaches to the uterine wall via its chorion or trophoblast
(Eckstein et al., 1959). The duration of the preimplantation stage is
determined by the species, but it ranges from about 4 to 6 days in rabbits
and mice, through nearly 20 days in some marsupials, to 40-60 days in
ungulates (Wimsatt, 1975). Implantation and the formation of the yolk sac
or allantoic placenta facilitate maternal-fetal exchanges; embryogenesis and
organogenesis generally proceed without interruption.
In some mammals, a period of delay occurs during this process.
Implantation itself may be delayed or, alternatively, development before
implantation may be delayed. The term "delayed implantation" is used to
denote a prolonged period in which the blastocyst is not directly attached to
the uterus although it remains within the uterine lumen. In many but not all
species showing delay, implantation follows immediately after the resump-
tion of development. For those animals whose blastocysts do not implant
immediately, the term, strictly speaking, is incorrect, since the delay occurs
before implantation and the process of implantation itself is not inhibited.
Several authors have suggested instead that "embryonic diapause" better
describes this condition in mammals (Tyndale-Biscoe, 1963a; Short and
Hay, 1966; Baevsky, 1963).
Insect dormancy is also known as diapause, a name used originally in
insect embryology to describe a stage just before the reversal of movement
of the embryo around the posterior pole of the egg. The meaning in insect
biology has now changed and refers to a "condition" of arrested growth,
whether embryonic or postembryonic, rather than to a stage of mor-
phogenesis. In these metazoans, diapause can occur at any stage of the life
cycle—in the fertilized egg, in larval instars, in the prepupal or pupal
instars, and in the adult instar. The critical point to note is that the diapaus-
ing insect requires an environmental cue coupled to a physiological trigger
to release it from diapause, just as mammals do.
Both "delayed implantation" and "embryonic diapause" are used more
or less interchangeably in mammalian studies. In this review, "embryonic
diapause" is used. Two types of delay occur, and, as in insects, distinction is
usually made between "obligatory" and "facultative" diapause. "Obligate
