Integration of Development and Physiology: Mechanisms Shaping Animal
National Science Foundation
Directorate for Biological Sciences
Division of Integrative Organismal Biology
A workshop entitled “An Integrative Developmental Biology” was
held in November, 2004, and sponsored by the Division of Integrative
Organismal Biology (IOB) in the Directorate for Biological Sciences
at the National Science Foundation. That workshop drew our attention
to what we now recognize as an emerging area of research that spans
the traditional areas of developmental biology, and ecological
and evolutionary physiology presently supported by IOB. With this
letter we wish to inform a broader community of scientists about
this emerging area.
The workshop participants took a broader view of animal ontogeny
than is often held by developmental biologists, as described in
the workshop report, http://www.nsf.gov/pubs/reports/idbwsreport.pdf.
This broader view comprises more than the unfolding of a genetic
and signaling cascade triggered at fertilization. The unfolding
of the animal phenotype, its variation within a species and the
causes of the differences between species, are much more complex
and less understood processes. This view considers the physiological
regulation and environmental inputs as well. The general questions
that follow are in some cases taken directly from the workshop
report, and reflect the scope of this emerging effort.
How are complex phenotypes built?
It is well known that complex phenotypes are determined through
the interaction of many and diverse genetic and environmental factors
whose effects accumulate over long periods of time. Yet, the development
of cells and tissues are typically studied in isolation and over
brief time periods. As a consequence, little is known about how
the development of different cells and tissues is integrated to
produce complex organs and physiological systems, and how the ever-changing
organism remains functionally well integrated throughout its development.
What are the interacting developmental and physiological
bases of phenotypic variation?
The genetic and environmental determinants of development and
physiology naturally vary in space and time. As a consequence,
phenotypic variation has both environmental and genetic causes.
Physiological variation as a consequence of environmental variation
is well studied. These latter studies have described mechanisms
of short-term physiological adjustments to environmental challenge
(i.e., acclimation, phenotypic plasticity) within the lifetime
of the animal. Fewer studies have mechanistically connected genetic
variation, physiological variation, and evolutionary physiological
adaptation to the environment. Although the relative effects of
genetic and environmental variation can be assessed statistically,
the developmental mechanisms through which normal genetic and environmental
variation produce natural phenotypic (i.e., morphological) variation
are virtually unexplored and therefore remain poorly understood.
Clearly, the interaction of developmental and physiological processes
produce natural variation in morphological and physiological sets
of characters, and both of these kinds of processes are influenced
by genetic and environmental variables.
Thus an important and emerging conceptual area is focused on mechanistic
processes at the interface of development and physiology to understand
How are developmental and physiological systems integrated?
As development proceeds and the animal grows in size, the coordination
of development of distant parts becomes increasingly a problem
of physiology rather than cell biology. Integration of development
must occur on a spatial scale, in that developmental progression
to different stages in a life cycle must be regulated. The mechanisms
by which spatial and temporal coordination of development occur
are largely unknown.
Additional questions that are relevant to this new area are shown
What are the mechanisms of homoplasy? What are the mechanisms
by which the same suite of physiological or morphological characters
arises despite variations in developmental mechanisms?
How do variations in gene regulatory networks express themselves
in altered animal phenotypes across and within species?
How does a given developmental genetic mechanism give rise to
variations in morphological or physiological states within or between
What are the physiological determinants of developmental
Does physiological variation differentially
influence developmental genetic mechanisms, and lead to phenotypic
variation in animals within and between species?
As we become aware of other emerging areas of research within
the Directorate for Biological Sciences, through workshops or other
means, we intend to alert the broad community of scientists about
them as a way to increase consideration of, and eventual participation
in, these newly emerging areas.
James P. Collins
||Environmental and Structural Systems