In this study, we examine 3 structures located at important morphological boundaries in the medial forebrain, septum, hem, and thalamic eminence and find that they are unified by significant common features.
It is well established that the anterior boundaries of Hox gene expression are concordant with some morphological boundaries established in vertebrates (Burke et al. 1995).
Changes in soil pH across the morphological boundary were much less pronounced.
Laboratory analysis showed that there were accompanying marked increases in chromium-reducible sulfide (CRS) across the morphological boundary (from essentially 0% above the boundary to >1% below the boundary, over distances generally ≤10 cm), indicating that the morphological boundary determined in the field was accurate.
In this laminin mutant, notochord cells initiate intercalation, but then migrate inappropriately to become dispersed in the tail, because of the absence of a morphological boundary around the notochord.
This suggests that the segment polarity gene engrailed has a conserved function in establishing the morphological boundaries between segments in both tardigrades and arthropods.
In both mouse and chick, the position of the Hoxb4 anterior expression border corresponds to the r6/r7 morphological boundary.
The boundaries of expression of the three Hox genes in the un-segmented body of the acoel do not correspond to any overt morphological boundaries as is found in the segments of arthropods, annelids and in the vertebrae of mice.
Therefore, molecular identification is a helpful tool in resolving taxonomic problems in cases where the morphological "boundaries" among monogenean genera or species groups are ambiguous [ 27, 61, 62].
