Pattern recognition in cranial ontogeny of bats and marsupials with X-ray microradiography and phase contrast imaging

ROCHA, H.S.; PESSÔA, L.M.; HÖNNICKE, M.G.; TIRAO, G.; C. CUSATIS; MAZZARO, I.; ESCARLATE TAVARES F.; GILES, C.; LOPES, R.T.

Rio de Janeiro

Congreso; Third Brazilian Symposium on Mathematical and Computational Biology; 2003

The key to understanding characters evolution lies on the elucidation of underlying observed patterns mechanisms. The comparative development can be used to access the derivation of form (size and shape) and homology versus the convergence evolution of characters. Ontogenetic data has been used to study homology by comparing analysis of ontogenetic sequences and the analyses of patterns of variability inter taxa. Phylogenetic homology refers to structure derivatives of the same feature in a common ancestor and shared by two or more taxa. Biological homology refers to characters that share a set of specific developmental constraints. Understanding phylogenetic and biological homologies is necessary to discern the evolutionary origins of characters. The work examined developmental patterns of cranial formation in bat pre born individuals as well as post born opossum by using microradiography. The work carried out microradiography for examining development patterns of cranial formation in both bat pre born individuals and post born opossum. The x-ray absorption contrast imaging, namely absorption radiography, was used to study cranial morphology of bats and marsupials. A direct conversion CCD camera of 1242x1152 pixels of 25x25 mm2 was used to provide micrometer spatial resolution in order to acquire highly detailed density images. This technique enables the observation of structures, mainly in cranial morphology, that were once impossible to be seen – at this early stage of development - in both bats and marsupials. The traditionally used technique, as clearing and staining, does not permit the observations of such structures in the analyzed scale. Some cranial characters have been described for adults in the literature, but the detailed description of the sequence of appearance of those characters in pre born bats and post born marsupials, are still obscure. Microradiography and Diffraction Enhanced Imaging can improve quality in analyzing morphological details and permit the identification of anatomical landmarks which are useful in comparative studies and are still unknown in both pre born bats and post born marsupials samples.In this study we access characters evolution in cranial morphology of bats and marsupials using both techniques.