New Imaging Techniques and the Integration of Morphology, Development and Physiology
Brainerd, E.L.
This is an exciting time in the field of morphology, particularly for those researchers with interests in development, function and evolution. New imaging techniques such as high-resolution CT scanning, magnetic resonance imaging, and laser scanning confocal microscopy are opening up vast worlds of cross-sectional and 3-dimensional anatomy. In developmental biology, continuing improvements in whole-mount immuno-staining combined with confocal microscopy are providing stunning, 3-D views of developing organisms. These images can target particular tissue or organ types, and can show spatial and temporal patterns of gene expression in the context of the surrounding morphology. This last bit "in the context of the surrounding morphology" is key. For a while, molecular approaches to developmental biology were somewhat divorced from morphology because researchers could only look at gene expression in homogenates of tissues. With in situ techniques, however, morphology is now in the process of retaking its proper place at the center of developmental biology.
In further, even more exciting developments for those of us interested in function in developing organisms, new imaging techniques for viewing gene expression and physiological functions in vivo are being developed. Transgenic organisms with fluorescent tags co-expressed with particular genes are allowing gene expression to be monitored in vivo (and repeatedly at different developmental stages of the same individual). The activity of individual neurons can now be monitored in vivo in small, transparent embryos using calcium sensitive dyes and confocal microscopy. Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) continue to improve in spatial and temporal resolution and may become useful in the future for studying developmental stages as well as adults. Nanotechnological developments and the fabrication of microelectromechanical systems (MEMS) promise the ability to measure pressure, force, and strain in the near future, and perhaps many other physiological variables in the not too distant future.
Many of these techniques may be relatively easily applied to diverse organisms, making comparative, evolutionary studies possible (assisted greatly by recent conceptual and methodological advances in phylogenetics and quantitative comparative methods). Some, however, will need to be pioneered in model organisms before they can be applied more broadly (see abstract from Martin Feder).
Most of the techniques mentioned above are imaging techniques; therefore these techniques have the potential provide simultaneous physiological and morphological information. This may allow the emerging field of Developmental Physiology to integrate morphology and physiology more completely than studies of adult physiology have in the past. This is an inspiring prospect – working toward an integrated understanding of morphogenesis and "physiogenesis".
Ecology & Evolutionary Biology - Brown University